Y axis all over the place

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Y axis all over the place

Postby gene » Sun Oct 30, 2011 9:52 pm

my x axis is working great, however I can't get the y axis to be consistent at all. It's moving all over in mach3.

so far Ive tightened up all the hex nuts and even added non-perm loctite. There is no slippage. Also made sure the gantry is running smoothly and tightened all y belts/pulley system. The gantry is square to the vrails (used two carpenters squares to confirm). I've tried all the diffent step options full, half, 1/4, 1/8, 1/16 and tried adjusting pulse frequencey from 25k to 60k (drivertest tool says system excellent when set up to 60k). Current stepper settings in mach - Velocity 40in (went up to 120 with no effect), Acceleration 2 (tried between 2 and 10), step pulse 1us, dir pulse 1us. (tried all pulse sizes 1-5)

What I"m noticing - when jogging the y axis it appears to stop it's motion for a split second then continue on. It does this repeatedly every x amount of seconds maybe 3 seconds or so in between. When the y axis is locked, the y stepper seems to be pulsing with that same time frame. When the pulse is going on, I can push on the gantry and it will move along Y and then lock again once the "pulse" is over. Having the laser off or on doesn't effect this. The X axis doesn't do this pulsing thing at all and it smoothly jogs. I've also notice that my Y- threaded rod on one side has some definite warp issues on one end (right side if you are looking at front of router or X+). The y axis slides smoothly when the steppers are not engaged. The y part of the gantry itself is not loose or wobbly and it is not making contact with anything that I can tell.
I'm using Bart's 3 axis control board I should mention.

Are there some standardized test files out that I can run that would give me an idea of where my problem lies or anyone have any thoughts? I'm out of ideas at the moment
gene
 
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Re: Y axis all over the place

Postby BenJackson » Sun Oct 30, 2011 10:04 pm

My guess is your pololu is overheating because there's no heatsink and it's set to 2A from the factory (only rated for 1A without a heatsink). When they overheat they cycle on/off rapidly holding max temp and basically having no torque.

Mine did this originally and I figured it out because I could jog ok for a few moments and then it would go wonky.

I'd crank down the power on Y just to see what happens. 1A runs my Y with enough acceleration to shake the whole machine.
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Re: Y axis all over the place

Postby bdring » Sun Oct 30, 2011 10:24 pm

I totally agree with Ben for the best guess. You can often hear it at rest too. There is a slow quiet clicking sound. With heatsinks and 24V I suggest about 1.5A. it is plenty for the laser.
Bart
"If you didn't build it, you will never own it."
bdring
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Re: Y axis all over the place

Postby gene » Sun Oct 30, 2011 10:40 pm

ah I see. i totally overlooked setting the pot on the driver boards so it probably is at 2amps right now. time to take things apart. Well fingers crossed...
gene
 
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Re: Y axis all over the place

Postby gene » Mon Oct 31, 2011 1:01 am

yep that fixed it. Axis is extremely accurate now. I read that entire manual but didn't really pay attention to that paragraph as I should have
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