I am in the process of building a 3 axis gantry type cnc router. The motor drivers are Gecko 340 and I am using them with DC Brush type motors. All three axes use acme leadscrews and circular rails with plain sleeve bearings; although I think I am having problems with stiction and will probably change over to ball bushings. The spindle I am using is a Rotozip or a Porter Cable 690 Router.
I don’t think it is skipping steps because the error checker on the servo drivers don’t let me operate unless the feedback from the encoder is within some allowable error.
I checked the tool, spindle and the hardware and it all appears to be tightened down. I measured some positions and made some tool marks to see if anything is slipping but it does not appear to be.
After giving it some more thought I think the problem might be the shaft couplings. I am using jaw type couplings so it easy to take the motors on and off, but these type couplings have backlash in them. Since the Z axis is moving up and down with such a high frequency I think the backlash error is adding up slowly and therefore giving me a tool offset error. I am going to try and switch to a rigid coupling or a beam type coupling.
Any thoughts?
Thanks again.
Regards,
Bob