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Building dulcimers with a CNC router

My dulcimers rely heavily on the accuracy of my computer controlled (CNC) router. I would even say that without it, I could not produce my current dulcimer designs. It totally amazes me that a relatively inexpensive machine that I built from a kit in a day and a half can hold tolerances within the thickness of a human hair over it’s 32” x 32” work area. It can mill the 0.023 inch wide fret slots in very hard wood (with a very small 0.023 diameter bit) or hog through an inch and a half of neck in successive passes. So you just get router and start making parts- right? Not quite. Like most computer controlled devices, the CNC router is useless without the exact control instructions to generate the part you want to make.

The process starts with a virtual model of the part in a solids modeling program. I was moderately proficient with 2D CAD programs when I purchased the router, but had no solids modeling experience. I taught myself to use Autodesk Fusion 360 over a somewhat frustrating nine month period. This was despite the fact that most parts I make are 2 1/2 D, meaning that they are flat 2D parts extruded in one direction to make a solid. There was a point in the learning process where things came together and models that took a week could be done in an hour. Then in minutes. There are still some challenges that come along. Milling the fret slots on Aaron’s radiused fretboard had me scratching my head for a few days.

Once you have generated a model of the part you are only half the way there. You must then generate the tool paths to cut the part on the machine. This can be done within Fusion 360 in the manufacturing portion of the program. Again there is a learning curve to select the best method and sequence for doing the routing. Router bits must be specified and speeds and feeds selected. Experience is needed to optimize the process. Amazingly, I got through this period without breaking any bits. I am sure I was erring on the safe side.

So you are finally ready to make a part. Well almost. You must first take the machine instructions (G code) you just created and run them through a program that interprets them for your exact type of router. This is call a post processor. Once run through the post, you can actually bring the instructions up in the router specific software you use to run the router. Whew! Rather daunting to the uninitiated. Nevertheless, it can all be self taught if you have the patience to work through each step. Once learned, the machine becomes like any other woodworking tool in the shop and you find yourself using it for more and more tasks. It is particularly good at making very accurate fixtures. My side bending and assembly fixtures were both made on the router as were many other jigs.

I feel fortunate that low cost technology became available at the right time for me to utilize it in producing my designs. It opens a world of possibilities. It doesn’t build the instruments for you, however. If you put very accurate blanks into the machine it gets you a pile of very accurate parts. From there, all the traditional woodworking and finishing skills come into play. Fortunately, I have been doing fine woodworking since I was 14 and spraying glass smooth finishes on my racing dinghy for as long. I guess I was destined to be a dulcimer maker all along.

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