Am having a bit of a problem with my rebuild. I have a rigidbot (10x10x10) and am switching out several components. I went to a Sainsmart 2in1 with DRV8825. It runs off 24v.
Problem 1: High-pitch whine from the steppers. I tried at 1/32 microstepping, and 1/16 microstepping. Either way, the whine/squealing is there, and the steppers get warm… no actually they get medium hot.
Problem 2: testing in pronterface. I can move in all 3 directions, but sometimes it will pause and do nothing, instead of moving.
Problem 3: So I tried a print even with the above problems. The x and y seem to go in random places, and it doesn’t really look like a print. more like some sort of plate of spaghetti. It will also pause in a spot and extrude filament creating a neat ball of plastic. At the end of test printing, the steppers were very warm.
Is it a matter of current? Or is it a matter of the DRV8825 being inxepensive ones from ebay?
Any suggestions?
Too much current. the 4988 are different to the 8825 so if you changed from one to the other i think it was 1/2 the current. There is a calculation somewhere on the web.
8825s will whine with some motor/PSU combos no matter what you do. It comes from the 30khz fixed-frequency PWM scheme – you often get audible 7.5 and 15 kHz subharmonics out of the waveform. Seems to be most common with low-inductance motors and 24v PSUs.
You can try switching to fast decay mode or fiddling with the current, those might help, but some setups just always whine or will consistently whine at certain microsteps.
My steppers whined and ran hot until i got my drv8835 voltage tuned correctly. There’s a nice post on the RepRapWiki that covers it here:
http://reprap.org/wiki/Pololu_stepper_driver_board#DRV8825
And I blogged about it as well:
http://www.akeric.com/blog/?p=3232
Thanks to all. The steppers were being driven too high. The default they were set for was 1.7v or so. I lowered them to a much smaller value, between .5 and .8 and it is working now! now to tune it up and get it back running.