Posts: 5
Joined: Thu Mar 14, 2013 10:46 pm

Alternative tool change sequence

Sun Jul 19, 2015 4:53 pm

I've designed a dual extruder that has only a single hot-end. This eliminates the problem of getting the offset set correctly. However since both filaments go into the same hot end, the tool change g-code needs to retract the old filament to make room for the new filament. The problem I'm having is that on the first layer, on the first tool change, the seconday extruder is not getting primed into place.

Each extruder is retracted 45 mm when not active. On the first layer, initially the primary extruder is active, so the secondary is retracted to -45mm. When the tool change happens, instead of issuing a G1 E45, S3D is zeroing out the secondary extruder with a G92 E0. Consequently, the secondary extruder, even after printing the priming isn't primed. Furthermore if the secondary extruder isn't used enough, the subsequent tool change retraction will back the filament entirely out of the extruder.

I'm looking at the tool change script, but I can't seem to figure out how to make one that does what I need. I'd appreciate any helpful suggestions.


Posts: 1435
Joined: Sun Feb 16, 2014 10:52 am

Re: Dual Extrusion problem

Tue Jul 28, 2015 5:21 am

Since this is very different than how a "normal" dual extrusion printer works, you will need to disable the default integrated tool change retraction stuff and write your own tool change script.

Click "edit process settings", go to the Scripts tab. Enter the following for the tool change script:

Code: Select all

G1 E-[toolchange_retract_distance] F[toolchange_retract_speed]
G1 E[toolchange_prime_distance] F[toolchange_retract_speed]
Now, anytime the tool is changed, you will perform a full retraction with the old tool, and then a full prime with the new tool. This distances and speeds for these retraction movements will still be based on the "Tool Change Retraction" section on the Advanced tab of your FFF settings. So you can edit the values there.

Note: anytime you use the [toolchange_retract_distance] and [toolchange_prime_distance] replacement variables in your tool change script, it will automatically disable the default integrated retraction commands so that you can define everything yourself. So make sure you leave those placeholder variables in there, otherwise you will still see the stock retraction commands getting inserted!

Posts: 12
Joined: Wed Nov 12, 2014 2:01 pm

Re: Alternative tool change sequence

Fri Jun 23, 2017 4:17 pm

How to perform a nozzle lift BEFORE the tool change ?
im using the script below but don't want the nozzle to stay still during the unloading and loading of filament.

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