Monday, March 28, 2011

Plastruder MK4 mod (this will be boring unless you're familiar with the makerbot)

I've had a Makerbot Cupcake CNC for a year now and I'm embarrassed to say I have yet to print anything on it.  I got frustrated with my inability to update the firmware on the extruder board, as well as the poorly organized instructions on the makerbot website.  Anyway, I have dusted off the ol' makerbot and am determined to print something before a friend of mine prints on his brand new RepRap.  He's had issues with his machine as well, but he's only had his for 2-3 weeks.  He already has some decent attempts at printing.

A few weeks ago, I successfully updated the motherboard firmware, as well as the extruder board's firmware, so this got me pretty motivated.  My main obstacle right now is the MK4 Plastruder.  This part of the printer feeds plastic filament into a heating chamber, which melts the plastic into liquid form.  As more filament is fed into the heating chamber, the molten plastic is pushed out of a tiny nozzle onto a build platform.  My MK4 has problems feeding the filament into the heating chamber.  The standard MK4 design has an aluminum toothed pulley (attached to a motor) and an idler wheel to grip and guide the filament.  The idler wheel is supposed to push the filament against the pulley so that the pulley teeth can grip and feed the plastic to the heating chamber.

Two problems here:
  1. The pulley teeth do not grip the plastic well. 
  2. It's nearly impossible to get the idler wheel pressed firmly enough against the filament for it to feed properly.
To solve the first problem, I bought a new pulley that makerbot claims "provides a significant (100%) increase in push strength for the filament drive of the MK4 Plastruder!"  This pulley is designed after the wire feeder on a wire welder, it has the same concave/knurled surface to grip the filament, so I truly believe it will perform 100% better.

For the second problem, I disassembled the plastruder and cut notches across the surface of the idler wheel (much like the teeth of a pulley) with a hack saw, to help the wheel grip the filament.  I put everything back together (still using the original toothed pulley) and tried it out.  It worked, sort of.  I had to hold the idler wheel against the filament to get it to feed, but it was performing better than it ever had.  No matter what I tried, I could not tighten the idle wheel bolt in a position that gripped the filament and didn't require me to push on it.

After brainstorming with my friend with the RepRap, we realized I need a better way to hold the wheel against the filament instead of relying on the axle bolt.  I came up with a bracket I'm calling the Plastruder Jack.  Here's a preview photo.  I'll continue this post later.

No comments:

Post a Comment