Axis Calibration Problem

Custom/new built, using a Ruida RDC6445G,
Mainboard firmware RDLC-V15.01.19
Lightburn 0.9.20

I’m please needing assistance with the X-Axis calibration, for now.
I calibrate on a long length cut, however a short length cut is inaccurate
Using Nema17 into 2:1 ratio then to belt drive HTD3M 20 Tooth Endless belt.

I believe it’s better to calibrate on a longer cut.
So I do this on a 370mm cut, adjusted in the LB Axis Calibrate section.
Then recut the same 370mm which comes out perfect.
I then go and cut a 20.0mm short piece of acrylic and it measures 19.50mm.
I have replaced the HTD 3M belt and pulleys on the 2:1 gearing.
Have also replaced the actual linear open ended HTD 3M belt. (The new belt is S3M out of desperation and lack of spares. The S3M has a trapezoidal tooth profile but is also 3mm pitch.

I have not yet changed the idler and drive pulleys on the endless belt.
(These are actually HTD3M pulleys)

In summary the problem is basically the same as original parts i installed. My train of thought was that my initial HTD 3M belt was very rigid and measured 2.7mm thick. The specification is actually 2.4mm. The endless belt pullies are 20 tooth (maybe a bit small) and I was wondering if this overly thick belt was maybe causing this problem by not being able to wrap around the small pulleys snugly enough.
I’ve played with belt tension with out much success.

I really don’t have any more ideas right now and still not sure if its hardware or software/settings side.
Anyone have any ideas?
Would anyone care to share their base settings for X and Y axis. (If you using NEMA17 and have 2:1 gearing?)

Thank you!

So i have always started my calibration cuts (370mm) on the left hand side of the engraver.
And then follow the 20mm cut starting at the left hand side.
I now did a test cut (20mm) on the right hand side more or less where the 370mm would have ended.
The result is a almost perfect 20mm cut. :grimacing:
I’m still confused, but maybe this will help with identifying the problem, i hope.
Thank you again!!

If you haven’t seen, this might be worth review. Configuring a Ruida - LightBurn Software Documentation

1 Like

Hi Rick thank you for highlighting the calibration process.

Before your post i installed GT2 2mm belts and pulleys as that’s the only hardware i have not changed up to now. I would prefer to use 3mm pitch but this is all have to test with.
(The endless belt, pulley and idler)
I’ve red through the link you provided and i believe i am doing the calibration correctly. (I hope)

Today i recalibrated with the new GT2 2mm Belt and pulleys at 380mm.
Please see the screen shot included.
The green cut was the 380mm piece cut after calibration and then the black rectangles are consecutive 20mm wide test cuts.
Below are the digital vernier measurements.
Not! terrible, but not great either. No consistency although the right hand side rectangles do appear better than the left, which is what i started picking up late yesterday as per UPDATE: on my first post.
Any ideas?
Thank you

Another test today after fiddling for hours on end!!!

Can anybody please offer a comment on these cut sizes.
Would you be happy with this or not?
The test is after calibration and rechecking that calibrated size is correct on a 360mm long cut.
I then do a cut every 20mm and the result is as per the screen shot.
Once again, it does not look very consistent. To me at least.
However i’m not sure what others think.
Thank you!

NOTE: This last test is vertical lines only. So X axis is traveling in one direction only. (From left to right)
The consistency is what’s baffling me.

Should i be using 0.9 Degree stepper motors? :thinking:
Currently using Gecko drive with 10u steps and then 2:1 ratio.

How are you taking these measurements? In what material? Wood can be compressed relatively easily, and nearly all of your output is less than 0.1mm away from 19.90mm. Are you certain your method of measurement is that accurate?

Hi, Thank you for your reply.
Material is 3mm Acrylic.
Using a digital vernier. Measurement very accurately and repeatable on the vernier.
Is +/- 0.1 reasonable? I thought not🤔
Out of desperation I’m going to try a 0.9 degree stepper motor tomorrow. I’ve heard that micro steps on stepper motors are not very accurate.
Thank you

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