My FrankenCube - 4 material Prometheus based printer

spegelius

Been meaning to do a write-up of my printer since switching to Duet Wifi some 4-5 months ago, but as usual other things have been taking my time. But better later than never, as the saying goes.

First about the printer itself. It's originally a 3DSystems Cube 2, which has been heavily modified. What's left of the original printer is basically this:

metal frame
X, Y and Z stepper motors and kinematics (Hiwin rails)
Y-carriage
some wiring
endstops sans Z

Everything else is replaced. Original board and hotend are still somewhere, but I doubt they'll be any use ever again. Proprietary stuff, not worth messing with.
I removed the original plastic covers because they amplified all the noices and made a frame of sorts from wood. Original extruder setup was direct drive, but I switched to bowden quite early.
Also designed new extruder mount for it, the original metal piece wasn't cutting it once I added bed leveling probe in the mix.
Original setup didn't have heated bed, but I built one from aluminum plate and a silicone heater from Ebay.

The whole build has never been quite finished as I've added stuff and modified it as needed. So please excuse the messy wiring :).

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Current HW specs:

Duet Wifi
Prometheus V2 hotend
4x ProStruders. 2x ProStruders come with the Promtheus System, as does the hotend
Capricorn tubing
ATX psu, controlled by Duet
145mm^3 heated build area
capacitive proximity sensor for bed leveling

The multi-material setup is Distech's Prometheus System I got originally from the Kickstarter campaign. It's quite similar to Prusa's first MMU, but supports only 2 materials and is meant as a kit for any printer. I was quite happy with HW, but the SW side was sorely lacking, only Cura was supported and even that was somewhat hacky. With 2 extruders, the RAMPS I was using at the time was enough as it has 2 extruder drivers. I switched RAMPS to Megatronics for a while (actually burned the RAMPS, partly due to my own mistake, partly due to RAMPS being RAMPS) which also worked fine.

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I got a 4x joiner part and 2 more extruders from Distech for testing a year ago and that setup worked also quite well, although the 4x splitter was bit more finicky with the filament changes, some PLA's would get stuck on certain channels. To drive 4 extruders when the board doesn't have that my drivers, I use a cheap 8x relay board, wired by these instructions: http://www.marlinkimbra.it/?p=280. I had to modify Marlin a bit so the relay control worked properly, using AUX pins from Megatronics. With Duet, this was very easy, I can use the expansion header pins quite freely (thanks @dc42 for help), no need to modify firmware. With the relay, only one stepper driver is needed.

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(Demon girl suffered a layer shift due to PLA curling, Stuart suffered detached purge tower...:( )

The whole setup has working very stably once I got the filament switching speeds and lengths tuned in. I've done some 20+ hour prints with all 4 materials utilized, no problems with HW.
Switching to Duet caused some issues with the filament changes where Duet was actually failing with the 50mm/s long retracts and loads. What I think is that the Mega2560 based boards were never attaining those speeds (1000 steps/mm for Prostruders with 1/32 microstepping, DRV8825) and the physical extruder limits came into play with Duet. After tuning the speeds down, prints have been successful.

For slicing the models, I use Simplify3D, KISSlicer 1.6 and Slic3r Prusa Editions. For generating the purge tower, I've been developing a tool called Filaswitch that supports the mentioned slicers. See: https://github.com/spegelius/filaswitch. I've tried Slic3r PE purge tower, and it works, but the g-code needs to be post-processed still, it's meant for Prusa's hw so things don't work quite right out of the box. Also my own tool has some options that work better for my needs (like configuring the purge speeds and rates).

More pictures here: https://www.dropbox.com/sh/lagel8zv6iq2kjy/AADvm0BC8pujH1xX-YbiFbRBa?dl=0

spegelius

As I mentioned, the originl 4x joiner part had some trouble with some filaments, probably due to having too tight bends inside the part. To fix that, I desgined my own part, trying to have the paths bend as little as possible, while keeping the part relatively small. After few iterations I got a part that has been working without problems for few months now. I printed it with PETG, but ABS might be better as it has higher heat tolerances. Still, PETG seems to be holding up quite well.

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