Extrusion Differences with Mixing Extruder
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Hello all,
I work at a startup where we print using ViscoTec ViPro extruders to mix 2 resins together and deposit a thermoset material, similar to the FDM process. Over the last week we noticed that there is a large difference in total amount extruded (definitely a problem) between relatively large and small extrusion commands.
For example, a single G1 E1500 command will extrude about half of the material compared to 30 G1 E50 commands.
Is there an elegant way to decouple (in a sense) the extrusion from the movement of the axis (so regardless of how many G commands a geometry is split into, the extrusion amount remains constant) that will still slow down the extruder proportionately during acceleration and deceleration of the X and Y axes?
The first idea that comes to my head is to have another micro-controller that will control the extruders with a constant pump speed while a pin on the Duet is high (signalling this is an extrusion movement) and then stopping when the pin is low, although this doesn't integrate acceleration and deceleration into the process.
Much Thanks,
Garth
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Maybe this would help?
https://duet3d.dozuki.com/Wiki/Gcode?revisionid=HEAD#Section_M571_Set_output_on_extrude
It sounds like the material is resistant to flowing due to viscosity, so it takes more force to get it to keep flowing where as the start and stop builds and releases pressure causing it to ooze more. Does that sound plausible?
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Hi Phaedrux, thanks for the reply. Yes, that is one of the ideas I was thinking about. Do you think there is another way to do it that would let us use the onboard drivers instead of needing to get more stepper drivers to hookup separately?
Your reasoning is very plausible, it is in-line with our thinking as well.
Best,
Garth -
I don't know enough about your setup to really venture an option.
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@Garth_42 said in Extrusion Differences with Mixing Extruder:
For example, a single G1 E1500 command will extrude about half of the material compared to 30 G1 E50 commands.
Is this something you can model mathematically? That is, the actual material flow rate during a movement?
If so, you may solve the problem by preprocessing the slicer's output, transforming the extrusions and gantry movement to fit your model. And then disable the duet's acceleration and jerk restrictions such that it will execute exactly the program your post processor generated.
Just a thought.
