Best way to cool down the A4988 drivers?

So after my last experiment with the moving print bed it got quite heavy which led to increased heat generation in the motor driver. I have a Chinese A4988 driver with a small heatsink and a 60mm fan blowing air over it.


Well, this seems to be insufficient because the Y axis skips steps even at low amperage settings (1A). The chip itself is very small (6x6mm) so it is hard to find a suitable heatsink. I thought that maybe the best way to go is to make a custom heatsink of spare aluminum parts. What do you think? How do you keep the motor drivers cool?

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Self-sourced Mendelmax 2.0-based Reprap Machine -- Ramps 1.4 & Mega 2560 -- DRV8825 (Z@1A, [email protected], [email protected], E@1A) -- genuine E3D v6 direct setup -- 350W custom silicone heated bed -- ABS 1,75mm -- Marlin 1.1.0-RC7 -- Cura 15.04.6

Those chips were never meant to be mounted on such a small PCB. Adding a heatsink to the top plastic surface of the part does almost nothing to remove heat either. You have reached the limits of what can be done with those poorly designed driver modules. It's time to start thinking about either an external driver or a new controller board with the drivers soldered to the board so they can dissipate heat as they were designed/intended.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I couldn't agree more, however, I am trying to make do with what I've got. I really am thinking about a new and powerful 32-bit electronics board but this is not the point here.

I tried this:





Once I do some testing I will report back.

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Self-sourced Mendelmax 2.0-based Reprap Machine -- Ramps 1.4 & Mega 2560 -- DRV8825 (Z@1A, [email protected], [email protected], E@1A) -- genuine E3D v6 direct setup -- 350W custom silicone heated bed -- ABS 1,75mm -- Marlin 1.1.0-RC7 -- Cura 15.04.6

When you say you have a 60mm fan blowing on it, is it a radial fan, or axial? Axial fans are not good at blowing, and get worse with ducting.

How hot is the heatsink now? Maybe a bigger heatsink?

Also, which direction is it blowing ? I gather the ideal is for air to flow parallel to the driver pcb (ie across it). Most fan holders I've seen for the RAMPS type board have a fan held above the pcb blowing perpendicularly down onto it.

Paul

It was blowing perpendicularly down onto the board but I moved it.

I tried printing a model where the Y motor typically used to skip steps using the modified A4988 driver from the pictures above and the fan blowing across the RAMPS.... And is still keeps on skipping steps. I will need to investigate further what the cause is.

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Self-sourced Mendelmax 2.0-based Reprap Machine -- Ramps 1.4 & Mega 2560 -- DRV8825 (Z@1A, [email protected], [email protected], E@1A) -- genuine E3D v6 direct setup -- 350W custom silicone heated bed -- ABS 1,75mm -- Marlin 1.1.0-RC7 -- Cura 15.04.6

Skipping steps, especially in the Y axis, is a speed vs acceleration vs jerk problem, not a driver problem. Driver thermal problems show up as the axis stopping at random times for some random interval, usually several seconds at a time. The skipping steps problem will be worse at low current settings because you're reducing the motor torque. You increased the mass of the Y axis- you need more torque, not less. You can get a little more torque, sometimes, by increasing the current, but if the driver overheats, you're all done extracting torque that way.

If I were you, I'd set the current to somewhere around 80% of the motor's rating, and start reducing the acceleration and jerk. If 80% of the motor's current rating causes the driver to overheat, that's a different problem and needs to be solved by getting a higher performance driver (preferably one that is properly designed/cooled).

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

OK, I increased the current to 85% of the motor's rating. My jerk and acceleration setting are already pretty low (jerk is 10 and acceleration is 300 mm/s^2)... I will report once the first test is complete...

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Self-sourced Mendelmax 2.0-based Reprap Machine -- Ramps 1.4 & Mega 2560 -- DRV8825 (Z@1A, [email protected], [email protected], E@1A) -- genuine E3D v6 direct setup -- 350W custom silicone heated bed -- ABS 1,75mm -- Marlin 1.1.0-RC7 -- Cura 15.04.6

@icefire, those settings are very low indeed. Check for binding on belt and bearings/rods, or even a faulty bearing locking up intermittently. There are many things that might be causing your problem, and from the sounds of it, im not sure it is a driver chip heat issue, under those settings, but could be. It may well be defective driver? Try swapping X and Y drivers around. I have drivers fail in all manner of ways, they don't always just die but can become glitchy or temperamental. Just some thoughts for you. in case they help.

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Flex3Drive.com

Thank you
There is no "obvious" cause for the issue, I can move the carriage with my pinkie finger when the steppers are disabled, the belt is tight, etc. I have already swapped out 2-3 motor drivers, so it is not the driver itself...

After upping the current, I have been printing for 5 hours straight with no issues... I still need to wait a bit and see if there are really no more missed steps but I guess that the heatsink I attached to the lower part of the PCB did the trick... (for now)....

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Self-sourced Mendelmax 2.0-based Reprap Machine -- Ramps 1.4 & Mega 2560 -- DRV8825 (Z@1A, [email protected], [email protected], E@1A) -- genuine E3D v6 direct setup -- 350W custom silicone heated bed -- ABS 1,75mm -- Marlin 1.1.0-RC7 -- Cura 15.04.6