Super-Simple Up Feed Mechanism with Adjustable Spring
by pleppik, published
This is a replacement filament feed mechanism for the Up! hot-end. It features an adjustable spring for holding the filament against the feed gear, and is designed to be easy to print and assemble and use a minimal amount of plastic.
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You will need two additional parts for this mechanism:
1) A pen clip from a Pilot Precise V7 Rolling Ball pen (or the equivalent). I got a package of these pens from Staples for just a few bucks. Other pen clips may also work, provided that the clip is made with a bent piece of steel about 0.5mm thick and 5-6mm wide.
2) An M3 screw, at least 12mm long, to provide the spring adjustment mechanism.
The assembly photos should be (mostly) self-explanatory. Here are the step-by-step assembly instructions:
1) Print both STL files. I recommend the highest fill settings for strength.
2) Remove the clip from the pen. You can use the pen for other purposes--they're nice pens.
3) Using pliers, make two bends in the pen clip as illustrated in the photo. The first bend should be away from the "bump" at the end of the clip, and about 7mm from the top of the bump. The second bend should be about 17mm from the first. You can be a millimeter or two inaccurate and it will still work.
4) Leave about 10mm of the end of the clip, and cut off the excess.
5) Set the clip at a diagonal between the three retainer pegs on the feed mechanism as shown in Assembly Step 1. Do not try to bend the clip or force it! This could easily knock one of the pegs off.
6) Rotate the clip so it is horizontal between the three retainer pegs as shown in Assembly Step 2. At this point it should be held securely to the feed mechanism, but slide back and forth easily.
7) Screw the M3 bolt as shown in Assembly Step 3. This will provide tension when filament is loaded, and keep the clip from sliding out.
8) Attach the Connector Holder as shown in Assembly Step 4.
9) Attach the connector PCB from the printer to the Connector Holder, using the original screws from the connector PCB, as shown in Assembly Step 5.
10) Attach the entire assembly to the filament feed stepper as shown in Assembly Step 6, again using the original screws from the Up.
Re-mount the feed mechanism to the printer, and you're ready to go. You can tighten the adjustment screw to compensate for variations in filament diameter--but I've found it works just fine left at a fairly tight setting all the time. The polished steel of the pen clip provides almost no friction against ABS.
Note that this design does not provide a place to mount the extruder cover. I haven't used the cover almost since Day 1, and I find it mostly just gets in the way.