Thing-o-Matic Extruder, Mk7 Upgrade

thingiverse

This is an upgrade for the Thing-O-Matic Mk7 Extruder. Features: * Easy filament swap * Open drive wheel for easy cleaning * Bearing idler * Non-printable parts are easy to source * Adjustable idler pressure * Quick to print I created this upgrade because I was having some issues with plunger pressure not being adjustable. I didn't want to go with some of the other designs on here because of the difficulty of adjusting tension or the difficulty of sourcing exactly the correct springs. Additionally, some of the really nice extruders out there are HUGE! I didn't want to spend hours printing and potentially lose the print on a faulty plunger. For the full troubleshooting story, check out the blog entry at http://slightlynybbled.blogspot.com/2015/09/makerbot-extruder-woes-and-successes.html Additional notes: * I have made a few minor upgrades to the assembly since printing my version. * I had a small crash near the lower right, but not enough to cause an actual problem. I have since raised the spring assembly 0.1". * This part is inspired by many things I have seen on thingiverse. I couldn't begin to name them all. * Basic design should be easy to adapt to other spring and bearing sizes. It appears as though there is a high-friction surface between the base and arm, but in fact, the two do come into contact with a small bevel around the rotation point that ensures smooth movement. I am supporting feed rates of 55mm/s on my ToM and don't want to damage anything, so I probably won't go much higher than this. If you have a different set of springs - say, 1" or 1.5", drop a line in the comments and I can remix this easily enough. Just send the complete spring dimensions (hole sizes at the ends, length when extended, and width). Things to purchase: * 2" tension springs (easy to find at Lowes or Home Depot for a couple of bucks) * Bearing, 10mm OD, 3mm ID, 4mm Depth (http://www.amazon.com/gp/product/B008DSKCI6?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s00) Instructions correspond to the order of the pictures. Print your parts. The file "extruder_printable_all.STL" contains the entire assembly. Individual parts are also supplied as STL files. I printed with 20% fill, you probably want to go with something like 40%. There is also a small chamfered overhang on the "bearing_clamp.STL" file. This overhang should be easily printed on most machines. Disassemble your stock Mk7 extruder. Keep the flat-head screws. You won't need to remove your filament. Assemble the bearing to the extruder arm. Place the extruder arm on the extruder base. Place the bearing clamp over the bearing bore insert. Depending on your print settings, you may need to bore this out slightly. Press the bearing clamp all the way down, it should require some force since the small overhangs on the edges are meant to hold tight to the sides. Apply the flat-head screw through all three printed parts. It should fit snugly. The arm motion should be clearly articulated around the screw at this point. Place the assembly on your motor, tighten the right screw a bit, and use the other flathead screw on the left side. Tighten both screws firmly, but you don't need a lot of force. Place the spring(s) on the right side. Make adjustments by adding/removing springs and by moving springs in or out. Re-assemble the fan to the front of the extruder. Happy printing!