Last fall I joined Generator, a new maker space in Burlington, VT. I'm super exited about it. I took a metal working class in November so I can do some basic welding now. They've got a rapid prototype area including 3D printer and laster cutter plus a Roland CNC milling machine.
I used the 3D printer to make some mounting brackets for the snare drum project and haven't thought of a good project for the laser cutter yet. My main interest is the milling machine. Of course I built my own, but the Roland is quite a bit more capable. My machine is quite good for working aluminum and making "machine shop" type functional parts. The Roland mill looks to be intended for prototyping industrial design type things.
I'm exploring the idea of using the Roland to make some plaster sculptures. Many years ago 3D modeling and animation was part of my full-time job. I was pretty good with Lightwave and Blender. Blender is an open source program which has come a tremendously long way since I used it last. I rediscovered it in mid November and have spent quite a lot of time with it.
I have some ideas for several sculptures that are sort of "relief" in nature, so a rectangular brick of material with one side carved out. The Roland mill supports 2-sided milling via a 4th rotary axis. I'll get to more sophisticated designs later. I created a model of a "bug" that was inspired by an origami cicada. I cut the piece on the Roland mill. Here it is:
The material is a mixture of plaster of Paris and glue (and water). The glue helps keep the dust down quite a bit. I'd even say there's no air-borne dust at all but I suppose there are trace amounts. Roughing the piece with a 1/4" bit and fairly high feed rate produces some nice "chips". High-speed finishing with the smaller bits produces powder that pretty much falls close to the bit, nothing getting flung against the side of the enclosure.
As you can see from the photo I'm getting air bubbles in the plaster. I'd like to push the machine to get some very fine detail out of it, but the bubbles ruin it. I've looked in to pressure chambers and vacuum chambers for eliminating bubbles but I don't really want to spend that much on it. I originally started using the plaster as a practice material because it's cheap.
I made a simple form for casting the plaster bricks and built in a "vibration" rod on the underside. I attach a drill to the rod and run it for a few minutes after pouring the cast. I'm also trying different mixing strategies.
The plaster is Dap - basic stuff from the hardware store. I'm told it's often "stale" whatever that means. I've been studying plaster and it turns out there is quite a variety of formulas. I was tooling around ebay looking for a good price when I found a seller that had several formulas. I contacted him through ebay and then ended up talking about it on the phone with him. He's going to send me some samples so I can mess around a bit to figure out what might be better. A more "pure" gypsum with less "filler" material may not bubble as easily. I'm also going to experiment with latex paint instead of the glue.
