Loosing Steps with MKS Robin Nano V1.2, TMC 2209 UART

General Discussion
1

Basic Information:

Printer Model: Sapphire Plus
MCU / Printerboard: MKS Robin Nano V1.2
Host / SBC
klippy.log (2.0 MB)
printer.cfg (8.1 KB)
klippy.log

Describe your issue:

Dear all,
I have a problem with my extruder. I have already measured it several times, but unfortunately I can’t help myself any more:
When I extrude “fast” at 5 mm/s, the extruder loses steps. Instead of 100 mm, I only extrude 88.5 mm. If I extrude slowly, it is suddenly 99.5 mm. This result always seems to be relatively identical. It is not the case that the extruder “jumps”. The amperage of 0.8 on my Nema 14 stepper seems to work well. I can also read out the TMC 2209 with the DUMP_TMC command.
I have already played with the command "step_pulse_duration: "… unfortunately this did not result in any change either. Now I am at a loss. Can someone please help me?

Thank you very much
Philipp

2

Hello @Flippo !

Losing steps in most cases are a issue of not enough current.

Have you tried to increase the run_current of the extruder?

[tmc2209 extruder]
uart_pin = PE5
run_current = 0.85
stealthchop_threshold = 0

Try in steps of 0.05 A, so → 0.90 → 0.95 → 1.00

3

Before changing the current on the extruder, a quick question; is this a new problem or something that happened when you went to Klipper?

Also, do you hear the extruder stepper motor “bumping” or “jumping” when you’re doing the “fast” extrude - this would indicated that you have a mechanical blockage somewhere that you need to resolve first.

0.8A is somewhat high for an extruder and, I did have a Sapphire plus a few years ago, I was running the (default Bowden) extruder at 0.5A without any issues.

I think there needs to be more information before a determination can be made.

1 Like
4

Hello,
yes, at first I thought that I had too little voltage on the driver. That’s why I increased the voltage. I have no detectable jumping in the extruder motor.
The motor is also getting quite warm now. I think I have reached the maximum voltage for the small motor.
The problem wasn’t there before. I think that the problem has only occurred since the conversion to Klipper and the installation of the 2209. I have already swapped them with each other to rule out a defective driver module.

Thanks Philipp

5

Please don’t mix up voltage and current.

2 Likes
6

Yes, sorry you are right, we only change the current with the software. The voltage is only set with the potentiometer in standalone mode.
Philipp

1 Like
7

Hi,

but I understand correctly that the extruder should extrude the same length regardless of whether it is extruding slowly or quickly, right? There is no reduction in quantity with fast extrusion, is there?

8

It should extrude the amount it was commanded to extrude, but this is an IDEAL situation assuming no jams, clogs, slipping etc.

There is also the issue with the nature of thermoplastic extrusion and pressure build up, but that’s what pressure advance is supposed to help with.

But to keep it simple, yes, if you command the extruder to extrude 3mm, it should extrude 3mm. Assuming your extruder is setup right in the config.