Stepper Motor Drivers (Page 2 of 2)

Please measure the temperature on the stepper to check if they are really overheat! The human senses are not made for precise temperature estimation - so just from touching everything above 40°C appears to be "extreme hot"!

I've did some comparison between the steppers and the hottest is always the extruder stepper. On my machine it get about 50°C - the others are about 45°C.

As long as the drivers are working I would not change them! I think you expecting too much just from a different driver. A possible reason for overheating can be a too high setting on the current limiting. What mainboard Version do you have? Are the drivers soldered on the board or can they be removed?

But in both case the current limiting is set by a fixed voltage divider - would be very unlikely that this has changed! But would be good to double check and measure the reference voltage - I can send you a picture where to place the voltage probe. Do you have a voltage meter?

Here is my board.

I am going to bypass Octoprint server and use the SD card exclusively for the next several prints.

Why is the resistance multiplied by 8?  Are there 8 equal resistors setup as voltage dividers?

I'll test the voltage, but I understand your stance that the drivers are likely providing appropriate current to the steppers.  Thanks for providing an empiric way to test that.

The only other thing I could think of that would explain shifts in the X and Y axis is that the octoprint server was creating those.  As you had previously suggested, I am now trying my prints from SD card, but those keep failing with SD card read errors!

The ohms law can not be applied as it's only an reference voltage used internal to control the current limiting.

BTW - to answer all these question mankind invented datasheets: https://www.pololu.com/file/0J450/A4988.pdf

... so you replaced the A4988 with a A4988 ... that does not make any sense to me!???

The difference you hear is the ROSC pin is tied directly to ground on the new A4888 what set the off-time internally to 30 μs. This will give a more smooth sound and not so aggressive as the 10µs in the original setup.

This could be achieved just by a solder bridge - no need to replace the driver PCB!

I too am thinking about upgrading my stepper drivers to the DRV 8825. I was told that you don’t have to re-flash my Repetier0.92 FW to do this (I did this a long time ago), but doesn’t the DRV 8825 have a better stepping resolution than the A4988 (1/32 vs 1/16)? Wouldn’t that be something that is set in the configuration.h file (I think that was the file) before you flash the printer? Any help would be appreciated. Thank you.

You’ll need to double the steps/mm.  Often times this can be changed in EEPROM instead of having to change it in configuration.h.  EEPROM chit chat needs to be enabled in configuration.h If that was the case when you flashed it last, then this is an easy change to make.