I started to design an open source disc shooter about six months back. At that time I was using Google Sketchup to design things. Since then I’ve been designing in OpenSCAD. Here’s a few things I learned while starting over:
- Solid modelers FTW. I find it more difficult to revise a Sketchup design than it is to redesign from scratch with a solid modeler. When you move a line or surface in Sketchup, it can push/pull any lines or surfaces connected to it. Since making a change to something in Sketchup means fixing all the things connected to that change, it’s often just easier to start over.1
- Sometimes starting over isn’t so bad. One of the reasons I set this design aside was that I had hit a design block. Starting over means that I now have a fresh perspective on the design. Since then I’ve also been inspired by mraiser’s 27-to-1 reduction gearset and it’s snap-together assembly to design the mechanism with assembly of this device in mind. Another more recent inspiration is Tony’s mars rover for many of the same reasons.
- Over design and scale back later. My initial designs had pieces that were 1.5mm thick. Now I’ve redesigned the parts mostly with 2-3mm thicknesses. Just so you know, making a change like this is really really simple in OpenSCAD. Just change the thickness variable, and the design instantly incorporates the new thicknesses. Once I get the basic design totally working, I’ll be able to scale back the thickness of parts later. It will be a lot easier to decide which parts to alter once I have a working prototype.
- Printing in clear PLA isn’t always such a good idea. Yes, it’s biodegradable. Yes, it doesn’t warp on large flat pieces. And, yes, it really does smell like candy as it melts. However, finding small clear parts on tan carpet can be a challenge. I think I’ll print in nuclear green for the next batch of discs. I had honestly never previously given much thought to the color of plastic I was using in a prototype.
- Design from the inside out. In this revision, I began with designing the firing pin that slides forward and worked my way outwards. My original attempt was centered around trying to make a printable version of an existing toy. Since then I’ve tried to design from what I perceive to be the most critical parts and work my way out. 2
- Design with clearances in mind. My previous attempt did not fit well together at all. This time, since I was designing from the inside-out, I made sure that each piece could fit with the others. Also, since the prior versions were so thin, they didn’t have much room for adding clearances later.
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