I have this OmTech 80 watts laser, 50x70 cms (20x28 in) that I got from Amazon two years ago. It has worked really fine, except for this issue on the X-axis that is really driving me nuts.
I try cutting 2 rectangles, 120mm wide.
I cut one on the left of the bed (close to mirror #2) and the cut the same design as far as posible to the right-
Using a digital vernier, I find the rectangle I cut on the left is 120.02 mm wide, while the one on the right is 119.44.
(If I do the same checking vertical size, I don’t see this problem. )
I’ve tried all the regular steps:
Mirrors are well aligned, and beam hits the center.
cutting head is vertical to the cutting bed on both directions (x & y).
Beam hits the head on the center
Focused beam comes out well aligned on the tip of the noozle on all 4 corners and the middle.
Bed height is even in every zone.
In another forum, someone suggested the X-Axis belt could be unevenly stretched. I just replaced the belt and got the same results. Thought of a loose stepper motor, but it’s not. Someone suggested a deformed dented wheel on the stepper motor, but since it rotates like 15 times to move the head from one side to the other, I discarded that option.
The Ruida controllers information can be read/saved/load/write options from ‘Edit → Machine Settings’. If you haven’t, make sure you save a ‘factory fresh’ configuration file. You can do that from the machine settings via ‘save’
Can’t remember is if was you I thought they might try the ‘rising’ or ‘falling’ edge of the motor control. This is also in the Machine settings.
So… on the left side, the same object is a smaller on the X axes?
I have to ‘percolate’ on this a while… Some things don’t make sense…
I made a test cut, cutting nine rectangles, each 100mm x 100mm.
The center rectangles measure 99.9mm which is fine for me.
Those at the left, mesaure 99.7mm
The ones at the right (fartest from mirror #2) measure 99.5mm
Regarding the vertical sizes, all of them measured 99.9 mm.
This is such a minor change I keep going back to the rising falling edge motor control I can’t think of anything, except belt stretch…
If the belt rides higher on one side because of where it attaches to the head or some other reason, as the head moves to that side, the tension on the belt increases slightly and cause a slight loss of accuracy. If the belt changes length, you will gain/loose position.
Your description of it starting low and steadily increasing may support this idea.
Don’t know if you’ve even seen the ‘curtains’ in engraving caused by the teeth in the belt riding up on the tooth then dropping into the notch, the belt tension changes and you can see it in the output.
I noticed on mine that my head’s left side belt attachment and the pulley isn’t exactly the same in a 3d spacial view. I can tell the belt tension increases slightly on that side.
Have you tried just moving the head by hand to see if there is a difference in tension as it traverses the X axes. Mine only does this in an area I can’t use, so I didn’t think of it. On mine the tension climbs quickly. Yours might be less obvious.
It seems a minor change in 100x100mm squares, but I have this specific customer who asks me for rectangles 225mm wide. The diference is about 1mm when you put them side by side.
Will try reverding the rising/falling thingy and see what happens.
If you don’t hear from me in 2 or 3 days, please call the cops.
