Friday, August 22, 2014

Once more, with feeling

My too-clever-by-half use of laser-cut plywood gears ended badly. Small errors repeatedly accumulated to make the gears fit unreliably. It was a mess. I needed another idea.

I started thinking about timing belts, especially something clever that Vik Olliver did on Rep Rap involving those ball chains used to switch ceiling lights on and off. I didn't really trust myself to be able to solder the ball chain together, and I continued scratching my head. Then I saw one of those bicycle chain bottle openers at a party, and realized that bicycle chain was the solution to my problem.

I started learning about roller chain and sprockets. It turns out sprocket tooth design is really pretty simple, much simpler than involute gear teeth, and I was able to design some sprockets with just a little study. It took a redesign because the first time, my stepper sprocket design assumed a friction fit would work, but when the part arrived, I discovered I'd need a set screw. In the picture to the left, I retrofitted a set screw on the initial sprocket design with sub-optimal results. This is probably adequate on a temporary basis, but an improved design is pending and should arrive by the end of August and should be in place for exhibition at Maker Faire.

 So this is the new design. I think it retains the Steampunk flavor of the original design, if perhaps not quite as pronounced. It's a bit simpler and all the plywood cutting can be done by hand with a compass and a jigsaw. So my design goal that it should be buildable by a person of minimal craftsmanship (like myself) is intact.

Barring some disaster, I expect to be exhibiting this printer (hopefully in operation) at Maker Faire NYC 2014, at the New York Hall of Science in Queens, on September 20th and 21st. If you're reading this, you're invited to come see it. If you can't make it, I'll try to post as much information here, on Github, and on Youtube as possible.

1 comment:

Amiya Sarkar said...

Pretty serendipitous and encouraging innovation! Bottle openers can be eye openers too.. Eureka!