Duet 3 rated stepper KHz

oarjjj

I am purchasing a Duet 3 to replace my somewhat broken Duet 2 wifi and was looking at the specs. The processor is much more capable, and I understand the Duet 2 is rated for around 150 KHz with three steppers running.

Is the Duet 3 providing 256 microstepping using interpolation? This relieves the strain on the Duet 2 by only requiring the processor to output 16 microsteps. Do we know what the processor in the Duet 3 can handle?

I understand the expansion boards have their own processor, so I'm also curious what kind of KHz to expect from those too.

Danal

@oarjjj said in Duet 3 rated stepper KHz:

Is the Duet 3 providing 256 microstepping using interpolation

That is the recommended config, and the way I run mine.

I don't have the math at my fingertips for max step rate. I'm curious what is the application that will be pushing this limit.

deckingman

@Danal For info, I too am waiting to know what the max step pulse frequency of Duet 3 is. My usage case is with a mixing hot end where any single filament may be contributing only 1% of the total. My research concluded that 16x is too course and that to obtain the desired resolution, I needed to use 128x microstepping. This works fine for print moves where the extruders run relatively slowly but I ran into the step pulse frequency limit during retractions so had to settle for 64X.
It's easy to check with gen 2 by looking at the hiccup count but unfortunately, all my extruders are connected to expansion boards and hiccups don't work on expansion boards (unless David has recently fixed that and hasn't told me).

JuKu

@Danal said in Duet 3 rated stepper KHz:

I'm curious what is the application that will be pushing this limit.

I’m looking at using Duet3 in a pick and place machine. There is no such thing as a too fast or too accurate pick and place.

zapta

The duet could benefit from a FPGA that gets from the CPU a description of the movements and generates the pulses to the stepper drivers. Or smart drivers that can do it on their own, if such thing exist.

oarjjj

Anyone know how many kHz we can expect from the duet3 mainboard? @dc42?

dc42

@oarjjj said in Duet 3 rated stepper KHz:

Anyone know how many kHz we can expect from the duet3 mainboard? @dc42?

Not yet. The step rate in recent versions of RRF (2.05 and 3.0) has dropped, and I have work scheduled to raise it again.