Hello Guest it is September 20, 2019, 12:57:47 PM

Author Topic: sizes aren't correct anymore please help !  (Read 3843 times)

0 Members and 1 Guest are viewing this topic.

Re: sizes aren't correct anymore please help !
« Reply #10 on: December 18, 2014, 04:28:52 PM »
If you've used the program a bunch of times, I'm going to guess there is something wrong with the table mechanically.  Is everything tight?  I've had it where I've had a loose pinion, a belt about to finally break apart, a loose setscrew, binding due to lack of lubrication, etc, etc.  I've had bad geckos, bad boards, bad motherboards on computers.  I've even had cables partially plugged in that will ever so slightly come just loose enough to keep the machine running but the router turns off.  I've also had loose wires going into the BOB.  Just a few ideas from my experience.
Re: sizes aren't correct anymore please help !
« Reply #11 on: December 18, 2014, 04:30:47 PM »
One other thing, on the BOB I've had it where the signals going to the x axis were behaving weird, so I changed all the wires to the aux part of the BOB and changed my pinouts in Mach.
Re: sizes aren't correct anymore please help !
« Reply #12 on: December 19, 2014, 04:46:46 PM »
Heres the latest update. I ran through and checked all the wiring to the bob and drivers and all seemed good and tight. I then created a new profile and started from scratch and still off by .020 . Has to be my machine then right? I'll be working on it tomorrow tearing it down and seeing if I can find a problem somewhere. What mechanically would cause it to lose .02 over a 2" travel but be able to return to zero without any backlash? This is killing me. I hate taking the machine apart.
Re: sizes aren't correct anymore please help !
« Reply #13 on: December 20, 2014, 07:12:28 PM »
If the error is repeatable it sounds allot like the "steps per unit" is not correct and its a compound error problem. Meaning the farther the axis moves away from home or zero the more error is developed. The other key piece of info you posted, is you made allot of changes to your driver board settings and Mach 3 kernel speed and who knows what else.

I would do the stepper per unit math and get a baseline number to use in motor tuning window and start from there. Then using the Mach 3 step axis calibration function and move 6 or 10 inches and see what the error is. I have a 12" digital caliper I use to calibrate my steppers.

Moving the axis 0.100 or 0.900 is not really far enough to get a accurate error measurement because the accumulated error is very small at that point. Being off 0.04 @0.900" and 0.02 @ 2" I'm willing to bet its way off at 6". 
Re: sizes aren't correct anymore please help !
« Reply #14 on: December 20, 2014, 07:39:11 PM »
One other thing... the driver you bought off of Ebay (Chinese I assume) could be failing or has failed. Basically these are low quality junk. You get what you pay for.  Go with a Gecko 540.   
Re: sizes aren't correct anymore please help !
« Reply #15 on: December 20, 2014, 09:11:47 PM »
I was just about to start shopping for new drivers. I'm trying not to throw crazy money into this machine as I'm saving up for a tormach.today I redid the linkage setup for the motors to ball screw and still nothing . I got fed up and decidedown to play with the steps per setting in the motor tuning. It was previously at 8050 and was leaving .02 after a 2" span. I backed it off to 7982 and it's right on and weirdly enough didn't affect short distance accuracy.  Perhaps is was my dial indicator the entire time not being that accurate ? It was after all from harbor freight
Re: sizes aren't correct anymore please help !
« Reply #16 on: December 21, 2014, 11:54:26 AM »
Thank you all for the suggestions and support . Love this forum