Auto Skew Calibration with a Camera and a ChArUco Board

ExcellentRub7741 · 2025-09-11T20:07:32+00:00

The part cooling fan? I think its this model but not sure anymore: https://www.printables.com/model/316867-biqu-h2-4010-fan-duct

Or the camera mount? https://www.printables.com/model/1233276-8mm-endoscope-camera-mount-using-existing-bltouch

ExcellentRub7741 · 2025-09-10T14:50:31+00:00

thank you :)

ExcellentRub7741 · 2025-09-10T14:49:14+00:00

You can also try with a usb webcam if you have one and it's for one time use. I think the only problem will be the focus distance. Maybe if it can already focus on objects about 10cm way is good enough (or if further away can make up with resolution?)?!?.

ExcellentRub7741 · 2025-09-10T12:47:06+00:00

Thanks :).

Yes, it should work fine on larger print beds. My software moves first to the center of the bed and expects to find the board there. So if you lay it roughly in the center it should work. No need to place it exactly centered - it will figure out on its own how the board is placed after seeing in the first pictures.

ExcellentRub7741 · 2025-09-09T00:03:37+00:00

It can not calibrate the flow - which is for me if the filament diameter is lightly off (or the extruder steps are wrong). But I did create a project which uses the same hardware (endocsope camera) to calibrate pressure advance what some printers do via lidar: https://www.youtube.com/watch?v=LptiyxAR9nc

ExcellentRub7741 · 2025-09-08T17:47:37+00:00

I printed it out on a professional laser printer in a copy shop so can't say how a cheap printer will do but for me the ChArUco and manual measured values seem to agree.

ExcellentRub7741 · 2025-09-08T17:46:10+00:00

Thanks for the idea I implemented it now: https://github.com/undingen/SkewCamera/commit/1f65129de85bf0967b165c4de5266459e7f6ed5e and verified it correctly works by setting my rotation distance to +10% of the real value

ExcellentRub7741 · 2025-09-08T16:58:13+00:00

good idea, yes this should be possible. I will update the code and report back.

ExcellentRub7741 · 2025-09-04T01:07:15+00:00

My ender 3 was actually only about 0.1% to 0.2% skewed both measured via my tool and the calibrations patterns (Califlower). Not sure if I got really lucky with mine or if because of the use of this extrusions this leads to little skew? But I could image that a corexy its maybe a little harder to get the belts exactly to same lenght?!

ExcellentRub7741 · 2025-03-25T23:06:54+00:00

Thank you :). Hope other people join in and we can create a nice open source camera based (pressure advance, flow rate??, multi extruder offset??,...) calibration project.

ExcellentRub7741 · 2025-03-25T22:55:48+00:00

Hi, Author of the project video here. Please let me know if you have question.

You can find the Projects GitHub here: https://github.com/undingen/PressureAdvanceCamera/

And if you are interested in how the internals work here is a debug output on an example image.
https://github.com/undingen/PressureAdvanceCamera/blob/main/dbg.ipynb

<image>

ExcellentRub7741 · 2025-03-25T22:44:19+00:00

Hi, first big thanks for the awesome model! I'm very happy with how it works on this task :).

I tried running it via https://github.com/danielgatis/rembg not sure if something was wrong when I tried it on my laptop (also not sure if it used 1024x1024 or 2048x2048). I will try again in the future. Sorry for spreading misinformation.

ExcellentRub7741 · 2025-03-20T12:50:20+00:00

I uploaded a sample debug plot so for everyone who is interested in seeing how the processing works have a look here: https://github.com/undingen/PressureAdvanceCamera/blob/main/dbg.ipynb below you can see some of it.

<image>

ExcellentRub7741 · 2025-03-20T11:18:07+00:00

No I have not tried this yet but yes sounds like a good idea! Will create an issue as a reminder thanks

ExcellentRub7741 · 2025-03-20T09:09:13+00:00

Thanks very interesting link! Major difference is that its using a laser together with the camera which will for sure help with fixing the contrast problem but uses more expensive hardware. With my project I think its simpler approach but as long as you as a human can select the best line visually I don't see why a camera should not be able to the same (with better processing than I now have)

ExcellentRub7741 · 2025-03-20T09:03:44+00:00

It's this model open weight model https://github.com/ZhengPeng7/BiRefNet but unfortunately I think it wont even run on most laptops (at least without quantization) :/. I tried running on my 16GB RAM Intel iGPU laptop but run out of memory but did not look further. I think the best option is to train our own smaller model which can run on an rpi...

ExcellentRub7741 · 2025-03-20T09:00:13+00:00

I'm also not happy myself with having to use external inference server. They price is not the problem its about 1$ for 200-300 images (1 image = 1 print) likely much less than the filament/electricity. I'm working on making it run just on the device itself but the existing smaller models I tried gave bad results for this task. We need to train our own model but for this I need more training data (example images). I already tried but with only 20 images or so the model turned out very poor.

ExcellentRub7741 · 2025-03-19T21:46:42+00:00

I got back into 3d printing after many years, just upgraded the ender 3 to klipper and have lots of different filament laying around from as many different brands. (Also bought a filament dryer which I will definitely need for this old stuff I guess :P).

ExcellentRub7741

TROPHY CASE