Set Extrusion Min Temp

enix · 18 Jun 2018, 16:52

Hi All, I have been searching for a while now and haven't found anything on this so I figured I'd ask here. Is there a way to lower the min temp for extrusion? I have some SOFT filament that extrudes well between 145-150°C but the firmware doesn't allow extrusion at those temps. I know I can allow cold extrudes, but I really didn't want to disable that feature. Is there a gcode to change that temp setting? Thanks.

wilriker · 18 Jun 2018, 18:44

@enix I just checked the source code and it appears that 160°C minimum extrusion temperature is hard-coded. So the only way to change this is by disabling cold-extrusion-prevention using M302 P1.

That's rare in RRF to find truly hard-coded values.

Interesting/fun side-fact: you can already retract starting from 90°C according to another hard-coded value.

enix · 18 Jun 2018, 19:17

Thanks for the reply. I was hoping that wasn't the case, but I can make due.

The fun fact you mention... I have never been able to get any movement from the extruder below temp without disabling cold extrusion, is that a firmware retraction setting verses gcode retraction?

wilriker · 18 Jun 2018, 19:28

@enix said in Set Extrusion Min Temp:

The fun fact you mention... I have never been able to get any movement from the extruder below temp without disabling cold extrusion, is that a firmware retraction setting verses gcode retraction?

I just tried it out - never used this before. I heated my hotend to 90°C, made sure that relative extrusion was enabled by sending M83 (might or might not be necessary) and a following G1 E-0.1 started the extruder motor and gave no error. To be sure I also sent a G1 E0.1 but got

Warning: Tool 0 was not driven because its heater temperatures were not high enough or it has a heater fault

So retraction is possible - DWC even enables the "Retract" button as soon as the hotend reaches 90°C. Never realized that before.

wilriker · 18 Jun 2018, 19:36

@dc42 Is there a reason why these values are truly hard-coded? I'd be willing to take a shot at making them configurable if this is

desirable
you could tell me to which command I add this? Intuitively I would add it as parameters to M302 but I could also implement a completely new command.

enix · 18 Jun 2018, 20:04

@wilriker That is interesting. Maybe I just never tried retraction, nor paid attention to the retraction becoming enabled at any temp because I was looking to extrude.

As far as it becoming configurable, I'd definitely like to see that. I know Marlin FW uses M302 Pxx Sxx with Pxx being the flag on/off and Sxx being the temp setting. I have used it to change the temp on a couple of my machines before for the aforementioned reasons. Just food for thought...

wilriker · 19 Jun 2018, 13:39

@enix I just implemented this and created https://github.com/dc42/RepRapFirmware/pull/181 - but as I wrote in the comment there it is totally up to @dc42 to decide whether this will be accepted at all and as he seems to be really busy right now it might take a while for him to respond. Plus it will take some time until 2.01 (I guess that's the next version number).

wilriker opened this pull request 19 Jun 2018, 13:34 in dc42/RepRapFirmware

closed Allow configuration of extrusion and retraction minimum temperatures #181

wilriker · 13 Aug 2018, 10:34

@enix My PR has been accepted by @dc42 and is included in RRF 2.02 beta 1. You can now use M302 Snnn Rnnn to set your minimum extrusion temp and retraction temp respectively.