Hello all,

It's been a while since I've dropped in since I'm not doing a lot of the laser work myself these days, mainly on the CNC router. My signature explains why that suits me just fine.

Anyways, we've noticed that some identically drawn parts vary about 1.5mm from point to point on the table. Doing a quick test now of 300mm rectangles shows the X low side (ie opposite the X motor) is out 1.5mm and the other two are about the same (actual is about 2mm too small and .5mm too small, no kerf compensation done). I've read Rich's posts about the timing belt stretch and even saw the new belt in person when I saw his machine prior to purchase....but I can't quite wrap my head around a size that is a) too small and b) only in one part of the machine as a stretching issue. It seems to be more of a crappy belt mold issue (assuming they use molds to make belts?)

Anyways, rather than changing out the belt and pully, I was thinking of maybe getting a better belt to try first. But, I can't seem to find one on-line long enough or continuous. (looking a little more before posting) I think I see why Rich did the change out he did.

So, two questions: Any other ideas that might be causing the problem? and any idea where to get a 3MM HTD Timing belt in the 2800mm plus length? Or suggestions on alternative setups (like Rich's) and suppliers for that?

Also, I tried the math Rich did for my machine's set up, and came up with a value of 4.8 um per step, based on stepper having a 24 cog gear, meshing with a 72 cog gear and then a 24 cog gear of 3mm pitch. Stepper driver at 5000 steps per revolution. So, 72mm travelled for 15000 steps = 4.8 um per step, the software has 4.79639. But that only changed the theoretical result on my 300mm rectangle by about .22mm. So, I don't particularly think it's the settings.

As always, I appreciate the help. If I can return the favour, let me know!