What is the standard domestic bench top CNC accuracy spec?

[KT88saturate]

I've got a camaster sr-24 I bought around 2022 that cannot cut the same shape out twice without going 20 mil off. Is this typical? This is my first cnc and I followed the advice of "buy your second machine first" and this doesn't seem like a "second machine."

[peteeng]

Hi KT - By 20 mil do you mean 20mm, 20 millionths of an inch or what? Cam master quote a repeatability of 0.002" or 0.050mm. This sounds Ok to me for this sort of machine. If you are getting a non repeatable part result then its probably a loose set screw on a coupling or motor or ballscrew end so I'd start checking through the mechanics... Peter

[KT88saturate]

Hi KT - By 20 mil do you mean 20mm, 20 millionths of an inch or what? Cam master quote a repeatability of 0.002" or 0.050mm. This sounds Ok to me for this sort of machine. If you are getting a non repeatable part result then its probably a loose set screw on a coupling or motor or ballscrew end so I'd start checking through the mechanics... Peter

I mean .020" inches. The x and y axis are rack and pinion with belt driven gear boxes. Everything looks like it is in good condition.

[peteeng]

Hi KT - Looking is not the same as knowing. The R&P still has a pinion with a grub screw. Hard to tell if its loose or not without pulling it out. Has happened to me before. Its unlikely to be electronic, likely to be mechanical. Is it always in the same direction? Peter

[joeavaerage]

Hi,
is there any backlash in the rack-to-pinion gear?

Ultimately the backlash represents the 'floor' of precision, it can't be any better than the lash.

Craig