2015.04.27

Imperial Gear

I find it interesting the way we address problems. Take for instance, this simple gear. For the Prusa i3 printers we are building at school we realized we didn’t have 8mm bolts, so we got a bunch of 5/16″ bolts, and then we realized we needed to print new gears…

Calvin started to edit the STL file we had, and I asked if he looked around for an existing 5/16″ compatible gear on Thingiverse. He said he didn’t even think of doing that, and got right to modeling. Sadly, Calvin’s new gear was slightly too small. The next day I mentioned it to Fred, and Fred decided to fix the gear. I told Fred that it might be helpful to just model the new bolt-head part and print it to see if it would fit. This has the advantage of printing much faster than the entire model. He took that advice, but it still didn’t fit.

Meanwhile, I found a gear generator library for OpenSCAD and tried to model a new gear, but that failed as it wasn’t fully parametric in regards to the number of teeth.

After all that, Fons came along and said “I’ll just put the hex head of the bolt on the grinder until it fits the gear that Calvin made.” Duh! A great hack to make it work!

While I loved the hack, I also wanted to make sure that others could easily have a gear that worked with a 5/16″ bolt and did not require grinding down the head. I’m also preparing for the future when a part fails, and someone needs to replace it, and doesn’t realize the bolt was altered, or heated with a torch to get it into place.

So I followed my own rapid-rapid prototyping advice, printed a few versions of just the hex head part until it fit perfectly, then dropped it onto the model of the gear, and printed a few. And they worked.

And then I uploaded the gear to Thingiverse and Youmagine in the hope that someone else who has the same problem in the future can just grab the one I created and get on with their day.

Sharing, it’s a thing.

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