text:
Warping of bottom of print
The bottom of my prints warp/curve upwards, most often at the corners. This is a very slight curve, only about 1-2 mm.

I print with a raft all the time.
I don't have a heated bed.
I print with PLA at 199 °C (390 °F) with a print speed of approximately 40 mm/s
I have a Sindoh 3DWOX DP201.

What slicer settings might be the cause of this phenomena?
Or could it be 3D printer settings?

The first thing to understand is what causes warping.  Warping is caused by the thermal contraction of the plastic when it cools down.
Simplifying things a fair bit, you can visualise the process like this:

hot, expanded plastic gets deposited on cooler, shrunk layers,
when the hot plastic cools down, it shrinks and pulls the upper part of the layer below inwards
at this point, the layer below has a differential in the compression between its upper and lower parts, and curls up
the problem is exacerbated at the very first layer (the one touching the bed) as this is "locked" to a rigid body (the bed) and cannot shrink, while subsequent layers are only attached to the somewhat flexible plastic beneath, and thus can contract.

Also notice that the larger the part being printed, the stronger is the force trying to curl-up your print.
Once one understands all of this, then it is possible to appreciate the many ways the problem can be mitigated.
Here are the common ones:
USING A MATERIAL WITH LOW SHRINKAGE COEFFICIENT
This translates in smaller tensions and thus less force "pulling up" the corners of your print.  Historically, 3D printing started with ABS because this material was one of the very few, relatively safe ones to source.  Nowadays there are materials like PETG which have similar mechanical properties to ABS but are much easier and forgiving to print with, so - unless you need ABS for some very specific reason (e.g.: acetone smoothing) consider never printing with it.
DECREASING THE THERMAL DIFFERENCE BETWEEN MOLTEN AND SOLID STATE
Concretely, this means lowering the "gap" between the ~200°C of the nozzle and the ~20°C of room temperature by using a heated bed and - possibly - an enclosure.
The heated bed not only drastically diminish the shrinkage of the first layer, but because heat radiates, and hot air goes upwards, the entire bottom of the print has shrinkage mitigated.
An enclosure just increase the benefit of the heating bed, by reflecting IR radiation back towards the print and preventing hot air to escape.  A heated enclosure just improve things even further.
Some slicers offer a "shroud" option, that encloses the entire print in an enclosed, sacrificial structure, that tries to emulate the benefits of a proper printer enclosure.
INCREASING ADHESION WITH THE PRINTING BED
That is the "brutal force" approach: if you face a strong "curl up" force, oppose it with a strong "anchor down" one.
The increase in adhesion can be achieved in a number of ways:

Lower print speed (more time for the molten plastic to "bond")
Overextrusion (more pressure, more material)
Disabling cooling fan (more progressive cooling, more time to "bond")
Using a brim (more contact surface between print and bed)
Using "ad hoc" material on the bed (PVA glue for PLA, ABS sludge for ABS, kapton tape, hair spray, blue tape, etc...)

REDUCING THE CURL-UP FORCE
This is typically achieved during design.  Designing is a vast field and it would be impossible to cover all the possible mitigating strategies one could use, but here are some of the most common ones:

Prefer assembling smaller parts over printing huge ones.  This is self explanatory really, as the curling force increases with the amount of material "pulling", the least material one has, the less force one gets.
Make relief holes above the first layers in long structures.  This will essentially "break" the build-up of tension in the layer, creating many points with a little "curling up force" rather than two with a huge one.  Something along the lines of this, for example:

Avoid extensive overhangs close to the bottom of the print (this is because otherwise you will have considerably more material "pulling up" than you will have "anchoring down".  Here is an example of what not to do (to be fair: this was specifically taken from a bed adhesion/warping test).

Of course all of the above strategies can/should be combined, when possible.  Even if not warped, a part with a lot of internal tension will perform less predictably and possibly worse than a part where such tensions are lower.

If you have a heat bed, heat it up accordingly (for example for PLA 50 °C first layers, 40 °C then can be a good starting point).
If the first layer isn't close enough, then warping can happen (Happened to me when moving from 0.3 mm layers to 0.1 mm).
If you are under extruding / have dirt in the system (the heat chamber) so that extrusion is uneven it can make warps.
And as always, you can try to print slower, it helps not always but often.
Please also do tell what temperatures (heat bed & nozzle) you are using and what material.

You do not want to drop bed temperature mid-print just because you're past the part that will warp. Unless you've mashed the filament into the bed with a nozzle that's way too low, turning the bed temp down will severely break adhesion due to different thermal expansion of the print from the bed material/adhesives. If starting with 50, stay with 50 til the print is ready to remove from the bed.

The higher temperature is only for the first layer, that's not a big difference to say, the plastic coming out of the nozzle. There will always be forces trying to warp so you have to contain them in some sort of way (object sticks well to the plate, forces gets absorben in the object as it cools slowly...). Just to add, I'm usually going for much higer bed temps nowadays, up to 90° for the first layer for some complicated plastics and then -10°. Would love to have a better control of the temp through the print though...


text:
how to get infill on self created stl via onshapes
I created my model in onshape then exported it to stl file then imported it to simplify 3d to convert to gcode.
However my model didn't go any in fill, it just continue to print layer after layer in the same fasion as the 1st layer.
Correct me if am wrong infill is used so that the middle of your model isn't completely solid hence saving on filament.
Is there something special I need to do in onshape or simplify 3d for it to use infill? To me it looked like it was just filling it up with pla

I don't use either of the two piece of software, but the first things to pop to mind:

Inspect the slicing preview: it should be self-evident if your GCODE is being generated correctly.  In my slicer the infill is red and you can discern the typical pattern within:

Check your settings: your shell thickness should be something reasonable (like 0.8mm / 2 shells) and your infill should also be below 100% if you don't want to print it solid.  For maximum strength, it doesn't help go much over 60%, typical values for light-duty parts are 20% and 30%.
Check your STL file: your mesh should be a closed surface, a "shell". Or the slicer won't be able to know what is "inside" and "outside".  Many slicers verify this for you automatically and have a built-in utility to attempt to "repair" a broken mesh.  I use slic3r Prusa Edition and this information is visualised at the bottom right:

Let the print finish: the wording of your question is ambiguous, but it sounds like you may have stopped the printer before the part finished.  Certain combination of settings can be deceitful.  For example, a layer height of 0.05mm and a shell thickness of 2mm means you will see the printer making 40 (forty!) layers of solid printing, before starting to create the infill.
Try another slicer: in case your slicer went berserk because of a bug (unlikely but possible), this should fix it.

On an unrelated note: the use of infill has a lot of different reasons besides "saving filament", for example:

relative to an empty print, even a very light infill (5%) provides a lot of added rigidity,
relative to a solid print, infill reduces weight and relief the tensions that are trapped in the FDM/FFF printing process
certain infill patterns allow to provide different responses to stressed in different directions (like for example a crash box that needs to give way in one direction but bear a load in another, or a wing that need to flex on its length but not on its chord)
infill provide support for top layers and other concave structures that may otherwise be non-printable
...

The infill portion of your model is configured during the Simplify3D process. After loading your STL file into S3D, edit the process and examine the Infill tab and Infill slider. You'll see a percentage indicator, as well as an extruder selection (left or right, if you have two) to be used for the infill. There are other options within the configuration that would have little to no effect on the problem you are experiencing.
Once you have checked and corrected the settings as needed, used the prepare-to-print option and press the play button for a preview to see the infill being printed before you send it to the printer.
100% infill is impractical, and one can create strong models with as low as 20% infill.
Infill is used to save filament, as you suggest, but it is also used to provide support for top layers on areas that are not vertical. Sometimes, one would use a higher infill figure to provide for smoother top surfaces although increasing the layer count for top/bottom can accomplish that.
Check your top/bottom layer figure in the layers tab to ensure you have a reasonable figure. Three or four layers are good for cosmetic reasons, more if you need additional strength. Anything higher or absurdly high would cause some of the trouble you describe.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

sort: votes


text:
Auto bed leveling with BL Touch sensor crashing to bed
I'm new to 3d printing and I recently bought a Geeetech Prusa i3 Pro B along with a BL Touch (3D touch) sensor to do auto bed leveling.
I printed the sensor holder, mounted it and the sensor to the extruder carriage and uploaded a configured Marlin firmware to the printer. It worked great for about 6 times and now, it crashes on the bed on the two points on the right of the bed.
I tried manually leveling the bed thinking that the nozzle was touching the bed plate before the sensor's needle could, but that's not the case. Even with the bed manually leveled, when using G29 (Auto Bed Leveling code), the Z-axis carriage crashes into the bed.
What can I do/check?

As it turns out, my Z-axis carriage mount to the X-axis was bent, causing the nozzle to touch the bed before the proble could get a chance to detect anything. Manually bending it back to the correct angle solved the problem.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Why all the excitement about linear rails?
Whenever a 3D printer that uses linear rails is announced (case in point: the cetus), the Internet (well... at least that corner of it dealing with 3D printing) gets abuzz with excitement.
I researched a bit the topic myself, and while I understand that linear rails can be produced to a fantastic degree of precision for super-heavy machinery, it escapes my comprehension why they are considered superior "by default", relative to the classic linear bearings on a shaft.
3D printing is a lightweight application, and the motion of at least 2 axis does not happen against a solid surface (where you could bolt a linear rail every few cm) but suspended between the 2 ends of the axis.  Furthermore, the internals of the bearings used on linear rails are substantially identical to those used on a shaft.
The cetus site says under the heading "Quality Linear Rails":

Self-lubricated | Maintenance Free | High Precision | Long Lifespan | Quiet

but this - in my experience - can be said of "Quality Linear Bearings on a Shaft" as well, and in some cases even bushing deliver to a high standard on 3D printers.
So, what am I missing?

Looks nice, easy to think about when constructing or assessing because linear bearings block all degrees of freedom except one. The linked one must be slow as heck but it's also in the ballpark for what people could spend kind of easily (~$400 with tax & shipping I guess. Could be okay too if it works okay and doesn't get all wobbly after some use or electronics fry or... there is definitely other things to a printer than the linear bearings :-)

ps. what is it in this community, does nobody like ever upvote?

It's probably down to the fact that they are expensive, and also the snobbery associated with over-engineered products.

@Valmond - I'm guilty of forgetting to upvote questions myself, a few days back I actually thanked in my reply the OP for a nicely formulated question and forgot to upvote it!  I don't take it personally.  My question was not about the cetus specifically, but yes... for the price it apparently is a fantastic machine according to various reviews.

The following is a compilation of the input from a number of sources.
Linear rails in general are mechanical components that - when designing equipment - offer great flexibility.
The profile of the rail can be designed in nearly infinite ways. This in turn allows for:

Different levels of stiffness in different directions (for example you may have stresses only on a given plane, or you may actually want the rail to slightly flex in one plane but not in another one).
Placing the surfaces for the rollers strategically, for example in a location that is unlikely to get contaminated, or where the maximum force will be applied.
Curved paths, so that the carriage can move along a line that is not straight.

Because the contact surface between the rollers and the bearings is flat, cylinders can be used instead of spheres.  This in turns diminishes the mechanical stresses, and the amount of play, increases longevity and allows for more bearing capacity, among others.
Linear rails can be anchored along their full length, rather that at their extremes, thus increasing the accuracy of their positioning, their stiffness and their bearing capacity.
Linear rails can be machined while pre-loaded, thus achieving maximum accuracy when in use, rather than when coming out of the factory.
The bearings on a linear rail only allow for one degree of movement.  There need to be two rods with linear bearings/bushes to achieve the same result.
All that said, when it comes to the specific application of consumer-grade FDM 3D printers, it seems that none of the above is very relevant, nor confers any real advantage to the printer in terms of quality of the final print:

the mechanical stresses involved in 3D printing are very small,
the movements all happen along straight lines,
most of the axis cannot be anchored to a large, rigid body,
...

On the other hand, the design with rods + linear bearings is cheap, effective, simpler and lightweight, all characteristics that are highly desirable in a 3D printer.
All in all, it seems that there is no good reason to prefer linear rails over rods in general.
Still, there may be specific designs that may benefit from their adoption. I postulate that the Cetus printer linked in the question may be such a design: the cantilever arrangement of its axis - for example - is well served by the fact that a single rail locks movement in all but one direction, and the orientation of the X rail offers maximum rigidity against the action of gravity.

The dynamic stresses are not that small...

They are if compared to other CNC machines that typically use linear rails (like CNC cutters and mills).  Or even compared to the humble lathe.  But sure, among all mechanical stresses a 3D printer has to withstand, those are probably the major ones and by a stretch! :)

Linear rails will always produce a high degree of accuracy and stability and more so than round rod with PTFE bushings and/or bearings.
One may argue the fact however even as a product developer and one who is involved with the mechanicals and development of machinery on a day to day basis comparing the two we see “significant” improvements using rails over rods and if properly utilized on a Z axis print bed you will have a bed free of leveling issues that can smoothly and accurately operate with one driver versus two.
I will further add that getting rods aligned perfectly is a difficult task for the average person and even a slight twist or angular position can affect final print quality. I’ve seen many linear rods that appear visually straight and when chucked into a lathe spindle with 0.0000 accuracy there will be 0.005 or more in runout. In fact I’ve yet to see one perfecting concentric motion that is longer than 6 inches. This tells me that they cannot plausibly be as accurate and that while they may function they will never function with a high degree of accuracy.
Do we need higher accuracy in 3D printer axis? Sure we can have quality control boards that compensate to some degree however the mechanics of the machine are utmost important before you choose the quality of board and software. Why install a \$300 motion control on a cheap linear rod printer if you’re not going to see the full benefits?
With technology further advancing into 64 bit and eventually 128 bit and higher degrees of precisional accuracy 3D printing is turning a page and will if not already be capable of micro resolutional accuracy and can only do so if all the components function properly together.
So sure, your rod guided printer works. However, it will never work as well as my linear rail guided printer with ballscrews and servos. You can have your layered fuzzy prints. I will keep my smooth finished injection molded looking parts that are made from materials a typical desktop cannot even print. So to argue it’s not needed is arguing that high quality isn’t accepted in a lower price point market.
One other addition here. Ask yourself how level and square is your printer? I’m not talking about using a carpenter's level for checking your machine they can be inaccurate up to a 1/4” per 10 feet. When you can dial your printers bed down to 0.00005 or less every direction and your structure is just as accurate than you know what a quality printer and print looks like.
I guarantee no printer priced \$300-\$1000 comes even close to that degree of accuracy. The average consumer is so drawn into the technology of a final print itself they overlook the precisional aspects involved and learn to settle for less. Then you wouldn’t expect your \$500 printer to compete with my \$10,000 printer either.
Bottom line you get what you pay for.

would you mind to add a few paragraphs to add readability?

With technology further advancing into 64 bit and eventually 128 bit and higher degrees of precisinal accuracy -- what does 64 or 128 bit accuracy mean? How do "bits" play into this? One $2^{64}$th of the distance to the sun is 8 nanometers; 64 "bit" (let alone 128 "bit") accuracy isn't anywhere near achievable, how does it relate to the choice between linear rails and smooth rods?

When you can dial your printers bed down to .00005 or less every direction and your structure is just as accurate than you know what a quality printer and print looks like
Nah... when you have dialled to .00005mm, you have most likely wasted time and money to something irrelevant, given that you will never print anything with that level of resolution. :)

Bits = Steps = Accuracy ..
1st boards were 8 bit..now 16 is norm
Stepper motors use micro steps 16 32....250 (
16 is the norm on a -1000 printer
Salmon skin, threads,fuzz, or problems are caused by tiny problems amplified due to repetition.. like how a 2$ seemingly innocuous plastic tube change can dramatically improve a print many fold(ptfe tube).
Pardon grammar, my pad is moving and I am eating.. cheers

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Oversized pieces
After a long time tweaking my new 3D printer I solved all the unexpected errors and I can print succesful pieces but I am facing a "problem", they are over sized, I found this problem trying to print a Raspberry Pi Case and an smartphone case, the printed pieces are bigger than the objects.
Here some related information
Printer: Geeetech Prusa i3 Pro B
Firmware: My GitHub (Marlin)
Software: Repetier Host with Slic3r
Does somebody know how could I solve it?
Thank you very much

Is this with every print? Or did you hit the scale multiplier by accident? And have you changed/modded your printer?

I could sure it is with every print, I tried to print yesterday another fixed size piece (the third one, in different dates) and it is bigger than it should be. I am suspecting about the step per mm option in the firmware.  let me mention they aren't too much bigger, just some mm, but enough to don't fit the objects

If you have changed any poulies or belts your steps per mm could have changed and with this your printer will go further or shorter than its actually supposed to be.

I didn't changed them, the oversizing problem is probably there from the beginning but I didn't noticed it until now, when I tried to print fixed size models. This evening I will try to check the step per mm configuration and let you know. Thanks @Granny

It would be helpful (to say the least!) if you posted the model of your printer and all the info you can find about the firmware & software on the printer as well as the application you're using to do the slicing.

Hi @CarlWitthoft I didn't do it because I'm away from my printer, I will try to add some info which I can remember now and the rest later.

I finally solved it by reducing the steps per mm in the printer firmware. Thank you all

You have to know:

distance between belt teeth (usually 2mm)
number of teeth on pulley
motor step angle 1.8 deg?
microstepping count, probably 16?

Then you can enter all these numbers info the calculator here:
https://www.prusaprinters.org/calculator/

This helps but I had to do some manual adjustment in the step per mm option to solve it. Thank you very much

Yes, the result of the calculation should be entered as the steps per unit, and if the information is correct this should be a first-time accurate solution. Experimenting as described in Alberto's answer will work if you don't know the mechanical parameters, but may not be very accurate and will take multiple iterations to get "close enough".

I will try it again because as you say my method can lead to errors, when I have done it I will update all the information. The changes didn't work as expected, some pieces keep giving size problems (usually too small now)

I changed it to the result from the calculator (80 steps per mm) but the extruder heater stopped working and I couldn't try it deeply. I am waiting for a new one, I will update this when I can do the tests.

I finally could try it and thanks to the calculator I could set the right steps per mm, I noticed too that the extrusor steps per mm I had set in the firmware were wrong, I had them in 98 and the default value is 158.8308. After changing these (X, Y and extrusor steps per mm) values the print size is the expected. Thank you

I finally solved it by manually adjusting the steps per unit in the printer firmware.
The process is easy just move the extruder to one position and draw two marks, one at the extruder position and another one 10 cm in the X axis from the extruder position then with Repetier or with the the printer controls move the X axis 100 mm, if the extruder stops after the mark reduce the steps per unit or increase them if the extruder stops before the mark, do until the movement matches both marks. Repeat for the Y axis.
You can see the changes I made to the firmware in my GitHub


text:
Z axis stopped part way through print
I got an Anet A8 for Christmas.
I am trying to print a calibration tower and the z axis stops lifting at approximately 100mm.
I checked that the gantry is able to travel along the full length of the threaded rods, and while resetting the bed height I noticed that the LCD display showed the extruder height above the bed.  It reads 0 at home (good) but goes back to zero when I manually turn the rods so that the gantry goes above the heigh at which the print stopped.
Any thoughts on what to check? I am double checking all the mechanical bits (connection to stepper coupling, ease of turning, etc...).
My slicer is Cura 3.1.

Can you move higher in Z  via the  "position - Z-axis"  menu on the printer?  DId you make sure that the current  z-limits for the printer volume in Cura are set correctly?

@CarlWitthoft - Cura won't produce any Gcode if the model doesn't fit entirely in the print volume, so I don't think that should be the cause.

I found two issues:

While cutting the cables to size, I made the cable for the z-axis too short.
In Cura the y height reset to 100mm rather than the 240mm I had earlier specified.  I assume the G-code I used was sliced with the wrong settings.


text:
What is the largest microSD card that a Monoprice Select Mini can read?
I have a Monoprice Select Mini v2 and it came with a 256 MB SD card. I have a bunch of 16 GB cards. I have made sure that the new SD card has a FAT32 filesystem. I copy the gcode file onto this card and when I put it in the printer, it can't find any files!
And yes, the file is at the root level of the filesystem and it uses the proper naming convention. The file works on the old card.
Since the old card still works, this isn't an emergency, but I want to have a backup and I don't have any other cards that small.

I would expect Repetier and Marlin to support up to 32GB (the maximum size for a FAT32 partition).

16 GB Micro SD cards don't work, at least the ones I have.

That's interesting. Maybe the firmware developers were trying to conserve memory? I shall have to try a 32GB card that I have (with my Tronxy X1). It is also possible that Monoprice have tweaked their firmware for some reason, rather than use default values.

Try to determine the actual file system on your working SD card, maybe you just need exfat or something. You can use Disk Manager on Windows (does not detect all of them) or mount utility on Linux. Your problem also may have something to deal with SDHC support in the SD reader of your printer. Try using different SDHC and SD cards (SDHCs start from 4GB iirc).

The exFAT system doesn't work, though that may be due to the size of the card. i reformated it to a FAT32, and that didn't work. I haven't been able to find a source for 256 MB micro SD cards.

You could try to use the least advanced SD card, the SDSC style.  These will be less than 4 GB.  Since you can't find 256 MB cards, try an SDSC 1 GB card.

@NomadMaker, I took too long to edit :)  Continued...  In my work, we've had to support many generations of SD cards, and there are occasional problems with backward compatibility of SDHC cards when accessed through an older signaling protocol.

I finally got a 16 GB card to work. Perhaps the previous 16 GB card I'd used was defective.

Unfortunately, the answer isn't as simple as that a specific size of SD card works and another size doesn't. The Marlin firmware wiki mentions:

The SD- or MMC- Card must be formatted as FAT and must have a MMC interface. This is more likely with cards <= 2 GB.

MMC is the predecessor of SD. SD cards are not necessarily fully backwards compatible with MMC. Apparently, Marlin uses some features specific to MMC, so your card should support it.
The SD card support in Marlin is based on the Arduino SD Card Library, which further mentions:

The library supports FAT16 and FAT32 file systems on standard SD cards and SDHC cards.

Based on this:

Cards should be formatted FAT16 or FAT32.
Cards bigger than 32 GB definitely won't work (not SD or SDHC).
Cards at most 2 GB will probably work.
Cards between 2 GB and 32 GB might work, depending on the specifics of the card.

Is there any way of knowing that an SD card supports the MMC protocol without putting it into the printing (but another machine or even from the manufacture's website?). Are some brands more likely to support it?

hopefully one day they add exFAT support. FAT32 is getting long in the teeth. MacOS and Windows are trying to make it actively difficult to format FAT32 partitions.

The maximum size is 32 GB, however using microSD has a little disadvantage:

The microSD adapter and Micro memory are wrong assembled and the chip are unable to be read.
Solution: stick with a tape adhesive to keep Micro memory and SD adapter well aligned

The SD adapter can't be read on the 3D printer
Solution: Add an extra tape adhesive over the SD adapter just like sticker, to make tight the assembly inside the reader.

Clean the contacts of the SD adapter, normally has the same issue like nintendo cartridge.
I´m planning to get a bunch of SD cards instead microSD's, none of SD 8 GB and 16 GB are failing due wrong contact assembly.

Get a copy of Partition Wizard (Free)
Take your 16G or 32G or ...? SD card and delete the existing partition.
Create a 2G partition and format it as FAT.

Yes, you are wasting a lot of the SD card space but given the price of these things these days, who cares. And it will work.


text:
Under extrusion towards the end of the print
I have really strange problem. Thing is that my print (first layer) started ok, not good nor perfect but ok and everything was going well but then all of a sudden, near the end of a print, quality drops drastically. I'm not really sure but I think this happened because of under extrusion. I'm not so good with English so here are pictures of finished print and some more details.

I'm using custom build Delta printer with RepRap and Repetier firmware, CURA for slicing and Repetier-host for printing.
Slicing parameters in CURA are:
- ABS 250 °C hotend and 70 °C heatbed
- Layer height 0.2 mm (initial layer 0.18)
- Printing speed 50 mm/s (30 mm/s outer walls)
- Infill 40 %
- Extrusion multiplayer 0.96 (96 %)
Do anyone have any ideas? What this can be? How can I fix this?

Is this towards the end of any print (regardless of height and size) or it is something that triggers at a specific z-axis height for all prints, or...?

This doesn't happen on all prints, and it seems that this is height independent because it happens near the end no matter how high object is.

Do anyone have any ideas? What this can be? How can I fix this?

At least judging from the pictures, that does seem like under-extrusion.  Some ideas for further investigating the issue.
The problem may be due to the gcode being wrong.  In this case, your printer is merely executing correctly... the wrong commands.  To check if this is the case:

The easiest, but inconclusive way, would be to re-slice a model that fails consistently, with a different slicer.  If the second print came out good, than you would know that the problem is with the slicer.  This method is inconclusive because you wouldn't not if the gcode is bad or if it simply happens that your printer cannot print well that specific sequence of commands (which may still be emitted by the other slicer under different conditions).
The more conclusive analysis would be to look at the gcode of a failed print where the fail happens between two geometrical identical layers.  This seem to be the case for the print in the picture, btw.  You should then compare the gcode of the layer that printed good with that of the layer that printed poorly.  If the gcode differs... then you positively know the slicer doesn't work as it should.

The problem may be due to a mechanical fault with the printer.  Here the only idea I have to offer is overheating of the steppers and/or their controllers.  This may in turn make the extruder servo skip some steps and therefore extrude less filament.  If you perform the conclusive test above, you will know if this is the case.
The problem may be due to a firmware bug.  This is difficult to investigate, my only suggestion would be: upgrade to the latest and greatest, if you haven't done it already.
The problem may be filament-related.  This could be a number of things, but since the problem seems to happen at towards the end of the print, and your are printing at relatively high temp, an idea could be that too much heat reaches the cold end of the extruder, interfering with its extrusion.  The easiest test here would simply be to re-print a failed print with a different filament.  In your case I would suggest some PLA, just to decrease the temperature and change the chemical composition too.
These are more or less all shots in the dark, but - together with asking here - it would be what I would do to debug, had I the same problem.  Keep up posted! :)

Firstly thank you for answer. I roughly checked Gcode for these few layers and there is no significant difference in E parameter. I also have decent cooling on motors and driver's so I think overheating have a very little change here, mechanical stability is not so good but shouldn't than all layers be bad? Firmware is upgraded, and last thing to try is decreasing printing temp to 230.

@Rakic, actually reducing the temperature is the first thing to try, because it's way too high for your printing speeds. Also check that your temperature sensor gives correct values (ideally you have spare thermocouple) and is in contact with your hotend.

Ok, so I just finished print successfully. I actually decreased temperature (from 250 to 230) and increase extrusion multiplayer a bit (from 0.96 to 0.98) and for now it seems to work. Thank you!

This doesn't look like a configuration error.
It seems very likely this is a partial hotend jam.
This happens sometimes because of stale filament but most often by not cooling down the heat sink (the part just over the heat break) enough which generates heat-creep, e.g heat creeps up through the filament, which eventually melts too early, creating a blob.
It's main characteristic is that at first the print is impeccable but after some amount of time, you get a complete jam or under extrusion.
This can be mitigated by higher print speeds, higher layers (so that the filament moves faster), printing at colder speed (if possible), lower retraction or usually completely solved with a fan cooling down the heat sink.

I didn't know that, really useful information, thank you. By the way I already solved problem by lowering printing temperature.

Good you fixed it! So it was most probably heat creep then ;-) Get a cooling fan for the heat sink, it will save you lot of trouble in the future!

I had a similar problem with PLA after upgrading to all metal hotend. My printer was in a cabinet and after some time in print had the same problem (heat creep). In the end, it was resolved by turning bed off after first 3 layers and turning on a fan to keep the cabinet cool.

You can try to reduce your retractions (try setting it to half what it is now and try again)
If your retraction is too big you can pull hot plastic into the cold area of the hotend and create a partial clog - this happened to me yesterday when I tried to intentionally print with way too much retraction to make demonstration photos for the retraction test model I uploaded to thingiverse.
note/disclaimer: that model I talked about above is here, I'm the author of that model

Good point but on this part of the print there is no retraction. I already solved problem by lowering temperature.


text:
Connecting Anet A8 to PC issue
I am still at calibration stage and need some info from the PCB. I connected the USB and ran Repetier. The PCB wants to talk at a higher baud rate than my serial port says it can do. I tried setting the serial port to its highest setting 125k and reduced the PCB baud in Repetier setting to 125k. No joy. PC port reverts to 9600 every time I check it. Thoughts?
PC running Windows 7 Home Premium 32bit.

Sorted. Repetier Server was hijacking my com port. Uninstalled it and Repetier host worked fine. As I have no desire to monitor or control prints remotely I have no use for the server software.
Hope that helps others.

Are you sure that the A8 connects to a PC using a serial port? I don't know of any 3D printers that do that. Typically, 3D printers connect to PCs using a USB connection, and there will be a type-B USB socket on the printer.
However, there will be a USB bridge chip on the printer's controller board that connects the microcontroller to the USB socket. This bridge chip does have a serial port that is used to communicate with the microcontroller. Typically, these serial ports operate at 115,200 bits per second (115.2 kbps), although this may vary. Some USB bridge chips are capable of operating at 250kbps.
Often, the software running on the PC needs to know what speed the serial port on the bridge chip runs at, in order to send data at a suitable rate. Of course, the USB connection is capable of handling data at a much higher rate, but the microcontrollers used in many 3D printers are not capable of handling such speeds.
Note that the USB bridge chip on the printer may appear as a virtual COM port on a PC.

You do know that a COM port is a serial port, right? (virtual or otherwise)

@Onno I know about virtual serial ports, but a maximum baud rate of 9600? That sounds like a hardware (RS232) port to me (or at least, Windows thinks that it is).

Don't know what happened , didn't change a thing but all of a sudden the pc started to talk to the printer.......weird.  Can only think my norton was away to internetland to see if it was OK to talk to this new stranger.  Thanks for the answers though.

@Mick Some computers detects as COM the arduino using the USB port, Serial ports normally uses COM1. USB ports can be detected as COM2 or more, for example my computer detects COM5, COM8,COM21, depending whicn HUB USB i'm using. The speed connection will depend on the baud rate which the Arduino was programmed sometimes @ 9600 for low processing and higher rates for high computing.

My A8 just started doing this.
I shut down repetier server, and voila, all is good! Since I will go do OctoPi eventually, I just uninstalled RS.

Hi, and welcome to SE 3D Printing! Whilst your answer may be technically correct, it is rather terse, and, as such, it has been recommended for deletion, unfortunately. If you could expand it then you may get a more positive response. I would recommend that in addition to reading some highly voted answers to gauge the standard expected, that you take a look at the help section relating to answering questions, in particular [answer], and take the [tour] for more information on how stack exchange works. Thanks :-)


text:
Printer going wild mid print
Mid way through prints the print head will crash into the print, then crash into the bed, raise up about 3 inches, and start swinging back and forth over one part of the bed.
I have had successful prints with the same firmware, but this just started happening and I cannot wrap my head around why. The part of the bed it swings back and forth over is the same on every print. It also do not occur at any particular time, on some prints it will happen after the first few layers, on other it will happen mid way.
My printer is an anycubic kossel delta running marlin. I have tried re uploading marlin and switching slicer software. I have used mattercontrol, cura and ultimaker cura.
Thank you!

Fried PCB board, or at least some loose contact / power issues?

You should post a video to /r/printersgonewild ;-)

I agree that it is likely to be a signal or power integrity issue, IMO most likely to be a problem with a ground connection.

For anyone having the same issue I found out it was due to a Z axis motor lock up because the pully attached to it would get stuck under the bed. I found out because I tried to print again and it locked up completely and I had to pull it out with pliers. Just finished an 18 hour print to confirm.

@deshawnjones05 could you stick that in as the answer?

For anyone having the same issue I found out it was due to a Z axis motor lock up because the pulley attached to it would get stuck under the bed. I found out because I tried to print again and it locked up completely and I had to pull it out with pliers. Just finished an 18 hour print to confirm


text:
How to modify 3D model of body?
I'm relatively new in the field of 3D printing and design. By now I've created and printed some technical objects with TinkerCAD, but now I've a task, which I don't know how to solve.
I have the following model as STL-file:

Now I want to "adjust" the arms of the model, as shown in the picture. I want the arms to hang besides the body.
I know that I could cut and rotate the arms and then merge them again with TinkerCAD but the outcome dosn't look good and the workflow feels wrong.
So what is the right tool/way to get this task done?
*Disclaimer: I'm not Denis Almaral, but he released this model unter CC license. So I kept his name on the image to credit him, as requested via CC.

Maybe Sculptiris  http://pixologic.com/sculptris/ , or other  "sculpting" tools?

Excellent STL file, BTW... :-)

@Greenonline Full creds go to Denys Almaral: http://www.denysalmaral.com/2016/11/free-lowpoly-donald-trump-3d-character.html

Basically there's no good easy way to do this.
At this point you only have the mesh - a list of triangles - the 3D model you have does not contain the concept of joints or moving parts so it can't regenerate the shoulder after the rotation.
The original author may or may not have the ability to do this, depending on his workflow and software.
If all you have is the STL your only choice is to rotate the arm and then rebuild the shoulder from scratch and manually fix anything that doesn't look good

Hi @Nir - thanks for your answer. That's what I initially tried - and failed. But then I'll try again. I thought that something like joints/moving parts is included - but if you say it isn't - I understand, why it isn't possible to do it in an easier manner.

@netblognet - I did start by saying it isn't easy :-) you said you tried doing it in ThinkerCAD, I think it will be easier in a program that let you draw/edit the mesh directly like Blender, it's not a simple software package but there are a lot of online tutorials

Ok - you and @mac brought me onto the right path. I read more on different file formats and realized that the author of the model also delivered a fbx-file. This contained a rig (did I use the word in the right context?) which allowed me to "form" the body and arms with https://threejs.org/editor/

The correct/good method to achieve this is called "rigging", but it is not an easy feat (as pointed out by others), as it requires plenty of knowledge about the software being used to edit the model, and a good understanding of the theory behind it.
Skeletal animation requires the designer to set up a skeleton (also called "rig", hence the slang term "rigging") for the mesh and define the variables controlling the motion range of the joints and and the geometry and deformation of the mesh.
It's quite some job to perform, so - unless this assignment is the first in a series of assignments having to do mesh movement for this model, or you have a keen interest in the topic - I would suggest you to take a shortcut and edit the mesh directly in a "one off" not reusable fashion.
(Rigging would conversely allow you to create a "rag doll" or at least a "rag arm" to freely and intuitively move around as you please).
The tool I would use for either task is blender.  If you want to take the shortcut, maybe a less complex software like meshmixer could also do the job (I don't have direct experience with it, though, so I'm not 100% sure).
The blender foundation have a nice series of videos on the topic, called "humane rigging".

authors: เรามันแค่ สิ่งของ


text:
How to generate gcode only for first layer?
As first layer is so important, I am looking for an easy way to generate  the gcode to print just the first layer.
I see that with Slic3r you can cut from a Z
But for test purposes I prefer just selecting a number of layers to be generated so I can easily generate different "first layer(s) tests" with different first layer(s) settings (width, height, speed, flow....)
The only way I achieve it is editing the gcode.
Any help?
Thanks

Are you doing this to set Z-height, bed levelling, etc., or do you have reasons to evaluate the first layer for each particular object being printed?

I understand your question like this:

I know I could cut the mesh and just slice the bottom of my model, but since I am interested in a given number of layers and the heigh of a layer may change according to settings (e.g.: 0.2mm, 0.1mm, 0.05mm...), I want to find a way to generate an arbitrary number of layers from the full model.  I use slic3r.

If my understanding is correct, then you can achieve what you want with a few steps.
Use verbose GCODE
The setting is under "Print settings → Output Options".  This will output gcode with comments in it.
Save the finishing gcode of a valid printing job
Basically, open a valid gcode file, and save the last few lines (comments will help you to understand which ones, it changes from printer to printer) in a separate file (gcode.tail).  These lines are typically those that move away the nozzle from the print, disable the heating element, the steppers and the part cooling fan.
Prepare the first-lines.sh script
#! /usr/bin/env sh
sed -e '/move to next layer (3)/,$d' $1 > /tmp/gcode.tmp
echo ~/gcode.tail >> /tmp/gcode.tmp
echo /tmp/gcode.tmp

What this script does is:

take a file name from the command line ($1) and savie into gcode.tmp only the part of it up to and excluding the line saying "move to the next layer (3)" (you should actually use the number of layers you actually want here, 3 is just an example).  Again, the presence of such a line depends from you generating "verbose gcode".
append to gcode.tmp the content of the file gcode.tail (here replace ~/ with the actual path on your machine.
output as a stream the full content of gcode.tmp

Set your printer to automatically run the script onto the generated gcode
This setting is again under "Print settings → Output Options". You have to type in the full path to first-lines.sh.  Also remember to make the script executable (chmod +x first-lines.sh).
You can also hover over the textbox to get additional information of how you can access slic3r variables there (for example you may want to read the layer height from the settings and compute within the script the number of layers you want to keep).
Profit
:)
Final notes:

I tried the sed command and have post-processing scripts running on my gcode myself, so it should work, but I haven't tried the full procedure myself, if you encounter bugs please leave a comment so I can fix the answer for everybody. :)
I use slic3r Prusa Edition (I believe these settings are the same, but just in case... you may wish to download that version.
All of the above should work out-of-the-box on all mainstream Linux distributions and OSX.  For windows, it has been suggested in the comments to install CygWin.
Since this procedure still slices the full model and then throw away most of it, you could make it faster by only slicing a reasonably thick "bottom part" of your model.  For example: say that you know you will never want to print more than 5 layers and never with a layer height past 0.3mm... in this case you could only keep the bottom 2mm of your model and you'd be safe for all other combinations of layers and layer heights.  Don't keep exactly 1.5mm though, as this is likely to generate a different top layer than the one in the full model.

Good luck! :)

Thanks mac.
I got an easy workaround as well from the Slic3r Github.
The suggested solution is quite straight forward: Just adding a small Perl script as postprocessing that drops all gcode of layers not to be printed.

That's pretty much the same suggestion than mine, just slower (as it parses the full file rather than splicing it. :) (and less readable because is perl ;) )

OSX uses bash by default in Terminal;  for Windows I recommend installing CygWin.

@CarlWitthoft - Thanks, added in the main body of the answer.

@LuisRosety - Since you solved the issue with this method (post-processing of the gcode via slic3r settings), consider either approving this answer or writing your own and approving that instead, so that others will have a clear indication this problem has a solution. :)

You could just insert an M30 at the end of layer 1, and the job will end there.

I have only one suggestion to add.
Appart from stopping the gcode execution it would be advised stopping heaters, fan etc.
M107         M104 S0 ;extruder heater off         M140 S0 ;heated bed heater off (if you have it)         G91 ;relative positioning        G1 E-1 F300  ;retract the filament a bit before lifting the nozzle
M30
I am not a gcode expert but I think it would be convenient doing something like this.

That's correct @LuisRosety.  Throwing the end gcode in the middle of the file achieves the same result than properly splicing the file (as suggested in my answer).  The limitations of just throwing it in the file like this is that you get to keep around hundreds of Megabytes of unused GCODE (beside having to do it manually, which is what the OP wanted to avoid).

True, this is a manual solution. I offer it because it is much simpler than manually deleting thousands of lines of gcode. One could also add M104 and M140 and other commands to return the printer to a standard state, but the implication was that the user will tweak settings and re-run repeatedly until the proper parameters are identified.

authors: Роза Касумова


text:
SerialException: 'WriteFile failed ([Error 22]...' Printrbot Simple Metal using Cura 15.04.6
Disclaimer: I have read about this elsewhere but haven't found a solution.
Printer: Printrbot Simple Metal with heated bed
Slicer: Cura 15.04.6 (also tried Cura 3.1)
Printing software: Whatever Cura 15.04.6 comes with when printing from USB
The print goes well for the first couple layers then just stops.  It stays heated, fan keeps blowing, but print has failed.  Here is the error:
...
Send: N19517G1 X47.047 Y59.035 E1574.00486*126
Recv: ok
Send: N19518G1 X68.604 Y74.097 E1574.44219*122
Serial timeout while writing to serial port, trying again.
Unexpected error while writing serial port: SerialException: 'WriteFile failed ([Error 22] The device does not recognize the command.)' @ machineCom.py:_sendCommand:565
Changing monitoring state from 'Printing' to 'Error: SerialException: 'WriteFile failed ...'
Connection closed, closing down monitor
I have gotten this using Cura 3.1 to slice as well as Cura 15.04.6 (though the error above was using the Cura 15.04.6).  I've tried using a different interface for printing, but nothing helps.
Any ideas on solving this?  I feel like I am missing a small but simple detail here to making it work.
[Edit] Added printing info at top to make it a little more clear what I was using.

What printer? what generate the error? what have you read? why what you read does not solve the issue? what other information do you want that was not available there?

Excellent questions, first two answered in the edit.  As for what I have read and why it didn't work, you know those times when you read so much and try so much that you forget what you've even read and tried?  That's the case here.  As for what else I want, honestly I just want to start printing again, and I couldn't find solutions to let me do that elsewhere (I'm sure the solution is out there, just didn't find it).

From the look of it, and given that you already two different slicers, it look like this may be a hardware issue.  I have had very similar error messages with my cheap Chinese printer and this is ultimately why I ended up always printing via the SD card and stop worrying.
That said, the error is about the serial connection over your USB cable.  I was about to write a list of suggestions, but I found out that your manufacturer already has a troubleshooting guide for your printer here.
Adding my own suggestions to those of Printrbot, this is the final troubleshooting guide (the linked page has detailed instructions for each step but 6 and 7):

Cycle power
Update your Operating System.
[Windows users only] run a VCP (Virtual Com Port) driver wizard
Check physical connections and swap power and usb cables.
Use a standard 2.0 USB input rather than USB 3.0, if applicable
Make sure that your printer is away from any potential source of EMI (Electro-Magnetic Interference).  Microwaves ovens, many types of energy-saving lamps and power bricks/adapters are known offenders.
If possible, reduce the serial speed of your connection (revert if this does not solve the issue, as it may effect print speed and quality).
Flash your Printrboard

To clarify what these tips are all about:

Step 1 is about making sure you don't have your computer and printer in "dirty states" (as in: with their serial buffer corrupted or stuck).
Step 2-3 are about making sure you have as many known software bugs and problems patched as you can, as well as all the latest features.  This is especially important if you are asking for help, as nobody is going to downgrade their own machines just to replicate a user' unique state.
Step 4-7 are about diminishing the possibility that the signal in your cables gets disrupted and mangled along the way between the computer and the printer.
Step 8 is like 2-3 but for your printer firmware, rather than your computer software.

Thanks so much!  I'll give that a try when I get home and hope for the best.

I tried using the SD card option way back when, but it didn't work for whatever reason (it was probably just heating up and I didn't know it, I was very new back then).  Tried going with the SD card option again, and boom.  Success.  Not sure what the issue was, but whatever it was, it is gone when using the SD card.  Thanks again!


text:
What is "HDPLA", and why is it so hard to find out more about it?
Googling 'HDPLA' has so far availed me very little.
http://3dinsider.com/what-is-pla/ indicates that /all/ modern PLA is 'high density' compared to 'the early days'. But a fellow at the local makerspace indicated that he was specifically using 'HDPLA', with [he claimed] markedly better properties than regular PLA in the final product.
A company named Florion claims to have some secret sauce they add to their PLA, and Maker Filament touts a high temp PLA; but neither seems to use the 'HD' prefix.
I haven't yet been able to track down the fellow to get any more specifics from him. There's no reel of the stuff sitting around so I can't look at its labeling for clues. He claimed to be fabbing lab fittings but I don't know the intended operating situation/requirements.
It's possible he meant something else, like HDPE, which would be quite inert and thus a good choice for lab fittings--but I'd like to think that if it was lab equipment he was making he'd get the name of the polymer right.
Comments, including any regarding the Florion or Maker Filament or any other 'high performance' PLAs, would be most welcome.

I see you are a new user around here, so I hope you don't mind if I bring to your attention that you should upvote any answer that helped you along the way, eventually accepting the one that was closer to solve your problem or - in case none of the answers made it for you - write your own answer and accept it (so that others will be able to benefit from it when searching). :)

Not a duplicate, but related to: https://3dprinting.stackexchange.com/questions/4982/what-is-pla-how-is-it-different-from-pla

So, low-teck, old-style investigative work from my side.... I contacted a company selling HDPLA and they got back to me with the following reply.

We created HDPLA as an industrial PLA with special additives. As a result, our so called HDPLA has the advantages of ABS, but prints as easy as regular PLA.  HDPLA has high impact, high strength and high heat deflection temperature (hdt). You can also print at high speed (max 140mm/s inhouse tests).  HDPLA has is own high strength, but is even more strong after annealing.  A heated bed is not necessary (50-60˚C recommended), and you can print with HDPLA with a 3D printer with open structure.

This is strikingly similar to the description of what 3Dprima calls "Prima SELECT PRO":

PrimaSelect™ PLA PRO ist the next generation of high performance PLA for demanding industrial applications. Designed to be able to print fast >120mm/s so you can save on production time. Very high heat resistance (95°C+) after annealing. Excellent mechanical properties combined with a matte surface finish that helps concealing the printed layers for optimum appearance.

While writing this answer I also found a page that escaped my googling until now, sating an additional property of "their" HDPLA: food safety.

With our HD PLA you have many more options. You can use this material in two ways. Choose the one you like best. You can use it as a normal PLA and get prints characterized by a very good adhesion between the layers and high precision. You can also make your prints acquire similar properties to that of ABS – better impact resistance and high temperature resistance. All you need is an oven. Yes, an oven! By annealing our HD PLA in an oven, in accordance with the manual, you will avoid all the inconveniences of printing with ABS, such as unpleasant odour or hazardous fumes. But these are not all the advantages of HD PLA. For the production of this material we have chosen raw materials that are approved for food contact in compliance with the EU directive and FDA regulations. HD PLA is also certified by RoHS.

So, it looks like HDPLA is not the shorthand of a polymer molecule, but rather a trade word indicating that the base PLA has been mixed with additives.  Furthermore, the answer I got via mail seems to indicate that "HD" refers to the high Heat Deflection temperature of the filament (the heat deflection temperature is the temperature at which a polymer or plastic sample deforms under a specified load).

I doubt that it means very much at all. Filament manufacturers are very tight-lipped about the co-polymers that they add to their base stock in order to improve handling and performance characteristics, so it is impossible to say. The only common attribute that I can see is an advertised diameter tolerance of ±0.02mm. Maybe HD stands for high-definition, rather than high-density?

This should probably be a comment, rather than an answer! ;)

On another note: PLA is already considerably more dense than polyethylene.  My chemistry is most definitively rusty, but I think it would be quite difficult to make PLA more "dense" as the PLA polymer doesn't branch out as much as that of polyethylene, and "pruning branches" is one of the techniques used to make polymers more dense, together with helping them pack more tightly in crystal-like structures.

@mac You may well be right. I was unsure which way to go. I usually get criticised for posting answers as comments, hence my uncertainty.


text:
Compiling Marlin 2.0
I've just finished building a new printer and I wanted to take advantage of a 32 bits board I ordered some time ago. The board is an MKS SBase 1.3
I've been researching the Smoothiware firmware but somehow I'm not convinced by it yet. One of the things pulling me off is the Z-Probe behavior. On my Arduino-Marlin 1.1.8 machine, I have a probe which serves as both probe and Z-Endstop without a problem and very elegant implemented whereas on Smoothie, it's not so trivial as far as I've seen.
Anyway, there is a branch of Marlin which is not yet for release but for testing and it supports 32 bits boards, being mine mentioned above one of them:
https://github.com/MarlinFirmware/Marlin/tree/bugfix-2.0.x
I have yet to find some documentation explaining how to install it. The closest thing I found is a thread on their GitHub "forum":
https://github.com/MarlinFirmware/Marlin/issues/8131
It seems that you have to build the project to create a firmware.bin file which you can copy to the microSD card and it will flash automatically to the board... again, no "official" documentation found.
I've tried the steps described in this thread but I'm not able to compile for my board as it gives an error no matter what:
Marlin/src/gcode/eeprom/M500-M504.cpp:74:5: error: no matching function for call to 'MarlinSettings::report(bool, int16_t&)'

Has somebody successfully compiled this firmware? Is there something I might be doing wrong?
I'm on a macOS machine, using Atom as editor with the Platformio-IDE installed.
Any help is appreciated,
Thanks in advance!

Hi, have you managed to solve your issue? Does it still not compile? Is there a released version of Marlin that supports 32 bit boards yet? I have just downloaded it from the first link, running on OSX 10.8.5 and Arduino IDE 1.8.6 and it compiled first time. Maybe I have different compile settings or #defines or maybe I have missed the point of your question.

Well I found the solution on Marlin's GitHub:
https://github.com/MarlinFirmware/Marlin/issues/9155
but it might have been solved without having to hack the file since then.

This is a Link Only Answer. If the link dies, this answer becomes worthless, so it would be nice to fix it by giving us an explanation what to do here.

Could you include the line that, apparently, needs fixing?

I have been using Marlin 2.0 bugfix for several months with no issues on my RAMPS 1.4 based printer. Installing it is the same as any other printer firmware, or rather, uploading any Arduino sketch. In fact, rather than searching "how to upload Marlin Firmware" you should instead search "How to upload an Arduino Sketch" as most printers are Arduino powered and the process is the same as making a simple LED blink program, granted the source code is MUCH bigger. The quick & dirty is: Download and install the latest Arduino IDE and make sure your board is recognized by following instructions for your board. In the Marlin directory from the downloaded firmware, open the .ino file in Arduino IDE. On the tabs above, you will see Configuration.H and Configuration_adv.h those are the 2 files to edit, and ONLY 2 unless you are familiar with what you are doing, plus Marlin 2.0 redid the file layout so you shouldn't get confused by 20+ other files open also as in 1.x. The comments give you a good idea of what to change & google will help with the rest. Once done, click on Compile & Upload in the Arduino tools, and done.


text:
Combing and Coasting
Here is my understanding of Coasting: Coasting stops extruding early in a move so that the string itself will finish the layer.
Here is my understanding of Combing: Combing reduces the need to retract during travel moves by making sure that the nozzle oozes where you want it to on the way to the next point.
I'm curious as to what types of prints these are good for, and also what types of prints these would be bad for.
So for instance, Coasting is good for prints that have a high propensity to exhibit stringing, but what types of prints would I want coasting to be deselected for?
Similarly for combing, although I know neither the pros nor cons other than it reduces the number of retractions (decreases wear on extruder?)
In short, basically I'm looking for the pros and cons of both of these settings. Also if my understanding of the settings themselves is incorrect please let me know. Any advice would be much appreciated.

If anything, combing and coasting allow to mitigate problems that are printer and filament specific, rather than dependent on particular STL models.
Combing helps - as you imply in your question - with materials prone to oozing (e.g. PETG)
Coasting is particularly good for printers with a bowden extruders and low jerk/retraction speeds.  This is because in bowden extruders there is a lot of filament compressed between the teeth of the extruder servo and the nozzle, and that pressure doesn't instantly disappears when the printer stop "pushing" (i.e.: turning the extruder servo).
I believe there are firmware implementations where coasting is also used when approaching sharp corners.  This is to mitigate the problem of "blobs" forming there.  The mechanics of this are similar to those explained above: the pressure within the extruder cannot be instantly relieved and coasting accounts for that.  The only difference being that - because of the micro-scale of the problem - even non-bowden printers are prone to corner blobs.
In my experience (I look forward to other answers to "compare notes") there are very few reasons not to use combing.  The only risk with it is that it increases the risk of the nozzle crashing into the print and destroying it.  It sound dramatic, but it is in practice it requires everything to work against you: a big blob on the previous layer, the nozzle passing exactly there, poor bed adhesion... for me that has proved problematic only when printing miniatures with a 0.2 mm nozzle and 0.05 mm layer height (on a cheap printer).
There is of course a (usually very small) time penalty in combing, as it typically requires the nozzle to travel longer paths.
In my experience (again: YMMV, I look forward to more answers!) the limitations of coasting are related to the way it is implemented.  For example, a given coasting setting may work great for getting rid of oozing, but will create under-extrusion in other parts of the print, as the calculations performed within the firmware may be spot-on for linear motion but inaccurate for corners, or vice-versa.
I believe this is the reason while some popular slicers (like cura) have this setting hidden under "experimental".

Coasting is good for filaments that ooze. The stop/up/start time at the end of a layer can be long enough that a visible seam appears if the layer starts in the same place. Transparent filaments also suffer from the velocity effect at layer shifts (more transparent when extruded slower).
The disadvantage is that it becomes another parameter to tune per filament.
Combing is most useful where a part has internal spaces, but might result in longer travel.


text:
MKS Sbase Probing
So I have an MKS Sbase v1.3 that I am trying to use in a delta printer. I am trying to use a PNP inductive sensor with it and it doesn't work. I have tried using a voltage divider with it already (10k ohm and 15k ohm) but it doesn't give any signal when the probe is triggered. Can anyone help me?
P.S Yes, I do know that the board has physical pullups. I am thinking of using NPN MOSFETS but I don't know how I should wire them.

After testing my z-min endstop pins, I found out that I could trigger the probe manually by using a jumper wire between Signal and Ground. I then used a NPN MOSFET to connect the sensor to the endstop by connecting the black wire of the probe to the base, the signal wire of the endstop pins to the collector, and the blue wire from the probe and the ground pin of the endstop connector to the emitter of my MOSFET. Note that my mosfet is a TIP120.


text:
My extruder does not reach the set temperature
Anet A8 with Cura. First time use. The extrusion temperature is set at 190 °C for PLA but the temperature never quite gets that hot, e.g. 189.2 °C. So the printer never prints.
The bed temperature is fine.
Any suggestions on how to fix?

Have you run a PID tune since you got it?

Did you manage to solve your problem since you posted the question?  If yes consider upvoting any answer that helped (and select as "accepted" the one that solved the problem if any), or alternatively, consider writing your own answer explaining what the problem was and how you fixed.  This is so that other users can benefit from your your question and the answers too. Thanks!

It could be as Carl Witthoft said, that the thermistor is broken. But it looks like the PID is not calibrated correctly. It probably can reach higher T's but stops, because the P portion is not high enough.
Anyways, before printing use a software of your choice (Repetier, Pronterface...) and perform a PID tuning specified here:
http://reprap.org/wiki/PID_Tuning
After that everything should work out fine.

Two common problems to look out for in this situation:

Make sure that your part fan (the fan that is supposed to cool the filament you just extruded, and that does not start spinning until the print starts) do not blow air on the hot end of your extruder.
Make sure that your hot end is well insulated.  If available for your printer, silicone sleeves are the best:

otherwise the most common, universal and low-cost solution are cotton pads:

Neither of those is capable of limiting a hotend this drastically, when typically a hotend can be driven to over 240 degrees C.

@CarlWitthoft - The fact you haven't experienced it does not mean that it can't happen.  That was a common problem one some batches of the Trinus, solved exactly with the sleeve (iirc that was actually the reason why they start selling them)

...although, to be fair, I don't remember what was the temperature it failed to reach (may have been 200°C rather than 190°C)

I am up-voting this because it turns out that it was because my extruder was not insulated. I purchased some cotton based insulation and wrapped it around just like the picture above and my temperature became stable again.

My hotend was touching extured motor metal holder. After giving distance between them it started to reach correct temperature. I also supported the situation with silicone cap and  cotton insulator.

Take a careful look at the thermistor in the hotend. If it's defective it might well not be providing correct temperature information back to the control board.  As a very quick check, try swapping the thermistor from the bed (if possible), or buy a replacement thermistor and drop it in.
I'm not familiar with the Anet controller but possibly there's a calibration pot on the board; if so it may be causing the digital hardware to mis-read the actual sensed temperature.

Please check that the power supply's (SMPS) output voltage is 12 V (while loaded).
Note: Be careful while measuring, as there is a hazard of shock.
In my case, the voltage was 10 V with one supply and 8 V with another supply. I bought a new one with 12 V and the printer is now running fine.
My printer Tronoxy i3 (Prusa i3 Mk-II).
Hope it helps you too.

Often it is the filament. Most PLA filaments start melting at 190 °C and have a good print consistency up to about 220 °C. If filament is ever getting stuck in the extruder, up the set temperature.

I had the same problem.
If your mains supply is 110 V, then make sure that the voltage selector switch of your PSU is set to 110 V... it should then print.
If the voltage selector switch is set to the default of 220 V, and the mains supply is only 110 V, then the PSU will not provide enough current.

Note: If your mains is 240 V then changing the voltage selector to 110 V will damage your PSU or worse.

This could be dangerous, destructive advice. If the OP's mains voltage is 240 V then doing what you suggest will fry the PSU, or worse. We don't know what the OP's mains voltage is. You should [edit] your answer to clarify this. Just to clarify, do you live in a country that uses 110 V as a mains supply?


text:
Is a dual extruder a reasonable choice for all-purpose printing
I'm new to 3D printing and I recently got a LulzBot Taz 6 printer.
I'm interested in doing dual extrusion printing (especially with dissolvable supports), but I'm also interested in doing single extrusion prints. In particular, I would like to experiment with printing flexible filament.
The LulzBot TAZ Dual Extruder v3 Tool Head says that it can handle all the filament types that I am interested in.
Here is the question: can I use a dual extruder (in particular, the LulzBot TAZ Dual Extruder v3 Tool Head) for general purpose printing (read single extrusion) or do I need to use a single extrusion head for single extrusion print jobs.
If you can use a dual for single use, why buy single extruders (I've been looking at LulzBot TAZ Aerostruder Tool Head for flexy prints) if you can get the same performance out of a dual head?
If you should use a single extruder for non-dual prints, please explain the shortcomings of using a dual print head for general purpose use.

Aerostruder: Weight: 495.75 g (1.09 lbs) • TAZ dual: Weight: 0.96 kg (2.11 lbs) As for "all purpose" if a purpose requires 3 or more filament types (or colors) for a job dual may not be enough extruders...

Not an expert by any means but I can’t see any reason you couldn’t use one half of a dual extruder. The benefits of not using one though would be decreased extruder weight. Especially given that this is a direct drive so there will be two stepper motors I believe. Reduced weight means faster print times and a reduction in certain print artifacts such as ringing etc.
Short answer, if your only ever going to need one extruder probably avoid a dual but if you want the flexibility this should work when a single extruder is required.

And of course you could reduce (but not eliminate) the penalty for extra extruders by changing to a remote drive/Bowden tube setup.

This may be too late to help, but I wanted to describe my own experience with the Lulzbot Taz Dual Extruder v3.  It was...not good.
In terms of your question, I spent a fair amount of time trying to do exactly this.  It is possible, but there are some major caveats:

If you are not printing with both extruders, you need to leave the one not in use unloaded.  The reason for this is that, at least with PLA, the extruder not in use will get hot enough to drip.
The Cura-Lulzbot software, at least when I used it last year, doesn't deal well with this.  It tends to default to printing with both extruders, and it made slicing much more complicated than it was with a single extruder.

As such, I personally gave up and swapped my old single extruder back in.
This isn't meant to contradict the other answer.  In theory it should be workable.  But in practice, with the device you mention, it's not.

This should be fully correctable with proper slicing settings.

Perhaps,  I was using the slicer from the printer and started out with the settings LulzBot said to use, then fought with the damn thing for a month.  (The drips from the second Extruder was a design flaw as far as I can tell.)

If you're not using the second extruder at all, the slicer should generate gcode that never heats it up to begin with. That's definitely possible with (stock) Cura or slic3r.

I was primarily using "Cura-Lulzbot", which was supposedly designed for the printer itself.  Part of the problem was I was having a lot of problems with filament breaking in the primary excluder, so I was trying to use only the second extruder and not the first.


text:
Can the `render` function be used to speed up rendering?
I am designing a moderately complicated piece in OpenScad.
It renders fast enough in preview mode (1s).
But when i do a full render so I can export to STL,
it takes ages (In the 10s of minutes)
I have read that sometimes the function render is useful to speed up overall rendering.

Is this correct, or have I misunderstood?

If I have misunderstood, what is the render function useful for?

How does this work?
In what circumstances can I apply it?

What  processor chip is in your PC?  Why do you think those particular functions (union, difference) are the problem?  Is there a reason you can't finalize the booleans into a single object prior to rendering?

What does it mean to "finalize the booleans into a single object"? (I kinda thought render might be the command to do this, if it is what I think it is)
PC Proc is  Core2 Duo E6750 2.66Ghz on one computer,
and i5-6400 2.70GHz on the other.
I think the bools are a problem because they are well known to be slow, they show up in almost every google result about rendering speed in every CAD program.

Though, to be fair, I gues Booleans probably show up in every nontirival openScad example, they are useful, I will tweak question

Fair enough - I was thinking in Meshmixer terms, where merging two objects can be done at any time, prior to a final cleanup or part rendering.

@CarlWitthoft - Boolean operations in CAD are extremely expensive, especially when the surfaces that need to be trimmed are curved.  In fact such operations are so complex that can't be solved in a sensible time, and for this reasons CAD packages use approximations that in turn makes most 3D models broken (and generate the occasional crash).  Google "Surface-to-surface intersection problem" if you want to learn more about this! :)

First a disclaimer: I am far from an expert on the subject, I'm just a regular Joe who happens to use OpenSCAD and have done some experimentation with it.  I believe the answer below to be correct, but I will be very grateful if errors or misconceptions were brought to my attention in the comments. :)

I have read that sometimes the function render is useful to speed up overall rendering.  Is this correct, or have I misunderstood?

I'm unaware if it is possible to use render() to speed up the "overall rendering", but I'm rather confident that the intended purpose of render() is to simplify the in-memory representation of the model and thus the responsiveness of the preview window, rather than speed-up its final rendering.

How does this work?

In order to understand how this work, one has to understand how Constructive Solid Geometry (CSG) works.
The entire premise of CSG is that using boolean operations between primitive solid shapes, it is possible to represent complex shapes.
However, while the human operator may see subtractive operations like difference and intersection as something that makes the model smaller in volume and thus possibly easier to handle, the computer sees each and every operation as adding geometry and complexity to the part, as the following image aptly illustrates:

When manipulating the model in the CAD viewer, OpenSCAD is in the preview mode and all that "invisible geometry" needs to be processed for each adjustment of the viewport. It is easy to reach a level at which the OpenSCAD viewer will become jittery or unresponsive.
What the render() function does, is telling OpenSCAD to compute the mesh resulting from the boolean operations enclosed in the render() call, and use that single mesh instead of the underlying boolean-combined primitives when handling the model in the viewer.  Meshes are what is normally used in the render mode of OpenSCAD (F6) rather than in the preview one, but here their advantage is not better visual quality, but the fact that OpenSCAD needs to handle a lot less geometry.

In what circumstances can I apply it?

You can apply it any time you like, really, but it is a trade-off: a model that uses the render() function internally, will take longer to display its initial preview (because generating the mesh is an expensive operation) but it will behave very well in the viewer.  Conversely, a large model that does not leverage render() will be jittery to handle in the viewer, but it will render to screen in a fraction of the time.  It has to be noted that OpenSCAD make heavy use of caching, so the first preview is the one that will take the longest, while successive ones may be a lot faster.

For reference, the code at the bottom of this answer (which generates the image above) behaved like this:

With render(): 15s for the preview, 1m29s more for the proper rendering (TOTAL: 1m44s).
Without render(): 0s for the preview, 1m45s more for the proper rendering (TOTAL: 1m45s).

I don't know if the fact that the totals resemble each other is a coincidence peculiar to my model or a general rule of thumb (the render() function effectively creating part of the final rendering during preview), but you are free to play with the code and if you find out a pattern, please leave a comment.
In the following code, you may need to increase the grid size to 20x20 if you want to see the difference in responsiveness between vanilla code and render() function.
Also remember to close and reopen OpenSCAD between tests, in order to flush the cache.

$fn = 30;

module shape() {
    render() difference() {
        sphere();
        cylinder(r=0.3, h=3, center=true);
        rotate([90, 0, 0]) cylinder(r=0.3, h=3, center=true);
        rotate([0, 90, 0]) cylinder(r=0.3, h=3, center=true);
        rotate([45, 0, 0]) cylinder(r=0.3, h=3, center=true);
        rotate([-45, 0, 0]) cylinder(r=0.3, h=3, center=true);
        rotate([0, 45, 0]) cylinder(r=0.3, h=3, center=true);
        rotate([0, -45, 0]) cylinder(r=0.3, h=3, center=true);
        rotate([90, 0, 45]) cylinder(r=0.3, h=3, center=true);
        rotate([90, 0, -45]) cylinder(r=0.3, h=3, center=true);
    }
}

module line(x, y) {
    translate([x * 2, y, 0]) shape();
    if (x > 0) line(x - 1, y);
}

module grid(x, y) {
    line(x, y * 2);
    if (y > 0) grid(x, y - 1);
}

grid(3, 3);

Thanks for such a detailed write-up. Five years in the future, this helped me understand why my model is so jittery to navigate in preview and so smooth after rendering.


text:
Anet A8 Hot End Spares Quey
I saw an extruder mod on Amazon "EAONE 2 Pcs PTFE Teflon Tube (2 Meters) with 4 Pcs PC4-M6 Fittings for 3D Printer 1.75mm Filament (2.0mm ID/4.0mm OD)"
Anybody know how this is fitted?  Is it simply tapping the feed hole on the top?

Are you sure your query is about the hot end?  Googling the replacement part name leads to the PTFE tube and fittings, which are to be used on the cold end of the extruder...

Is this what you are referring to?
If yes, the cold end of the extruder is nomally already tapped and you simply have to screw the new fitting in it.  The PTFE tube itself needs just to be fed through the hole in the fitting until it cannot go any further.
Failing to do so will most likely result in a clog and/or leaking.
It is a self-locking mechanism, in order to release the tube you have to press down the plastic flange on top of the fitting while pulling up the PTFE tube.

Yes that's the part. I can see nowhere on the extruder assembly for this to go unless it is at the top "hinged" part that moves the cogged wheel and guide wheel apart for inserting the filament. I had a look online but the only pictures of an assembly with this fitted all looked to have a modified "hinged" part.

@Plodmore - I just googled "Anet A8" and it looks like that model has a direct extruder.  This part only work with bowden extruders.

Thanks, will raise supplementary question on another thread.

that item is for a bowden setup. (the a8 does not come with a bowden setup, but can be modded to have one.)
when installing the bowden setup on a a8, the first thing you will need to do is move the motor to somewhere else, there are tons of choices on thingiverse.
then the PC4-M6 fitting will screw into the black aluminum piece that the throat used to screw into.
and the other end will go into a customised hot end. again tons of choices
now this is oversimplified, because installing a bowden extruder on a anet a8 is a lot more complicated than explained above due to the sheer number of options.
just search anet a8 bowden and you will have lots of choices.
but it works as mac said, the PTFE tube slides into self locking fittings, the PC4-M6.
to release simply push the top of the fitting down and pull out the tube.
source, my own anet a8 modded to have a bowden setup.


text:
Marlin's bed leveling Mesh Validation Pattern ignoring home offset
I'm using a Prusa clone with Ramps 1.4, Marlin 1.1.5 and an inductive proximity sensor Z-probe. Due to the design of the printer, the X and Y end-stops and the Z-probe are not exactly aligned with the heated bed, so I must use Marlin's Home Offset feature to align the coordinate space to the print area, using the G-code command M206 X-18.5 Y-2.5 Z1.1.
I am now attempting to use Marlin's Unified Bed Leveling feature to compensate for a slight but significant curvature of the bed.
Unfortunately, it appears that the Mesh Validation Pattern command (G26) is not taking the Home Offset into account when printing a test pattern. The printed pattern hangs off the left side of the bed and the center printed circle is clearly misaligned with the center of the print bed by the bed offset amount.
Does this suggest that my firmware is misconfigured? Or is there an alternative method for aligning the mesh validation test pattern with an offset print bed?

which Prusa-i3 clone?

A Marlin developer confirmed that bed-leveling and probing are now performed entirely in the machine coordinate space.
To clarify further, if one has a non-zero home offset enabled, the following commands refer to different physical locations despite the supplied parameters being the same:
M206  X10  Y10 ;  Set a home offset in X and Y
G30  X100 Y100 ;  Probe (100, 100) in machine space
G0   X100 Y100 ;  Move to (100, 100) in print space, ie. (90, 90) in machine coordinate space

I was able to correctly align the bed-leveling grid by altering header files in the source code. I defined the XY offset using two new macros BED_OFFSET_X and BED_OFFSET_Y in Configuraion.h and altered the following lines in Conditionals_post.h.
#define X_CENTER ((X_BED_SIZE) / 2) + BED_OFFSET_X
#define Y_CENTER ((Y_BED_SIZE) / 2) + BED_OFFSET_Y

The mesh is now physically aligned with the bed and I have not observed any adverse effects.

I have this problem too - but how would i know what the value is for the bed offset macros?  I haven't conciously changed the home offset - yet the validate mesh is printing relative to the centre of the bed instead of the bottom left corner. See: https://3dprinting.stackexchange.com/questions/20685/validate-mesh-in-marlin-causes-whole-test-print-to-be-offset-from-the-bed-hom


text:
How can I rotate a 3D model to be parallel with the build plate?
I have an STL that has a flat surface which should contact the build place when 3D printing. The model has an unknown rotation. How can I rotate the 3D model to be flush with the build plate?
I am very comfortable with OpenSCAD, and I can use it to rotate the STL if I know the correct angle. Is there a tool that will let me analyze a single face (triangle) of a model to determine it's normal? If I can even get the coordinates from 3 points from the desired face I can calculate the normal and use that to calculate the rotation vector.

I made a little bit of progress: Meshmixer's "Mesh Query" analysis tool allows me to select individual triangles. The "Triangle ID" it shows is a 0-based index to a "facet" of the STL file in ASCII mode. It looks like the normal of the 3 vertexes is already computed for me. I am going to have to do this several times, so if there is a better way I am open to suggestions.

I needed to get something started on the printer so I just imported an STL into OpenSCAD and started guessing values for the rotation vector. Since I had a large flat surface, I was able to use orthogonal view and the static camera angles to align the model to each axis. It took about 6 passes using 2 decimals of precision to get it to the point that the slicer treated the bottom as a single layer. That took 5-10 minutes per STL. Doing this 6 times was pretty manageable. Much more and I definitely would have probably done the math and scripted the process.

Some tools like Cura or Repetier Host have slicers that analyses and tell you if it is ok to print or not. Both of them allow rotations.

Cura's rotate tool has a "lay flat" function! I just had to manually get the rotation in the general direct and it was able to rotate it the rest of the way. Thanks!


text:
Anet A8 hard to insert filament
I had been printing with ABS and took the advice to alter the fan so I can see the filament when I am loading it into the cold end. It was tricky but doable. I am now trying with PLA and getting it to line up with the whole is a nightmare. Can the driving cog and guide wheel be moved? A couple of mm would stop the driving cog pushing the filament off line.

Why don't you try to cut the filament on skewed shape? if not, try in other angle.

I was having the same issue as you and know what you are talking about and there is a file that you should print that will help you (I have printed this).
While the file says for the Anet A6, I think the extrude are the same on the Anet A8. It goes under the gear and bearing and guides the filament to the hole. Should work well for you.
Other things that you can do is straighten out the filament. That is what I do, it helps that much more. You can also cut the end at a angle to sharpen the end with a pencil sharpener, also helps find the hole.
So try the file, I think it will help you would.
File --> https://www.thingiverse.com/thing:2242903

On the A8, the idler wheel is fixed, but ought to be in-line with the top of the hot-end if everything is properly assembled. You can also check that the top of the throat is smoothly finished (it should be OK, but you might have a poorly manufactured example).

Thanks, I will have a look. Is the idler wheel the one I was calling the guide wheel?

Yes. As I think about what you're describing, inserting the filament between gear and idler, then using the extruder drive might be the answer you're looking for - it certainly worked for me after installing a printed guide (and manual feeding didn't work)

Just wondering. The gear is direct mounted on the motor so it cannot have scope for movement but could I possibly have moved the top of the hot end out of alignment when I modified the fan for easy removal?

Doubt it. There are two aluminium extrusions bolted to the stepper. All that can move is the top part with the idler, everything else has no flexability.

A lot of people complain on the filament insertion of the Anet A8. Personally, I have no problems at all. I cut the filament under a sharp angle and pre-bend the filament (not completely straight) and push it in the hole, it works every time without having to disassemble the extruder fan. Note that if you have the throat screwed in too much that it sticks out of the aluminum throat holder of the extruder (so not the part where the brass nozzle screws in) it is way more difficult to insert. I kept the top of the throat more or less flush with the block.
Other techniques to insert filament include:

cutting the old filament (straight cut) and let the extruder feed while you press the new filament on top of the old filament stump, if done correctly the friction will feed the new filament right after the old,
print filament guides for inside the extruder gear cavity,
removable or magnetic fan brackets.


text:
Filament starts extruding as soon as hotend reaches melting point
I have a homemade 3D printer running on ramps 1.4
When i start a new print and the hotend reaches melting point of PLA, the PLA start coming out of the hotend.
This goes on for as long as the temperature is kept above melting point, without moving the extrusion gear.
The extruder is a bowden type.
Hotend is a J-head.
I am currently using simplify if that makes any difference regarding configuration.
Any ideas what to do to prevent this from happening?

Is filament advancing, or is it just expanding with the temperature change?

I will have to look into whether its advancing on a micro scale, I had not considered that. I am fairly certain that it is not advancing, not easily visible atleast.

@Claudi Is it a lot or a little? With my Anet A6 some filament will extrude as the filament heats up and expands. It does stop shortly after for me. That is my thought, the filament is expanding.

I will say its a lot, it goes on for at least a couple of minutes, the oozing ends up as a fair amount of filament on the bed before print starts.

Any ideas what to do to prevent this from happening?

You cannot prevent it entirely, but you can probably mitigate the problem by depressing the lever that squashes the filament against the hobbed gear of the extruder before starting to heat the nozzle.
In bowden extruders, the long portion of filament between the stepper motor and the nozzle is subject to compression during the print.  Because of the hysteresis in the filament, and of the slack between filament and PTFE tube, this filament acts like a slow-releasing compression spring.  When the nozzle cools down, the potential energy stored in the filament is "frozen" in place.
By depressing the lever, you allow the spring to extend "backward" towards the spool, rather than "forward" through the nozzle.
Some oozing is still bound to happen because of gravity and - as highlighted by others - thermal expansion, but it should be significantly less.
If you adopt the lever trick, remember to print with a skirt, as you will want the printer to recreate that "compression" in the filament before the model proper begins.
Another way to address the issue would be to add a little bit of retraction in the closing stanza of your GCODE (the part where you also tell the printer to unpower the steppers and stop heating).  This will prevent any "compression" to be "frozen" in the first place.
This anwer is based on the assumption that the stepper motor is not actively spinning (i.e.: yours is not a hardware/firmware issue).

This will probably end up being the solution i'm seeking, as i am in the testing/calibration part of my project i often stop prints before they are done, thus rendering any added added end G-Code useless. If i understand you correctly i just need to release the mechanical lever before heating up.

@Claudi -  yes.  Beware it will only improve the situation, not eliminate completely the problem.  If you are there when the print stops, you can release the lever immediately (before cooldown) for even better improvements.

Does it really go on for more than a minute or so?  You can't get filament from nowhere, so if the feed gear isn't moving, sooner or later all the material in the reservoir inside the nozzle & hotend will be melted and gone.  Leakage like this is normal, and probably a lot more noticeable if you have a larger diameter nozzle.
I would recommend checking to see if your gcode includes a large retraction at the end of the print.  That would reduce the pressure and the amount of material left inside the hotend.


text:
Glue for attaching PLA pieces to titanium
I'd like to attach a piece I printed out of PLA to a small titanium rod. I've previously used Superglue (cyanoacrylate) to glue PLA pieces to each other with great success, but the problem is that if you don't apply it perfectly cleanly, it leaves very noticeable stains on the PLA.
Can anyone recommend a good glue for this application that won't leave stains like that?

Not an answer... but have you considered tackling the problem from another angle (i.e.: still using cyanoacrylate but masking the PLA next to the part that need to be glued with some tape, that you can remove afterwards)?

Try using one of the "gooey" forms of cyanoacrylate.  Any of the major brands sells this-- it has the consistency of toothpaste, so it  won't "run" along your pieces.

@mac The water-thin CA glues will wick under any common masking material -- it makes the problem worse rather than helping, not to mention the issue with gluing the masking material to the part.

I've been a fan of epoxies for unusual adhesion problems. I found on Amazon a product with titanium in the name, but there's a caution regarding polypropylene plastics.

PLA is not of that family of plastic, which gives it a good chance of success. Epoxy is typically more viscous than cyanoacrylates, giving you a bit more control of the application, but also creating the need for care with "ooze-out."
The big glue company, Gorilla, also makes an epoxy that includes plastic and metal in the adhesion listing.

As PLA is somewhat sensitive to heat, one would consider that fast-cure epoxies generate more heat than slow-cure epoxy, but the amounts you'll be using are not likely to create enough for concern.

"Titanium epoxy" sounds like a marketing term that doesn't actually have anything to do with titanium.

Marketing does go overboard in many circumstances. I suppose that since the packaging reads "contains titanium" they can get away with it. Of course, does 1 gram of titanium allow for such claims? Even what might be considered titanium debris would qualify and validate the packaging. Who can say if it adds strength to the product?

Try using one of the "gooey" forms of cyanoacrylate.  Any of the major brands sells this-- it has the consistency of toothpaste, so it  won't "run" along your pieces.  Here's one that I've used with success:
loctite goo

After perusing http://www.thistothat.com/ I decided to give J-B Weld epoxy a try.

So, how did the epoxy work for you? Your experiences could be very valuable to someone who has to deal with this question in the future.

A glue gun would IMO work very well, and you can use transparent (or almost transparent) glue sticks to minimize ugly looking stains.
Things glued together usually break before the glue (in my experience) and it's cheap, you can get one for $10 with some glue sticks. It's fun too, I glue everything since I bought one :-)

Most glues will leave some type of visual stain.  The glues that won't leave some type of visual stain probably won't stick as well.  For example, you can use rubbery RTV type glues, but you will need surfaces designed to minimize the need for glue strength.  However, an advantage is the glue will flex.
My favorite is Gorilla impact resistant superglue.  Superglue breaks easily when flexed if not impact resistant.  If you want to go to the trouble, epoxies are best.  Rubbery type glues will work if you have enough surface area, especially if it is not all planar.


text:
Extra data appended to the Y values when issuing `M92` & `M500`
I am still trying to dial in my Anet A8.
The Marlin firmware takes too long to scroll through the axis settings when I change them, so I use Repetier Host instead issuing M92 followed by M500.
I noticed in the log window that X goes in as typed but that Y has a *75 after the value i input. Can anybody tell me why/what it is for? I suspect I know what it does just no idea why it is doing it.

*75 is the checksum value, (a method for verifying the integrity of the transmitted information).
RepRap wiki gcode : checksum
There is probably an option to not use/disable checksum generation in repetier/slicers, however this may only be advantageous for use with code run from the sdcard as it is extra processing (and probably less relevant when not being transmitted over serial connection. )

Thanks. Calibration getting closer but not quite right yet. I just wondered if this was a possible source of my X Y problem of circles not being round....grrrr. I will ignore it.