(190504: I have made further upgrades to the selector, please also see "De Luxe selector for prusa i3 mk3 MMU2s")
With the mmu2s upgrade, filament movement is indirectly detected by sensing the idler movement using an IR sensor. However, the setup is not sensitive enough to reliably detect very flexible materials such as filaflex and ninjaflex. To solve this issue, I made a variant of the design. The features are:
- even filaflex can be detected when entering the idler
- the bowden tube is not surrounded by a tower anymore, making it easier to service the extruder.
- the sensor cannot move around freely anymore, as it is locked in position by attaching the signal cable.
- you can easily customize the tower height (column B3 in the freecad spreadsheet)
I also added a space for a magnet (you likely got the magnet as a spare when upgrading to mmu2s from mk3 or mk3s) that improves the FINDA. The feature:
- FINDA will be less sensitive to thin threads and "filament clouds". I do not like filament clouds in FINDA ruining my prints, not at all...
These items are based on STL-files found at: https://github.com/prusa3d/Original-Prusa-i3/tree/MK3S and https://github.com/prusa3d/Original-Prusa-i3/tree/MMU2 under GNU2 license (please read the LICENSE file)
Please note wrt IRsensorholderII.stl when slicing with slic3rPE:
- activate support
- set the object to "auto generate support = NO"
- add the "IRsensorholderII_SUPPORT.stl" as a support ENFORCER
- print the object with the tower in VERTICAL position
Installing the selector (you must print the new selector BEFORE this)
- 2x M3x10 screw from motor axis adapter
- 3x M3x10 screw from motor
- 2x M3x10 screw from selector cover
- 2x TUBE
- 1x M3x10 screw from FINDA holder, and carefully remove FINDA
- 1x zip tie from motor cable
Partly take out the motor, holding it whilst removing the 2x metal bars then the selector is loose.
Remove 2x M3x10 for knife cover. Carefully remove and keep cover and knife.
- Insert Nx M3nS nut into various holes (same places as old selector)
- Insert 1x M3n nut into various holes (same places as old selector)
- Insert 2x TUBE
- Insert 2x6x10 MAGNET (see image)
- Put knife back, lid on, tighten
- Put idler in place, add 2x metal bars, put motor in place.
- Add 2x screw to motor axis adapter
- Add 3x screw to motor
Place a filament in the filament path, add FINDA with care and add 1x screw to lock FINDA
- Add 2x screw to selector cover
Did I forget something?
Installing and configuring the IRsensor (you must print the new selector BEFORE this)
I removed the brass thread from the obsolete "mk3" design by cutting the plastic using pliers. It is easily inserted in the new part, and this part is compatible with both prusas original design and this improvement.
- remove idler (2x screw), sensor (carefully!), sensor-holder and fs-cover (2x screw).
- Carefully remove the metal shaft and the bondtech (incl 2x bearing) from the old idler
- Re-assemble carefully the ond tech setup in the new idler
- Add the spare brass thread to the new fs-cover
- Add necessary nuts into the new parts (see old parts)
- Add the sensor to the new sensor holder (PLEASE see the images! Completely different setup as compared to before!!!)
- 2x screw for mounting new fs-cover+sensor-holder.
- 2x screw for mounting new idler
Calibrating for filaflex
For filaflex, please loosen the idler pressure (spring load) to a minimum. Calibrate the idler by checking the sensor status before and after manually loading/unloading filaflex (move axis->extruder, load around 25mm is enough). It is NOT good enough to use a thin steel thread as in prusas instructions.
It is a horrible design (my part, not prusas initial design)! I just took the STLs (my freecad failed when loading the scad files, unfortunately, likely some error from my side) and added some cubes and stuff, cut and paste. Please don't look too close.
About the freecad source file
The item was constructed using freecad. I use the "freecad-daily" updates (which I strongly recommend for any freecad user). I have not tried using the construction with the freecad stable release.
If you prefer to edit the design, in the freecad-document you can change the major parameters (eg diameter, height) easily by adjusting parameters in column B in the spreadsheet included in the document.