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Issues with Auto Bed Leveling
I have enabled auto bed leveling on my 3D printer. I have used a 6-36 V inductive sensor with a 7805 voltage regulator running the sensor at 10.78 V.
I am using Marlin 1.1.9. This is my configuration file for Marlin firmware. I used this video for marlin setup.
I have done a voltage regulator setup by using this video.
I have place an Aluminium plate with insulated copper wire. (I also tried an Iron plate). After Setting this I use Pronterface to control the printer. While homing command is given the XY axis gets home and Z axis moves downwards and doesn't stops even the Light in the sensor gets ON. This video I made shows that it does not stop.
And also once the Zmin gets TRIGGERED, it is always TRIGGERED.
After I enabled SAFE_HOMING, the XY axis comes to the centre of the printer. And Z axis goes down again without stopping.
Please help me in this.

Problem solved. Just downgraded the marlin version to 1.1.0 and done the same changes. Now it works. Thanks for your suggestions @Oscar

Please look into this answer, it explains the necessary steps to enable ABL. Maybe it is better if you start with a fresh configuration.h file.

It is advised to use the latest firmware version 1.1.9. With the answer below and this anser you should be able to get it running in 1.1.9. If so accept the answer, if not, please add your own answer and accept that after 48 hours. A downgrade of firmware does seem like a quick fix, better said work-around, but not an actual solution.

Hi, I see that your original question has been answered. If you have additional follow up questions, then please post them as separate questions and not as comments as these are not searchable and will not be as useful to other people who may have the same issues. Please feel free to ask as many questions as you like, but just post them as new questions, rather than comments. You can always refer back to this (or other) question's URL in your new question, if you feel that they are related. If they are clarifications to your original question then please edit it and add them there. Thanks

As this is a Q&A site, and not a forum, unfortunately it is not possible to ask user to share config files. There is no central repository to share them to, and the config file would be too large to post in its entirety in an answer. Direct correspondence between users (outside of comments and answers) is also not allowed, I'm afraid. Apologies and I hope that you understand.

Your problem is that the hotend carriage does not stop when the sensor triggers. I assume you mean "on homing", not "while printing" (UPDATE: after watching the video it is confirmed that it is "on homing"). First, the working and this difference is explained. Thereafter your configuration file is assessed and typical errors or inconsistencies are reported. Note that assassing an existing configuration file is more work than for you to start over taking the consideration below into account. Also look into this answer which describes what you need to do starting from a clean configuration file.

Note:
Why not test if the sensor works at higher Z values by using a metal screwdriver to test if the head stops, then you do not run into the bed (with way less chance to damage your printer). From the video you can see that the sensor triggers, does the signal also gets registered by the printer board? With M119 you test the endstop status of all endstops.

Auto bed leveling theory
An auto level sensor does not trigger exactly when the nozzle hits the bed like in normal leveling using switches. The sensor is meant to detect the bed before the nozzle touches the bed. It is the offset that you define with command M851 e.g. M851 Z-1.85 that determines the correct offset between sensor trigger point and the nozzle. After homing G28 and auto bed leveling G29, the nozzle needs to get under the sensor trigger point (e.g. in the example above it is then still 1.85 mm away from the platform) so while printing it is perfectly fine that the sensor stays triggered until printing height gets above 1.85 mm. This gives an answer why you see the head go past the trigger point when printing, when homing or leveling that should not happen.
Configuration file observations
From your configuration can be seen that
//#define Z_SAFE_HOMING

is not enabled, this is advised to enable. This is important, but not the complete solution.
Also, you have not defined the auto leveling area by setting the boundaries for probing (where the probe can reach). In your config you will find disabled constants for (see also this answer or question: "How to set Z-probe boundary limits in firmware when using automatic bed leveling?"):
//#define LEFT_PROBE_BED_POSITION MIN_PROBE_EDGE
//#define RIGHT_PROBE_BED_POSITION (X_BED_SIZE - MIN_PROBE_EDGE)
//#define FRONT_PROBE_BED_POSITION MIN_PROBE_EDGE
//#define BACK_PROBE_BED_POSITION (Y_BED_SIZE - MIN_PROBE_EDGE)

You only have defined a Y sensor offset in your configuration :
#define Y_PROBE_OFFSET_FROM_EXTRUDER 43

but the video and the comments say otherwise, you should therefore should have set:
#define X_PROBE_OFFSET_FROM_EXTRUDER 43

so e.g. the following could work (depending on the offset from limit switch position to printer origin):
#define LEFT_PROBE_BED_POSITION MIN_PROBE_EDGE
#define RIGHT_PROBE_BED_POSITION (X_BED_SIZE - MIN_PROBE_EDGE)
#define FRONT_PROBE_BED_POSITION MIN_PROBE_EDGE + Y_PROBE_OFFSET_FROM_EXTRUDER
#define BACK_PROBE_BED_POSITION (Y_BED_SIZE - MIN_PROBE_EDGE)

Another part in your configuration that need further inspection is your offset from limit switch position (when homing) to printer origin; you have:
#define X_MIN_POS 0
#define Y_MIN_POS 0

This is very unlikely, but possible, it means as is that the X=0 and Y=0 is exactly on the limit switches for X and Y. Usually this is not the case and you see negative values for these constants.
All-in-all, your configuration file has a lot of problems which need to be fixed. To solve your problem you need to read into configuring Marlin. Once you got the printer working fine you progress to an ABL sensor and make the correct settings in the configuration by using the hints above.

As I have placed the proximity sensor in right side, think so don't need to change in printer origin position.
Please do me a kind favor, If possible will you change some settings in my configuration.h file which is needed for Auto bed leveling and send it to me. I will check it and report it to you. I will be thankful to you if you do so.

I have placed the sensor in right side and it is aligned to be straight with nozzle's tip. So I set 0 for X probe offset.

Not right side (in config that is), you have configured it at the back: #define Y_PROBE_OFFSET_FROM_EXTRUDER 43 furthermore, I would like to help, but I do not know what printer you have nor do I have access to it, I simply can't. Please beware that this is not a forum, we answer the questions of people that post them. I have posted the errors I found in your config, please address them and see what happens. The problem you face is a printer configuration issue. Please post your printer brand and type. Also add a picture to the question.


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What are the advantages of gyroid infill?
I've seen a few print time-lapse videos lately which use gyroid infill: wavy lines, which deform across layers so that the waves end up alternating between the two axes. Other than making the time-lapse videos look much cooler, what are the benefits of this infill style compared to the more common hatching or cross-hatching?

From this reference you can read that:

A gyroid is a naturally occurring structure which be found in
  butterfly wings and even within membranes inside cells. In 2017, MIT
  researchers discovered that when graphene was shaped into a gyroid
  structure, it had exceptional strength properties at low densities.
  They then discovered however, that the crucial aspect of this was
  actually the gyroid structure itself, and that other materials such as
  plastic could benefit from this.

It is assumed that this type of infill has better properties against failure than the normal types of infill we know.
A test conducted by an author named Martin is found here. He printed test specimen and subjected them to bending to test the resistance against shear stress.

From the figure can be concluded that the gyroid infill has a better resistance against bending for a lower weight.
The advantages of gyroid infill over the tested infill types are:

high shear strength, and
low weight (so less filament needed).

On top of these advantages Gyroid infill prints relatively fast with respect to some other infill types and is close to isotropic (i.e. uniform in all orientations), meaning that is very suitable for flexible prints.

0scar gave a great answer, but I wanted to add to it.
Stefan of CNC Kitchen does a lot of 3D printer technique testing. He covered the gyroid and other patterns. While there's a difference in filament used, the significant differences are strength* and print speed. Here's his 8-minute infill pattern testing video; some screenshots follow. I stopped printing honeycomb once this video came out. Perhaps I should switch to gyroid too.

* yes, I'm calling it "strength". Don't at me, physics and materials science peeps, I know it's inaccurate.

If I read this right, cubic and gyroid are the best 'all round' choices, and also gyroid has no clear lead?

correct, Sean. they seem really close.

Benefit of Gyroid in contrast to cubic is, that gyroid never crosses itself in the same layer, while Cubic does.

A downside of gyroid that is not often mentionned is that it can make your 3D printer wobble quite a bit.

This answer builds on to both 0scar and tedder42's answer:
Martin's experiment was about shear strength, where as Stefan of CNC Kitchen's experiment was about compressive strength on 2 directions.
From their experiments, it is reasonable to conclude that gyroid does well on sheer strength, and above mediocre on compressive strength.
Why use gyroid?

If your print requires shear strength, use gyroid.
Else if your print requires compressive strength from transverse or both directions, use cubic.
Else if your print requires only perpendicular compressive strength, use triangle.
If your print infill naked, each pattern has its own beauty.

See also:
Martin's experiment (Note how he used a bottle of water to test different structures for their shear strength):
https://www.cartesiancreations.com.au/gyroid-infill-tests/
Stefan of CNC Kitchen's experiment (Note how he used his self-made machine to compress different structures):
https://www.youtube.com/channel/UCiczXOhGpvoQGhOL16EZiTg
Examples of gyroid's aesthetics can be found in Matt's links:
https://mattshub.com/2018/03/15/gyroid-infill/

For 2. I would use triangles: the low value is similar (there are no uncertainty bars in the graphs!) to cubic but on the strong direction is much better. And then 5. if you need speed, go rectilinear, which is still a very good compromise but quite faster.

About a decade ago, we looked at the 'Gyroid infill structure' (which we called sheet solid). We looked at it as a linear-elastic solid and as possible bone scaffold design:
https://www.sciencedirect.com/science/article/pii/S0142961211006776
What came out of that study that lots of the triply-periodic minimal surfaces (a broader class of structures that comprise the Gyroid) had interesting elastic moduli.
One thing that's worth noting though is that the Gyroid is not isotropic. Rather, it has cubic symmetry, ie 3 rather than 2 linear elastic constants. But it comes fairly close to isotropic

Many thanks for sharing the paper and the info. Good to know it is close to isotropic!

source: Stack Exchange

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

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How to avoid collisions with already printed objects?
When printing several objects, I recently encountered a problem that arises when the structure in itself is relatively thin or the support towers have a small surface: the printhead would in motion tend to knock one or more over as it traveled or catch at them and create layer shift.
How can I avoid collisions with the already printed parts of a layer?

The problem was twofold:

Lack of bed adhesion due to the small contact surface
motion into the already printed objects.

The quick and dirty way was to change two settings:

Print with a small (3 mm) brim to stick the supports to the print and provide more surface. Other materials than PLA may need considerably more brim!
Activate Z-Hop to force the nozzle to lift over the print when traveling

These tricks don't solve issues with very thin structures or in all cases. In those cases, it can be mandatory to increase the structure's (support) thickness or change the alignment.

This will help, but for thin vertical rods, the lateral force during deposition can cause bending of the structure, leading to effective random layer shift.  No way around that other than to print in a different orientation or build in a "scaffolding."

For the Creality Ender 3, I had the same collision problem and after a while I found it was because of the X-axis not being level.
I found right hand side was more than 3-4 mm below the left side when the Z-axis height exceeds around 8-10 cm. Below that, the two sides were even. I made some calibration by turning the eccentric nuts of the wheels and tighten them.
If you use Creality Ender 3, that might be the problem. Take a ruler and check between base extrusions and X-axis left/right hand sides at different Z heights.

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


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Does PETG fade in the sun?
I'm looking at scanning in a statue on my pond and making a print of it. I'm wondering if PETG will fade and how fast. I'm thinking of using white or maybe a bone color if possible.
If PETG fades kinda fast, what material should I use? Keep in mind this will deal with all weather types, full sun, and it will have water coming out of it.
I've been 3D printing for a bit, but I never made anything to stay outside for looks. I know PETG is pretty good at water, and I think it's stronger than ABS when it comes to weather. But I'm in NC, and I even lived in FL at a point. Shockingly, I found the sound in NC can bleach wood in a matter of days to weeks in the mid of summer where it might take all summer in FL. So I'm worried what I might make will get that yellow fade look that plastic does in the sun.

tl dr: For the most part, yes it should be color fast in the sun. It should be good for outdoor use.
This website claims the following:

Filament materials ... for outdoor use include ASA and PETG that are perfect for use in extreme conditions without changing shape or appearance. Printed pieces do not change colour either with the sun's UV rays and do not take on a yellowish appearance as does ABS, for example.

Please realize, this is partially an advertisement (and no, I have no affiliation). What it boils down to is, PETG and ASA are going to be better for outdoor use, but every brand of each is going to be a little different in how well it reacts to the elements. Without advertising on the site, you'd need to do a little investigating on your own, with the possibility of testing different brands to come up with what you believe is the best. Beyond that, it's just an opinion.
I doubt any filament, no matter what it is made of, is going to be perfectly colorfast in the sun. The sun is a harsh beast. It will bleach a printed object over time. Some colors are going to be more susceptible than others, especially red. This is due to the color of the sun. Again, some filaments are going to be better than others, but I'd not expect any filament to be perfect.

Funny thing is, I'm actually going back and forward if I will use red. It's a statue of a crab.
Anyways, thanks


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How can I have a large 3D printed object?
I have a concept that's roughly 18"x30" (about 457x762 mm), and I just realized that the Makerbot and similar printers only allow dimensions around the size of a piece of paper. What are other options? Are there large 3D printers I just don't know about? I looked up TMC injection mold, but couldn't find anything on size (most links go to PDFs with printer images).
Is injection even in the same "world" as 3D..? Sorry for confusing the two.

Welcome to 3D Printing! Think of 3D printing as "Proof of Concept" or "prototyping" (one off or minimal production). Think of injection molding for mass production after you've proven the concept. You could mass produce with 3d printing, but it wouldn't be economically feasible, in both time and money. Using injection molding is, after the forms are paid for, much cheaper/easier if you're going to be selling something on the open market in large quantity. NOTE: These are the ramblings of a mad-man, so take them for what they are worth.

The question about TMC injection molding pretty tacked on and might warrent its own question. I focussed on the main question.

Agreed - please post the "injection" question, with clarifications, as a separate item.

As Trish states, a print service would appear to be your best bet. Building a printer large enough may work out costing more than the print service, especially if it is only for one print of a proof of concept.
Anecdotally, I visited a 3D Printing shop in Bangkok, JWH High tech Garden, that had a huge Delta printer that had, reputably, cost a million baht (~£20000) if my memory serves me correctly, and was capable of producing prints up to 1000 mm x 600 mm (39.37" x 23.62"):

However, the print service was not cheap at all. In May 2017, I was quoted 68000-100000 baht (~£1360-2000) for some printed parts (the proteins) for a Wilson II 3D printer, which are about only £70 on eBay!

However, it is worth taking into consideration that, at the moment, Thailand is very expensive for 3D printing in general, as it is relatively new there, and so prices for both printers and print services are high.

I do not know about your project, but the size of the final object.
Smaller prints glued together
Just design smaller parts and glue them together. Take a look on this video, where Joel Telling glues OpenRC Formula parts.

Hangprinter
Interesting concept is Hangprinter where volume size depends on your room size. It's a RepRap so you have to build it yourself. Components price should be around 500$.

Buy a big printer
If your budget is bigger then you can buy a printer. See following lists:

https://all3dp.com/1/best-large-3d-printer-large-format-scale-3d-printers/
https://www.aniwaa.com/largest-3d-printers/

Print service
If you have higher budget and you need just one, two prints, then you can use 3d printing services like 3dhubs. Such services use large printers. See a list on all3dp.com.

YesIf you have the money
Either read here or look at the ones I plucked out of that list to show you:
First of all, 3D printers on FDM basis can become quite large, if you pay extra. And the price goes up really fast as the dimensions grow because the demands on stability grow exponentially.
Larger Printers?
One example of a "scaling" printer family is the CR-10: The baseline CR-10 is about 300x300x400 mm, so about 12x12x16 inch for 400\$. Not enough? 400x400x400 on the CR-10 S4 for ca 760\$. 500x500x500 on the CR-10 S5 for 900\$. That's 20 inch in all directions. But that's still not enough, isn't it? Well, if you need to go larger, you need to go professional...
Going Big!
Well, there are printers like the gCreate gMax 1.5 XT+ (406x406x533 mm) for a mere 3000\$. That's enough, isn't it? Well, we can even go bigger: 610x610x610 mm for a mere 3500\$ on the Modix Big 60.
Still not satisfied? Industrial machines can go even larger! A BigRep Studio for the little price of 50000\$ could achieve 500x1000x500 mm.
Even more? Go Parametric!
As amra mentioned, the Hangpringer project of printers has no "set" build size, but you will have to provide a build platform of fitting size and a room it can work in undisturbed and with filament supply ready... just... bring a ladder? And be wary of people tripping over wires... and somehow find a ginormous, evenly heated bed somewhere...
Ways around
Assembly
That is a little overkill, isn't it? Well, the first thing you need to remember when 3D printing is: unless you make a functional part that has to have certain dimensions, feel free to scale it down if it is just for visuals. Then, you can assemble prints. Like, take a smaller printer and print the object in halves or quarters. Then glue it back together.
Order
You don't want or can't assemble the part? Well, there are printing services out there that have these larger scale printers I mentioned (or at least similar ones) that offer to make your parts for you and then ship them to you. Usually, that is much more cost effective than buying one of these ginormous printers yourself.

I build my own with 600 x 600 x 750 for around 800EUR

@profesor79 building yourself is definitely cheaper than buying a ready made printer.

So long as you are not dealing with MortonThiokol issues,  there is a simple tradeoff: high-cost printer vs.  breaking down your design into smaller parts with assembly features.
Many designers publish designs which snap-fit together; others suggest glue;  still others go the safe route of providing clearance holes and requiring metal nuts&bolts to assemble.
In sum - if you can deal with separate parts, you can print everything on a standard bed size.

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How do I add auto bed levelling to my Marlin-based CNC?
I just finished a CNC that uses Marlin Firmware. The dimensions of it are quite large (3200 x 2000 mm) and the table is not perfect. I'm thinking of adding a proximity sensor to store a mesh in the eeprom and thus compensate for any errors. I'm not sure how to do this. I would like to be able to execute an action from the display (full graphics) and have samples taken over the whole table, but I do not know how to tell the firmware where to take the samples, nor what the dimensions of it are.

Welcome to 3D Printing!

Auto bed leveling requires some settings (constants) in the configuration of your Marlin firmware.
It is recommended to read about the implementation of automatic bed leveling first. There are a few options to choose the kind of leveling, for 3D printers a commonly chosen option is AUTO_BED_LEVELING_BILINEAR which is the best option if you do not know if your bed is flat or not. If you are certain it is flat but tilted (e.g. when you have a milled bed or a glass plate in 3D printing) you could go for AUTO_BED_LEVELING_3POINT or AUTO_BED_LEVELING_LINEAR.
What further is important is the sensor type you choose. Do you want a touch or a proximity sensor. The latter is your preference (as specified in your question), which is a little simpler as you do not need to configure for servos for deploying and stowing.
You need to set:
#define FIX_MOUNTED_PROBE

for using a fixed proximity sensor.
In the configuration file you also need to specify the position of the probe in relation to the nozzle (in your case tool center):
#define X_PROBE_OFFSET_FROM_EXTRUDER 10  // X offset: -left  +right  [of the nozzle]
#define Y_PROBE_OFFSET_FROM_EXTRUDER 10  // Y offset: -front +behind [the nozzle]

and optionally:
#define Z_PROBE_OFFSET_FROM_EXTRUDER 0   // Z offset: -below +above  [the nozzle]

This latter is not necessary as you can always set the distance of the sensor trigger point to the nozzle/tool plane by G-code command M851 Z-x.xx
You would also need to set the boundaries of the probe area to prevent the tool to hit unwanted positions (fill out values or leave the constants):
// Set the boundaries for probing (where the probe can reach).
#define LEFT_PROBE_BED_POSITION MIN_PROBE_EDGE
#define RIGHT_PROBE_BED_POSITION (X_BED_SIZE - MIN_PROBE_EDGE)
#define FRONT_PROBE_BED_POSITION MIN_PROBE_EDGE
#define BACK_PROBE_BED_POSITION (Y_BED_SIZE - MIN_PROBE_EDGE)

Once properly setup, command G29 runs the leveling of the bed, options are available for that command to store the bed mesh to EEPROM.
Enabling LCD_BED_LEVELING constant in the configuration file will add a Bed Leveling sub-menu to the LCD. But you could also work with SD-card stored files that load these codes.
This reference explains the automatic leveling in more detail, but there are many more detailed guides to follow from the internet. Be sure that you get a recent guide to that is easier to set in the latest firmware.

Thanks!. Can I uncomment MESH_BED_LEVELING and AUTO_BED_LEVELING_BILINEAR at the same time?. I want to test the result of this manually before going to the automatic solution. With both methods activated, both options will appear on the menu?. (auto and manual).

No I do not think it is possible, if you look into the config file you see that if you enable both, AUTO_BED_LEVELING_BILINEAR is executed is some #if statement and it will then never go to the #elif of MESH_BED_LEVELING .


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Strange walls/faces when importing self made model from Blender to Cura 3
I wanted to create a coin stacking device similar to this one:
https://www.thingiverse.com/thing:499177
But I wanted to only 3 coins, 5c, 2c, and 1c. Unfortunately the STL came in pretty messy after importing to Blender, which made it difficult to edit the model to have only 3 stacks. So I decided to create my own. I used a box and three cylinders with the diameter of the coins + 2mm so the coins can fall loose into the stack. The cylinders where used for boolean modify the box to create the stack gaps.

Exporting the model as an obj and importing them to Cura showed it getting strange diagonal faces at the stack gaps and at the top.

After slicing however the faces were gone and the test print came out pretty decent, even on low quality settings the measurement were quite exact.

Still I would like to know why these additional faces appear and how to prevent that. I am not a blender expert, but I guess it has to do something with the topology/faces? I started creating additional edges in Blender for the isolated vertex created by the boolean modifier, but I don't know if that's actually necessary for a 3d printed model that's not going to be textured ect.

It is quite common for modelling operations to result in 'non manifold geometry', meaning that some of the faces intersect or are not perfectly joined.
Although there is nothing obvious in your model, you can check in blender by going into edit mode, unselect all, selecting nodes, and 'select all by attribute/non manifold' Ctl-Alt-Shift-M (if I remember right).
Usually this happens with boolean operations where you merge the same object twice (i.e. union for the hole, then difference with the cut part). You would need to apply the boolean to see the non-manifold result.
Any of the standard mesh fixing tools will attempt to clean up your exported STL, and you could then import the model back into blender (but then it is a one way process, and you can't make updates to the base model).

Judging from your second screenshot, I'd say that Cura does not like n-gons very much.
An n-gon is any polygon with more than 4 sides. Most software tries to convert these polygons into triangles, with solutions that may not be what you want. Obviously, if you triangulate your surfaces manually this problem becomes moot.
Go to Modifiers, add the Triangulate modifier, click apply.

Not sure about Blender, but MeshMixer has a "Plane Cut" tool that would allow you to take the source STL file and cut off the parts you don't want.  That might save you some pain.
But if the final sliced gcode file works,  don't worry too much.


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(Cura setting) How can I fix this? No top layer
problem solved by resetting cura.
I have problems like this: How can I fix this? I can't find the right setting.

Also, what are these yellow lines? Do you know how to remove them? They disappear when I disable to show the brim/raft/skirt.

Number of top layers set to zero?

I cant modify that setting.. when I tick the box in cura settings, it doesnt appear on the right side. The problem occurs on many different prints so it has to be the software.

I would suggest that you reinstall Cura. You must be able to configure the number of top and bottom layers.

Hi Donald, please could you post your answer (that a Cura reset was required (assuming that was the solution)) as an actual answer and marked that answer (and not Fernando's) as the accepted solution (using the tick button) and not in the question, as it breaks the Q&A format of Stack Exchange and will be confusing for other users of the site who come here looking for a solution.. Thank you.

This problem appears when a face is inverted, so the slicer confuses and expect the other wall to close the object. So you need to reverse that face to show the face out and the back face inside the shape to be filled

I will edit this answer with more examples

I'm pretty sure the yellow lines are showing the full path of the extruder head, including where it's retracted.  Somewhere in Cura's maze of menus, there's an option to turn on/off various displays related to the slicing.
As to why the top layer isn't there -- most likely it's too thin in your source  model.  You might try enabling "Print thin walls" options in the Preferences advanced list.  BTW, if you post the original STL or CAD file, we might be able to provide more accurate diagnosis.

Thank you. Sadly the thin wall option didnt solve the problem.. How can I upload a stl file?

@DonaldEnte  Best thing to do is upload it anywhere you have a repository (git, DropBox, GooglePages, etc) and put a link here


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Print speed and settings for printing below 0.1mm resolution on PLA
I recently purchased an Anycubic Kossel Linear Plus delta printer, and I'm interested in trying to print slightly below the 0.1 mm stated lower limit of layer height. I'm not interested in trying to push much below 0.06 mm, more just 0.08 mm to give some better surface roughness on critical parts.
I've found several articles that suggest that going below 0.1 mm requires lowering the printing speed, but the top answer on this question suggests that there are flow rates to consider in order to prevent jamming.
I'm referring to PLA in particular as I have read that the filament viscosity is also a factor, with ABS differing from PLA.
I'm interested in some benchmark settings, preferably for 0.08 mm printing. What is the ballpark range my print speed should be in to successfully print at that height?

Why not try it by printing calibration cubes or calibration towers? Do note that temperature is also a parameter to play with.

@0scar experimentation is always good, but that's not what I'm here for - I was looking for some empirical data, from those who have run more prints than I have so my first print on this Delta would be a bit more than "winging it". Nonetheless, I'm running the printer on a 25mm calibration cube, 0.08 mm layer height, slowed down to 45 mm/s on print speed at 200°C. I will post an answer with the results (will test with calipers) when it completes in ~90 minutes.

To answer this question for anyone who will find this of use, I printed this calibration cube at 25mm to a side (125% scale in Cura) with my Kossel Plus using the following settings:

0.08 mm layer height
45 mm/s print speed
200°C extruder temperature with PLA

Based on articles I read, I wanted to play it safe with the speed, staying well below the printer's rated speed of 60 mm/s, but still keeping the speed reasonably high to avoid any nozzle flow issues as describe in the linked question. The results were pretty good for a first test; the deviations, as measured with calipers:

X: -0.09 mm
Y: +0.38 mm
Z: +0.11 mm

This makes the average deviation across all axes about 0.13 mm, which is better than what I was hoping for, as that is about 5/3 of a layer's thickness. Whether or not running slower (or faster) or modifying temperature will result in better accuracy, I cannot be sure - but in this case, running the speed conservatively yielded positive results.


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Can the glTF format be used for 3D printing?
Can the glTF format be used for 3D printing?
If not, is there any tool can convert it to another format such as STL, OBJ, STEP, and IGES?

As far as can be found it should be possible to convert glTF into STL (or OBJ).
You could try to use an online converter to do this, e.g. this one (greentoken); and this (assimp) may be useful too.
According to this greentoken supports glTF as input and STL as output, but it is reported by @Trish that that does not work. Assimp could output STL files which then could be used by slicer programs to generate the specific G-code file to print the model on your printer.

Greentoken does not accept GLTF, Assimp though does.

No, gltf is not a format that slicers accept commonly, and indeed, it is not even intended to be reverseable in the 1.0 format version. This has changed a little for the 2.0 standard. Some programs that allow exporting into the sliceable stl and  obj formats can also import gltf:

blender has an importer plugin - more  info here
SketchUpp has an importer plugin

You have to be careful though: formats like dae or stl are meant to transfer 3d objects usually without the loss of information or with just a minimal loss (stl, for example, does technically not contain a scale natively), while gltf is end users and does not contain all the information. This can lead to models getting distorted and destroyed on importing them into a rendering or modeling software.


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Clamps / clips for glass on heatbed
I'm looking for clamps to fix the glass on my heatbed. After some search I found that some people use clamps printed of PLA. Can I use PLA clamps for a heated heatbed (~60 °C)?
I also tried foldback clips but they block my nozzle. The Anet A8 starts in the front left corner. When I start to print, the nozzle moves a little bit up on z, then up on y and right on x. At this first move it moves into the fold back clip. I'm looking for a way to fix the corners and not to fix the edge in the middle.
What other clamps or clips can I use to fix the glass (~3 mm) on the heatbed (~2.5 mm)? I don't want to use glue.
My printer is an Anet A8.

How about the Ultimaker clips? Ultimaker uses 2 mm heat bed and 4 mm glass, that should be within reach by bending the clips a bit. They have quite a low profile/footprint.

These clamps are very cheap and can be found on those typical auction or Chinese sites.
Alternatively, you can also tape the glass to the aluminium bed using kapton tape if you are concerned about hitting the binder clips.
Note that e.g. in Marlin firmware, you can define a Z-offset to prevent hitting the binder clips on movement.

There are some clips similar to Trish's answer that aren't mounted but have a spring in them to apply pressure. Looks like they are called Swiss clips: Glass retaining clips – Swiss made:

These look great, very low profile.

PLA has two problems that keep it from being usable for your purposes.
First, it deforms under load.  I've used printed C-clamps for various jobs; by the time I'm done, the clamp is generally warped by 10+ millimeters.
Second, PLA has a very low heat tolerance.  The glass transition temperature of PLA is around 60-65°C, right around your intended heatbed temperature, so not only will your clamps deform from the load, the plastic will flow from the heat.
If you were printing on a cold bed, you might be able to use printed clamps, printing out a fresh set whenever deformation of the current set gets too high.  On a heated bed, not a chance.  Look for some sort of metal spring-based clips instead.

Let's analyze the problem:

We have a 5.5 mm total thickness.
We want to (semi)permanently affix the two layers together mechanically.
The clips shall not be higher than about 0.2 mm to allow the nozzle to pass over them.

(non)Solution attempt zero:
Let's look at the problem objectively... we can print something, can we? Well... 0.2 mm or below of PLA means 0.2mm of PLA that need to withstand the stress of trying to push the glass to the bed. PLA, just like any plastic, isn't super strong in thin layers, especially when heated to 60°C to get a good bed adhesion. And then you might want to print something like ABS, which demands an 80°C or higher bed temperature. The result will not be pretty: either the clip breaks after a very short time or it starts to bend. The result: no clip, bed slipping free.
Solution attempt one:
Let's look at old picture frames that consist of just a glass sheet and a paper/wood backing. A "Frameless Picture Frame" like this one1. These clips do need some kind of mounting on the underside.
Using this design as a base, you might either get these clips or make similar ones yourself. But how to mount them?
Well, here comes the nice part: we got some options.

Glue or solder the clips to the underside of the bed. Removing the sheet gets a PITA, but is still possible
Cutting mounting slots for the clips. The sheet can be removed by removing the clips now. But the bed heating might not like us cutting slots into the aluminium.
Adding a mounting point. Again, we can use glue or solder to add some kind of framework that we mount the clips to. Like a piece of aluminium U-profile with the opening to the centre of the bed, giving us mounting points for the clips.

1 - This was just the first one that I found that had the right setup. I am not affiliated with them and don't get money for this.
Solution attempt two:
Take this idea up a notch and look for this same principle applied.
There is the "Swiss Made Glass Retaining Clip" Perplexed Dipole mentioned. Good idea, and instead of having to cut a notch into the aluminium bed, a simple, small hole would be sufficient. About the same price than a frameless picture frame but less construction work!
And then there is, of course, the option to look at the Ultimaker and its Build Plate Clamps like 0scar mentioned. If you can get them (also in the same price range as the other options) you even might have an easy installation: they are supposed to be mounted in the corners of the build plate by being held by the springs. For the A8, you'll have to possibly adjust the mounting point some, maybe even give them a little nub to pivot around to secure them in place, but this clearly is a solution too.

That's what I'm currently looking for. I think the easiest solution will be to buy some picture frame and use the clips. Can you say something to the other option, PLA clips on a heated bed?

Pla in 0.2mm thickness has little to no strength

They might not work for every printer, but how about old fashioned bulldog clips:

Attached at both end in the y-axis, they will avoid your Z-axis rods and frame (attached in the direction of the x-axis I have noticed them catch against the Z-axis frame).
Like so (except the image below uses the foldback clips that (I assume that) you refer to):

The lever/handles aren't as long as those on foldback clips, and more sturdy too. Also, they have no curled edge that can catch the nozzle if mounted right.
You should obviously route any wiring/tubes away from the clips travel at the rear of the printer.

I think with bulldog clip I get a similar problem

I went to OfficeMax and got some Small clips. They are bigger than the Micro/Mini clips that ship with the printer and seem to fit just right on a glass plate.
One of the Mini clips that shipped with the Ender 3 is shown to the left. The Small size that works best is obviously centered. The Medium in the back seem way too big.
For an added bonus, they sell this sandpaper with a rubber back and it really increases traction. An oversize chunk of that worked really well. But it's optional.


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Unknown issue affecting print quality
I have been having issues with a vase print using a FlashForge Creator Pro.
I am using the default slicer for the printer(FlashPrint) because the Creator Pro only accepts .x3g rather than .g/.gcode.
The issue is that the printer seems to be both under extruding and over extruding.

I am printing ASA filament at 0.18 mm layer height at 240 °C with a heated bed at 110 °C. I am running the print with the fan on. I am also running at 80 mm/s print speed.
I have tried both lowering and raising the temperature, changing the print speed from 80 mm/s to 60 mm/s, and changing the extrusion multiplier.
At this point I am not really sure what to do in order to get this to print nicely, any advice would be welcome.

After a few more prints and the link that "E-Doe" posted I am beginning to think that the problem might be with the z-axis. My reason for thinking this is that the layers that bulge out do so consistently for the entire layer and then stop for a bit. I think I also ruled out temperature variation. I measured the temperature in the enclosure with a separate device and it stayed pretty constant the whole time.
Not really sure how to fix that but I will call this question answered.

Welcome to 3D Printing!

What is your nozzle size?

The nozzle is 0.4mm

A very helpful page for troubleshooting common errors is: Print Quality Troubleshooting Guide - Lines on the Side of Print
It seems like your problem is inconsistent extrusion or temperature variation. From the photo you posted I guess that you use a big diameter nozzle. Keep in mind that your extruder might not be well equipped to deliver such a large amount of plastic consistently. This most likely is a problem with the heating capacity.
You can try to lower the speed even more to give your extruder more time to heat the plastic.

To elaborate, over extrusion is at the points where movement will be slow, under extrusion occurs in the longer travel where speed will be higher.

It is odd though because the under extrusion is in the spots where it should be going slower. the tips of the walls should be going slower than the rest. Also the over extrusion happens for 1 full layer. and then stops for a bit.

@Sean It is not that odd. The printer will adjust its plastic output when the speed is altered, so you won't see any changes between slow and fast parts of the prints. When the temperature drops, the viscosity of the plastic decreases, which leads to less material output. This leads to a longer time in the melting chamber, which leads to a higher temperature -> higher viscosity -> more plastic output. Rinse and repeat.


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Does auto leveling result in sheared prints?
I asked this question as a small question under an answer of another question (How bed leveling is achieved without table screws?), but have been asked to post this as a separate question to answer it with more detail conform SE policy.

One question with respect to automatic bed leveling (also known as ABL): If the bed is tilted and the auto leveling measured this and then the printer adjust the z axis over the position on the bed, will a x-y-point on the first layer be located exactly under the (in model) same x-y-point in a higher layer, or will it be shifted to? I mean, if the bed is 1 mm lower on one side over 10 cm then a top corner of a 10-cm-cube should be also 1 mm shifted, so that the cube still is real cubic and not sheared.

Using automatic bed leveling assists you in getting the print to stick better to the build platform as a result of the print head following the non-uniform geometry or tilt of the build plate.
In, e.g. Marlin Firmware, the bed level correction is fading out over a predefined distance, this is determined by the constant #define ENABLE_LEVELING_FADE_HEIGHT in the printer firmware Configuration.h file  and the height can be set with M420 Z<height> (see here).

M420 S1  ; Enable compensation using current grid/mesh
M420 Z10 ; Gradually reduce compensation until Z=10

If Z equals zero, leveling compensation will be fully applied to all layers of the print object.
Yes, a cube will not be perfectly cubic, that is why even with auto bed leveling you need to provide a bed as level as possible, it only should correct for very small deviations.
When the print is smaller than the fade out height, you would indeed get a sheared print, if larger, then the top of the print would be level with respect to the reference plane (machine true; this is the level of the X-Y plane, basically the level of the hot end carriage). Note that that still can be skew if the printer is improperly calibrated (e.g. when using 2 Z steppers or misalignment of the height on either side).


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3d print first or board design?
I am trying to make a controller(Who doesn't want that?) for PC. Just before starting the build I wondered if it would be hard to 3D print to scale of my board. So I was stuck in a paradox... 3D print first or PCB board design first?

Cons: PCB design first

Building to scale is difficult
Parts may not line up

Cons: 3D print first

Eagle design needs precise measurements
PCB may not fit correctly

Which is better to do first?

This might be the wrong forum. Please inform if so.

The question is not very clear, but without a printer you cannot print any object, so cutting from cardboard would be an option if you want to look at the size. Generally, people buy their controller boards.

Im designing my own ... have both ready but wondering which to do first so i edit the other later

Welcome to 3D Printing! I'm no expert, but would highly suggest doing the PCB design first and get a working prototype. Redesigning a 3D print to accommodate the PCB seems far easier than the other way around.

Board first and enclosure second. Seems the most sensible, unless you are constrained primarily by size. However, even so, it seems sensible to get the board working first, with space for all of the components required and then make the case.


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Which is a more accurate linear motion system?
If someone looking for accuracy, which is the better linear motion system:

Maker slide,
Smooth rod - bearing,
Linear guide way,
V slot,
Open rail

Please let me know if there's a better one other than above list.

If you're using belts, the difference in accuracy will be negligible - provided you have good quality bearings in whichever style(s).

"more accurate" is way too open: in WHAT way more accurate? in the direction? in other directions? under what loads? in which design? there is no "in general" as each of these guidances has its planned applications!

The accuracy of a printer depends way more on the design and engineering of it that on the motion system used. Using expensive super high-precision components won't make a bad design good.

This seems like a relevant topic. What does the question need to be good? Is it 3 questions for each of the 3 comments so far? Obviously the question can link to the current relevant questions, bu that else?

@SeanHoulihane it is relevant, but the question is not framed well for the Q&A format. there might be a question for each design, or there might be a question that might work out a comparison for one specific design or design goal (e.g. "I have a super lightweight toolhead in a bodwden setup. What kind of motion system would serve best?")

What I want is positional accuracy. I agree that belts play a huge role in that. How to improve belts.?? Is there any other way to move the rails?. I read in HIWIN that using ball screws with linear guide ways improves accuracy significantly. But using screws instead of belt, wouldn't it affect the speed???. I think using ball screw for Z axis is a good idea, but it's lead should not be so large that weight of the platform + print shouldn't cause it to slide down(I don't know the technical term for that).

@Athul please edit your question to reflect that. As a side note: the linear guidance has only little to do with the positional accuracy of the belts/screws. The other thing you ask about is a question of its own, a rather good one.

I used a few different linear rail systems in my build:

plain smooth rods for Z motion
smooth rods bonded to a T-haped steel base for a 1200mm Y axis (similar to those at https://cdn.automationdirect.com/static/specs/suremotionlinear.pdf)
igus "low profile linear slide" for X (https://www.igus.com/drylin/profile-rail-guide)

They all seem to work pretty well. The one problem I had was with the igus slides, which I found had a little too much play -- so each change of direction on X had a slight backlash, from the "cars" twisting a tiny bit within the rails. I improved that with careful tuning: shifting the rails a tiny bit farther apart, so they kept the cars under a little tension against the inner sides of the rail -- some call this "preloading".
I think systems that use actual bearings should generally be more accurate than spring-loaded slides. But the igus rails are still pretty good, and they're quite light, compact, and reasonably priced. I still use them, though once in a while I think about swapping them out to do a serious comparison.
The rails aren't the only factor in accuracy, though. I can't detect any play or warp in my Y rails, but that says nothing about accuracy and repeatability of motion along them. That's controlled by the motor and the belt, leadscrew, or other things actually moving them. Leadscrews, in particular, vary quite a bit in accuracy, depending on the shape of their threads, the kind of "nut" riding on them, and other factors.
You can even make your own leadscrew system from just a threaded rod and a nut -- but those threads are not the same, and they allow far more play than a real leadscrew does. Nice article on the "backlash" problem at https://www.liutaiomottola.com/Tools/Backlash.htm.

I recently replaced my linear bearings with Igus polymer bushings. I didn't find the same thing. The bushings were, if anything, a bit tight. I was more worried about them sticking on the rods than there being too much play. Your solution seems like a reasonable one, though, to take up the slop.

I have a 3D Printer (20 x 20) using linear guide way, a clay print(700 x 700) using V-Slot and a CNC using makerslide. I dont't have a positional encoder to check repeatability


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Filament isn't going into the Bowden tube, instead it goes "into the room"
The pictures explain my problem. I have already tried to reduce the retraction but that showed no effect. Thank you for your help.
The effect is a total stop of the print (no material is extruded).

Creality CR 10
Cura 3.4.1

I recently added this new feeder aluminium block because the 3D printed stock version was bad quality.

Can you also add what does work, what changed since your last good print, etc.

Does it seem to anyone else that the teeth marks are excessive in the filament, as if the tension idler force is set too high?

I've always run my extruders at max pressure and haven't seen any issues related to it.

What printer is this? and is the hotend running?

@Trish It is a Creality CR 10. The hotend is running. Usually the raft is printed without any problems but afterwards the filament starts to fail.

This is typically caused by resistance in the tube or hotend but in your case it appears to be mostly caused by a very poorly designed extruder.  The filament needs to be constrained closer to the drive gear.  You may be able to drill out the PTC connector to allow the PTFE tube to reach closer to the gears or print a spacer to fit in between but you need to support the filament in that gap.
You can try raising the hotend temperature as a band-aid until you can fix the problem, do not exceed 240 C if you have a PTFE lined hotend. Long retractions can also pull molten filament into the cold zone where it solidifies and make extrusion harder.
As an example, here is a picture of a Bondtech BMG extruder.  Note how the extruder constrains the filament path all the way from the drive gear to the hotend entrance.  While this example is extreme for normal PLA/PETG/ABS, it is required for flexible filament.  A 4mm gap (or closer) should be fine for PLA/PETG/ABS or other hard filaments.

Thank you very much. I just installed that "upgrade" extruder (aluminium) and I'll try switching back to the stock version.

Your extruder is encountering resistance and the filament path is too open.
Your teeth seem to be biting in too hard. Loosen up your tensioners a bit.  Teeth biting too hard deforms the filament. Does that rough looking stuff feed through the tube smoothly? Any rough bits can catch anything in the filament path?
It is preferable for the motor to skip when there is a problem, rather than waste filament, so maybe turn down your motor vref too.
How well does filament feed by hand, and with no teeth marks on it? Significantly better, or about the same? Does the bowden tube have and kinks or bends in it? Those effectively shrink the diameter of the tube and really put the squeeze on filament passing through.
Does your hotend have proper thermal preparation? Lots of insulation on the block, and a good strong cooling fan? Too little insulation will cause too much power to be used, and raise the melt area. Too little cooling (especially with PLA) will also allow the melt area to rise (called heat creep). If pointing a big fan at the printer fixes the problem, it's probably hotend cooling related. If it makes it worse, it's hotend insulation related.

The bowden tube is perfectly new as well as the whole hotend (it works perfectly) . I will try the difference of feeding with and without teeth marks. Thank you for your help :)

There are two parts to this problem.
First, the extruder is meeting too much resistance in the print. There can be several causes, from the first layer being too low, a blocked nozzle, too low a print temperature, or printing too fast, so the viscosity of the filament just makes it too hard to pass through the nozzle. Usually, several of these will be in play together.
Second, the extruder design allows the filament to bend as it leaves the drive gears. Typically, this problem is seen most with flexible filament because that will obviously collapse more easily under compression for a given unsupported length.
The trigger is the first group, the second part determines the resiliance of your setup to this problem. Once the break point is reached, there is no recovery. You can retract the filament, but trying to resume the print will just set the extruder back to the same absolute position.
First, check that you can extrude OK in free space, without any drop in temperature. Also check your extrusion steps calibration - if you're extruding 110% of what the print is expecting, the extrusion back pressure can build up to a point of failure. Check the first layer, check the calibration.

You just have to cut the filament at a 45° angle. Then push down the extruder and push the filament in. Then heat up the nozzle. Next, hand feed the filament until the filament starts oozing out.

authors: rтемный Лорд


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Bowden tube clog
There's PLA filament clogged in my Bowden tube, is there a best practice for cleaning it out or do I need to replace the whole tube?
Also, the couplings are totally stuck, so I guess those would need replacement too or are there ways to get stuck couplings off?
Click here for a video.

I use a pipe cutter and cut the last quarter inch off - what I want to know is why it happens in the first place

As a short-term fix,  grab a twist drill bit that is on the order of  1.5 mm diameter (assuming a 1.75 mm tube).  Using a hand drill, slowly and gently drill out the clogged filament.  Obviously you want to try to avoid scarring the teflon lining, so better to use the thinnest drill that will work.
With a little training and a little luck, you'll get the clog cleared. I would recommend removing the nozzle first so that the chips don't fall into the nozzle.

Usually, the Bowden tube is 2 mm in inner diameter

@Trish 1.9 mm is also pretty common these days.

If you are able to force the filament from the interior of the bowden tube without causing damage to the tube, you will be able to determine the cause of the clog. My bowden tube clogged recently, but it was because I left the system idle with old filament inside. The filament broke from brittleness and the edge of the broken pieces managed to wedge against the tube.
I was able to use a "healthy" piece of filament along with great force (pliers pushing close to the tubing end) and remove the damaged filament.
Once removed, the new filament slid easily within.
Your PTC fittings may not have to be replaced if the tubing is not damaged inside and if the existing spacing meets your requirements. A PTC fitting has a ring of teeth which gouge and/or grasp the outside of the tubing preventing removal. It is frequently necessary to push the tubing into the fitting, then compressing the release ring followed by pulling the tubing.
The PTC fitting at the end where only the filament exits is probably a stock fitting. The fitting which has the bowden tube extending through it has been drilled and may be challenging to find. Your best source for such a fitting is the original manufacturer.
It's clear in the video that the threaded portion of the two fittings are different.

The problem is I can't force the filament anywhere. It's totally stuck even with pliers. The ptc fittings are also totally stuck in place even when the lock mechanism is released. I just bought a replacement

that's good that you have a replacement. With such damage, even if the filament was removed, it would probably give you problems in the future.

I haven't tried this, but it's possible to melt filament inside a PTFE bowden tube; some have even used this for splicing filaments. The examples I saw were over a flame but controlled heating would probably be better. If you do this, weld the clog to another piece of filament then push or pull once it's started to cool.

Most standard filaments soften at 200 °C, meaning a pot of near-boiling water should soften whatever is stuck, allowing you to either fuse another strand of filament to it or use it to push it out of the tube.


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Can I reuse 3D printed parts?
I need to show a demo to people on a daily basis. But every demo is for a different 3D printed part.
Can I reuse the material? Is yes, what is the maximum number of times that the material can be reused?

Hi user144627 and welcome at 3D Printing.SE! Please clarify your question; are you implying re-use of the filament spool, or re-using the printed parts themselves?

As it is asked, I barely grasp what you want to ask for as you are missing on the description of the problem. The better you explain the question, the better the answer will be.

I checked amazon , the price per lb is 20 usd

@user144627 - The price per lb for what? Most new filament is not that expensive on Amazon (off-hand average being $15-20 per kg). I'm really unclear about what you're asking now. Is there anything you could add to your question to clear things up for us?

What good is a demonstration if you don't show the printer in action?

@user144627 I meant that the cost for raw plastic, that is, plastic pellets from which filament is made, is around $2/kg in bulk. The main cost of filament isn't the cost of the plastic, it's the cost of turning the plastic into filament. So my point is that when you discard 1kg of printed parts, you're not throwing away $20 worth of filament, you're throwing away $2 worth of scrap plastic.

I ground up some prints and extruded them into new filament. The quality of recycled filament is not very high so I would not recommend it.
As pointed out earlier, the shredded bulk material you would create from your old prints would cost more in time and energy to produce than buying new raw material (pellets, not filament), and you still need to extrude it into filament to be able to use it in a printer.

authors: Андрей Береговой


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How to create 3D printing file (e.g. STL, OBJ and IGES etc.) from DEM?
I have DEM with 1 m resolution, how can I create 3D printing file (e.g. STL, OBJ and IGES etc.) from DEM?

Welcome to the stack. I suggest you take the [tour]: "What is best" questions are not allowed on the stack usually, as recommendations don't work in the Q&A style it tries to serve. If you would reword to "How to" that IS an answerable question.

This question has been answered on a sister site, GIS Stack Exchange. It's a rather comprehensive answer posted, which means it's impractical to summarize here.
GIS answer
The answer does indicate that a plug-in for QGIS software is needed in order to accomplish this objective. If you do not use/have the QGIS software, my answer is invalid.  All three answers to the question linked above appear to point to the same program/plugin.

Thank you for the help. I was tried that QGIS plugin before when input DEM is  5MB the output is around 700MB. When I try bigger size DEM the plugin stop working. So if I want to deal with big DEM is there any better solution?


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Cura acting REALLY sluggish all of a sudden
I've been using Cura on my computer for a while now, (at least a month) but all of a sudden the entire interface has become noticeably sluggish. Whenever I scroll through the profile parameters list or the settings visibility dialog, the list lags and doesn't fully appear.
I'm at a loss to explain why this is happening.

Not the machine itself? Have you looked at your performance monitor to see if there might be something in the background? Have you tried reloading Cura?

Surprisingly, @Pᴀᴜʟsᴛᴇʀ2, there isn't anything in Tskmgr (or Performance Monitor) to suggest there is a bottleneck outside of Cura. Plenty of free CPU cycles, an abundance of free RAM, etc.

Wrong settings on the video or your video driver has changed. Another thing is over heat on your CPU or chipset Or some sectors on your hard drive are damaged. :p 21 years repairing PC's

Uh... a) what such driver settings? b) doubt it's CPU temp, not thermal throttling c) SSD, not HDD.

does any other GUI-based tool show sluggishness?   Have you tried clearing out various log and preference files related to Cura?  Did you verify you don't accidentally have more than one instance of Cura running?

@CarlWitthoft No. Cura is the only one acting this way.

Cura has and/or had a memory leak (or some other similar phenomenon) that occurs if you leave it running for a long time.  I have left Cura running for days or a week or three and eventually ran into a similar problem.  One could infer that you've left Cura running for a month, though it's not clear in your question.
I update Cura a few weeks ago (maybe a couple months) and noticed that it had a substantially smaller memory footprint, so that tells me they are working on memory management.
Looking in the release notes, you can see that 2 versions ago they implemented analytics, which is possibly a reason for the poor performance.  You'll also notice a lot of new features and bugs fixed int hat version.  That means a lot of work went into it.  Coupled with the short time to another release, and I think they're working on  fixing things.
For a more precise answer, include details and specs about your PC, internet connection, mother's maiden name, SSN, etc.  I'm kidding about the last 2, but it is probably a PC or software problem that you're running into.

Ah! That could definitely explain it; I do leave Cura open for extended periods of time, sometimes as long as a week. However, a memory leak would be odd, seeing as how my system isn't at capacity when this happens.

Cura installs itself as a 64 bit program, but it's less than 400k and yet consumes ~250mb on startup.  It has more DLLs than you can shake an army of sticks at.  Who knows their bit depth, memory management, etc.  It looks like there's some python in there too, so the python interpretor or one of those scripts might be causing problems.  There are a lot of opportunities for failure in all of those parts and pieces of code, including cascading failure.

I'm not too familiar with the ramifications of what you just mentioned. How does Cura being 64-bit impact its likelihood to have memory leaks?

64 bit means it can use more than a few GB of RAM (the limit is 3-4gb).  Importantly, all of that first few GB is reserved for 32 bit apps, so they have to play nice with each other (unless newer OS's fix that).  I notice 32 bit Firefox become extremely sluggish between 2 and 3GB of RAM usage, but restarting it fixes it.  You said that Cura isn't standing out for memory usage, but didn't provide numbers.  When I had problems with Cura, it was consuming lots more RAM than normal, indicating a memory leak, or some other memory-related problem.

Oh, Cura never uses more than 500MB of RAM. Question updated with a screenshot of tskmgr.


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Ender 3 is capable of food safe printing?
I've been looking into the viability of manufacturing a replacement part for a kitchen blender that has a broken part. I found this page that talks about what makes a print food safe. One of the items mentioned was:

... a brass extruder may contain lead, and lead contamination can cause some nasty health problems. ...

I own an Ender 3, and I haven't replaced the nozzle yet. How can I tell if my printer is capable of creating food safe prints in its current state?

Note that the concern about lead is mainly theoretical; nobody has demonstrated that you can actually detect the lead in finished prints. The nozzle has around 2% lead. How much of that makes it into the print, and then how much of that makes it from the print into your food? Probably not that much...

While mainly theoretical, food packaging manufacturing standards are very complex.

I'm voting to close this question as off-topic because this is a metallurgy question, not a printing question

@CarlWitthoft Sure, but it is directly related to 3D Printing, How is that not applicable here?

When you say "manufacturing a replacement part", are you talking about something you would do commercially and sell the part, or just a repair for your own blender? If the former, your question is about regulations; if the latter, it's about understanding any risks well enough to make an informed decision.

I would like to state that I am in the in-mold labeling company. Here, we print the mechanisms to carry the labels on the printer using powder material. The material used is completely food-grade. The powder used is PA2200.

Food packaging needs to comply with regulations. One certification agency informing about these (and their service to certify for them) is TÜV Süd, another is SAI global. A summary of the GFSI can be found here. Inform yourself about the standards you wish to apply! The stack can not give legally binding answers.
No
The Ender 3 is not approved to produce food products (and not usable for them out of the box) for lack of certification. In the design it comes from the box, you need to replace a lot of parts for food rated ones:

The whole print head/bed need to be swapped out for food rated parts due to the exact composition being not known. They might contain banned materials. As a result:

You'll need an all-metal hot end that can be taken apart for cleaning up to the standards if needed.
You'll need a food rated PTFE tube.
You'll need a stainless steel nozzle that complies with food grade manufacturing demands.
The extruder gear should be stainless steel as well.
You'll need to add some part to prevent filament shreds/flakes from the extruder to enter the print area as they might act as contaminants or carry germs.
Similar measures have to be taken for the wheels on the hot end carriage, as it might shred.
As you include a volume of air into the print, you are likely to be demanded to print under a protective atmosphere to make sure no germs are inside the print.
We do not know the composition of the build platform, so you'd need to replace the back surface with something that is food rated.

You'll need to post-process your prints as smooth as possible, especially because of the small edges at the layer boundaries, which can and will act as spots where germs can grow.

This can be achieved with a material that is smoothable in some way.
Alternatively, a sealing lacquer/coating that is food safe might help here.

Remember, safety first:
Printed plastics that are rated for food are not necessarily food safe because of the quality or blend of the material. PLA and ABS can be made food safe, but that is usually pure material. We usually don't know what kinds of fillers or coloring is in our filament. The heating process might destroy the colors or fillers, which in turn might make it unsafe.
Indirect manufacturing
If you are stone set you want/need, you can use indirect manufacturing: you don't print the actual object, you print a mold that makes the actual object. Clay and other ceramics can be made food safe very easily and they can be shaped with plastic molds.
Boxing
There is also another way to facilitate food safety in a 3D printed container, and that is checking where the food will actually make contact. For a lunch box, that is the inside. We could line this inside with a food safe surface, for example placing a steel cup in our plastic cup-holder. Accessories like a cup holder or a decorative container for the actual food container do not need to adhere to the food packaging regulations themselves.
Exposure time
I know this is all looking at industrial food rated production. The Primer given in the question does include a point about time the product gets into contact with the food - if there is just a short exposure, you might get away with it, but it doesn't make it certified food safe. Another good read in this regard is this short discussion about the Pros and Cons.

they specify how a process has to be in some sort. When foaming boxes for food transport, this has to be done under protective atmosphere for a rupture of the foam would release trapped germs or contaminants. Whenever something could be brought into the product, it needs to comply, so my understanding

@TomvanderZanden Also, most of the points I mentioned are in the pimer the OP mentioned.

But there is a huge difference between "Certified food -safe"  and "is actually perfectly safe for you to use at home" .

@Kilisi no. You need a printer that is certified. Which basically none but a few industrial machines are. Think Stratays-industrial.

@Kilisi there's a line between "probably safe" and "certified safe" - I can't help with finding that, you need to do your own research there.

Yes you have to change brass nozzle it contains lead.
If you are planning to print in PLA don't do that because  PLA filament we are using in 3D printer are not food safe it contains some nasty colour dyes which are not food safe. Consider some special food safe filaments available in market. I think extruder gears are also made up of brass. Consider also changing them.
Steel extuder gears are available in market like below

Nice note about the contributions of brass extruder gears, but the question was specific to the Creality Ender 3.and whether or not it would need new extrusion hardware.

Ender 3 nozzle and extuder gear are made up of brass.Before printing any food safe print you have to change nozzle and extuder gear.

Just not scientifically correct.

Parts printed in pla are food safe, as pla is usually made from corn starch. However, most 3d printed parts would not be food safe for they have many crevices where bacteria can grow. Also, if you printed with materials other than pla with that nozzle, traces of the material (which  would make it into the print.

Do you know what kind of paints and colors are in PLA? Pure PLA is food grade, but you get a PLA blend as a spool. This goes for all materials btw: while ABS is generally food safe, Printing filament isn't always.

great point about sub-layer pockets, which create a hazard even if the parts and material are food-safe


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What is this weird support line doing in this print?
I am a newbie to 3D printing and ran into a weird infill line on my second 3D printing object on a new Qidi X-Pro machine (which works great). I've included a screenshot of the infill line, which is deliberately printed the full height of the object. I'm thinking this line has been deliberately inserted by the Qidi slicer for some reason, but I have no idea why. Do all slicers generate these kinds of lines? If so, why?

Hello Kevin welcome to 3Dprinting stack exchange. Seeing your image seems to be your are printing with a high temperature with out retractions; there are a lot of melted points. Follow 0scar's recommendation.

I do not know the Qidi slicer, but if you look closely, you will see this line is thinner than the normal support infill lines. You could try to visualize the G-code in a viewer, usually this can be done in the slicer itself, but online viewers are available. The viewer will not only show the printed lines, but also show moves by the print head (usually in a different color). You can check whether this extra line is actually printed or a move. If it is a move, this extra line is caused by your hotend which is leaking when it moves. You need to properly tune the hotend with respect to the retraction settings and temperature. There are numerous retraction test print objects to find on the internet.
Depending on your slicer settings, some slicers are able to define where each layer starts printing (e.g. random, or start at sharp corner). The fact you see a support structure "printed the full height of the object" tells you that each layer starts at the same position. It is not uncommon in uniform simple parts where each layer starts at the same position (X/Y) as this is instructed by the slicer setting. In Ultimaker Cura such an option is called Z Seam Alignment.

Bottom line, all slicers will do this when your printer is improperly tuned (incorrect settings for e.g. print temperature, retraction, coasting, travel speed). It is up to you to find the correct settings, test print objects help you with that.

I agree, that is not support but the leaking filament on the path from the end of infill to shell!

Thank you to everyone for your help. This pic is from the second object print that I ever did. I was using the slicer defaults (plate 50C, nozzle 0.4mm @ 200C, 1.75mm PLA, and I think that retraction was set to 1.5mm by default.) I tried increasing the retraction to 2.0 mm (before this post), but it never made any difference. It's odd to see such a solid wall from a leaky nozzle using 200C and only in the one place (apparently moving from infill to outer wall, which is an interesting idea itself.

I switched slicers from Qidi to Cura and noticed a big difference in print quality using the same temperature settings for plate and nozzle. Print speed was 40mm on the Qidi slicer and I set Cura down to 40mm too (20mm on outer walls, 40 on the inside, and it uses 100mm/s !! on travels). Cura does better path planning and controlling but I still see odd walls in various places. I will try to collect and post more images. Thank you again for all your help.

@Kevin A higher travel speed also helps minimizing resulting stringing (I forgot about that one!), I'll add that to the answer

Hi Oscar, thank you for the tip! That's the opposite of what I've been trying. I reasoned that slowing the print head down would give better adhesion, etc., so I set it down to 80mm/s to see if that helps going forward. Please see my other post where I (possibly incorrectly) reason that a high travel speed prevents adhesion in one corner of two prints. I can see that tuning will take some time. Thank heavens Cura lets me save profiles! I read a book called 3D Printing Failures (very good book) to get an education, but I still get stuck!

You can set one speed (slow) for printing moves and another speed (high) for non-printing (or "travel") moves.

Here have a posible solution -> How to remove unwanted filament trails from sharp corners
I think, that can be a combination of z-hopping and combing-mode in the slicer that you use.

Hi welcome to 3DPrinting.SE! Stack Exchange sites are not ordinary forums of threaded messages, but focussed on questions and answers. Your answer is sort of a link only answer with a hint to a possible solution without going into details why that might be the solution. Please take the [tour] for some more information. Thanks!


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Infill failure at the far corner of two different prints
I am a complete newbie at 3D printing (although learning fast). I switched from the default Qidi slicer to the Cura slicer on a Qidi X-Pro machine (which is wonderful). Using: plate 50 °C, 0.4 mm nozzle 200 °C, 1.75 mm PLA, print speed 20 mm/s outer wall, 40 mm/s inner wall, travel speed 100 mm/s (the cura default, I think).
On two different prints, the same far corner (front left) had initial infill problems. Does anyone know why, or how I can solve it? My working theory is that the nozzle shoots across the whole print at high speed to start again at that corner and sometimes the infill filament doesn't bite enough to stick.
Eventually one of the infill layers gets a bite and the rest of the print is fine. But it's disturbing that it occurs on different prints. (I carefully level the plate before every print, so I don't think that's the issue.)

UPDATE
In another question here, turning the Cura combing setting off solved an issue. It probably solved the issue described here, too, or at least contributed to solving the problem described here.
My theory is that with combing on (as it was for that question), the oozing pulls filament out of the nozzle during the travel, so there's not enough filament at the destination corner to bite and bond to the corner wall. Turning the combing setting off seems to have solved the missing infills in the corner. It also greatly improved the quality of the infill walls, too, which relates to the problem described in this question.
UPDATE: Here's a paragraph from a forum posting here that explains how oozing caused by combing can result in "underextrusion effects." That's what I think is happening in this post - the nozzle gets to the corner, but it has no filament to bite and bond with the wall. Credit to @0scar for giving me the forum link. Quote from the link:

Even on interior layers, combing as implemented in Cura is a bad idea,
  as it doesn't perform retraction, and that can result in the head
  oozing as it moves, especially as each time the head crosses a line of
  infill it can tend to pull our some plastic. You can also get some
  long moves (e.g., all the way around the curve of a 'C' shaped object
  when moving from one side of the opening to the other). This can
  result in the head being empty when it starts printing the perimeter
  again, with resultant under-extrusion effects.

Now that you are using Ultimaker Cura, the default (probably hidden) parameter Z Seam Alignment is set at Sharpest Corner, so it will always start in a sharp corner. The default retraction settings are pretty high in Ultimaker Cura (I think about 6.5 mm as default Retraction Distance). What happens here is that the filament is not available for printing in time (this is dependent on the extruder type), so the distance should be less than the current value.
It is highly recommended to print a retraction test to find what is best for your setup. For me the 6.5 mm works very well on my Ultimaker 3 Extended and my large custom CoreXY printer as they both use a Bowden extruder setup using 2.85 mm filament, this can be different for your printer. Choosing a different Z Seam Alignment option, e.g. random prevents the use of the same location at every height, but could result in a less aesthetic print.
Furthermore, you could try to visualize the G-code in a viewer, this can be done in the Ultimaker Cura slicer itself, but online viewers are available. After slicing your product, change the combo drop down box from Solid view to Layer view to show the sliced object. Nowadays there are 2 sliders to interface with the model; the vertical sets the layer, the horizontal the progress of the layer. It is advised to play with this to understand how your print is actually printed.

About your settings, print speeds are not high (could be increased), travel speed is fine (is only for non-printing moves). The brim is looking good and the level of your bed is also good.

Hi Oscar, I checked and you are correct! The default retraction was 6.5mm, so I reduced it to 4.0mm. I will report back after my next print. Should I change z-seam alignment to Shortest or Random for better results? Thank you

PS. If the problem is caused by the filament not being ready enough to bite in the corner, why isn't Cura smart enough to push the filament out the right amount in the right amount of time? It knows that it retracts 6.5mm, so shouldn't it extrude 6.5mm (or whatever is best) to get a bite? I really appreciate your help. It sounds like you should have a book out that I could buy too... :-)

@Kevin, the problem is that right after the +6.5, the filament is melting and being forced through the nozzle. This takes a small amount of time, and is exacerbated by any loss to oozing at the start of the layer change. These are really small effects, but enough to affect some prints.

@Oscar, it looks like you updated your answer with a retraction test. Thank you - I didn't even know there was such a thing. Perhaps you could point me to a checklist of all such good tests to set up my printer? Does such a list exist? Sean, thank you for your reply too. I thought for the corner problem I would reduce travel speed so that the head allowed more time to bond before taking off. Also I reduced retraction a bit to give more output in the corner (didn't help much, IMHO), and chose "Random" for starting each layer so the starts didn't add up in the same corner.

I still have some hairs and strings (esp between short 5mm support sequences on the build plate), but now at least I know about retraction tests! I will do my homework and report back. Thank you both again.

I marked this as an answer because it lead me to the answer, as described in this related post here. The two questions are two very distinct symptoms of the same underlying problem (or so I think, as a newbie).


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Anet A8 - SkyNet3D freezes randomly at boot
I have a problem with my Anet A8. It is a little strange because it does not always happen.
When I turn on my printer, it freezes on boot in the second splash screen.
If I turn off and turn on several times, the printer works OK.
The printer firmware is:

SKYNET 3D - V2.1 - BASED ON MARLIN RC7-BUGFIX - FOR ANET 3D PRINTERS

It was modified by me but I promise that I did not touch the boot section.
Could the Anet A8 motherboard be dying ? (before this issue it worked perfectly)

Update 1:

I am changing some wires (power supply and hot bed). I think it has improved...
In my opinion, I think that is better change all wires...

Update 2: Some wires were black :-( (I changed them and the printer run well)

Skynet3D is an obsolete firmware! Please install a more recent firmware, e.g. Marlin.

The Anet A8 is a low end printer which works better after installing a better (read safer) than stock firmware (stock firmware does not have thermal runaway protection which is considered to be a hazard). It is good that you flashed another firmware that does have thermal runaway protection.
The electronics of the Anet A8 are also questionable, the stock connectors are not rated for their task and wires could have been of better quality and thickness.
Now that your older SkyNet3D firmware does not boot properly anymore, it would be time to check all the leads, possibly use new wires of proper gauge and flash a new version of a more recent firmware. SkyNet3D has been forked from Marlin Firmware and is no longer maintained as all functionality has been implemented for Anet printers in the Marlin sources.
If your printer still is giving you problems then when booting, a new set of electronics (e.g. board and steppers) would help out.


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Ball screw: Maintaining Z axis position when motor is OFF
I'm building a 3d printer of size 500 x 500 x 500 build area. For the Z axis, I'm planning to use this Linear actuator.
The maximum weight Z axis might encounter is 15 Kg due to it being a clay printer. A single linear actuator can, according to the specs, lift 10 Kg. So I'm planning to use two of this.
My question is a ball screw of pitch 4mm or 5mm, will it be able to Maintain it's position when the motor is de-energized under a load of 15 kg shared by two systems.
What effect the diameter of rod has on it??
Is there any way to find that??

The question about load is design dependant. What kind of design you want? A Prusa "printhead moves up" or something like a Hypercube with the print platform moving down? Can you give us at least a sketch?

My question is a ball screw of pitch 4mm or 5mm, will it be able to Maintain it's position when motor is deenergized under a load of 15 kg shared by two systems.

The detent torque of a typical NEMA 23 stepper varies between around 3 and 7 N·cm. This is the torque produced when the windings are not energized.
Using this leadscrew torque calculator, you can find that the torque required for a 12 mm diameter, 4 mm pitch leadscrew to hold up a 75 N load, is around 5 N·cm - assuming there is no friction. If there is friction, then the required torque will be lower.
So, the torque required is almost equal to or possibly even higher than the detent torque. Therefore, you should not count on a de-energized motor holding up the build platform. In practice, you might see that friction is enough to hold up the build platform, but that any disturbance (such as somebody bumping into the printer) is enough to get the leadscrews to start spinning and have the platform drop like a rock.

What effect the diameter of rod has on it?

Increasing the pitch also increases the torque required (so, go with a lower pitch leadscrew). The diameter does not affect the torque directly, but having a larger diameter increases the friction and so is beneficial.

This is all good and well, but one could also increase the load bearing ability with some design tricks, for example not mounting the Z straight but slanted. This does change the steps/mm for the benefit of turning some of the vertical weight force into horizontal force trying to shift the plate, which will be taken care of by other parts of the construction (the rails)

@Trish That's not what the question is about though. Besides, I'm not sure that's a very practical design.

it is if you need to reduce the load desperately and can use a pin-in-slot or a slider-on-rail as the connection between the Z-Motor and the bed. It is not the most simple solution, but uses the Aristotele law on levers: we get a longer way for each increment of height, but we need to apply less force. With a 45° slanted Z-rail one could achieve a theoretical bearing of double the calculated load, but one has to account for the same force trying to move the bed horizontally, demanding a very stiff back rail/side rails to counteract

a side effect of tilting the Z-actuators would be to allow smaller Z-stepping as the number of steps/mm increases.

@Trish Note that comments are not for secondary discussion or providing alternative answers. The question only asks whether the given leadscrew will support the given weight, and my answer addresses that. It doesn't ask for alternative solutions.

Using zero coefficient of friction in your calculations would be inaccurate. No ball/lead screw mating will have zero friction. Depending on the material used in both will modify the friction coefficient. Using the lowest measurement given (0.04), you'd have 9.59 N-cm of torque, going up to 28.9 N-cm on the upper end. With two stepper motors, this would be doubled. Secondly, the linear actuators the OP showed also have guide rails. This, too, increases the amount of holding power of these when the motors are not energized. Realistically, I don't think it'll be an issue to hold things up.

@Pᴀᴜʟsᴛᴇʀ2 I have a printer that uses two steppers (albeit nema 17) with 8mm pitch leadscrews to hold up a small bed (200mmx300mm) and has accompanying linear guides. I know from experience that it drops like a rock if you even look at it the wrong way when de-energized. Admittedly I have double the pitch and steppers with half the detent torque, but my bed only weighs around 1-2kg. I would not rely on the friction of components that are supposed to provide smooth motion to hold my 15kg print bed in place.

@TomvanderZanden I couldn't find threaded road with large dia and 1.25 mm pitch. Currently I'm using 8 mm dia 1.25 mm pitch. It holds position but I know in time it's gonna bend. Also problem with threaded rods are they wobble a lot. I think I'm doing something wrong when calculating torque. With pitch dia = 12 mm, Force = 75 N, thread density 6.35 in coefficient of friction = 0.2, The value I got was 14.1 and -4.32 Ncm

Will it be more stable for 16 dia and 5 mm pich

@Athul The larger pitch means increased torque, making it less stable. The bigger diameter means more friction, making it more stable. It is impossible to know which one will be more stable without knowing the exact friction coefficient.

@TomvanderZanden Can you explain how you got 5 Ncm as torque. With pitch dia = 12 mm, Force = 75 N, thread density 6.35 in coefficient of friction = 0.2, The value I got was 14.1 and -4.32 Ncm

@Athul Because I used a 0 coefficient of friction. 0.2 is on the high end of possible friction coefficients. We don't know the exact friction coefficient, and I don't want to make any guesses. Therefore I was very conservative in the calculation. If I use the calculator with a 0.1 coefficient of friction with the parameters from my own printer it tells me it should easily hold up the bed, yet it doesn't.

@TomvanderZanden Any idea what negative value specifies. Is it for just representing down ward torque?? If Calculated value is negative and detent torque is positive, what does that mean?

If the calculated value is lower than the detent torque then in theory the axis will stay in position.

Let's pull out physics...
We have a load of 15 kg, which is a weight force of 147.15 N, PLUS the bed. Let's take into account about two kilograms of bed and cables that need to be carried too, so 166.77 N. That is in the margin of error of 150 N, which simplifies calculations a lot, so let's just assume that. $$F_{g_\text{total}}=166\text N$$
Let's assume we use 2 lead screws, one left, one right, and both go exactly vertical. Then we get, that the load is half, so $$F_{g_\text{per lead}}=83\text N$$
Now, let's look at the specs of the lead screw: Pitch is 4 mm, Diameter is 12 mm. For the calculator we need Pitch Diameter (=Diameter) and the Thread Density (=Threads/cm), so I pull up the pitch conversion table and look under 4 mm Pitch. Also, we check the table and grab an intermediate "steel on steel" friction coefficient of 0.2 for dry, or 0.15 for oiled.
The results I get with those numbers are $\tau_\text{dry}=-0.0478\text{ Nm}$ and $\tau_\text{oiled}-0.0222\text{ Nm}$ respectively. That's the torque that needs to be applied to our motors to move it down. Wait, that number is negative?! Yes, it is, and that is actually not a bad sign:
Let's assume a higher high pitched thread. Like, REALLY high: 1 rotation per inch. One thread. It is pretty much "straight". The calculator drops us a result of $\tau_\text{dry,super-steep}=0.273\text{ Nm}$ for 0.2 friction coefficient that the motor would need to keep working against to not have it moving.
So, when do we stay, when to we move? Well, if $\tau_\text{calculated}>\tau_\text{detent}$, it moves down on its own. if $\tau_\text{calculated}<\tau_\text{detent}$ it stays put for friction. The $\tau_\text{detent}= 0.027\text{ Nm}$ for a single length NEMA 23. Our negative Torque just means we need to apply some extra torque to overcome friction before we get the bed going.
That means, with the 15kg load (+2kg bed), it is to be expected that the bed stays up. If you would use a more slick combination of materials, you might start to slide.
Always remember, there is the caveat of overcoming the detention strength with a short impact, or applying force directly to the rods when bumping into them. If the machisnism starts to spin, the friction from the nut on the bar and from the motor is all that can provide a breaking to the machine.

Adding to the other more scientific answers here. The backdriving force will move the lead screws depending on the stiction between the lead screw and the nut. If it was friction less then it will always slide. Basically you need to keep the lead screw from turning while the machine is off. You can make a basic electromagnetic clutch which will add some resistance to turning by using double pole double throw relays to short the motor leads to ground when the power is off. You can test this yourself by just connecting all the lead wires together and then try turning the motor spindle by hand.

https://en.wikipedia.org/wiki/Electromagnetic_brake

Without a plan for how these devices work or are constructed, this answer is of quite low quality. Please consider expanding it by linking to relevant literature or plans, or including such into your answer.


text:
FreeCAD: Scene doesn't look 3D
I finished a 3D object for 4 wheels, but something seems wrong with the final scene to me:
The nearer wheels (#1 and #2) appear smaller than the far one (#3 and #4), and the distance between wheel #3 an #4 seems longer than between (1) and (2), like you can see in this picture:

I want to achieve the scene like this:

How to do that in FreeCAD?

Welcome to SE.3DP! Your question is not specifically on-topic for 3D Printing Stack Exchange, it may be on topic for another Stack Exchange site.

You might want to consult the manual at https://www.freecadweb.org/wiki/Getting_started

FreeCAD, like many other 3D programs (including blender) does use Isometric/Orthographic display as the default displaying option as it allows to see on one view if some lengths or angles are "equal".
In many cases, a perspective view can be toggled on to allow visualization in a room, especially for architectural one.
In the case of FreeCAD with all its options, this option gets swamped out of the user's field of view sometimes, and the documentation is not that easy to navigate without a proper keyword, making the right thing slightly hidden in the documentation. But once you know it, it should be obvious:

View > Perspective View toggles to perspective view.
View > Orthographic View toggles back to isometric.

CAD programs uses parallel view not perspective view.
So the length of 2 objects with the same length are displayed as 2 objects with the same length on the screen.
This is better for constructing stuff.

while you explain WHY Isometric/Orthographic is chose, it does not explain how to switch to perspective


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Resources for making 3d scans of electrically conductive materials?
I would like to make a 3d scanner for accurately modeling very small metal parts.
I figured I might be able to take advantage of the fact that metal conducts electricity, and avoid using light. This might be cheaper, easier to make, and wouldn't get thrown off by shiny surfaces.
Basically, I am imagining an object on a rotating stage, and a movable "feeler" probe. The probe is moved towards the object, and when the probe touches the metal object, a circuit is closed. The distance and angle of the probe and object are then recorded, and used to model a cross section of the object.
My question is:
Is this technique already being used? If so, where? Is there a name for this technique? What resources should I look at for researching this?

Welcome to SE.3DP, but I'm afraid this question is not within the scope of SE.3DP, please read What topics can I ask about here?.

@0scar, arguably, this comes under technology, although I feel that it is too niche to get a good answer here (doesn't make it off topic, just unlikely to be answered). 888, you need to define small. A physicist/chemist/biologist might suggest Electron Tomography (and related techniques) as being well established solutions.

While I'm not sure if it's off-topic, I do know this technology is used regularly in the machining world (CNC). It's called Touch Probe Scanning

I suspect you'll find the accuracy and precision required of your probe (and the servos which position it) will lead to a rather expensive project.  And a very time-consuming method, given that you basically have to trace the entire object in 50-micron stripes.

The target of the question is in the question, but the way how it is asked is not (imho)

I have heard of similar scanning not using the electrical connecting but using the capacitance of the metal object to detect it. Capacitive Scanning works by detecting a metal object near the prob so the prob doesn't have to touch the object being scanned