[brento]

I have had my Sieg x3 for over a year and a half and have not gotten one single decent part machined in it. While trying to make a part today it began stepping its cut along the Y axis, like usual.

Normally, I would just curse at the machine and break out the well used files.I then had the idea that perhaps it was a backlash problem and proceeded to try to adjust it using the backlash function in Mach 3. Not only did this have no discernible effect, the longer I ran the mill, the worse the step became. I tried to photograph some of the circles to show the test.

Its hard to make out in the picture, but the step becomes progressively worse. My question is, is this indicative of a bad stepper motor or some other electronic/ mechanical issue? Any suggestions on how to salvage this machine?

[awerby]

I'd start by turning off the backlash compensation in Mach3. It often causes more problems than it solves. If the problem persists, try turning everything off, waiting a bit, then switching the leads from the problem motor to one that's been working okay. Switch the ports and pins designations to fool Mach into running it as the axis you switched it from, then do your test again. If the same thing happens, it could be the motor's fault or a mechanical issue, but if the problem transfers over to the new axis, then it's something upstream.

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[brento]

I traced out the x and y axes. Should I just switch the 4 wires that lead to the x and y axes on the driver boards?

[jalessi]

Brento,

I would bet you find a mechanical problem such as a warped gib or binding ball screw that is causing missed steps. Try lowering the feed rate 50% and run the test.

Jeff...

[109jb]

It is hard to diagnose problems without having all of the information.

1 - what stepper motor
2 - what kind of driver board
3 - Power supply voltage?
4 - what kind of breakout board
5 - Ball screws or stock screws (how tight is backlash adjustment if stock screws?)
6 - Are you running microstepping
7 - what size cutter?
8 - What spindle speed
9 - What feed rate
10 - how tight are the gibs?


All we know right now is that it is an X3 running mach3. Some of the cheaper drivers and breakout boards use slow optocouplers that could be losing steps if you have microstepping set too high. If you are running voltage too low you are sacrificing torque. If the feed rate is too high or the spindle speed too low you could have too much cutting force for the motors. If you are running stock screws the they use a lot of torque just to turn the screw when compared to ball screws. Add the cutting force and you could be over the edge. If the gibs are too tight, or if the stock screw backlash adjustment is too tight they could be tight enough to cause missed steps.