Assignment 1: Cutting Stuff.....

Overview:

Initially, I had high hopes of playing with geometries, shapes and forms. As the week went on, the focus shifted to evaluating tools and trying to get the tools to work. As I started cutting materials, I also started experimenting with the materials themselves.

The final "product" is a lighting construction set, with a walk through making motor mounts, and grids.

Experiment 1: Learning CAD, Experimenting with Cardboard and Mounting Motors

    Several of the 3D CAD packages had tutorials for making plates with holes in them.    I decided to make a plate that I could mount a NEMA23 stepper motor to, out of cardboard.    Surprisingly, the center hole came out a perfect fit to the face of the motor.
    I was wondering if cardboard could be used as a low cost material that could be used as a partial replacement for plywood or plastic.    Cardboard isn't strong enough to support several pounds of motor, so I thought I would experiment with using "Minwax wood hardener".    This material costs about $11/quart, and I used a couple of tablespoons for several cats on the entire assembly.
   This made the cardboard stronger, and looks pretty strong the length of the ribs, but would buckle if I tried to bend it across the ribs.    Layering two pieces perpendicular to each other may help.    The assembly is weak near the edges/corner.    A better quality cardboard might also help, or some better "wood hardener".

   Conclusion:

Wood hardener makes the cardboard stronger, and more robust.
Two layers of cardboard with the ribs perpendicular will make a stronger assembly.
The corners and edges are not strong and will still crush.

Experiment 2: Press-fit Pieces

Next I tried to make cardboard pieces that would fit together in a grid, with an eye towards extending to more complex surfaces. (With the hope that it could be used to make a construction kit that would allow making structures/surfaces for prototype furniture.) This was successful, although the laser-cutter would make multiple passes over the lines several times. Setup and cutting time was long, so I only made a handful of pieces.

Experiment 3: Lighting Construction Kit

The press-fit pieces made me wonder if they could be used as a multi-segment light-pipe. I resized the strips for acrylic, and made a circle with slots that could be assembled at angles. I cut holes to embed an LED in the pieces.

Discs with LED's

To not violate the "no adhesive rule" of the assignment, I used a "Star Trek Captain Kirk would be proud" slit and wrap wire wrap gun. When used with proper wire-wrap pins it creates a MIL-Spec gas tight joint that is very reliable. I had problems with the LED pins being too round (the wire-wrap pins are usually square) and too thin, so I crushed them slightly with a pair of pliers. The LEDs are powered off a USB battery, and a 330 ohm resistor is in series with the positive lead of each LED. (Looking at the LED, the smaller internal part is the positive.)
slitwrap gun

Results/Lessons Learned:

Acrylic isn't the best choice for press fit pieces. Too tight, and it cracks, too loose, and it does not stay. Try it too many times, and it scratches.
Sheet acrylic varies from piece to piece and end to end in thickness.
CAD -- Parts seem to deteriorate when I cut and pasted them. Details seem to get dropped from generation to generation. This could be my lack of cad skills. There may even be variances from cut to cut.

The Final Result:

Future Ideas:

Add more shapes
Figure out better acrylic/led mounting.
Think about adding contacts to slots, so that the thing wires itself.

Implementation notes:

   The majority of the files ended up being drawn on Inventor, and exported to Autocad.    This resulted in 3D models in Autocad, and the laser cutter would cut the lines multiple times.    This may have made for wider kerfs, and made plotting very slow.

Notes on using the Epilog 60 laser cutter.
    The kerf through acrylic is .159-.138 = .01 inches per cut (2 for a slot.. i.e. .02 inches)
    For cardboard it is .172-.133 = .019 inches per cut (2 for slot, i.e. .039")

    This may be with the multipass bug in my cad files... Not sure.

    Using Inventor, and chamfer of .03 on openings of slots for cardboard.

    So for .125" plastic we will try .108ish slots, which are too narrow for the power settings I used.   In the end, I ended up setting the slots to .125"

    Copper foil with backing .006" (for conductors later).