# UM2 - Stepper Motor Speed (rpm)

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Posted · UM2 - Stepper Motor Speed (rpm)

Hi,

I am thinking about the Flow Rate Setting regarding the practical and the theoretical Extrusion Rate and the following grinding-problem through a too fast moving stepper motor. I don't know if the Flow is somehow connected to the stepper-motor speed, but to verify that, I need to know how fast the motor really is. So, can you guys tell me that?

Best Wishes

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Posted · UM2 - Stepper Motor Speed (rpm)

We don't think in RPM. We think in mm/s, or even better, mm^3/s.

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Posted · UM2 - Stepper Motor Speed (rpm)

Ok, then, can you tell me how fast the Stepper Motor moves the filament (in mm/s or mm^3/s), when there is no "blocking" hot end? How do I adjust the Stepper Motor Speed?

Best Wishes

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Posted · UM2 - Stepper Motor Speed (rpm)

Depends on the machine, see the topic about extrusion tests. Most UM2 machines reach about 8mm^3/s and the UM Original seems to reach 10mm^3/s

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Posted · UM2 - Stepper Motor Speed (rpm)

I don't understand the question and what the speed has to do with it. The speed of all the motors change together on every (many) line segments. So they are constantly speeding up and slowing down. The faster you move the XY axis, the faster the E (Extruder ) axis moves. All XYZE moves are linear. To achieve linearity you have to run the E axis very slow compared to how fast is possible.

The speed of the E axis is set by the speed of the other axis. So for example if you are moving the head at 100mm/sec with .2mm layers and a .4mm nozzle that is 100*.2*.4 or 8 cubic mm per second. So the E axis moves at the correct rate to extrude 8 cubic mm per second.

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Posted · UM2 - Stepper Motor Speed (rpm)

I don't understand the question and what the speed has to do with it. The speed of all the motors change together on every (many) line segments. So they are constantly speeding up and slowing down. The faster you move the XY axis, the faster the E (Extruder ) axis moves. All XYZE moves are linear. To achieve linearity you have to run the E axis very slow compared to how fast is possible.

The speed of the E axis is set by the speed of the other axis. So for example if you are moving the head at 100mm/sec with .2mm layers and a .4mm nozzle that is 100*.2*.4 or 8 cubic mm per second. So the E axis moves at the correct rate to extrude 8 cubic mm per second.

And that's without counting for acceleration, which makes the whole thing a lot more difficult.

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Posted · UM2 - Stepper Motor Speed (rpm)

Ok, I understand. But then, what can I actually adjust with the "Flow Rate Setting"? With this, I thought, you can slow down the hole material movement, which equals a slower E-Axis Stepper Motor ...?

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Posted · UM2 - Stepper Motor Speed (rpm)

Yes, if you set flow to 50% you will get half as much plastic extruded as normally needed. Or 200% will give you double.

So for example if you are printing a solid layer and there are gaps between each line and the gap is 10% as wide as the line you can increase your flow to 110% and it should fill perfectly.

I haven't changed my flow from 100% since about a year ago. 100% works almost always perfectly for me.

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Posted · UM2 - Stepper Motor Speed (rpm)

Ok, then I understand the thing really. My problem is grinding at lower printing speeds, but everything else is just fine. Neither is the hotend clogged, nor anything else lose. (and if I can't get better results with the flow setting, I know at least more about my printer)

So, thank you two. You helped me a lot.

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Posted · UM2 - Stepper Motor Speed (rpm)

You might have too much pressure in the feeder if its grinding filament. It can also be cause when too much pressure is in the bowden tube due to irregular filament size or previous grinding that produce a chunk of filament that is stuck between the filament and the tube...

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Posted · UM2 - Stepper Motor Speed (rpm)

Try increasing the temperature by another 10C (but I recommend not going any hotter than 240C) which will reduce the pressure in the nozzle. Also maybe reduce the spring pressure (or increase but more likely decrease) on the feeder.

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Posted · UM2 - Stepper Motor Speed (rpm)

You were right. I played a bit with the spring pressure and now, I haven't any problems with grinding.

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