# Handling retraction when using a mixing extruder (2 in 1 out)

I have a Zonestar Z5FM2 running Marlin 1.1.8 with a mixing extruder.

That is, 2 extruder stepper motors feeding a 2-in 1-out hotend (similar to the E3D cyclops).

I'm slicing with Simplify3D and I have set up:

• T0 set to the first extruder;
• T1 set to the second extruder;
• T2 set to a virtual extruder consisting of a 50/50 mix of extruder 1 and 2(made by having M163 S0 P50 followed by M164 S2 in the start code)

I was wondering how you handle the retraction. Currently only the active tool (e.g. extruder motor 1 when using T1) retracts, which leads to a lot of oozing since the filament in the unused half is still applying some pressure.

I read that for a setup like mine it is necessary to get both extruders to retract. How do I do that?

I've seen the documentation for programming G10/G11 firmware retract with M207 but there does not seem to be a way to specify the tool to use.

I could make a find-and-replace post processing script in Simplify3D to replace retracts of T0 or T1 with retracts of T2 (so both motors retract), but then how would I get it to switch back to the proper original tool when resuming printing?

Is there a way to address an extruder directly in G1 commands (so I could force both to retract), or temporarily switch a tool for just one command (so I could switch tool for the retract command only and it would go back to printing with the previous tool afterwards)?

• In Slic3r and Prusa Slicer 2.0, you can set a seperate retract value for when the extruder is inactive. – towe Jul 2 '19 at 11:01