MK7 Hack to Enable Filament Changes Mid-Print

thingiverse

The MK7 is great. But one thing never made it into the design spec: the ability to switch filaments mid-print. Switching filaments enables multi-colored prints without fusing filament first. It also ensures that if you run out of a given filament, you can load new stock mid-print. This is very helpful for long prints. The MK7's Stainless Steel Thermal Barrier Tube is not seated close enough to the Knurled Pulley, which makes it nearly impossible for a new filament to chase another into the Tube. However, raising the Tube ~3.5mm brings it close enough so that the new filament will not bend or slip off the old filament as it enters the Tube. Another benefit is that you gain an additional ~3.5mm in Z-height! Here's some video of the results http://www.youtube.com/watch?v=I25pOHE91xY UPDATE: Zach posted a solid filament block for the MK7, so you should print this out and modify that instead of your purchased one. http://www.thingiverse.com/thing:12147 Instructions You'll need a Dremel or other tool (see photo for reference) to carve away a small portion of the Molded Drive Block. 1) Keep the Molded Drive Block attached to the stepper but remove the Knurled Pulley to avoid damage and dust. Remove ~3.5mm in by ~5mm wide to accommodate the raised Stainless Steel Thermal Barrier Tube. (See photos for reference.) 2) Re-assemble your Stainless Steel Thermal Barrier Tube inside the Bar Mount so the end protrudes ~3.5mm above the M6 Nut. 3) There should be just enough thread left below the Bar Mount to secure the entire hot end back onto the Mounting Plate. 4) Test-fit the Molded Drive Block against the raised Stainless Steel Thermal Barrier Tube. If desired, secure the Bar Mount to the stepper with M3x18 screws and make a test extrusion. Insert a new filament after snipping off the old one (see video link above) to be certain it pushes the old filament through. 5) Re-attach the Fan and Heatsink assembly.