Working on rebuilding a controller for a old large format laser cutter. The X and Y steppers are 2.2A units. Due to the required raster rates the full 2.2A is required.
Reading the documentation the DRV8825 it should be able to do 2.2A with “sufficient additional cooling”. Anyone have a any experience driving these modules at the higher current levels and what external thermal controls (larger heat sinks / min air flow) were needed?
Looking at the module it looks like the bulk of the heat will come out the thermal slug and through the PCB. If so would it be best to mount the modules upside down and add a larger heatsink to the slug? Or is the included mini heatsink on the top of the module enough with a bit of airflow?
We do not have any specific advice for heat sinking, and we generally view adding a heat sink as an advanced modification that should only be made by those who have experience with this kind of thing. As you alluded to, the square pad on the bottom is one location where a heat sink could be added, but we have not characterized how adding a heat sink there compares with adding one to the top of the IC. Also, we have noticed that the headers have a tendency to rub against the current limiting potentiometer when they are soldered in upside down (which it sounds like you might be doing if you mount a heat sink on the bottom pad). Note that this can make it hard to turn, so you might consider adjusting the current limit before soldering in headers. You might still need to do some minor adjustments afterward, but it should still help.
Please note that getting 2+ amps per coil from this driver is going to require substantial cooling (likely involving forced air flow and a large heat sink), and I am not sure how practical it will be for you to achieve this level of performance from the DRV8825.
Alternatively, you might consider our AMIS-30543 Stepper Motor Driver, which has a higher current rating. Note that it has a different form factor and more complex interface as the DRV8825 carrier, and it is not compatible as a drop in replacement. However, it has some handy features like the ability to change the current limit over SPI (so you can try things like reducing the current when the motor is not spinning and does not need to hold its position).
If you do decide to try our DRV8825 driver with a heat sink, we would certainly be interested to hear about your results.