I received some queries asking what exactly I did with my CNC router for making model parts, so having just finished cutting out the upsized cannon parts I thought I’d share:

The first thing I do is draw the parts in a vector graphics program called Inkscape (the open source alternative to Adobe Illustrator). It’s a great program! I then choose to make a copy of the artwork and convert everything to toolpaths. I’m using a 1mm diameter cutter for this so the toolpath will be 0.5mm (the cutter radius) outside of the line I want to cut. While there are automated tools for converting vector artwork into toolpaths, I’ve found that doing it manually doesn’t take that much longer and is less error prone. More importantly it allows me to precisely control the locations of the tabs which hold the part to the sheet. Kind of like sprue gates on injection moulded parts (although a different purpose).

Once I have the toolpaths drawn up I export them as a dxf file. This can be loaded directly into my machine control software.

I have an abundant supply of 1mm and 1.5mm styrene sheet, so I cut them up into approximately A5 sizes to fit on my router table. The styrene sheet is clamped down and I run the program. It generally takes anywhere between 5 and 15 minutes for most stuff I do. Note that I’m cutting out solely in 2.5D: cutting out 2D shapes.

This is what I end up with:

I then cut the tabs and start assembling. Easy! While it’s not a 5 second process, it’s still WAY faster than having to cut out all of that detail by hand (especially if there are duplicate parts) and provides such precise curves and geometry I shudder at the thought of doing many of my parts any other way!

So tonight I’ll start assembling the new cannon. I’m really pleased with the design tweaks I’ve made too.

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