Thermal issues

Hey Alden, thanks for the swift response.

-I’m using grbl 0.7d according to the text that appears when I open a com port
-The stepper I’m using is this one
http://www.mindkits.co.nz/store/movement/stepper-motor-58-oz-in-400-steps-rev
and its datasheet:
http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Robotics/42BYGHM809.PDF
-I’ve tried the tests on all three axis individually, it seems to have no effect
-I don’t have a 24v supply to test it on, but I am looking to get one in the next month or so
-Currently I’m running a simple hand coded script that draws a 28.6 square (ie g0 x0 y0; g0 x28.6; g0 y28.6; etc) but i also did G1 of the same script and g0/g1 x1000 y1000 and other tests. I also have the same issues with the grbl settings at defaults, the shapeoko setup (first grbl setup i found on google) and my settings.
-I see solder in the holes but three of the holes (both of Z’s, one of Y’s holes) have tiny pin holes in the solder blobs, I can’t tell how deep they are but there still seems to be a lot of solder there and X also has thermal issues and doesn’t have these pin prick holes.

Update:
I’ve had some other weird issues in the last couple of days:
-Initially thermal cut out was 30-45degrees from the maximum trimpot travel, and 45-60deg from max for the lowest setting that the motors would turn (with no torque). Max torque (measured by hand so it’s a rough guess) occurred around the thermal cut point. Today I switched it on, and on all three axis those points had moved. The thermal cut point is now 160deg from max, max torque at 180 deg. This is the same on all axis. The wiring setup hasn’t changed at all (everything, including the arduino/shield is fixed to a sheet of wood, with all connections done with terminal blocks screwed into the wood), i tested every connection with a multimeter (before and after the weird shift), and the PSU is still putting out 11.98v.
On the upside the max torque position now no longer trips thermal shutdown, but the chips do get too hot to touch. It still moves precisely too.

If you like I can post pics of the pin prick holes and my setup

SIDE NOTE: Is there a command/is the grblshield capable of locking an axis?

A speedy reply once again 🙂
Yeah, I’m pretty confused about what’s going on, but the reference voltage thing might be a source of variance: the arduino is powered by USB that’s connected to a laptop… it’s possible that when charging the voltage from the USB ports may be different (though theoretically the arduino should stabilise that to 5v). The laptop in question is permanently plugged in though and I would assume that when the battery is full the laptop’s battery management circuitry would trickle charge and not be spikey… but that’s just a guess from me.

As for running close to max power: The odd thing is the thermal shutdown point moved from approx 85% trimpot travel to approx 25% trimpot travel which is a huge jump and the max torque point moved pretty similarly. I’ll multimeter the voltages coming down the USB and from the arduino and make a note of it, if the shield changes behaviour i’ll check again and see if the voltages have moved.

As it is for now I’ve removed the black thermal adhesive on the copper heatsinks and glued them down with a thermaltake two part thermal epoxy, and I might get a friend to mill a tiny waterblock that i’ll expoxy to the underside of the shield.

Oh and as for locking an axis i mentioned before: yeah, i vaguely remember an old stepper driver I used to use would energise the motor at 70% current to lock it in place while not being actively moved which would be pretty handy for my current application (a gimbal-style turret with an RGB laser array for light painting in photography) – currently I get a little movement in other axis due to inertia and gyroscopic effects if i spin only one axis, but I can work around it.

EDIT: Oh and I might try powering the arduino with the computer PSU that’s powering the shield, at least then I’ll get a known stable voltage.