A250 extruder gear unexpected direction change

A250 extruder gear suddenly rotates in the opposite direction during printing.

The behaviour is not reproducible. Sometimes the gear turns in the wrong direction during the loading/unloading filament procedure, sometimes from the start of printing, sometimes during printing and sometimes it turns in the correct direction. I print with PLA, 210°C as I always did before this strange behaviour. 1+ power off-on cycles help to revert the behaviour.

The behaviour occurred for the first time after I did my 1st firmware upgrade. According to the description, I had to do the update for all 3 tool heads, so I had to unplug the 3DP module for the 1st time, as I have only used the 3DP module so far.

Any Idea?

Sounds like something’s broken. To get a replacement you’ll need to email support.

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Hi @gruemscheli
On the touchscreen, please go to Control and heat up the nozzle to 200℃. After that, click on Load/Unload, will the gear rotate properly? Can you upload a video of the issue here? Thanks

Thx Tracy
I did what you mentioned. In the behaviour I described, the filament is unloaded at the load command and loaded at the unload command. The stepper turns in the wrong direction. Really weird!

It sounds like a problem with the head. Is there any audible noise out of the norm? What firmware did you update to?

@gruemscheli i don’t know what firmware you updated to, but reflash it to 1.10.1, but if that’s the one you updated to then update to 1.9

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Thank you, there should be something wrong with the chip of the controller.
test firmware.zip (141.8 KB)

Here I attached a test firmware for you to test.
–The machine is not connected to any tool head.
–Upgrade the machine via the attached firmware.
–After you upgrade the machine, please do not use the toolhead port in the controller. Now the Add-on1 port is the toolhead port.
–Power off the machine, connect the printing head to the Add-on1 port, and power on the machine.
–On the touchscreen, please test whether the gear rotates properly.

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It’s not something strange in the gcode like an M83 command?
When you do extruder calibration unless you use the M83 to get into relative mode it feeds the opposite way that you’d expect.
But you said it was intermittent and not reproducible.

Did you try re-flashing the firmware in case there was a problem with it?
Or reverting to the firmware prior to having the problem?



Thank you Tracy for your quick reply and the test FW. I’ll be off for a couple of days so I’ll give it try it later.

After trying it, please kindly tell me the result. Thank you :slight_smile:

Hi sdj544

I am not sure if it has to do with Gcode: I generated Gcode with both Luban and Simplify3D and had the same behavior. I had used both Gcode that was created before the problem first appeared and Gcode that was created after. So I can exclude out the possibility that something changed when generating the Gcode.

One observation amazes me: Both Luban and Simplify3D create a G1 at the beginning of the GCode to extrude some material (G1 X1 Y1 E10). At this point the extruder gear always turns in the same direction - no matter if the problem occurs later during printing or not.

M82 ;absolute extrusion mode
M104 S205
M140 S55
G28 ;home
G90 ;absolute positioning
G1 X-10 Y-10 F3000
G1 Z0 F1800
M109 S205;Wait for Hotend Temperature
M190 S55;Wait for Bed Temperature
G92 E0
G1 E20 F200
G92 E0
G92 E0
G1 F3600 E-6.5
G0 F3600 X47.913 Y109.408 Z0.3
G1 F3600 E0
---- from here, skirt and regular printing starts ----

M106 S0
M140 S55
M190 S55
M104 S200 T0
M109 S200 T0
G28 ; home all axes
G1 X1 Y1 F3000 ; move to starting position
G1 X1 Y1 E10 ; extrude (MSC)
G1 Z0.2 F1000 ; set priming height
G92 E0 ; reset extrusion distance
G1 X90 E10.0 F500 ; prime extruder
G1 X110 F3000 ; quick wipe
G92 E0.0000
G1 E-1.0000 F1800
---- from here, skirt and regular printing starts ----

I don’t see any significant difference apart from the fact that the commands are not in exactly the same order. Furthermore, M83 does not appear anywhere further down.

I’ve loaded your test firmware as recommended, reconnected tool head to Add-on1 port and tested. Gear turns and filament is extruded as expected, despite of the fact that I didn’t calibrate the bed so there was on offset between the nozzle and the bed (which is ok for testing). See video: extruder gear OK after test firmware

After bed calibration (which I did many time before I had the problem) I started printing. I had to adjust Z-offset by 0.05mm and — boom — extruder gear suddenly reversed direction from “forward” to “backwards”. I am trying to reproduce this behaviour with power-off-on cycles to make sure I have the exact initial situation … and: Whenever I adjust the Z-Offset during printing, in the middle of a route, the Z-offset is adjusted at the end of the route. This is the moment when the extruder gear reverses direction.

After aborting the printing process (once again with Gcode from Luban and then from Simplify3D), I “reloaded” the filament (it was unloaded during printing because of the reversed gear direction). Again, the gear turned in the “unload” direction. During “unloading” the gear turned in “unloading direction”. There must be something that makes the gear turn backwards - be it a Z offset change or something random.

However, this does not explain why it sometimes happened without changing the Z-Offset (while I had my fingers off) …

Sorry to say this, but I think the test firmware does not seem to solve the problem.

If you altered the z offset right before printing, and that’s the only time it does it… makes me suspicious of the controller, just because they had it switch what port it is using doesn’t mean it’s not the controller

What then is the role of the controller? Is it just “the computer” that interprets the G-code and sends commands “over the wire” to the tool head? If this is the case, it would be a software problem, which I don’t believe, because I tried to reproduce the problem so many times with exactly the same scenario and the behavior was still unpredictable.

If the role of the controller was to directly power the individual components of the tool head, such as sending pulses to the stepper motor that drives the extruder gear, then the cable from the controller to the tool head would need more “thick” wires to power all the components (e.g. a stepper motor has at least 5 power wires). And why would the tool head then have its own “mini controller” inside (this is how it is seen on youtube)?

That’s why I think it’s not the controller. However, if you know the roles of the components and how they interact, I would be interested to learn more :slight_smile:

@gruemscheli I wasn’t saying it IS the controller, I was just pointing out that more troubleshooting would be needed than just switching ports in order to rule it out, sorry if my previous wording caused confusion. The controller is a CAN bus. You can read about the basics of a CAN bus here. It was designed for cars but has since been adapted to other use cases. Personally I don’t think it’s the controller, I think it’s the head.

This is the CAN bus of Snapmaker.

Irrelevant here as all steppers are directly controlled by pulses from the controller (EN, DIR, STEP) using 3 using 3 dedicated wires in the cable and do not use CAN at all, including the extruder.

The DIR circuit from the controller into the stepper driver in the toolhead could be suspect, bad solder or something.

CAN is used for non step related data such as temperature, linear module length detection at startup, endstops, etc. Fun fact the laser PWM is driven by the extruder stepper pulse driver directly from the controller using the same wire in the cable.

A teardown of the toolhead and controller may be in order to check there are no cracked solder joints. Additionally the cable might have a break internally. Alternatively yet get support to send you new cables tool heads and a controller.

Gotcha, thanks for clearing that up. I haven’t had a chance to go playing inside of it yet.

Thxs for info, Artezio! So many things to learn here, just great :slight_smile:

Thx brent113. In the mean time I’ve ordered a new tool head. If it doesn’t solve the problem, then I’ll have a spare part :-). Hope it’s not the controller. I have no idea how I could find out…

You’ll find out if it doesn’t fix it. I’m pretty confident Brent is right, possible cracked solder joint. But where is up for debate. Contact support and get a new cable as well.