I’ve got a couple of questions.
How many DRV8825s can an Arduino powered RAMPS board run on a standard sort of i3 Cartesian Printer? I’m running 4 without any issues right now but I’ve only done a couple small test prints but haven’t had troubles. I’m using an LCD and auto z-leveling during printing, too.
And… I’ve doubled all my step counts in Marlin including the extruder. From what I’ve read our steppers do 200 steps per 360° and this comes to 1.8 degrees per step and this is called 1/16th stepping?? So 1/32 stepping should be 0.9° per step?? Is this correct? I’m confused because my X and Y steps in Marlin are both set to 800 and this works out to 0.045° per step…
My prints are dimensionally accurate and the printer is almost silent so I’m liking the setup.
Thanks.
The number of DRV8825s doesn’t really affect performance, because the firmware fires all the steppers in a single shared stepper interrupt cycle for each set of step pulses. What matters is the step pulse frequency of the fastest motor, because that determines how many times the stepper interrupt has to fire per second. If that number goes too high, the firmware will bog down and start running the motors rougher (double or quad step pulsing) to compensate.
For your 200 full steps per rev motors, at 1/16th microsteps the driver does sixteen smaller partial steps to achieve each full step. So it becomes 200*16=3200 step pulses per motor rev. (Or 6400 for 1/32 stepping.) Then you divide that 3200 by the circumference of the belt pulley to get the steps/mm value to plug into firmware configuration.
@Ryan_Carlyle thank you.