Motor max speed variability
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Hello,
At my workplace, we are noticing some odd behavior with extruder motors. About a month ago we systematically sent an extrusion command to the extruder and varied the flowrate (without moving any of the gantry axes) such that we could determine the experimental max speed that the stepper motor could achieve (which aligned with the motor's specified maximum speed). The test was effectively sending a G1 E1000 F4000 command and increasing by 1000 until we reached the max RPM of the motor, around F14000 using a mixing extruder with an index of 0.5:0.5. We are using a steps/mm of 207 and a micro-stepping of 1 on a Duet3 MB6HC, relative extrusion.
Now about a month later we tried the same test again and the max realized speed of the motor is under half of what it was previously, after this speed the motor starts "under-extruding" where we command it to move a certain amount and it doesn't revolve the full commanded amount.
We more-than triple-checked the configuration file and feed-rate and flow-rate overrides too, motor current, etc. that it is the same as when we tested a month ago.
Are there other commands in the config file that we may be overlooking that would affect the performance of the motor?
What is especially weird is that we tested the same motor on a Duet 2 + Duex5 with the same settings in the config file and it was able to rotate at the motor's max speed at F14000.
Best,
Garth -
@garth_42 If you used a mixing hot end with a mixing ratio of 0.5:0,5, that would imply that you had a two in one out hot end. I which case, to attain a filament throughput of n mm/min means that each extruder runs at n/2 mm/min. i.e each extruder runs at half speed with a mixing ratio of 0.5:0.5. Are you by any chance repeating the test but with a single extruder being driven? That would explain why the maximum speed is about half what you were seeing before, because that's the speed that each extruder was actually running at to attain the combined filament flow rate.
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@deckingman Thanks for the response. That is the case, and all the tests were performed at 0.5:0.5 index.
