Circles not circular on Z1 10W laser. Y belt issue?

Lasers
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I recently got a refurbished 10w Comgrow Z1 Laser engraver/cutter.

Assembly went fine (for a refurbished/return item, it looked like whoever returned it gave up before they got it fully assembled), and I proceeded to set fire to things.

I noticed on the material tests that the text was being smudged, which I took to be a speed issue, because the squares with the cut tests were perfectly fine. But when I did a circles cut test, they also have an odd notch. It seems to be whenever it’s done in one spot and moves to the other, but reducing the jog speed to 1000 mm/min didn’t help (it was 6000 mm/min before)

I’ve tried tightening the y-belts, but the issue persisted. I thought it might be the odd way the belts are held in place - a screw is pressed against the belt, which means that the belt will be a tiny bit twisted when I tighten the screw. I added a piece of rubber between the screw and the belts and tightened them again, but I had no time for a test because it’s 1am :smiley:

Am I on the right path here? Is there something else I should be checking? The belt on the X axis was assembled already, and I tried to make sure that the y-axis movement needed similar amounts of force.

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I’ve tentatively solved the issue - re-tightened the belts, it didn’t make any difference. Made sure the frame was square, made sure the X axis was square to the Y axis, etc.

Then I did a bad fix… I made two changes at once. Turned down the acceleration on both Y and X by half (from 1000 to 500) in the controller… and enabled the Backlash hiding in Lightburn. I don’t know what the fix was, but it’s tentatively fixed and I’m not poking it anymore

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It sure seems likely that something is loose.

Turning down acceleration can hide problems from loose components. If it comes back, that’s where I’d start.

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One of the suggestions I found was that maybe something was too tight… ended up finding a video of someone showing just how much slack there should be in the timing belts, did my best to replicate… didn’t help. Will definitely keep an eye on it

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I’m thinking more of whether the head can wobble. See if anything that isn’t the belts wiggles when you gently manipulate it, if you want to investigate further.

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The head is fixed tightly, doesn’t wobble or moves at all outside of sideways when I push it

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Try tightening the bolts that attach the gears to the motors.

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Everything on the motors is also tight. I am slightly worried that I made the belts too tight now, there’s a vague straining noise when it moves… but it might have been doing that before and it’s just in my head. The Y belts have more give than the factory-assembled X-belt, even.

But, it works (got a honeycomb and built an enclosure!)… so I’m not going to touch it :smiley:

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