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Filament slipping

Posted: 09 Jul 2019, 09:28
by raven
When printing small holes (fast movements) the filament slips backwards, breaking the extruder calibration. When moving forward, the distance is not enough to compensate the slipped distance and it results in under extrusion.

My nozzle is clean (checked) and if I lower the retraction distance it solves the problem. Hence, if I lower the retraction to 0, this doesn't happen.

thank you in advance for you help.

Best regards

Re: Filament slipping

Posted: 11 Jul 2019, 09:05
by raven

I've been looking to this issue more carefully and which seemed to be the filament slipping is, in fact, the motor running backwards.

Since this print uses linear advance, the pressure created within the hotend, in some prints, pushes the filament backwards and the motor doesn't have anough torque to stop the push. Due to limitations of the TMC2130 drivers, it is impossible to increase the current to supply enough torque to stop the motor running backwards.

I tried a geared extruder I have and this is more visible since, because its geared, the filament pushes the motor harder, making impossible to use geard extruders with linear advance and TMC2130 drivers.

Is there anyway to change the extruder drivers to others with more torque (p.ex 2208)?

Best regards

Re: Filament slipping

Posted: 12 Jul 2019, 12:10
by DomingosRodrigues
Hello Raven,

The motor/Stepper driver combo on the B2X300 has been tested on various filaments and no such problems are observed if you follow the recommended procedures and configure the profile accordingly, most importantly:
- Ensure the Filament oiler is well damped in WD40 especially on ALL PLA an PETG filaments as they have some problems when "dry" with full metal heatbreaks which this printer has to allow usage at much higher temperatures.
- Ensure all the PTFE tubes are fully inserted and the bowden lockers are intalled.

The profile used is very important to avoid blockage problems, some PLA filaments require much lower retraction than the original retraction value and/or use a different temperature, the temperature convertion table on the B2X300 is tuned to represent the nozzle temperature vs most printers that show the block temperature.
I recommend printing a temperature tower in order to find the correct temperature for that filament, use the lowest that allows good extrusion.

Just to be sure the nozzles aren't being conditioned due to some dust please follow the cold pull procedure on the B2X300 LCD, in Maintenance, repeat 3x per nozzle ensuring the filament is well oiled prior to loading.

As a last chance you can disable the bowden tube compression compensation that the printer uses (allows the high print quality the printer has), it does a mini retraction and prime on rapid extruder movements to avoid oozing and extrusion delays. This can cause some filaments to stop extruding. To do so change the gcode line:
M900 Kxxx (xxx is the value of the compensation, usually 100-250 work well on the B2X300 deppending on the filament used)
to M900 K0 (this disables the compensation)

As for the geared extruder you can use one with no problem you just need to choose a stepper motor which rated current is fit for the TMC2130 which can deliver 1.1A RMS aka 1.55A Max, for example E3D titan and Bondteh BMG have a recommended stepper motor with a average current of arround 600mA which is well fit for TMC2130, you can even use the original motor with them.
The 2208 have a usable maximum of 1.3A which shouldn't be significantly stronger. You could use a TMC5160 that supports up to 3A RMS but the firmware has no official support for it.

Best regards
Domingos Rodrigues