On Saturday we started by assembling the Moineau pump. The It was about 6 inches, and the pumping chamber and drive shaft about half that length. While the last component was printing out, I saw that it would not fit onto our stepper motors without a connector or adapter piece. It also did not have an obvious way to mount on the stepper motor. This was a bit of forshadowing for later issues which came up around the them theme of "needing to think about how to mount many components together.

An attempt was made to drill a wide bore in the top of the pumpt to mount the circular end of the stepper motor, but in the process the pump was broken. Daphne started to print out a new part, but with little time to spare I wanted to confirm that the pump would actually work before we spent the rest of the day working on it.

I had unresolved questions about whether frosting could really be drawing through the pump by suction, as the design of the pump implied. Joe wisely pointed out the frosting is an emulsion (solid mixed with gas), which means is compressible, unlike water and other liquids which would be used in the pump. When the pump tried to pull the frosting, we thought the frosting might simply expand in volume, and resist being pumped by the small pressure gradient create by the pump.

I realized that even with the motor tube shattered, we could still test the pump by filling the chamber with frosting, and sealing every opening but the extruder end. We could then drive the screw from the bottom and see if it pulls frosting. I drilled a pilot hole in the motor and mounted a drywall screw into the 3D part, and then used the Dewalt do drive the shaft clockwise (looking from top-down). Frosting came out! But it was inconsitent and slow to pump.

At this point, the peristaltic pump/water balloon method seemed to be the best option. It was getting late, so I tried to figure out how to mount water ballon and frosting tube on the chassis. The Harvard shop was closed and there was only some rudimentary scraps around the shop. I tried to make a kind of hook and clamp to mount the bag from, but it looked like shit. Joe thankfully came to the rescue and helped me work on a wood frame from OSB scraps. He showed me how to use a Miter Box, which I had never seen before. It was a simple plastic guide with 90 and 45 degree slots in the Y and Z planes, which could help guide hacksaw cuts to be cleaner and smoother. I'd been spoiled with having compound miter saw growing up, and I never realized that there was a simple device to help you make some similar angled cuts (in a much more limited range) using just hand tools.

Unfortunately the story did not have a happy ending. The mount was problematic and heavy, and we still had concerns about programing a DC board to interact with Gestalt to drive the peristaltic pump. I also realized (the next day) that the "scraps" we were cutting up were actually pieces to Jeff's CNC project, and they were in a bin with his name on it. I felt bad about that one. After growing frustrated, I went home. I decided to redesign the extruder completely from scratch, so that it could be driven by a stepper motor and take advantage of a design I had put forth in the first group meeting - creating a giant frosting "syringe", driven by stepper mounted plunger. I took measurements of the Gestalt arm when I left, and then spent the entire rest of the night and morning making a new design in Rhino.

The new design had two main components - a stepper driven syringe/frosting extruder, and a frame for mounting and alignment. The plunger consisted of an 8" long and 2" diameter PVC tube; five 3D printed components (2 in nozzle, 3 on the plunger). the plunger also featured a press-fit cardboard plunger rod, which was study enough and much less time consuming to make than a 3D printed handle would have been. I also designed the 3D components to interface with the cardboard, inseting into fitted slots and aligning with horzonal through-holes for mounting bolts, if necesary. The top of the plunger was in two parts, the bottom one which fitted over the traiangular coupler which came attached to Nadya's steppers, and then a top piece which constrainted the other side of the coupler, and clapmed to the lower piece.

The other main component was the frame. It was large enough to fit over the entire Gestalt arm, and because of the lenght of the stepper shaft, the motor needed to be mounted above the highest point of the arm. Components were held in place by gravity, and by resting in 2-layer recesses in the cardboard, cut in the silouets of two horizontal layers of the component, preventing downward or rotational movement. The frame was press fit, and the syringe would be supported by large tabs on the nozzle end, which rested on the bottom of the frame. The plunger would be guided by two wooden-dowel rods, made from some nice scraps I found it the shop, which ran surprisingly true.