3.5beta2 cold unload filament macro doesnt work

Adrian52

I have a simple macro to unload filament cold (I do a short hot retraction at the end of a print job)

; Unload filament cold
M302 P1
G1 E-870 F3600
M302 P0
M84 E0

which works fine with 3.5beta1, but with beta2, the extruders do not move. There is no error message, and cold retraction is enabled(retract and extrude are no longer greyed out). The extruder drives in dwc also show -870 movement.
running duet2wifi stand alone, with 2 orbiter extruders running in tandem.

Adrian52

@Adrian52 Seems to be a problem with M302.
A filament unload macro that works fine when the hotend is at operating temperature does not work if the hotend is cold and M302 P1 is entered at the console, even though 'retract' and 'extrude' are no longer greyed out in dashboard. As before, the extruder drive numbers decrease by the expected amount, but the extruder does not move.

dc42

@Adrian52 I will look into this. The mechanism that implements cold extrusion prevention changed in beta2.

dc42

@Adrian52 I confirm this is a bug: allowing cold extrusion/retraction doesn't work. I have implemented a fix in the RRF source code. The fix will be present in beta 3 and in any intermediate builds that I provide before then.

Adrian52

@dc42 Excellent, thank you.

jp.douarvil 0

@Adrian52 just for info if that can help, you can use M302 P0 S0 R0 in the mean time.
@dc42 Thank you very much for the tremendous work.