Scanning Offset Not Applied to All Speeds?

I spent some time with the scanning offset adjustment, but am getting some weird behavior. I ran tests at 100 to 600 mm/s (in 100mm/s increments and identified the offsets for each speed).

    • I put those settings into the table (half value) and it seems to resolve the 100 and 400 tests, but all the others seem essentially unaffected.
    • Using the full offset, the 100 seemed unaffected (was smaller to begin with) and the 400 seemed to over correct (as expected that it should). The other speeds still seemed unaffected.

For lightburn setup, I tried setting only the 100 and 600 speeds in the configuration, as well as, also trying to enter settings for each speed individually…doesn’t seem to make a difference.

I made test grids in 2 configurations (2x3 grid) and a 6x1 column test for all speeds (since I noticed that the 2 speeds that seemed corrected in the 2x3 grid were both in the first column… Spoiler alert… It doesn’t matter)

OMTech 50W CO2; Ruida KT332N




bump
Anyone have thoughts for this testing?
I’m attaching a couple other “single column” tests as well.


I have the idea that you might be seeing the interplay between mechanical backlash and machine bounce. It may be what is producing erratic line ends on your x-axis in this case.

Jog the engraver head over to the general area where you were working. Turn off the power. Open the lid and grab the engraver head and wiggle it in the direction of the x-axis.

Let me know if you have a small amount of looseness and springiness.

My reasoning is that mechanical backlash is loose and open. Machine bounce or resonance is related to the elasticity of the structure. You can compensate for some of it in software at specific speeds - but when you change the speed the effect from the elastic response changes.

I feel that some of the light machines may not be stiff enough but this is speculative.

Have a look for looseness and missing fasteners as you have been exceptionally thorough on the software side.

Hey John(John),
Thanks for the reply and apologies that I haven’t gotten back quickly. I did the “backlash test” but forgot to report back. In that feel test, I do not feel any slop in the laser head motion. That is, when powered off, I do not feel any motion when applying force back and forth…up to the point of overcoming the “sticktion” resisting that force before allowing the laser head to be slid along the x axis (all components moving).

Same test, with laser powered on, results in no slop being felt…and I did not apply more force to try attempt motion against the motors. (We are talking about sub-millimeter distances though…!)

You’re comments, however, have refreshed some brainstorms that I was thinking through. My laser is setup on a metal rolling cart capped with a wood “box”. (Ideally, allowing me to get to the back of the laser for adjusting, cleaning, etc) No observable motion of the laser itself on the cart, but I’ve observed that the entire structure can “wobble” slightly back and forth with the laser head zipping back and forth. The relative motion inside the laser bed should be zero (since the entire structure is moving) so the material position inside should not be changing relative to the laser. That said, I have my material, that is sitting on honeycomb, that is sitting on some foam (damping), that is sitting on the machines raisable bed. I’m pondering whether the inertia/properties of each of those components might get into some harmonic with the overall head motion.

My thoughts against this having an effect is that I do not see any change at some speeds regardless of the offset used…

Any more brainstorms?

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