Class 2/6/13: Joining things!

After formally testing the bottle openers (everyone's worked, especially mine!), we split into four groups to rotate around stations to learn how to join together pieces of plastic.  We used piano wire to make a rotating or fixed hinge, melted plastic at 400 degrees to fuse it together, played with calipers to measure the diameters of Delrin rods and bushings to see which would fit, and finally made a plate with notches of various sizes and semi-matching pegs to see how accurate our measurements needed to be to make a peg fit into a hole.  There are pros and cons to each joining method:

Piano wire:

Pros:

• Can be a slip fit for a hinge
• Can be tight fit that doesn't wiggle
• The drill press is really cool

Cons:

• Must be able to drill all the way through the piece--limited length of the hinge

Heat press:

Pros:

• Very sturdy seal
• Aesthetically pleasing

Cons:

• Bubble on the back (may cause instability of final structure if trying to stand on that plane)
• Can only join small pegs (not much fits inside the heat tip)
• Difficult to join things at a non-90-degree angle
• The cooling air is really loud

Pegs:

Pros:

• Can be any size
• Measure exactly with SolidWorks

Cons:

• Must fit exactly; difficult when trying to account for the laser cutter
• Only 90-degree fitting (unless file by hand)

Delrin rods/bushings:

Pros:

• Screw-in bushings are very sturdy
• Loose bushings allow for rotation, and can serve as a sort of washer or spacer between larger pieces of Delrin
• Tight bushings may be used to attach rods to larger pieces of Delrin, like nuts to hold on an axle

Cons:

• Loose bushings tend to make joints wobbly and less sturdy
• Loose or tight bushings must be sized perfectly; difficult when trying to account for the laser cutter
• Tight bushings are difficult to put on or remove