MMU2 Filament Selector w/ Mag FINDA Sensor fix 6mm

thingiverse

This is a version of the original Prusa MMU2 Filament Selector that includes some modifications on the Filament feed, Filament cutter blade holder, and most important addition of a fix for the FINDA sensor which includes a fix for the ball getting stuck in the chamber holding the ball between the sensor and the filament. History There has been a mixed bag of success with the MMU2 and here are some of my observations and discoveries. 1. One of the issues people have been having is layer skips. There are a number of reasons for this but the primary reason for this is that the filament never reliably or consistently feeds the filament to the bondtech gear in the extruder head. In the stock firmware, the success of this path is completely depended on accuracy of calibrating the distance from the FINDA sensor to the bondtech gears in the extruder. 2. I mentioned the tip shape calibration and this will be a never-ending story of a mixed bag of how to get this reliable and consistent. If you don't get a clean tip without strings, then this daisy chains into a whole bunch of other issues that come from getting the filament stuck in the bowden tube to screwing up the finda sensor so that the MMU2 never knows that the filament was loaded or unloaded. 3. Prusa designed this Pinda column at about 8mm with a 7mm steel ball, which leaves a little bit of room for the ball to move. It does leave a little room for junk to build up and then there is a little bit of extra room around where the filament leaves the selector to hopefully clear the junk. Design changes from Prusa V1 1. Chamfered inlet to the selector from the MMU2 idler (this opens the tolerance needed to succeed a feed to the FINDA). 2. Changed the tolerance to add pressure in the filament cutter to hold the blade better (I did this before I discovered that I wanted to remove the blade all together). 3. Added a 6mm round chamber to hold a magnet at the bottom of the FINDA ball chamber. Note: As I mentioned, I also removed the cutter blade all together. It is no longer used in the stock firmware anyway and I found that it sometimes just got caught on the filament and caused problems. My recommendation is to remove the blade. Required materials 1 - 6mm x 2mm magnets (get the strongest you can find) These worked for me: https://www.amazon.com/gp/product/B01NAL9I5H/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1 You will need a longer M3 Stainless steel bolt to hold the POM nut. I think the original is 10mm, you will need at least a 15mm-16mm. Obviously not too long.