Z-axis driver overheats - quickly

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Z-axis driver overheats - quickly

Postby dalewheat » Wed May 30, 2012 12:54 am

My Quantum's Z-axis driver keeps overheating. I'm using a RAMPS 1.2 (I think... it's not marked but it's not the 1.4, it's older) using a genuine Arduino Mega 2560 and 4 of the Pololu drivers.

I've adjusted the driver current down until the Z-axis just stops then bumped it up maybe 15-20%. It's really hard (for me) to accurately adjust the current limit on those things.

I'm using Marlin and Pronterface. When I run the Z-axis up or down, the little heatsink on the Z-axis driver jumps from near ambient temperature to over 70C in just a few seconds, then starts cutting out (as it should at that temperature). I've got it set to 16x microstepping because everyone else seems to be doing that. I have no idea why this is being done on this axis.

All the dimensions check out on all the axes. A 1mm move in any direction moves what looks like exactly 1mm. All the axes move in the correct direction, as well.

I've got both Z motors wired in parallel. I'm using an ATX power supply that's rated at 10A on the 12V line. Might it be better to wire them in series?

Ideas? Suggestions? Reminders? What am I doing wrong? I've already swapped drivers with the so-far-unused extruder driver, so I don't think it's a bad driver.

Thanks for any help!


Dale
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Re: Z-axis driver overheats - quickly

Postby bdring » Wed May 30, 2012 1:31 am

Make sure you break in the nuts and lube them so they need as little current as possible. Make sure Marlin is setup so the Z motors disable whenever they are not running. The Z should be the coolest one under normal use.


Code: Select all
// Disables axis when it's not being used.
#define DISABLE_X false
#define DISABLE_Y false
#define DISABLE_Z true
#define DISABLE_E false // For all extruders
Bart
"If you didn't build it, you will never own it."
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Re: Z-axis driver overheats - quickly

Postby nrp » Wed May 30, 2012 4:38 pm

Be careful about letting the Z drivers shut off. When I did that on my Mendel, I found that on large prints, X and Y vibration was enough to cause the carriage to drop down slightly, resulting in prints that were a few percent shorter than they should have been by the end.
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