text:
3d Print pops off before complete
I recently got my first 3D printer, however when I print taller objects, sometimes the piece pops off the build plate and moves around before the print is finished, the piece then is missing the top few layers and is burnt from the nozzle, Just wondering why this happens and how to fix it...
Here are some pictures:

It's unclear what your question is: if it is about how to improve adhesion, you should provide more details.  What printer, what filament, what type of printing bed, what temperatures, etc...  Or maybe the question is about why it happens at the top of the print?

I have updated the post, sorry about that! I also believe that it was due to bed leveling as the first layer did not have a lot of contact to the print surface...

The issue you are having is with bed adhesion.  Basically your print is not sticking well enough to the printer bed for it to resist the mechanical forces the part is being subject to during print.
This the most common issue in FDM 3D printing and you can find a lot of material online on how to mitigate the problem.  Just as a "teaser":

You need to ensure your printing bed is dead flat and at the right distance from your nozzle.  Search online for: "3D printer bed leveling": the procedure is normally the same for most printers, but if your model is a common one, chances are you will find a video/how-to/blog post for it.
You should use print settings that facilitate bonding of the plastic to the bed (typically: slow speed, no cooling fan, a bit of overextrusion...)
You can tell the slicer to add a brim or a raft to your part, to increase the amount of material holding down the print.
You have the option to cover your printing bed with some material that increases the bonding of the plastic (this is type-of-plastic specific but typically: PVA glue or painter's tape work well for PLA, and kapton tape or ABS sludge for ABS).
If you have a heated bed, use it (each filament brand has their own recommendations, but typically 50-60°C works well for PLA).

As for why your problem is happening towards the end of the print, there are a series of factors contributing to it:

The tallest the print, the more mechanical advantage (leverage) the nozzle has over the adhesion surface.
It looks like your top layers are progressively small, so they print very fast and this in turn the does not allow for the plastic to completely cool down before going to the following layer, so when the nozzle prints on top of it the still-warm layer is "pulled up" by the action of the nozzle, creates a blob that sticks to the nozzle and that only makes situation worse.  Snowball effect.  Most slicers have an option "minimum layer time" that delays the print of a layer until X seconds have passed from the start of the previous one.
It may be possible that the Z axis is inaccurate and the nozzle catches on a previous layer.  Most printer have some kind of accuracy issue with the Z axis the furthest up the head is, especially if the Z-axis has only one threaded rod (as for example in the Creality CR-10).  Another source of inaccuracy (see comments below) could be the movement multiplier for the Z being slightly off, causing the nozzle to dig into the print if there's overextrusion and enough cumulative error.  Z axis inaccuracies are however unlikely to be the primary source of troubles for you, but it's a "nice to know" thing to know about 3D FDM printers, nevertheless.

printing bed should be heated bed?
In addition to the Z axis inaccuracy, the movement multiplier for the Z axis might be off, causing the nozzle to dig into the print if there's overextrusion and enough cumulative error.

@onno -  thanks, fixed! will add your comment in the answer when not on mobile! :)


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Increasing rigidity of curved, long, thin parts
I'm attempting to model and print a globe.  The semi-circular arm that holds the globe has an outer diameter of 98mm and inner diameter of 92mm, so the arm is fairly thin.  The arm has a small hole on either end that fits around a protrusion at each pole of the globe to hold it in place.  The hole extends into the arm only a few millimeters, so it doesn't go all the way through.
I printed the arm in ABS and it ended up being a bit too flexible to hold the globe securely.  Obviously I could do things like making the arm thicker or extending the globe's protrusions all the way through the arm, but I'd prefer not to if I don't have to (you know, artistic integrity or whatever).
Would printing in PLA result in a more rigid part?  I've tried to do some googling on this, but couldn't really find a definitive answer.  Most comparisons focus on strength which I assume doesn't necessarily correlate to flexibility.
I'd also welcome any other suggestions for making the part more rigid.

Just curious... did you get around to solve this?

Unfortunately, I haven't had much of a chance to play around with things.  I did one test with PLA and while it did seem a bit more rigid, it was still too loose to securely hold things. I am hoping to try playing around with the infill settings in the next few days. Sorry it's taking so long to accept your answer. It's looking like I'm going to have to make some design modifications, though. One detail I neglected to mention in the question was that the outer ring is actually holding an inner ring of a similar thickness, so the idea of inverting the pins and holes sadly won't work for me.

The flexibility of 3d plastics has a lot to do with the additives manufacturers use.  The same base material with additive X may have very different properties than the one with additive Y.
That said, generally speaking PLA is known to be more rigid (and brittle) than ABS, but less strong.  So: you have a fair chance at giving it a go with PLA, albeit you my end up with a more delicate object in the end.
There is a well known youtube channel, whose author has performed a lot of quasi-scientific testing on common brands of filament (PLA and not) where you can get an idea of the relative rigidity of the filaments.  You can find the table with the results here (look for the "bend test" columns).
However the very firs thing that came to mind when reading your post, is that you could simply swap pins and holes by putting the holding pins on the arm, and the holes on the globe instead.  This would allow you to preserve your design and to have longer pins.
Things you could try when it comes to printing (unless you are already doing them):

Print the arm flat so that the layers stretch from pole to pole uninterrupted.
Print with near solid infill (solid infill can be problematic if your extrusion calibration is not perfect), like 95% and cubic infill (for more uniform properties along the full length of the axis.

Finally, you could try to anneal the arm in your kitchen oven.  This process works by warming the part until it becomes pliable and then letting it cool very slowly.  The end result is that the molecules arrange themselves in a more "crystal-like" way and the part becomes stronger and more rigid.  Beware that annealing changes your part dimensions so you should definitively do some experiments with a test cube and find out the direction and percentage of the shrinking before going "all out" on the arm.

Besides Thomas, there's also Stefan / CNC Kitchen that does (quasi) scientific tests of filaments and print patterns

To make it more rigid I would add more shells than to use solid infill.
There are higher strength PLA's, but they only gain their higher strength and temperature resistance after annealing. From reviews I've seen, there is only a percent or two difference in size, but this is more complex than it seems because the difference is different along the layer lines or crosswise from them. However, even normal PLA will anneal, so if you have any you could do some quick experiments.
If you have a high-strength nozzle, you could use NylonX. This is nylon with carbon fiber to make the part rigid. There are also carbon fiber PLA's ad ABS's, but I've never experimented with them.
Otherwise, I like the answer from @mac

Print thinner layers. Also, you did not mention the other dimension of your arm. If you view the globe with the arm to the left, then you have said the thickness in the X direction (left to right) is 6mm. But what about in the Z axis (away from you)? You could make it thicker in that direction to improve its rigidity.

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Ultimaker Original+: print has lumps and small gaps are being filled
Brand new to 3D printing and have an Ultimaker Original + using PLA (2.85mm).
The nozzle/extruder temperature is 200C and the bed/plate is 60C.
I installed the Cura software on my Windows 10 box. I then head on over to tinkercad.com to make a model of a comb. I then exported my .STL file and loaded it up in Cura. I hit the print button. I waited a bit, but noticed that my print was getting lumps in it. Not crazy drastic lumps, but because the object was small, gaps (between the comb teeth) were being filled... not all of them, just some.
I tried adjusting the flow rate from 100% to 90% and it seemed a little better (not perfect, still filling gaps), but when I dropped it lower, it got worse.
I also tried to lower the print speed from the default of 60mm/s to 50mm/s - no change. (travel speed at 120mm/s)
I tried to adjust the bed height multiple times, trying to make sure that it was 100% flat at 180 degrees.
What is wrong here? Is the printer over extruding? Is the temperature too high? Is the flow rate wrong? Am I missing something else?
Check out my prints:

I also tried printing something else:

Any help would be really appreciated.
Update
Okay, so thanks to macs answer, I took another look at the nozzle and noticed a massive leak - I actually dismissed this earlier as "glue" - OMG.
Anyways, here is the picture of the leakage:

It's very bad. It leaks down and runs over the nozzle. The nozzle also leaks... Is that normal? All I did was turn the printer on, heat up the nozzle to 200C and it started to leak. I suspect that it should not do this... I'm not ready to change the nozzle just yet - I've no idea which one to buy or even where to buy it from (I'm in the UK), so I'd like to get this one working (if possible).
On another note, I have checked the filament settings - All good. Heat settings all good too:

Did you lower the temperature? I use 190-195 degrees for PLA and 50 degrees for printing bed. It looks like the object does not stick well to the printing bed. Am I right?

@Marco I didn't try to lower the temperatures, no. However, the object actually sticks very well to the bed... I need to pry it off.

What nozzle diameter?    And have you played with the retraction setting?

Are you sure your nozzle isn't dripping?

What is wrong here? Is the printer over extruding? Is the temperature too high? Is the flow rate wrong? Am I missing something else?

It is always difficult to diagnose problems from a set of pictures only, and without the original model to compare it with, but yes, from the pictures it looks like your printer has a severe case of over extrusion, possibly in conjunction with a thermal problem.
The first picture in the set is particularly interesting for a number of reasons:

The chequered pattern of the top layer looks like being generated by the nozzle "digging" in the layers below and rising the plastic around it.  A well calibrater printer should have a top surface with a very subtle texture instead.

The teeth of the comb and the gap between them are inconsistent, as are the shape of the tip of the teeth.  This let me think your printer actually doesn't operate consistently, over-extruding in some places a lot more than in others.  A pinter should be able to accurately replicate its performance along the full length of the comb instead.

The plastic has a different finish and colour in different places.  Namely, it looks burnt and glossy where the worse print quality is, white and matte where the problems are not so bad.  Both the colour and the finish let me thing the plastic in the dark spots have been heated way over its operational range and/or for too long.

In essence what I think it is happening (mind it: this is just a theory) is that your printer is over-extruding and in addition your hot end may have issues with keeping its own temperature constant and within the designed limit.  Other factors that may also play a role could be:

Wrong settings in the slicer as for example a nozzle diameter set to 0.5 mm when it really is 0.4 mm instead, or the filament diameter being wrong.
Blobs of over-extruded material forming and sticking to the nozzle, where they take too much heat for too long and burn before "falling" in the print and damaging it.
Filament that is old/of bad quality and that has impurities in it, or has an inconsistent diameter along its length (thus causing over-extrusion in places, but not in other).
A nozzle that is not well fixed to the heating block, thus allowing molten plastic to seep out from the joint and run down on the outside of the nozzle and ultimately on the print itself.
A nozzle that got damaged and whose opening is not circular and/or not matching its nominal diameter.
The extruder hobbed gear not e"biting" in the filament and thus the filament slipping at times, thus being inconsistent in the quality of material being extruded.

So, here's the the trouble-shooting I would go through at this stage:

Check your printer setting in the slicer.  Doh! :)
Take a close look at how the print works while in operation.  Do you see blobs forming and sticking to the nozzle?  Plastic seeping out from places it shouldn't?  Is the nozzle round and true?  In case of doubts, just change the nozzle with a new one (it is a less-than-1€ part anyways), easily outspent by the cost of filament in a failed print.
Calibrate you extrusion (and thus your flow-rate) by performing accurate measurements over at least 3 length of filament.  Matterhackers has a nice how-to that you can follow for this.
Manually check the diameter of your filament (at least 5 measurements at at lest 200 mm distance between them) and adjust the corresponding "filament diameter" setting.
Calibrate your temperature by using a test tower.  This one has extensive instructions on how to use it in the thing description, plus is customizable directly from thingiverse.
Print again your model and see how/if your changes affected the print quality in any way.

If the above fails, you could also try to use another slicer, but it's unlikely the problem is with the software.
UPDATE
I'm not familiar with your printer model, but the updated pictures seems to show the leakage happening between the heat block and the heat break, rather than between nozzle and "whatever". ;)
This can actually be caused by two different problems (or the two of them compounding).

The two parts, which are normally just screwed together have come loose.
If your extruder is not "all metal" (which is normally not the case in most printer), the PTFE tube (the whitish plastic tube the filament slides into) may have dislodged upwards, so instead of being a tight fit in the heat block, it leaves room for the molten filament to seep upwards.

In both cases, a reassembly and thorough clean-up of the head is in order.  I would suggest trying to find specific documentation for your printer online, but the general process is:

warm up the head to printing temperature.  All subsequent steps will have to be done at this temperature (wearing protective gloves is highly  recommended)
remove the filament
remove the PTFE tube
remove the nozzle
remove the the heating block from the heat break
wipe as much the plastic as possible (bit drills work well for the hole in the heat block
increase the temp a further 20-30 degrees
reassemble everything
profit

Please note:

the heat break is relatively fragile: be gentle when unscrewing.  When removing/attaching the nozzle is worth keeping the heat block in place with a spanner to prevent twisting the heat break
if you can't remove the plastic when molted, you can try letting it cool and scrape it
it essential that the re-assembly be done while hot.  Metal expands with heat, so what feels firm while cold will eventually become loose at high temperature

Hey, thank you for the detailed response. Your question Plastic seeping out from places it shouldn't? caught my eye - I do indeed see leakage. I took a closer look... turns out it is leaking very badly between the nozzle and the tube/pipe/whatever. I'll add a picture to show.

@pookie - I updated my answer above, let us know how it goes and mind that disassembling the hot end is probably the trickiest maintenance operation to be done on a printer, so don't get discouraged should you find it difficult to perform!  Take your time (or find a friend/hackerspace that may show you how it is done). :)

Thank you :) I will go through the process of removing, cleaning and reassembling the unit and let you know how I get on. I've read a lot of stories about people snapping the tube... It's my wife's work printer, so what the heck? I've got nothing to lose! :)

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Delta printer misalignment at first few layers
At first few layers, each layer has offset to -X/-Y direction base on previous layer. But above ~2mm, it is vertical.
I've checked the printer build that there is no noticeable error in towers. Tried both manual calibration and Marlin auto calibration G33 with z probe.
No idea what's the cause and don't know which part I need to check with.

Finally I found out that it was caused by not enough torque output by B tower stepper motor. Increasing current didn't work. I replaced the stepper motor and it prints perfectly.

How did you conclude it was tower B's stepper that was at fault?

@dibs I just put my hand to try to stop the slider.


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How can I read this 3mf-File
So I am trying to get the XSD-Schema from this object. When I open the File I just get something like this code (snippet):
¸†2¡Q·2ºyƒeCã2ï…w ïÀ|¼ðAøä[0Ÿ |>‚|ó‘å2²ºFƒ¼Æò1ùàåcj@Þ`ùÐ¸Ì{áÈ;0/|¾
 ùÌ'Ÿ„ Á|d½¬¬¯Õ ¯±|l¾…Œo@Þ`ùÐ¸Ì{áÈ;0/|¾ùÌ'Ÿ„ Á|d½œ¬¯Ó ¯±|h\æŒo@Þ`ù¸|
 ßBs¦5–Œ~ôè»£(™c´“Ç£[yp1:æ'Ã‰c4Jó Uâ˜ÍÇ<h—8^'Ð¯É

What is this? How can I convert it back? I need to edit the structure manually.
Thank you in advance.

Three likely culprit:

The file is compressed but your machine can't detect it.  So for example the 3MF model has been zipped, and what you are trying to do is opening the zip archive in the text editor, rather than the file that is in the zip archive.  Solution: try to see if common decompress utilities like zip, gzip, 7z can open the file.
The file is a 3MF model but the character encoding in the file being different than the one your editor is expecting (typically Unicode/UTF-8, these days).  Solution: read on the rest of this answer.
The file is a binary one that is totally unrelated to 3MF.  So in essence: an error, you are trying to open maybe an MP3 or a JPG file believing it to be a 3MF instead.

As for the "wrong encoding" option...  Oversimplifying a bit, the story goes like this:

computers write data to files in bytes,
a byte can only be set to one of its 256 possible values,
in the early days of computing, when computers were just glorified calculators, it was enough to have a 1:1 ratio between the byte possible values and the symbols one wanted to use, so ASCII was born (actually ASCII only "mapped" the first 127 values of the byte, but that is a detail).  So: value #49 would represent a 1, value #90 a Z and so on...
shortly afterwards, computers became powerful enough that people wanted to use them to process human languages, so the need for more characters (like accented ones åáä or the ones from non-latin alphabets like Cyrillic язы́к or arabic عَرَبِيّ, or...) came to be and engineers speaking different languages had the "brilliant" idea to each use the other 127 "free slots" in a byte for their favourite languages, thus a plethora of extended ASCII encodings was born, each using the same byte value, but each mapping to a different symbol.
later on, people began to realise the need to combine the use of say Gaelic, English, Japanese and Farsi with mathematical symbols, and thus they came up to way to map symbols to values expressed as the product of more bytes (so for example: 2 bytes encoding could map 256x256=65536 symbols).  Again: each system using the same values but different symbols.
finally after decades of frustrated users and expensive bugs, engineers around the world settled for a multi-byte standard that has 1,114,112 possible values that could contain all characters one can possibly need, and Unicode was born.

Back to your question: despite unicode having been around for a few decades now, legacy software and sloppy programming are a thing, and there are still systems that do not use unicode internally but some legacy "special purpose" encoding.
Unfortunately, it is impossible to say with certainty how a file was encoded, so occasionally you may find yourself opening a file and starting decoding it according to a "conversion table" that is not the one used by the author of the file itself.  This is what it looks like is happening to you.
Onward to what you can try to do to fix this...
First of all: as attentive readers may have already inferred, you will need the actual file for this.  In fact if you cut-and-paste its "content" from an editor what you are really doing is cutting-and-pasting the decoding your computer did of the byte values, and not the byte values themselves.
Then your best bets are:

Try one of the online detectors like this one, using "English" as a language.  These detectors work by trying all the decoders they know of until the decoded file will have English (or another language of your choice) words in it.  This may not work for you as a 3MF file is mostly numbers, not text, but it is worth a shot.
Guesstimate what encoder may have been used.  For example: if you got the file from an old windowsXP machine from Eastern Europe, chances are it may have been encoded with "windows-1251".  Use an online converter to see if you were right about it.
Use brute force.  For this you will require to write a simple programme or ask somebody to do it for you, but the key idea here is to have a script taking your original file and decoding it using all encoders in that programming language knows of.  Then it will be up to you to open each decoded file individually and verify if it worked or not.

Preventive comment: I am intimately familiar with the difference between UCS and UTF.  I chose to conflate the two for keeping the answer (that focuses on the rationale behind the existence of several encodings) more to the point. :)

I less words, he has the wrong file editor or viewer.

@FernandoBaltazar - nope, 3MF is a textual, XML-based format. Any text editor is capable of displaying it correctly. The problem is either the unexpected encoding or the file being corrupted/not being a 3MF one.

This happens if you are using a wrong file editor or viewer, even if the file might be corrupted. All windows files has internally this ascii code.

@FernandoBaltazar - I suspect you are using the wrong terms to express yourself.  Windows never used ASCII as a character set.  As far as I know the first version of Windows already had CP 1252, while DOS used CP 437.  I am not a Windows expert, but I believe Windows switched to Unicode/UTF-16 with the XP edition.

try to see a file inside with the wrong file editor, then make a comment; I personally modified some programs on 1990 and still I do with some files. Is nice to see the ascii and hex, while externally CPXX and UTF-xx are to see text and wyswyg, of course on DOS computers was an oddisey to get it.
If Tom Unger can't read the file with the right file editor or viewer then the file is corrupted, just like this with less words.

"The file is compressed"; this is true. In Ubuntu, the default app to open it is Archive Manager. For example, as I opened a .3mf file as a compressed one, there were three directories and a file in it.

Seems to be your are trying to edit a file with the wrong file editor.
If you have Microsoft® Windows® 8.1, you can print directly using the 3MF format included. Simply set the print options in the 3D Print PropertyManager and print to the 3D printer. A preview of the print bed and the model's location within the print bed lets you modify settings before committing to a 3D print job.
To access the 3D print dialog box and specify print options, click File > 3DPrint.  The print dialog box that is available depends on your installed 3D print driver.
If you need to get the STL you may need to use a file conversion, here is a youtube tutorial to makeprintable


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Pronterface window question
I switched to a Raspberry Pi 3 to use with (Linux) Pronterface for my 3D printer.
This Pi 3 has a 3.5" 320x480 LCD display. When Pronterface is loaded, only part of its window can be seen and some of the UI elements are unreachable. I have the Pronterface source code from GitHub.
Where do I start to shrink the app window?

You can change your Pi's resolution using raspi-config or the Raspberry Pi Configuration app.
To use raspi-config, access Terminal and run raspi-config. Then navigate to Advanced Options > Resolution.
If you'd rather use the GUI, open the Raspberry Pi Configuration app and select Resolution from the resultant dialog. This may help with the rendering issues.

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TinkerCAD Align to Odd Shaped Object
I have an odd-shaped object (I'll call it "A") that I have imported into a TinkerCAD drawing. Its dimensions do not align to any specific size, and therefore I can't really use the grid lock to help.
However, I need to get some other objects (called "B+") a specific and precise distance from the outside edge of "A". I was trying to get the ruler to lock to the edge of "A", but I can only get close.
Is there a way to do this so that I can get "B" perfectly positioned from the edge of "A"?

Consider to construct an object of any suitable shape that will properly align with the edge of "A."
The attached image is certainly an odd-shaped object (from a previous test project).

Add a regular/symmetrical object such as a cube and size it appropriately for your purpose. It would not have to be a cube, although such a shape provides for convenient alignment in this case:

Use the alignment tools feature in Tinkercad to align the desired edge(s). In this case, alignment is common right side, centered top to bottom.

After clicking on the alignment button, lower right corner:

Group the two objects using the Group feature.
I created a sample alignment reference in this image and placed it in contact with the group.

Move the group or reference item the desired distance:

Select the group and ungroup it.
Select the initial alignment item and delete it.

Objective completed.

Excellent answer fred.u.  To the benefit of the OP I would add that if they find themself in need of doing this often, they would be probably best served by switching to a more powerful CAD package like FreeCAD, OnShape or Fusion360.  Those packages typically have much more concise and unobtrusive ways to express these kind of constraints... as constraints (so the relationship between objects will hold true even if you manipulate them).

My experience within our makerspace is that many Tinkercad users tend to shy away from parametric packages. I'm a fan of OpenSCAD, but the math-phobic folks are terrified at using something that requires manipulation of numbers.  I've attempted to assist some users with Fusion 360, but tend to give up in short order due to the "numbers" aspect.


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24 V heated bed from -12 V and +12 V ATX power supply?
As long as there's a MOSFET in between, can I supply 24 V bed/extruder heat from an ATX power supply using -12 V and +12 V and ignoring the common rail?
I assume so, I can't think of a reason why not, but want to check.

Nice question, I had wondered the same. However, without wishing to sound daft, why would you need the MOSFET transistor? To act as a switch, I presume?

@Greenonline Yeah, to switch the bed on and off. In other words, the original heated bed wires from the controller would switch a MOSFET, and the 24v would be isolated. That's assuming the controller can't be run at 24v.

Did the answer helped you to get an answer on your question or helped you come to your own conclusions then please do vote and accept the answer. This helps us reduce the unanswered questions list. Found an other answer (then the already posted) yourself? Please add that answer (and accept after 48 hours) to share your experience with the community. If you have not been able to address the problem please update your question.

No, this is not possible with most ATX power supplies. While in principle you can get a 24V supply by combining the +12V and -12V supplies, the rails are not symmetric, and the negative 12V supply is usually designed for a much lower load than the positive supply. In the example in the following picture, there are two positive 12V rails, capable of sourcing respectively 12A and 15A each, but the -12V rail is only good for sinking 0.5A. If you tried doing what you're proposing, using this supply, you'd be limited to only 0.5A from your "24V" supply.

It is very unlikely that you'll find an ATX power supply with a negative 12V rail capable of sinking significant current since computers don't need such large amounts of current from their negative supplies.
There are also issues with using a MOSFET as you describe. I assume that by MOSFET you are referring to a complete board with various support components, and not just a bare MOSFET by itself. Usually these boards have optocouplers and thus they will probably work correctly, but using just a MOSFET by itself this would not work, as the gate needs to be driven below GND (namely: to below -12V plus the gate threshold) to turn the MOSFET off.


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Z axis Stepper motors not working correctly
I have been searching around the internet for the last 3 days trying to figure this out. My Z axis motors for a pursa-i3 3d printer are not working correctly. I have marlin firmware and using repetier host. I send a command to move the z axis and I get it to move, however I if I send the same command again the motors will sometimes spin the other way. feel like They almost randomly choose which direction they turn.
As I said I have been trouble shooting this for a while now. What I am suspecting is the firmware feedrates and acceleration or some setting is not correct.
Here is my code:
//// MOVEMENT SETTINGS
#define NUM_AXIS 4 // The axis order in all axis related arrays is X, Y, Z, E
#define HOMING_FEEDRATE {50*60, 50*60, 2*60, 0}  // set the homing speeds (mm/min)

#define DEFAULT_AXIS_STEPS_PER_UNIT   {80,80,4000,590}
#define DEFAULT_MAX_FEEDRATE          {300, 300, 3, 45}    // (mm/sec)
#define DEFAULT_MAX_ACCELERATION      {1000,1000,50,500}    // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for Skeinforge 40+, for older versions raise them a lot.

#define DEFAULT_ACCELERATION          1000    // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION  1000   // X, Y, Z and E max acceleration in mm/s^2 for retracts

#define DEFAULT_XYJERK                10   // (mm/sec)
#define DEFAULT_ZJERK                 0.3     // (mm/sec)
#define DEFAULT_EJERK                 5.0    // (mm/sec)

I tried swapping the drivers around and the motors will work perfectly on another axis so I don't suspect it to be a driver issue. I have been turning the pots ontop of the drivers to make them work but can't make them to go the same direction i want them to.
I've checked the wires and I almost sure they are wired up correctly. (could be wrong but have checked it over with a multimeter.)
I am new to this and it's my first time building one of these would appreciate any help I can get and and maybe I have over looked something I have tested.
Just really want the axis to move in the direction That I say it to move in.

More details about my setup is: A Robocraze 3D Printer Controller Board RAMPS 1.4 using A4988 stepper motors drivers and my motors are the nema 17 stepper motors. I currently have the two z axis motors wired in parallel but have tried before using series, however the problem of being unable to control the direction of the Z motors still arises (can easily switch back to series).
currently trying with no load just to get the motors turn in the correct direction when I send a G-code command. I am using Repetier host on ubuntu 14.04.5.
I have also check the endstops and they are working perfectly, so they ain't a problem (I don't think :p)
Thank you,
Bobby

Not sure if I asked a clear enough question, hoping for some help and can provide more details if needed?

Try adding more specifics on your wiring, the servos you use, etc. There is something not completely obvious going on here.

Added a few more details and yeah I can understand :(, hoping someone has faced the same issue?  really odd because when I send the exact same g-code command repeatedly The Z axis will turn back and forth clockwise then Anti clockwise with each different command! Such a headache hahaha, Thank you

Did you try with just one of the motors connected? What if you disconnect the motor coupling? You need to isolate electronic/software and mechanical issues as the potential cause.

Hello, Yes I have tried with just one motor connected to the Z driver and still same issue, even different motors completely. I know it is something that is wrong with the Z pins, driver or firmware (feed rates as such are different). I have tried swapping the drivers and it works in other slots for the x,y or extruder motors, so i don't think the driver is the problem. Could be maybe the RAMPS board slot for the Z motors is faulty? I am guessing that since no one has jumped up and said anything about the code, the firmware is fine? so it must be the RAMPS board Z driver socket???

So after 5 days of trouble shooting, Bob-the-Kuhn over on the marlin github forum solved it for, anyone else who faces the same issue can head over to github for my solutions.
https://github.com/MarlinFirmware/Marlin/issues/9287#issuecomment-359428147
Conversation from link:

Bob-the-Kun:
Problem does not follow the driver. Problem does not follow the
steppers.
I'm thinking that the Z socket has a problem. Sounds like an open/poor
contact.
Try bending the DIRECTION lead on the Z driver a little and see if the
problem disappears. It's one of the corner pins. Sometimes it's called
DIR. If your driver's pins aren't labeled then bend all four corner
pins a little.
Another option is to move the Z function to the E1 socket. Replace
your pins_RAMPS.h file with this one. pins_RAMPS.zip
FYI - if this really is a hardware problem then it's the second RAMPS
hardware problem within a week. Most unusual.
Post reply:
Yes the socket I am now assuming is just broken (not sure what exactly
but possibly one of the connections), After using for pins_RAMPS file
and changed the motors back to series and connected to the E1 slot I
successful got the printer to work!!! Thank you very much Z axis is
working as I would expect! I am now calibrating the printer as it
definitely needs it.

It's great that you took the time to come back and share that you solved the problem.  It's sub-optimal - though - that you just put a link.  Stuff changes / get moved / is deleted from the internet, and the risk is the link will break at some point in the future.  It would be great if you could al least add a summary of what the solution is all about. :)


text:
Nozzle reducing flow as it comes close to finish layer
I've have observed that when the printer is finishing a layer, the flow of plastic through the nozzle starts fading out as it comes closer to the point of layer change.
As an example, let's say that I'm printing the first layer of a cube. The nozzle first prints the perimeters ok. Then it begins to print the inner part, beginning from one corner and finishing on the opposite one. As the nozzle comes closer to the finishing corner, the flow of plastic diminishes, resulting in the lines of the filament to touching each other.
Maybe it's not a big deal, but it's annoying because it's stopping the part of having a very nice first layer and finish.
My setup is:

Anet A6 running Marlin 1.1.8
Bed auto leveling before each print
Slic3r Prusa Edition, latest release (as of 20 January 2018)
PETG from Das Filament

I tried disabling all "retract" settings but the issue persists.
I'm beginning to think that this could be a software bug (Slic3r), but before I submit it to GitHub, I'd like to be sure.
Any opinion is welcome!

Does this happen only on the first layer? If so, you have an uneven bed.

The bed is very even

"Very even" doesn't mean anything.  But more to the point: you should review the Layers View (or whatever Slic3r calls it) to see what the software thinks is being created.

@CarlWitthoft - AFAIK slic3r preview does not render filament width to volumetric scale, so underestrusion would not be rendered to screen even if intentional by the slicer...

Just curious... have you managed to try out some of the suggestions?  Did you succeed in solving the problem?

yes @mac, more or less. I haven't had the time to see all that you guys said because I've been dealing with some other stuff that rendered 3d printing, not on the top-ten of priorities. But I've found a problem with my bed. The glass was not as planar as I thought it to be and also the nozzle height was not as close as I needed it to be. So, for now, by addressing both issues I've been able to get nice first layers again. When the things calm down a bit I want to go step-by-step on everybody's suggestions because I saw a lot of interesting points.

The behaviour you are describing (stopping to extrude before the nozzle finish moving) is called coasting and is actually a desirable one if tuned correctly (which is clearly not your case).
Here's a primer on why coasting is good: the hysteresis (think of it as "springiness") of the filament between the point where the stepper motor pinches it and pushes it towards the nozzle, and the point in which the filament liquefy, makes so that there is always a residual pressure whenever the stepper motor stop spinning.  So coasting consists of stopping to actively extrude before the nozzle has reached the endpoint of the line being "drawn", and relying on the residual pressure to finish the job.
Many slicer have a dedicated setting for this, but - to the best of my knowledge - slic3r PE has not.  In your question, you seem to think this may be linked to filament retraction.  It is definitively worth trying (why not!) but filament retraction normally refers to the act of relieving that residual pressure after the line being printed is finished and before moving away the nozzle, so... if that setting turns out to be the key to your problem, then it would be quite a misnomer.
A quick way to verify if this is the case could be toggling the ceckbox "use firmware retraction" in the printer/general pane of slic3r settings.  If the problem is with the retraction settings you chose, this would ignore them completely.  A clean print would confirm your theory.
Failing that, the best way to debug would probably be to slice the same model with a different slicer (cura is a common one) and see if the problem persists:

if it does, then the problem is probably in the firmware or the extruder of the printer itself
if it does not, then you would have a set of "good settings" in the second slicer that you could try to replicate in Slic3r PE.  Or - as you believe it may be the case - you could have found a way to trigger a weird bug in Slic3r.

Good luck and let us know about your findings! :)

whereas I kind of solved the issue in some other fashion, I've looked and some of what you pointed out and, preliminary tests seem promising.

This answer is outdated and should be updated to reflect the current state of slicing software and printer firmware.

If you think it is a slicing problem, look at the G-code. You might want to arrange for the infill to be orthogonal to the axes, but it ought to be easy enough to calculate the ratio between printhead motion and the extruder. G-code is just text, and fairly easy to make sense of. The RepRap wiki has a good reference to the commands, and all you care about are X-Y movement, and E movement.
An alternative explanation might be that your extruder is struggling with the extrusion rate, and after continuous extrusion is failing to heat the filament fast enough to melt. The layer change could be providing a sufficient respite that walls start off OK on the next layer. Also check (in the G-code) that the speed of walls and infill is the same.

The one about temp drop is actually an easy one to check.  If you are correct, diminishing the printing speed should solve it.  Definitively worth a try @Felix-Hauser...

I'm already printing at 50 mm/s...

@FelixHauser that's way to fast to rule out speed related problems. Some filament I needed to drop to 20.

As mac's answer says, this is coasting, but contrary to that answer, coasting is not good. At one time (that answer was written way back in 2018 when the state of software was much worse than it is now), it was an idea a number of people accepted as reasonable, but it was operating at the wrong layer, and was a very bad hack, necessarily extruding less material than needed to accurately construct the part being printed. Leading to exactly what OP saw.
Nowadays, printer firmware has a feature called Linear Advance (Marlin) or Pressure Advance (Klipper) that can be calibrated with test prints and compensates for the increased backpressure when extruding fast - or more importantly, seen from the other direction, the reduced backpressure when slowing down at the end of an extrusion path, that results in continued oozing after the extrusion was supposed to end. This feature eliminates the need for hacks that underextrude and produces very accurate extrusion regardless of changes in speed or flow.
Anyone experiencing problems like OP hit should check that their profile does not have coasting (and hacks meant to compensate in the other direction for problems it causes, like "extra prime") enabled in the slicer.

The Prusa Slic3r edition has specific help references in the manual that may be of value to you. One of the entries that catches my eye is the line marked "Retract on layer change" which appears to be just as you are describing. You've noted that you've disabled all retract settings, perhaps overlooking the check box?
The above linked document also refers to a print setting that prevents retract of filament when not crossing perimeters. This again appears relevant to your difficulties.
Your post says "resulting in the lines of the filament to touching each other." I expect you mean "not touching each other" but I do not wish to correct/edit your post if I am incorrect in this understanding.

yes exactly, I meant not touching. All retract settings were off, including layer change.


text:
Problem With large prints on Lulzbot Taz6
I have got a Lulzbot TAZ6 3 days ago. Last night I started a print which is 21 hours long and when I returned check on it this afternoon it was a complete mess.
These are the objects that I wanted to print:

I used Cura LUlzbot edition for printing this, the settings I have opted are:

I need to print them with 100% infill for my project. I printed it over USB, and the cura was still running when I checked now, so i guess its not because of the computer shutdown. This used to happen when I tried printing these on Lulzbot KITTAZ i have, but its not working so I got TAZ6. Please let me know where i'm going wrong.

This was the state of the print(some of it was sticking to the printbed, this picture was taken after i removed it from the printbed)
Edit:
Thanks for the suggestion. I have calibrated the extruder and tried to print only the vertical cylinder. I have changed only one setting, changed the extrusion multiplier to .99. I kept the infill density to 100%(my project needs a cylinder to be completely filled without any air gaps) to see which of those two has greater influence on the print quality.   All the other settings were the same
here is the result(After I saw this I cancelled the print):

Like you suggested the infill is overflowing. What should I do next, i'm concerned if it is printed with reduced infill percentage its density will decrease. Shall I try to print it with 97% and see what happens?

Unluckily - for as much information on your settings you share - it is very difficult to diagnose the problem without knowing how the print failed.  Did a piece become dislodged? Did the nozzle caught onto a printed piece? Did the head began extrude in mid air? ...?
However this are my guesses:

From your temp settings it looks like you are printing ABS.  If this is the case, have you placed your printer in an enclosure?  With ABS, It is very very difficult (if not impossible) to print anything above "small", without an enclosure.
Printing 100% infill is normally a bad idea.  If you are doing it for strength, then you should know that the strength gains are progressively smaller on anything above 60%.  100% infill also means that unless your extrusion is perfectly calibrated (which I suspect it may not be the case, given that your setting is the default 100%) any amount of overextrusion will likely let the nozzle "catch".  Finally, 100% extrusion also increases the warping forces on the piece considerably.
Printing a cylinder "laying down" is hard: you basically have zero adhesion to the printing bed and must rely on the support material to stabilise your part.  But the support material is designed not to bond securely to the main piece and it will be unable to counterbalance any "curling up" that your part may experience due to thermal contraction.

So, my suggestions:

Use an enclosure (even a simple cardboard box on top of the printer will do for a starter).  Definitively use an enclosure if you are printing with ABS
Calibrate your extruder.  Here is a handy guide. :)
Reduce your infill density to something between 60% and 97%.
Print your parts one at a time, start from the vertical cylinder and - when you have got that right - try the horizontal one.
If you must print one of the two horizontal...

Increase the support density considerably, and diminish the Z-distance between support and print to the bare minimum.  If your edition of cura has that setting, use support interfaces at full density.
Alternatively eliminate the headache completely and print two semi-cylinders instead (cut the cylinder in half along its length, printing them with the "cut" as their base) and glue them together afterwards.  If you are using ABS you can "weld" them with acetone instead.

Hi please go through the edit, I have posted the results after a few changes in the settings.

@vedanarayana - The extrusion rate still does not look correct.  You may wish to check your hot end does not leak.  Check that nothing similar to what happened to this user is also happening to you.  Additionally: if it density of the part that you are after, you could print the cylinder hollow and fill the pocket with sand while pausing the print mid way (or printing two halves and gluing them a|terwards, while keeping the infill below 100%.


text:
Supports for dense Voronoi pieces
I have printed 1 voronoi piece before. I was able to get the supports that were inside the structure out with tweezers because the holes were big enough. This one (pic below) I do not think I can do that with. I looked at the proposed support structure preview in my slicer (I use Cura) and it wants to print them inside the torso here as well. Is there a way to force the slicer to not print supports within a hollow piece? I use cura but I can use another slicer if need be. Or any other recommendations for a successful print here would be fine as well.

In general, Voronoi objects shouldn't need any support at all.  Have you tried printing without support to see how it turns out?

@CarlWitthoft - that may be true on a resin printer, but on an FDM printer, voronoi objects have some pretty severe overhangs in places.

One feature of Cura is the ability to set supports to build plate only. This would remove any supports internal to the model, as your model has a base that is not considered the build plate or raft. In the image provided, you would have some complications, I believe, as there would be no supports on the outside of the model if it was directly over the base.

As you are not eliminating other options, you can also turn off supports in Cura, load your model into Meshmixer and make use of their support feature, which allows you to adjust placement, size and other parameters in order to get a good result.
The flexibility is limited only by your imagination:


text:
What is the best way to print a model with support material in first layer?
I am trying to print a model that requires support material to be on the first layer, what is the best way to accomplish this? I am currently using Cura. It seems that the support material is too flaky. I have the infill for the support at around 8%

If you can post a picture of one of your "failures" that would be a big help.

I think one of my issues is that my belt is really loose and it skipped

I had the same problem printing a miniature just recently.  As always, settings are somewhat dependent from the object you want to print, but here are some suggestions:

Increase the support density: 15% (8% is very low!)
Support pattern: zig-zag with "connect zig-zag" option enabled (add stiffness to the "column" of support)
Enable support interface (increase adhesion to the plate, and provide a more "beefy" base for the support material)

For reference, here's a screenshot of my settings as I tweaked them for that miniature (printed a 0.1mm layer height).

("Support line distance 1mm" is the same as "Support density 15%", or at least it is the same with my nozzle size)
If your problem was not only with the "flakiness" of the material, but also with it adhesion to the bed, then prepping your printing bed somehow (with a bit of painter tape, glue, etc... can help.  Alternatively using a brim or a raft (as also suggested by another responder) could also help.
EDIT: all the above still standing true, it turns out the OP had a hardware problem as well, his timing belt being loose (see comments).

Alright thanks! I figured it out by using Brim and my belt is really loose so it skipped a lot. Lots of wasted filament lol, thanks man though!

Alright man, did it, hopefully other people find this post useful

Oh sorry man haha, your answer is still a good one and helped with the issues at hand

I cannot comment on your infill percentage for supports, since I never use them. In any case, increasing the infill may well have little or no effect.
However, you could try two things: If your slicer includes supports when generating brims, then use brims. Otherwise, use a raft.


text:
3d printing of which plastic out of polyurethane, e-glass, and PTFE is easiest?
I am looking for a plastic which is transparent to radio waves.  I want to place my transmitter in a cylinder. That cylinder would be placed in a big RC plane  ( whose body is made up of cardboard). I want the plane to be both telemetry, and RC controlled.  That cylinder should allow the signals,  should be strong and light.
So which material would you suggest and is that material easy to do 3d print?

It's unclear what you are asking for.  All plastics are transparent to some wavelengths and not to others (think to two food containers that are both opaque to visible light but one is safe for microwave use and one not).  What spectrum are you looking at?  Also: you should define "easy" (safer to handle? better adhesion? less warping? easier to post-process? ...)

I am looking for the 900 Mhz - 2.4 Ghz band. Easy here means safer to handle, lesser warping  and easier to  post process. Ultimately, what's most important is that it must be strong, RF transparent and somehow shock absorber.

For the kind of application you are looking for, transparency to radio signal shouldn't really be an issue, so you are more or less free to choose whatever suits your taste better.
Looking at the 3d printed drone community, the 3 most common materials I see being used there are:

impact-resistent PLA
PETG
ABS

This order also match their "ease of use", with PLA being very easy to print even without heated bed, behaving well with glues in the assembly and being easy to paint on.  The impact resistance of "though PLA" still doesn't match that of - say - ABS, but is typically considered "good enough" for anything but the propellers.
PETG is tougher. Print relatively easy (stringing and oozing being the typical problems) but it is known to be somewhat difficult to glue and paint.  It is also quite dense, so - dimensions being the same - it will weight more than PLA.
Finally, ABS is a classic.  It is strong, durable, easy to finish (with acetone) but it is the most finicky material to print with, requiring an enclosure and proper ventilation (the fumes being toxic).

To second @mac,
For drone usage, ABS will be your pal*. Both tough-PLA and PETG are relatively heavy, which is a disadvantage for flying saucers. Unless you power up and don't care!

And I say this as someone who does not recommend ABS for general printing and I don't like printing ABS myself because of the smell, how much it warps, and most importantly the harmful nano particles it releases when printing (yes, all filaments do this, but ABS is on the very bad side of the spectrum).

Note that tough-PLA differs manufacturer to manufacturer - basically it's not supposed to behave like PLA, so you get proprietary blends. PETG is traditionally tougher than PLA, but with the modified PLA, who knows. I have not personally met tough PLA tougher than regular PETG.

SO:

PETG if weight is not an issue. It prints well and it's tough.
ABS if weight is an issue. It's not easy to print; and make sure it's well well ventilated area (while venting during the print would mess up your print.)
Tough PLA if you only have cold bed.

Good answer (+1!).  A couple of comments though: A) tough-PLA is heavier than ABS, but also more rigid.  If optimising for weight, PLA may still be the better option for drone arms especially when using long arms, big propellers, powerful motors or a combination of the three.  B) if using ABS, a recommendation would be to print in black or another very opaque colour, as ABS tends to be more sensitive to UV light than other materials.

Good point @mac, forgot about the UV here! I tend to go PETG all the way, and my limited experience with modified PLAs has not made me a believer. (I only tried polymaker from the name brands, which others like, so maybe I had a lemon spool...)


text:
Nintendo Cartridge Print?
I am trying to make a device with an old NES cartridge.  If I were to take an already existing cartridge, I would need to make some precision cuts into the plastic and not sure where to get advice on that.
The flip side, is if I print my own 'NES' cartridge with the cuts built into the print.
So my question is two part.  One, if I were to print one on my own, what is the cheapest price point I could obtain a printer that could do enough detail to make it hard to tell the difference from the real thing.
In case you are just curious, I'm needing to cut a perfectly sized rectangle into the case for an LCD panel to fit into.  Or print my own.

I see other have suggested to close this question.  I personally disagree as I think your question is salvageable, but the help centre contains various advice on how to ask questions on this site that - if followed - would have helped making your question a better one.

The original question asked about laser cutters to cut holes.  It was off-topic, but some general advice on how to cut holes in 3D prints and other plastic objects: "For such a small job, a rotary tool (like the dremel) and a set of precision files + sandpaper in ultrafine grits is all you need.
A laser cutter typically cuts flat panes that need to rest on a specific surface, plus not all plastic can be safely used with lasers. A CNC machine could potentially do the job, but I don't think the end result would be much better than with a rotary tool + filing."

If I were to print one on my own, what is the cheapest price point I could obtain a printer that could do enough detail to make it hard to tell the difference from the real thing.

Around 15.000 US$.
FDM printers (the most common consumer-grade ones, the ones with the roll of filament beside them) all print with distinctive layer marks.  Next are resin printers, but resins tend to have a very peculiar feeling to it, that is difficult to mistake for ABS or other injection-molding plastics, when you hold them, plus they typically struggle with largish objects.  So you would probably be looking at a sintering printer, melting nylon powder with a laser.  That is expensive to buy and very expensive to operate.
Now, while the above is all technically true, it is only half the story...
In fact prints done on a cheap FDM printer can be post-processed to look almost indistinguishable from an injection molded model.  That takes probably more work to accomplish than modelling the object in cad and printing it though, so it's a matter of setting your expectations correctly (don't think to your print as "the product" but as the "base material" for your finished product).
I would say that you essentially have two options:

if you are looking at picking up a new hobby, and do a lot of sanding and polishing in the process, then: "welcome to the club!".  There are plenty of relatively cheap printers that can print acceptably well (more on this below).
if your interest is not towards 3d printing in general but is really limited to getting project done, than you could consider having a printing service doing that for you instead (basically you send them the file with your design and choose what kind of printer and material you want them to use, and they send you back the end result). It will be cheaper and probably of a higher quality than what you could achieve yourself.  Certainly it will require less time investment from your side.

If you go with option one, an affordable printer that got very good reviews from trustworthy reviewers is the cetus.  It is 299 US$, have quality components and is very very silent.  The build volume is not huge but should be more than enough for your project.
However don't take my suggestion as "this is the best you can buy for your money": there are plenty of models out there that will get the job done in the price range 300-500 US$, and if you are wishing to spend a bit more, you could get an Original Prusa MKIIs (the printer that topped the charts last year) for 600US$ as a kit or slightly more fully assembled.
Should you go for using a printing service instead, there are a lot of them.  Two among the most well known are 3dhubs and shapeways.

NES cartridges have a textured surface finish that's probably impossible to reproduce with a 3D printer.


text:
How to improve resolution using 0.3mm nozzle?
What are the best settings for a Simple Metal printer using a 0.3mm nozzle, knowing that the min layer height can be 1/4 the size of the nozzle?
I posted some photos on the link below and the STL file.
Thank you for your advice.
https://www.reddit.com/r/3Dprinting/comments/7scdug/how_to_improve_print_quality_using_a_03mm_nozzle/

The firts layer can be 1/2 of nozzle size; with 3Dsimplify I'm using 3/4 of nozzle size and prints well. For your nozzle you can print at from 0.1 to 0.25 but, heating on small part would be a problem.

Photos can be added to questions which you should do in case the Reddit link is lost.

With most materials, I've had the best results with layer thickness being between 20% and 80% of nozzle diameter.

@tjb1 - Can a new user with 1 point of reputation actually do that?  When I started using stackexchange sites years ago, a new user could not embed pictures...

knowing that the min layer height can be 1/4 the size of the nozzle?

I'm not sure if that is a limitation of your printer specifically, but going "down" there is really no hard limitation to the layer thickness ratio that I know of or have experienced myself.  At least not on modern printers using standard stepper motors and 1.75mm filament (older 3mm printers were more limited on this).
Going "up" you will hit a hard limit at around 3/4 of your nozzle diameter, as layers will have a hard time bonding to each other past that, and the wall surface will be very corrugated (but I take your question about "best settings" is about making the print better, so with thinner layers...)
If you print at reasonable (as in: not too fast) speed and have calibrated your extrusion properly, you should be able to print at any layer height your printer supports, the limiting factor normally being the mechanical precision of your printer / the gearing of your stepper motor.
In particular, you should try to print at layer heights that are multiple of the distance your printer will travel upwards for each step of your stepper motor.
Simplifying a bit how stepper motors work: say that your screw raises 8mm for each revolution of the stepper motor, and your stepper does 200 steps per revolution... your printer will raise 8mm/200 = 0.04mm per step.  If you print at 0.05mm, most layers will be 0.04mm, with 1 in 4 being 0.08mm to compensate for the lost 0.01mm at each layer.  This will produce noticeable defects in the print.
The information on how your Z axis is geared is seldom available in the official specification sheet, but usually there is always somebody knowing it on the printer user forums.
As for "best settings", those depends typically from the type and brand of filament being used, as well as from the 3D model geometry.  Printing slowly is always a good idea though, as it limits the "noise" on the print due to vibration.
In your particular example, threads (which are substantially a very long overhang) will actually benefit from a high ratio between nozzle width and layer height (so a larger nozzle or a lower layer height).  This is because, the overhang angle being the same, higher ratios will give more material to extrude onto at each layer.  You can visualise this by thinking to how easier is to offset a stack of books compared to offsetting a stack of dice.


text:
Quality drop in vertical axis printing
Dear experts and 3D printer users;
I am a beginner in 3D printing field. I read couple of answers in forums and i cannot find exact answer to my problem.
Printing quality dropped when i try to write vertical axis (i mean, columns). There is no problem in horizontal axis.
My column width must be 0.5 mm, and printer nozzle diameter is 0.4 mm. I think I should write 0.5 mm column with 0.4 mm nozzle with ease.
I added messy structure to this post and you can find writing details below.
What do you think? What is your suggestion to overcome this problem?
Printer:Ultimaker 3,
Slicer:Cura,
Printing Details;
Nozzle diameter:0.4 mm,
Profile:Fine 0.1 mm,
Layer height:0.1 mm,
Wall thickness:1 mm,
Top bottom thickness:1 mm,
Infill density: 100 %,
Gradual infill steps:0,
Printing Temp:240 C,
Build plate Temp:65 C,
Diameter: 2.85 mm,
Dimensions of the material:10X10X5 mm

Do you really mean 0.5mm columns?

Yes, i mean that. I know it is unusual but column width must be 0.5 mm. The picture is taken in macro mode.

The main problem with your setup is the nozzle width.  It is simply too big to accurately print a structure that tiny.  An integral part of the filament deposition is the "smearing" of the molted plastic, that clearly can't happen if the structure is about the same size of the nozzle bore.  Also the printed structure is too flimsy to resist the "suction" of such a big nozzle moving away.
I would suggest to use a smaller nozzle and/or increase the size of your pillars.  A good combo would be 0.2mm nozzle with 0.6mm or 0.8mm pillars.  For these small details, it would be best to have a pillar size that is a perfect multiple of your nozzle diameter.
Other settings that will help you:

reduce the print dramatically (try 20 or 30 mm/s)
use retraction (or increase its amount/speed)
make sure your cooling fan is 100%
use a sensible "minimum layer time" (try 10 seconds for a start)

The first two settings should reduce the force/impulse applied by the nozzle on the pillar.
The latter two should make sure your pillar is "solid" when extruding a new layer on top of it.

Thank you for your comment. I already tried to reduce speed to 20 mm/s but it makes things worse. We got the best shape with 40 mm/s. But it is still bad. I will certainly try the settings that you recommend. Do you agree with Mick? I mean, Is there a chance that I produce 0.5 mm width column with this nozzle diameter? It is so good to discuss with experienced users and learn from them. I am really appreciated your help.

@OutcastJedi - Yes, as I wrote, "[the nozzle] is simply too big".  The key is the lack of smearing, not the 0.5mm thickness per se.  If you could have the columns say 1mm x 0.5, you would increase dramatically your chances of success.

@OutcastJedi - 0.2mm nozzle is your best chance of success. 0.1mm nozzles being very prone to problems (clogging and printer inaccuracies).

@OutcastJedi Well, you have some HINT from Mac and Mick, but some recommendations are not a "good choice" when you don't have money to afford for another nozzle. So try to use a lower temperature with a lower speed 400mm/s and layer 0.2mm or 0.25mm, then try a little more of speed until you have a better shape.

Something you might be able to try is changing the angle of the print. So for example if you change your print to print at 30 - 45 degrees. The model will need to add a lot of external support to the print. But the vertical columns will then be printed as a slope with a longer area for the smearing action of the printers nozzle. I expect this would most likely just introduce other issues for you and add a lot of external support that would probably break the model when you remove it. But if you have exhausted all other options and are still looking for a solution it could be something to try.

User802599, Thank you for your creative approach. But this is the one small part of the whole big structure and structure must be printed at once. It may solve my problem with this small part but introduce new problems to other areas. I am really appreciated to listen to such creative comments.

Mac, I had a chance to try your solutions this week and first two is done. I increased retraction speed from 25 to 45 mm/s. But Cura does not allow me to increase retraction speed further than 45mm/s. As I understand, minimum layer time value must be increased. But again Cura does not allow me to increase it above 10s. I have also stringing effect. I tried to decrease temperature to eliminate it but lower than 225C gave me bad results in terms of shape. I noticed that printing head movement was very fast when it was writing columns. I also try to decrease travel speed but it did not work.

You cannot hope to print 0.5mm columns with a 0.4mm print head successfully using an FDM printer. Basically, you are asking the printer to lay down tiny blobs of filament, one of top of another. You have two options:

Use a finer nozzle (e.g. 0.1mm). However, such nozzles are reported as being very difficult to use.
Switch to a different printing technology (e.g. SLA). Resin and powder-based printers have much finer resolutions, and will have no difficulty printing the model that you describe.

Thank you for your comment. So it is a physical limit and no matter what I do I will not overcome the problem with this setup. Unfortunately, because of its price, SLA is not a good choice right now. Thank you.

@OutcastJedi You could switch to a finer nozzle (maybe). However, I doubt if 0.2mm would do the trick. You would probably have to go down to 0.1mm, and not many people do that. If you do manage to print at 0.1mm, you will still have the problem of providing support for such narrow columns.

Thanks for the advice but I do not think I can buy another nozzle right now. I achieved fair shape with 0.8 mm width columns but it is too thick. I would like to ask something else. I know many people in 3D printing field try to avoid or get rid off pores or small bubbles inside of produced samples. But, Is it possible to create homogeneous pores inside thicker columns with changing just temperature and printing speed values?


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Anet A8 Calibrated but print sizes are wrong
Anet A8 printer, Github Marlin, Repetier Host, Cura slicer
Just setting up printer and printed 20mm calibration cube from Thingiverse. X,Y,Z & E not too far off but not quite right (centre hole was oval not round) X19.5mm, Y19.5mm & Z20mm.
Followed Youtube calibration help and updated firmware to Marlin. I ran several iterations of request travel, measure result and tweek stepper settings (M501,M92xxxx, M500) Live Die Repeat...
When I now print the calibration cube I get X25mm, Y20mm & Z19.5mm.
Could the issue be with the firmare being upgraded to Marlin? The cube was sliced by Cura and I have used the same file for all of the prints. When I stop the print and ask Repetier to move the steppers the distance is as they should be for a 100mm travel.

If you have a stock printer, your calibration values should be stock - i.e. 100 steps/mm for X/Y. Also, as an extra hint, X and Y steps should be identical since the mechanics are identical (unless you swapped out one of the motors or drive gears).
It sounds like you have Y correct, but something wrong with X. This could be the belt being damaged, or slipping (or having slipped during your initial cal, and not later). Try increasing/decreasing print speed, this might show up some dynamic problems with the movement.
If you print something bigger (like this) you don't need to worry so much about measurement precision and under/over-extrusion (which adds to the error, but doesn't scale with size).
You don't make it clear if you've started by calibrating your extruder. This is the most important first step, and ensures that you extrude the right length of filament during the print. All this requires is that you mark out 10cm of filament and extrude it into free space.

It was the different answers from printer and configuration.h that I was questioning. Sorry if I was not clear. All the other variables I can tweak/deal with, but not knowing which settings are in charge it is hard to see what to change.

In that case, I don't understand your question.

Bear with me. I noted the values of XYZE in the fi

Sorry, tinterweb dropped off twice. The question is why the steps/mm in configuration.h are not the same as the printer reports.

Eeprom values, I assume.

Does Marlin not load the "sketch/values" into the eeprom? Have I missed a step when I compiled the file and uploaded t? Should I have sent M500 to save the settings? I am working on the basis that I am learning this stuff from scratch and quite possibly making a hash of it.

We're way off track from what your question looks like. No, the firmware can't know that it's at 'first run' state. M502 might be what you are missing. M503 shows the current active settings (regardless of how they were obtained).

Thanks Sean, May have my M numbers mixed up, typing at work, crib sheet at home. What does "first run" mean?

How should the firmware know it's default values take precedence over the eprom value? M502 followed by M500 is reset and store in eeprom.

There could be a number of issues causing this.
Since you just set it up here is a list of questions for you to go through:

Are your belts tightened? (With an additional belt tightener)
Are your carriages are sliding smoothly?

Both might cause some irregular movements explaining the results being off.
Having said that, I wouldn't worry too much if you're <0.5 mm off. This is still a cheap DIY printer (I have the same one, by the way).
This video actually goes into some details why you shouldn't worry so much about 100% accuracy and what you should actually care for when tuning your printer: https://m.youtube.com/watch?v=Mbn1ckR86Z8
Also Not sure how you measured the cube but callipers are often also not that reliable.

"callipers are often also not that reliable".  Quotation needed.  All tools come rated for an error margin, calipers are typically accurate to 0.05mm.

That's true but with 3d printed objects your walls can be inconsistent so depending on where you measure or how hard you pressed when measuring can affect the readings.

measurement error is not the same than instrument accuracy though.  Calipers are accurate, but as any instrument, the operator needs to know how to use them! :)

Ah good point

All good points however it doesn't explain why uploaded configuring


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Adhesion problems with masking tape
I have been playing around with the bed for a while and I still can't get the first layer to stick properly. I think I am getting the bed leveled good, I use the paper method. But yet I find myself with the filament lifting off and getting pulled away with the nozzle or some balling in rare situations.
I use masking tape, which I found for $3 at Dollar general. I heard something about shine being a factor, but why is that important? And is more expensive masking tape worth it? I don't want to buy it because I would hate for it to tear when I take off a print.
I also use some glue stick, which seems to sometimes not help, almost like it doesn't allow the filament to stick. I don't think I was adding too much, maybe I was. But is glue stick needed? Does it really make that much of a difference?
So other than that I don't know what to try. I can't get the first layer to work properly. Maybe it is my speed, what is a good speed to print at for the first layer, I am doing 60 mm/s, just like the rest of my print.
Any advice from there with first layers would be great. I am tired of wasting time and filament over failed first layers. But when I do get the first layer done, the second+ layers all work fine, no issues.
Here are the specs of my printer, that should be helpful for people:

Printer --> Anet A6
Print area --> 220 x 220 mm
Heated bed? --> Yes
Bed temp --> 50°C
I use masking tape on bed
nozzle dia. --> 0.4mm
Nozzle temp --> 210°C
Print speed --> 60 mm
Material of choice --> PLA
Fan is on after 3 layers

I think that covers everything, Let me know if I need to add anything else.

@Martynas I have heard of this ultrabase. But would it be compatible with the Anet A6 which has a 220mm by 220mm print surface?

As i know Ultrabase is 214*214, and yes why it shouldn't be compatible? Its heatplate with glass on top

@Martynas I ask if it is "compatible" because of the screw placement.

Oh I don't know mate. Shouldn't be to hard to google it :)

@Ljk2000 tape will 'eat' heat, for my a8 with blue tape adding 10°C to the bed has helped, I'm printing in a relatively cold room also (around 16°) so it may be part of the problem also. Cura default is 60°C for the heat bed for PMA, raising the bed temp worth trying IMHO

@Tensibai I will try raising the temperature to 60*c. It will be interesting to see if it makes the difference. Thanks for the advice!

@Ljk2000 - Did raising the temp to 60°C help at all?

@Greenonline I found it did not help, but using a good glue stick did. Also I found a option in the slicer to slow the print speed on first layer, which helped. At the time I was also very new to 3d printing and never got the bed leved correctly, which I have now gotten pretty good at, with nothing more than a piece of paper. The the kicker with temp is I had it at 50*c without issues since, and now I have the bed cool down completely which when bed is leved correctly makes it super easy to take off the print.

@Ljk2000 - excellent, that is good. It could be worth making a permanent answer out of that comment - it might help others with the same issue. Also, it would allow mods to tidy up the comments, which have got rather long :-)

Masking tape (and blue painter's tape) is coated with a wax-based release agent in order to prevent the tape sticking to itself on the roll. This release agent must be removed with an organic solvent in order to obtain good adhesion. Isopropyl (rubbing) alcohol is good for this. Acetone will also work, but it is a much stronger solvent (which is not necessarily a good thing).
For blue painter's tape, rub freshly applied tape with solvent until the blue dye starts coming off. Then give it a quick wipe between prints to remove any fingerprints, etc.

I will try the isopropyl alcohol. It will be neat to see how much of a difference that will make. Thanks for that bit of information.

That's odd - I have never used any prep on blue tape and often find the tape is bonded more strongly to the PLA than to the bed itself!

@CarlWitthoft Other users have told me the same. Maybe it has something to do with using a heated bed (my printer doesn't have one). The heat from the bed may cause the release agent to be absorbed into the tape, and thus allow good adhesion.

Instead of masking tape, I would use BuildTac or some other similar surface. These are self-adhesive and come in various sizes. You can cut them down if they are too large for your bed.
I'm using it on my Monoprice Select Mini with a heated bed and it works fine.
I did have to experiment with the PLA I'm using in order to make sure it didn't adhere too well.
And yes, I use alcohol prep pads to clean the surface. You can get these at the first aid or diabetes section of any pharmacy.

I heard buildTac is easy to tear if not careful, which is why I have not bought it. Would you back these people (on YouTube/reviewers) that it is weak, or are they just being that rough...?

I've never had BuildTac tear on me. I use these removal tools to get between the pla and the BuildTac. These are very thin and good for the task. I also had to use patience until I lowered the extruder temperature so that the pla didn't stick quite so well.

Mick (other answerer) is spot-on with his advice on how to prep the masking tape to work well as an adhesion enhancer.
Additionally: what material is the surface of your printing bed, and is the bed heated?  If it is, just know that you may want to try with both heat on and off if you are using tape (it works worse for me and at least a friend of mine with heat on, but down in the comment others report it working better...).
As for general advice on bed adhesion strategies: in case your bed is glass and heated, then the best, fastest, cleanest and cheapest method is to just print on it without anything else.  The secrets to success here are:

A clean glass, without contamination from solvents or additives to solvents that are often used (like many types of alcohol).  Use dish soap and warm water only, and be extremely careful not to touch the printing surface with your skin, as your skin contains natural oils that will make plastic not to stick to the glass.
A dead flat glass.  This should sound obvious, but most cheap printers have glasses that are not flat enough (CR-10, I am looking at you!).  The best tip here is: use mirrors.  They are very cheap at home improvement stores, can be easily cut to size and - most importantly - they are normally extremely flat, as otherwise they would deform the image they reflect.
A perfectly levelled glass.  You can achieve this with the paper method and some patient, but if you want to make your life easier, and have better first layers, do yourself a favour and buy an indicator.  Thingiverse is full of user-made mounts to attach them to all sort of printers.

The last point is good advice even if your bed is not glass, although you won't benefit from it as much.

Just to ask quick, does glue on masking tape make a huge difference? Also, like everybody else thank you for the advice. I will be trying what you say and what others say, find the best. Now with glass/mirrors I have 2 questions. 1) How much longer does it take to heat up and 2) What is the best way of keeping them in place (clips?)?

@Ljk2000 - 1) Glue on tape: I don't know, I never tried myself 2) temp speed: impossible to answer without knowing target temp, glass thickness, what you are comparing to, wattage of the heating element. I'd guess we are speaking of a few minutes though. 3) clips is surely the most common method, and works perfectly.

Have to disagree:  blue painter's tape is commonly used and works well with a heated bed.  The warmth keeps the first layer soft and thus "flows into" the tape's rough surface for a better bond.

@CarlWitthoft - I guess it may depend from the tape as well? I never tried the blue one.  Where I live it is not commonly sold. but. But good to know is worth trying!

@CarlWitthoft - also edited the answer to account for your input

I'll go out on a limb and suggest that, while your bed may be well-levelled, the Z-axis zero might be off.  A difference of 10-20 microns can be the difference between strong adhesion to the bed/tape and having your print float away.  If your first layer doesn't get "squashed flat" a bit by the nozzle, your extruder head is slightly higher than optimal.

I'm Using Masking tape with no problems, your parameters are OK and just need to sand the surface before sending to print, use sand paper #120 or #150. The first layer height is 0.18 mm to 0.25 mm. The masking tape can be used for a lot of prints, you can change it every week to keep a good adhesion.
I found that not all brands works fine, for example TUK has a good adhesion and can be used for several prints. 3M has an stronger adhesion but is needed to sand on 100 % area and can be used only for one printing. Jevelin has a good adhesion but, if the heat bed is above 40 °C this masking tape starts to peel off. and the other ones might have the same issue near to 50 °C or more.


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Sending G-code commands to Hyrel System 30M using python
I am using python 3.6 with pySerial library to connect to the Hyrel System 30M 3D Printer. I am able to read the data from the device but unable to write any commands to it
Here is the code:
    ser = serial.Serial()
    ser.port = 'COM4'
    ser.baudrate = 38400
    out = ser.readline()
    ser.write(b'M106 T14 S30\n') %This is the command to turn on the fan at 30% power

Can somebody suggest me how to write commands to printer through python

If the one in your question is your complete code, a possibility is that your computer is just buffering the output for the serial port, withholding it in memory.  Try to add
ser.flush()

after your last line.  This command will... well... flush anything into the buffer through the actual connection.

Sorry for the late answer, but with Repetrel v3 and later, we have the option for you to configure a secondary COM port, and relay G- or M-Code commands from your other source through the Repetrel software to the printer. Please contact us for assistance.
Note: I work for Hyrel 3D.

authors: Олег Мельников

authors: ชินวัตร คําเหลือ


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Anet A8 extruder motor moves back and forth

This is what is happening to my motor. Any suggestions would help.
1. I have tried adjusting the trimpot.
2. Rewire the connector to match the one on the motherboard.
3. Anything else I found on the internet.

Does it continue if you ask an extruder move from the control panel? I think I remember this behavior from my electronic courses where a stepper motor was halfway from a step and sending a move command did fix the issue. (no guarantee, my memory could be faulty)

Low-hanging debug options: 1) connect the stepper to the driver of another axis 2) swap cable with another stepper/driver combo.  The behaviour will allow you to understand what part (cable/driver/stepper) is at fault.

What Mick said was exactly the issue. Went to check the continuity between all of the wires and found out that the black wire didn't have any. So I took the black wire out of the connector to take a look at it and the wire just feel out. It wasn't even crimped. Once I recrimped the wire and tested the connection. It works beautifully. Can't wait to start printing. Thanks Mick!

Check the continuity of the wires on the cable. Sometimes, they are not crimped correctly. Another common fault is crossed wires. In either case, the easiest diagnostic test is to substitute another cable, but please note the color coding of this replacement wire to match the cable you replace.

The Anet A8 stepper motor 4 lead cable need to be correct in colour arrangement:

mother board end: black-green-blue-red and extrauder
stepper motor end: black-red-green-blue.

I bought DIY RepRap Anet A8 3d printer which came with one of the red lead end not attached, so in order to complete the build I used another lead from the Kossel delta 3D printer which has a different colour arrangement from the Anet A8 and made the motor rock back and forth as in your video.
It seems each colour lead carries a specific current and there are many different 4 colour cables out there.

I didn't realise that the order of the wires can be different.


text:
Own build with 28byj-48 motors, 1.4reprap, Arduino mega, how to "Marlin" the settings !-)
seeking advise
How do I set "marlin" to Operate 28BYJ-48 steppers on all axis?
Thanking you Kindly

It is not at all clear what you are asking. Normally, it is sufficient to adjust the reference voltages on the stepper motor drivers so that they deliver the required current for each motor. No firmware changes are required at all (unless your driver currents can be controlled by firmware). Of course, if you have a completely non-standard build, you may need to change the Marlin header file so that the correct microcontroller pins (and other things) are used. Although you indicate that you are using an Arduino Mega, you do not say what controller board you are using (unless it is RAMPS 1.4).

Also, you need to state what stepper-motor drivers you are using.


text:
Over-hangs in prints
I would like to ask this in more of a general sense than anything, just for people to make note.
I am printing out things for people and some files have some edges hanging out the side. I always worry, since it is printing in mid air, that it would screw up the print. But I was able to go, maybe 1mm(I am not to good with metric when it comes to guessing). My question is, how far at 90* from a wall can a printer pull off before it is necessary to have support? This would help me when slicing up files.

If I understand correctly, your question is specifically for overhangs at 90° (so an horizontal plane that has no support under it.
The first to notice is that you can only pull this off if the extrusion happens perpendicular to the surface from which the overhang is coming off (the closest to 90° the better) as effectively what is happening is that you are building a cantilever structure as you extrude.
If you think about it in terms of a cantilever structure you will quickly realise that the stiffer the structure, the furthest you can go without it drooping. The main parameters you can tweak to increase the stiffness are:

Cooling. The cooler the plastic, the stiffer it is, so crank the cooling part fan up to 100%!
Speed.  Plastic need time to cool off, so the slower you print (within reasonable limits), the more time you will allow for plastic to cool under the fan.  On my rig I seem to get the best result between 15 and 20mm/s, but your mileage may vary, obviously.
Layer height.  The thicker the layer, the more weight it will bear before drooping, so higher layers work best.  A slicer that is very convenient to use for prints that have a couple of overhangs like these is slic3r PE, as you can vary the height of the layers at specific points in the print.
Material.  Some materials are more rigid than others.  PLA is probably the one that works best for overhangs. PETG and Nylon are somewhat more problematic, and flexible filaments are the ones being more difficult to use.

For bridges (unsupported filament extruded between two supported structures) the considerations are identical but for speed: in my experience having the speed not too low helps the nozzle keep tension in the extruded filament by "pulling" it and keeping it horizontal.  But again: each printer, firmware and slicer is different, and you should experiment yourself to see what works for you.
To sum this up: "how far you can go before needing support" is a question that cannot be answered with a fixed number as the answer depends from a lot of factors that vary from printer to printer and material to material.  Without mentioning: how many defects you are happy to tolerate before calling the print a failure.

It is typical for a 3D printer to be able to manage one-half the width of the nozzle for unsupported layer printing. This frequently calculates out to a realistic 45° from the start point.
If you are getting 1 mm extension from a 0.4 mm nozzle you are doing well. It's possible that the layers are not strongly bonded at the point of extension from the vertical wall, but are then strengthened by the layers printed above, if they do not extend excessively.
If your part is designed well, the extension will be distributed gradually over more than one layer, allowing that 1 mm extension over 2.5-3 layers without impacting the appearance of the model in an excessive manner.
The above does not apply to bridges, as it involves a different dynamic for the printer/slicer software.

To add to what mac described, there are small detail effects which sometimes change the behaviour of an overhang (and not necessarily in a predictable manner).
Concave overhangs might sag (rather than turn out like a bridge).
Convex overhangs might pull tight.
Cooling plastic tends to shrink,so might sag less.
I'm often surprised how well overhangs turn out, but equally often see failures which I don't anticipate.


text:
Z height incorrect on calibration cube
I tried to print 30mm calibration cube with my TEVO Tarantula. I found that a few bottom layers was missing as shown in picture. I noticed that a few bottom layers looks thin during printing. Anyone know how can I solve this ?

Most probably a problem of the model being sliced with its base at a height below the printing bed.  What slicer are you using?

I 'm using Slic3r.

@3ORZ Seems like your nozzle is lower than Z0, probably Z -0.5 with this you will miss a couple may be 3 layers. Is needed to adjust the Z offset.

I set Z offset 0 How can I know what value I should set ?

Anyone know how can I solve this ?

In order to know how to fix it, you must first diagnose what the problem is.
Two things you should verify in Slic3r:

Check that under "printer settings" the Z offset is really what you want it to be (if you don't know what that is, you want it at zero).
Check that in the preview (Plater plane, the "preview" tab is on the bottom), you can actually see the bottom layers being generated by the slicer (you can verify this by moving up and down the slider on the right of the main window).

If both of these checks are positive, then the problem is probably not with the slicer but with the printer or printer setup.  The ultimate proof of this would be to try another slicer like for example cura.
If the problem is with the printer, the only obvious one I can think of, is that the bed is too high, the nozzle touches is, and the plastic cannot be extruded for the first few layers.
You can confirm or refuse this hypothesis by simply observing the printer while in operation. If it is the case:

you should observe the nozzle moving "as if" it was extruding the first layers
the nozzle should be touching the bed
very little plastic should remain onto the bed
you should hear some grinding or clicking noise from the stepper motor of the extruder (as the printer will try to push the filament, but the filament will have nowhere to go)

If you realise this is the problem, stop the print immediately: this is the typical situation in which you could generate a clog in the cold end of your extruder, which is not a permanent damage, but fixing it is a somewhat complex and tedious procedure.
The good news is that if this is the problem, the solution is trivial: you should simply set the nozzle height correctly.  How to do this changes from printer to printer and you should refer to the user manual of your printer.  Here is a video showing a few of the most common method to achieve that.

Oh, obviously !!
Few bottom layers I hear clicking noise and very little plastic remains as you said. I will try to adjust limit switch of Z axis right now !!

The bottom layers appear !!
But still missing 2 mm on Z axis. Can I adjust Z offset to fix this missing ?

@3ORZ - you can use Z offset (that's the reason that setting exists in the first place!). It is normally consider best practice to tune the hardware instead though, as otherwise you will have to remember to to set the Z-axis on every slicer you will ever use.  The offset is normally there as a last resort, or for when you use multiple beds with different heights.  But the effect is the same: so there is no technical disadvantage in using it. :)


text:
How do Repetier coordinates setup work
I am using Repetier Host and Slic3r Prusa 1.36.2 - (the website says 1.2.9 is the latest version - however I don't believe this is the problem) .  The printer is a Anet A3
With my current setup I am printing mirrored - I can mirror the objects in Repetier before slicing , however then the preview picture is wrong, and worse I have to remember.
I have a Anet A3, the connectors for the motors are polarized and if I swap the X and Y cables when I home the X and Y motors move in the wrong direction.
I believe the problem is the coordinates and I don't fully understand the Repetier coordinates. This is how I believe it is setup (these are Slic3r screen shots )

Which I will call "Front Left" however my home position is Front Right - ie I believe it should look like this

However these two screen shots are from the slicer - and these settings do not get used.  In the Repetier they use a different system for setup.  I tried these settings shown  in Repetier

Then everything printed in a line along the left most edge. That is the head was moved to the very right , never moved again then the platform just moved
Can someone explain what settings I should be using for Repetier for a platform setup as I have.
If I've misunderstood the Slic3r/Repetier interface then you can point that out as well.

I'm not sure exactly sure if you have one problem or two distinctive ones.  However a few notes:
The latest version of Slic3r PE can always be fetched on their GitHub release page.  At the time of writing that would be version 1.38.5, but I concur with you that that is unlikely to be the problem.
Mirrored objects are a clear indication that one of the Cartesian axis is swapped (not that it is translated).  Any of the axis can be swapped, but since the peculiarity of your printer is that the homing point is at the front RIGHT, I would guess the axis that got messed up is the X one.
I have no way to test the following, but if I got the meaning of your first two pictures, then I guess the correct settings in Repetier may probably be these:

If even that fail, check the handedness of the coordinate system of the software generating the model you are trying to slice.  Modelling software like Blender and others are typically right-handed, but many tools for processing those model for on-screen application (movies, videogames) are left-handed.  That means that even if the model display correctly in the native editor, it may be rendered mirrored in another software.

Thanks -  yes its reversed not translated - so I'm not looking at the correct settings . The CAD program, the load object screen (pre -slicing) and the print preview screen , post slicing all have the correct handedness.  So I'm going to have to abandon this question and ask a completly new one

authors: ชาตรี สิงห์โต


text:
Anet A6 fan issues
I just noticed, and I KNOW it was not a problem before. But recently the fan that blows over the nozzle has been acting funny. I have it set to start blowing after 3 layers, and then turn on at 100%. I decided to watch so I can give more information and what I found...
After 3 layers, it does seem to start, very slow, barely moves. After a little bit it stops moving all together. After a short amount of time (I was elsewhere for a min) it got really warm. So I think it is putting current through the fan. I gave it a small turn and it started to speed up like it should have. And this is every time.
Do I need to replace the fan or something else wrong with this? What kind of fan do I replace this with?

It is impossible to say with certainty without a tester, but my educated guess is that some of the induction coils in the motor are broken.
Electrical motors that need to spin in a defined direction have multiple sets of coils (thing "magnets"), so that at any given moment the rotor will be pulled (more strongly) in one direction than the opposite one, thus determining the direction the motor will spin.
From the description of your symptoms, it seems that one or more of these coils have broken, and now the fan can stall in one specific point, as it misses the "pulling" force that should move the motor past that point.
If you spin the fan manually, the momentum of the fan will allow the blades to move past that static equilibrium point and reach the next position where the working set(s) of coils will begin to pull it again.
While theoretically it is possible to open the motor, do some testing and fixing this, to all practical effects is much more effective to just replace the part (which is a regular fan for computer CPUs).
I don't own an Anet A6, but from a quick googling it seems the correct one would be a 40mm one rated for 5v (albeit I found a link suggesting a 12v instead).  My suggestion is to simply look at the specifications of the fan you have now.  The specifications are normally on a sticker at the very centre of it (the side with the sticker may be facing the extruder, so you may need to unscrew the fan first).

You may also wish to check that there's no mechanical strain on the fan body. If it's bent, overtightened, etc, you can get similar symptoms. Mindless test: unmount it, then turn it on while it hangs in the air. If problems persist - replace it.