EXTRUDE_MINTEMP and M302 questions

[willnewton]

Ok, I understand the minimum temperature at which the extruder motor will operate is controlled in the firmware using the line- define #EXTRUDE_MINTEMP 170. If you are a firmware modding kind of person, then you can change this to whatever number your like and reload the firmware.

If you want to do it the easy way and have S3D, you can go to the Machine Control Panel and under the Communications tab, type M302 and press SEND to disable the mintemp setting. This only temporarily disables the mintemp setting. Once you use Disconnect/Connect or power down and restart, the M2 will reset to its default mintemp setting

Great, but what if I am REEEEALLY lazy and just want this code to be inserted automatically in an fff file using the Scripts -> Starting Scripts and Ending Scripts function? That way I don't even have to think about this stuff and can just download some smartypants guys FFF settings.

I found a couple of posts mentioning you could send M302 SXXX (where XXX is the desired mintemp). This would allow you to set AND reset the mintemp for a filament using the Scripts Tab. For Example: Under Starting Scripts add in M302 S80 and under Ending Scripts add in M302 S170

It makes perfect sense!

Except it doesn't work for me.

Well, sorta it does. The M302 command definitely disables the mintemp setting altogether. The other half of the setting , the SXXX code or "sS80" or "S170" does not work to reset or re-enable the mintemp setting.

Why might that be? Can someone else try this to confim it or let me know how I have messed up? Or just show me an even lazier way to make it work?

Thanks!

[willnewton]

OK, I am not going to lose a lot of sleep over whether I can reset the min extrude temp via G-Code. I found that you end up turning the machine off or pressing EMERGENCY STOP for one reason or another and it resets itself to the MG extrude_mintemp settings. Its just not a big deal to worry about. At worst case, it will make the extruder gear eat away at a spot on the filament.

I have messed around a bit and this is what I decided after testing out some low temp filament and seeing when I NEED to use M302.

When using Simplify3D you will need to send it when you are loading the filament, which is before an .fff file is loaded. So, that means you will need to open the Comm. window in the machine control panel and enter M302 (use a capital letter) and SEND. You will be able to load the low temp. filament.

Next you can embed the M302 g-code into the .fff file using the Edit Process Settings->Scripts->Starting Script dialog. Doing this keeps you from having to visit the Comm. window every time once the filament is loaded. I stuck my code in the line before the nozzle purge.
Example:

G92 E0 ; zero extruder
M302 ; turn off cold extrusion protection so filament will extrude at low temps
G1 E30 F175 ; purge nozzle

It will print merrily away at whatever temp you like.

[jsc]

The official versions of Marlin from the M2 Wiki are all based on older versions of Marlin. The S argument to M302 only work on newer versions.