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« on: April 15, 2013, 10:21:19 PM »
Rich,
Found the member's doc's and did the calibration today on the motors using the function in Mach. (much easier than doing by cutting and manually changing the number) Thank you!
I will check for backlash in the next few days when I get a dial indicator. I did all checking today by rigging a 12" micrometer in a solid position and running the bit to open it. Did it many times and took an average and entered that reading into Mach to make the adjustment on the calibration. It was only off a few thousandths. I did notice that when running the micrometer open in the x-axis that the motor would stop and there would always be a few thousandths gap between the bit and the micrometer jaw, indicating that the bit was bouncing back a bit. This was under no load so I am sure when cutting material this gap may not happen, but it says to me that there is certainly some backlash? Is this something that Mach can compensate for in the Backlash settings?
We ran a small part and it came out fairly accurate. But if I run a bigger part, especially with some holes cut in it, the part comes back way out of square, 1/16" at least. I should mention that I am cutting cast acrylic, but that shouldnt have any effect on things.
Stirling,
The rack is not plastic, but the gear that the motor runs is some sort of plastic or fiber, not metal. It was originally on crooked (spun kinda like a bike tire with a bent rim). I shimmed it a bit to get it to turn smoother when I first checked things out. I attached a few pics showing the setup of how the motor turns this gear. There are 2 of these, one on each side of the gantry which runs the y-axis. Each motor has its own driver and while testing it today appeared to be somewhat accurate (not under any load) on both sides. But, when cutting parts (especially ones with any sort of circles) the parts are aout of square. I am trying to narrow down if it is a mechanical problem or if it could be a driver/motor/other electrical issue.
A pic of the stepper running the x-axis is also attached.....same plastic gear.
This setup, with the plastic gear and the way it transfers the motion through the steel and to the rack, just doesnt seem like a precision way of building a precision machine.
So, my question is: Is there a way to retrofit this machine (without major rebuilding) to a system that might be more accurate? Would new drivers help? The ones in there have to be some cheap Chinese ones.
Thank you all for the time to give me some advice...should have joined this forum 4 years ago when I got the machine! It has really helped. Chris