This weeks assignment was to design or modify a machine. We decided to build a 3D printer based on the Ultimaker. The major change to the machine will be a taller build platform. Due to the size limitations of our laser cutter we decided to out source the cutting. John did the case design mods and had them cut. We also bought several of the electronic components from Ultimaker and outsourced the pcb fabrication. My major contribution was on the hot end. The hot end kit we got from Ultimaker did not come with all the parts so I volunteered to fabricate some of the missing pieces. The big ones were the aluminum plate that the extruder nozzle attaches to and the tube connectors for the bowden tube. To make the plate I started with the laser cut piece that attaches to it and a drawing from Bruce Wattendorf's git hub page. The dimensions on the drawing were somewhat confusing and incomplete so I used the sketch and based all my dimensions off of the laser cut piece. I used vernier calipers to take all of the measurements. Overall dimesion of the square, size of the holes and several measurements to calculate the center locations of the holes. The Ultimaker is all metric so I had to convert to standard and make things as close as I could. I machined the piece from a scrap of 1/2" aluminum plate. I rough cut the square with a sawzall then performed all of the machining on a small mill. The piece came out pretty well with only some minor ajustments needing to be made for final fit.
The bowden tube was the only part of the original design that was not metric. Unfortunately I had Teflon tube that would work but it was 6mm. The big challenge wasn't the tube but the push to connect fittings. Ultimaker gave very little info on them so I decided to modify some that I had. I basically machined off the end of a 6mm tube x 1/4" NPT fitting and removed the guts. I then adjusted the diameter of the hole in the laser cut part and pressed it in. It fit perfectly and should work better than the Ultimaker part.
