MMU2s Building a Better Base

prusaprinters

<p>This is the 2nd installment of my major MMU2s overhaul.</p> <p>Goals:<br/> -Stop getting so many "Your MMU needs attention" errors<br/> -Reduce part count as much as possible<br/> -Improve other areas to make the base function better for assembly and maintenance.<br/> -Printable without supports</p> <p>Changes from the original and some reasoning behind the change:<br/> -Increased base thickness by 1.5 mm. This improves the sturdiness of the base especially for the tray under the selector.<br/> -Modified access to the lower mounts for the idler motor for easier installation and access. The narrow channel on the stock piece makes the screw difficult to install and even more difficult to tighten down well.<br/> -Removed two hexagonal indents on the front right of the base as they are un-necessary and I prefer clean lines.<br/> -Incorporated the front PTFE tube holder into the base unit. This eliminates the need for the 5 small PTFE tubes, 4 mount screws and 1 printed part. Part reduction 10!<br/> -Incorporated the rear PTFE tube holder into the base unit. This makes maintenance to the MMU easier by adding Festo mounts to the back. No more manually feeding filament through a meter of PTFE before it gets to the selector. This eliminates the PTFE rear holder and 4 mount screws. Added 5 8mmx3mm M5 inserts so net part reduction stays at 10!<br/> -Changed the mounting system for the pulley body removing the two small 6mm pins on each side and replacing them with a single 6mmx120mm smooth rod. This provides for better tolerance on the hinge. Removed two small rods, added one long one. Net part reduction at 11!</p> <p>Initial tests are great with no filament jams. Along the filament path I was careful to taper each entry and exit point to prevent jamming.</p> <p>UPDATE: 01/29/2020</p> <p>I discovered that the left side of the base was 2mm shorter than the body so I extended the left side to match the profile of the body. Both STL files are available.</p> <p>UPDATE: 01/30/2020</p> <p>I took a look at the spec sheet for the 4.4mm Festo mounts and I think they should work, it looks like they have the same insertion depth but the other one has a lip.</p> <p>UDATE: 02/21/2020</p> <p>There was some concern that the STL file had some slicing errors (8 were auto-corrected). I found the artifacts causing the problem and while I was working on the file I found some places to improve.</p> <ul> <li>Improved filament path, all internal paths are now exactly 2mm and the profile at each filament input/output is the same profile as the tapered PTFE tubes.</li> <li>Added 4th mount for the selector motor</li> <li>The mount was difficult to access so I added a hole in the tray so an allen wrench will easily fit. This also serves as a nice place for all the cut off filament bits to fall out of. This could lead to a bit of cut off filament falling onto the mesh bed during a print. So I added a small cover that snaps into the bottom, just pop it out when you want to clean out the bits. To accommodate the cover I had to put a notch in the frame holder so that file is included as well.</li> </ul> <p>Update 03/01/2020</p> <p>A user noted that the filament path was too narrow and causing jams. The original file has a filament path of 2.2mm diameter. I have not had any jams with the filament I am using so the feedback is appreciated. I have added a new file with a 2.5mm path for those who want that option.</p> <p>Links to the parts needed:<br/> <a href="https://amzn.to/2ULE7sb">https://amzn.to/2ULE7sb</a> 5mmx120mm smooth rod<br/> <a href="https://amzn.to/39Bqd0d">https://amzn.to/39Bqd0d</a> 8x3 m5 inserts<br/> <a href="https://amzn.to/2SSZTIf">https://amzn.to/2SSZTIf</a> Festo type Inserts (best deal I could find for ones that work well)</p> <p>If there is enough demand I will put together a hardware kit for this project as well as the other mods I have for the MMU2s.</p> <h3>Print instructions</h3><p>This was not standard at all, the 3mf file should have all the print settings. Anyhow 0.2 quality with 3 perimeters should be fine.<br/> YMMV</p>