Multiple extrusion - Alternative to smart temp management?
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Since many popular slicers (PrusaSlicer, Simplify3d, ...) don't (yet) support smart temperature management (i.e. preheat the 2nd tool while the 1st one is still printing) and thus the only alternative is to either waste a lot of print time by waiting for the tools to heat up at each tool change or ignore the standby temperature and let the tools "cook" at print temperature while they're inactive, I wonder what alternatives there are.
For example, would it be sufficient to retract the filament out of the melt zone (i.e. the nozzle + hot block + part of the heat break & sink) at each tool change? This way, there would be nothing in the hot zone to cook.
Or let the material cook and simply purge the amount upon tool change.
I wonder if there are any multiple extrusion users here and how they handle this issue? I know that Cura supports smart temperature management but unfortunately Cura has many other issues and bugs, so I'm kinda looking for an alternative.
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I use Cura so I have this feature.
You can't just retract and hope for the best. You will not have a clean melt chamber and stuff will cook if you leave it for an extended period of time. You can only retract the unmelted filament, whatever melted filament is in the melt chamber will still remain in the melt chamber. The results of the cooking depends on the filament being cooked. I would also not trust a normal purge to clean up all residue from cooking.
Retracting beyond a certain amount can easily cause a clog if the soft tip end cools and possibly expands. I have had many clogs that way before I learned to be very careful on the retract.
The only alternative that I can think of is to print a purge tower with every loaded filament at every layer and that is assuming a shortish layer time of only a few minutes.
I haven't used Cura in a while for multiple material printing but I believe Cura, if set up to print multiple materials and purge tower, will purge both tools ... but I can't say this for certain. -
@jens55 said in Multiple extrusion - Alternative to smart temp management?:
I would also not trust a normal purge to clean up all residue from cooking.
What about an extensive purge over a purge bucket of e.g. E30? 30mm should be enough to cover at least the hot zone.
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@TechNi
Prusa has developed a tip-forming method for their MMU2 extruder to avoid jammed filament caused by long retractions.
I wished it was a G-code we could add to our toolchanging macros. But afaik it's hardcoded in their MMU firmware. PrusaSlicer has access to a few parameters, but no full control. -
@TechNi
Would this not be possible with a post processing script?
At start of print set all active and standby temps then quickly loop through all tools to active and set to standby.
In the script...
Search for tool change
Go back X lines (or time) and raise standby temp of next tool to near print temp
In tool change reset standby temp -
Well going back x lines can be either a very short or long time, depending on the model's dimensions. In the worst case you might even skip a layer, thus you will need to take that into account, too.
The tip forming method sounds interesting, has nobody found out what Gcode they use for it? If the tip is formed inside the hot zone, it's probably just a sequence of retractions/unretractions and maybe a temperature change.
