Shapokeo missed steps - drivers overheating

[Jim S]

The Shapokeo was being used last night but missing steps occasionally.  I quickly touched the driver chips on the grblshield to see how hot they were and burned my finger.  It is running much too hot.  Uncomfortable to touch for more than a quick touch is ok but it is hotter than that.  A quick google search shows that this can be the reason for missed steps as the chip has thermal shutdown to try to protect itself.  A small fan blowing across the board seems to be a better solution than a heatsink on top of the chips because the best thermal path is out the leads of the part into the circuit board foil.  Even if that's not the reason better cooling is needed to reduce the stress on the driver.  The other thing would be to turn the current down a bit.  Perhaps it was turned up to try to prevent missed steps?  The motors were warm but not overly hot. 

[Andrew Ricke]

Do they have heatsinks?  I have some more chip sinks somewhere and a fan we could strap on top.

It's also wired to drive 2 motors with one driver if I recall. That's a lot more stress as well.

Current also requires a fine balance, too high or too low will cause heat and skips.  Not sure on the voltage range the grbl shield has, but upping the voltage input also helps reduce heat in the drivers.

On Wed, May 10, 2017, 7:32 AM Jim S <jimski...@gmail.com> wrote:

The Shapokeo was being used last night but missing steps occasionally.  I quickly touched the driver chips on the grblshield to see how hot they were and burned my finger.  It is running much too hot.  Uncomfortable to touch for more than a quick touch is ok but it is hotter than that.  A quick google search shows that this can be the reason for missed steps as the chip has thermal shutdown to try to protect itself.  A small fan blowing across the board seems to be a better solution than a heatsink on top of the chips because the best thermal path is out the leads of the part into the circuit board foil.  Even if that's not the reason better cooling is needed to reduce the stress on the driver.  The other thing would be to turn the current down a bit.  Perhaps it was turned up to try to prevent missed steps?  The motors were warm but not overly hot. 

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[Jim S]

No heatsinks.  I don't know a lot about this board but from my quick google-fu it was suggested a fan across the board foil would be more effective than heatsinks on the parts (the plastic parts doesn't transfer heat  to the heatsinks very well).  Both would be best but for a quick test a fan could just be put beside the board to blow across it.  Here is one of the links I found:

https://www.shapeoko.com/forum/viewtopic.php?f=4&t=739

It would be easy to see how much this helped with an IR temp measuring "gun". 
All axis drivers seemed to be running hot, not just the one driving two motors.

I also ran across something about the bootstrap caps being wrong on some boards making the boards run hot.  Don't know if our board might have this issue and a bit of searching didn't turn up any more on this issue so it may not be good information...

https://www.shapeoko.com/forum/viewtopic.php?f=3&t=4577&start=20

I suggest we add a fan and check temps.  That may be all it needs.

[fredspartan104]

I had a problem with my 3d printer stepper motors over heating and I had to adjust the current on the motor driver.  On my drivers there is a little potentiometer that can be adjusted to control the current to the stepper motors.  It took some testing because if you dropped the current too low the steppers would not turn or they would make a clicking noise.  Hope that helps.

-Fred

[Myles Farrell]

So I was using the shapeoko pretty heavily in Dec. It was skipping then as well. I thought I had solved it as I had two eight hour runs that ran without issue.One of the problems was that 2 leads for a Y-axis stepper were disconnected. However, in the course of troubleshooting I did use the Pots to reduce the current until the motors stopped working and then turned them slightly back up. We can always do this again as it is not that hard, but the current should be about the minimum needed to run the machine. A fan certainly can't hurt as they do get very hot, even just for safety, as I have burned myself on they as well. That being said I don't think we should get tunnel visioned on the heat as I'm not convinced it is the only issue. It is definitely the easiest place to start troubleshooting and adds benefits even if it isn't the cause.

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[Keith Rogers]

Curious, what voltage power supply is being used?

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