how to make [almost] anything mas.863.12   work about
pressFit: week_1  

press fit drawing(s)

The focus of this week was cnc cutting. I have used both the vinyl cutter and laser cutters before but as with moving to any new shop environment there are slight differences in machines, software, interfaces and workflow. With the end focus for the final project being a being a tool or machine I decided to use press fits and the laser cutter to develop a simple machine.

The machine is a drawing machine borrowing inspiration from some of the earliest of machines used by artists, architects, and designers. Some excellent examples include the machines of John Baptist Suardi, Jean Tinguely, Charles Babbage, Desmond Paul Henry to name a few.



I designed the base of the machine to be press fit with finger-like joints and allowed for adjustable attachment on 3 varying tooth gears. In addition variable joint length arms, and a pen holder components were developed in rhino 5 beta. Unfortunately at this point rhino 5 does not have a gui interface for making gears and while a side project would be to write a quick python script to generate gears I actually found with a quick search that one of the freeware vector software that Neil recommended (inkscape) has a built in feature to draw gears. The user inputs the number of teeth, circular pitch and pressure angle and you have all of the vector gears you could ever need. I could not seem to take inkscape straight to rhino so I had to briefly pass an .eps to Illustrator and then to Rhino 5 Resulting in the final cut sheet above.

I had initially thought of trying to construct the entire device using the material constraint of corrugated cardboard as it was one of the two materials provided for this section but while designing the gear and moving parts I suspected the amount of movement might be a bit much for cardboard alone, though it would be fun to try to make test machine prototypes from cardboard. In this case I went for the acrylic for this week. I thought the gears would last a bit longer and I would need to use some mechanical fasteners for the moving pieces. After a few test on the laser I found that the laser cutters kerf was too much to use simply the press fit joints from the rhino model so I oversized the male press pieces by .004 and enlarged the mechanical fastener holes by .002 to allow the bolts to move a bit more freely than the exact bolt measurement.

I used 8-32 x 0.75 phillips head machine screws and nylon lock nuts for the mechanical fasteners. I found that the moving parts especially the gears wanted to loosen the nuts with many rotations and in the future I would probably use a sleeve between the bolt and the rotating parts. The gears are interchangeable but at the moment are prime number gears to test their drawing oscillation.

What was just as interesting as designing and building the device was seeing what it might produce.

As well as what multiple ‘toolpaths’ on the same material might look like.

Detail of the pencil pressure collet and tool paths. It would be interesting to catalog all of the possible combinations of the gear and arm positions.
  -- jared laucks -- © 2006-2012 --