I though it’d be fun to make a tiny bicycle out of our little 3″ x 4″ piece of delrin. I could have tried to make it all one piece, but I wanted the wheels to be able to rotate, so I decided to use pegs to hold it all together.
It started with an Illustrator sketch. I sized the artboard to the delrin block I had so I knew how much space I had to work with. I then sketched out the frame, wheels and pegs that would hold it all together. Two pegs will act as the front forks, one will act as the chain stay, and one as the seat stay. I would have like to figure out a way to have 2 chain stays and 2 seat stays, but I didn’t have enough room to add more pegs and I didn’t want the bike to be too tiny, so I settled on one of each.
But pulling this into Otherplan, I quickly realized I’d need to be smarter about how I cut it. Otherplan isn’t smart enough to cut exactly what I expect, so I had to break the sketch up into several files, which I could tune once in Otherplan.
I brought them all into Otherplan and set each file to cut how I wanted.
I put my 1/8″ bit into the machine without a hitch. Adhered the delrin with about 5 pieces of double sided tape, and readied the machine to cut. Homing and setting the bit height were a cinch.
One thing I ran into was that in my design, I assumed I could basically just drill out holes the same diameter as my bit, and found out that Otherplan doesn’t let you do that. It incorporates a factor of safety, and after playing with various diameters of holes, I found that if I set hole diameters to 0.13″, rather than 0.125″ (the diameter of the bit), and set the path to engrave, rather than cut, I could get the holes I wanted. It worked out really well.
Everything was going so smoothly until the very last piece to be cut. But this would have been way too easy if something didn’t go wrong. Just because of the way the cutting went, by the time the last peg was being cut, the corner of the block was separated into a small piece (see below). Which mean, that only a tiny piece of tape remained holding this piece to the bed. So, naturally, the bit ripped that part right off the bed. That part was lost.
And all my parts, after prying them off the bed:
While I lost one peg, not all was lost. I still had enough pegs to put the bike together, although not quite how I wanted to. But sacrifices must be made since that was all the plastic I had.
I went to hardware store and got a 1/8″ dowel, which I cut and used to hold the parts together.
One thing I didn’t spend time on was cleaning up the part after they came out of the mill. All the shredded edges. It doesn’t look great, but I’m still super happy with how it worked out.