mixing nozzle vs dual nozzles

Why does the single nozzle mixing extruder seem to be less popular than using dual twin nozzles? I have no experience with either though i am getting ready to install a mixer. But it seems to me that a single nozzle dual extruder would be far easier and cheaper to use. Am i missing something?

I think there are two significant problems with mixing nozzles:

• It takes some time for the filament to be purged before printing can start with the next filament
• There is little or no possibility to change the temperature, nozzle size and possibly other factors between filaments.

While your requirements may vary, I can find few things that would work within these limitations other than multiple colour designs..

Mike

... one of my older ideas for "mixing" nozzles is based on a ring of several wire-feeders (not melting extruders!), pushing 0.3mm thick plastic wires to the same spot -- and a laser is heating/melting this spot, so the "combined" plastics will melt, intermix (different feedrates for different mixing params) and fuse to the underlying surface or already printed part structure

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

... here another interesting "mixing nozzles" approach

[www.youtube.com]

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Well ive spent a few days playing with the mixing extruders and now realize why they are not more popular for the reasons stated in the replys. The amount of wasted material and time that goes into printing a prime tower is ridiculous. For a small part i had probably 3X more material and time in the prime tower than in the finished part. The qualtiy of the finished part is very good, but not worth the added time and material waste. I have since attached both my mixing extruders to an X carriage and switched to standard dual extrusion. I suppose i could add two more extruders and convert it into a quad extrusion if ichose but who needs 4 materials in a single print. Anyway, lesson learned and moving on. Least the mixer extruders were cheap.

It's possible to cut that extra time dramatically. See [wp.me]

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].