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CAM and CNC Machining guitar body

CAM and CNC Machining guitar body

After long time finding out a workflow for making the guitar body on my DIY CNC machine, I finally found the time to actually make it happen.

The video takes you through the settings in CAM and also shows you the actual job as well as the endresult. In this post I’ll give you my ideas on how to improve my results.

The FACING strategy eats away much of the top of the stock and leaves 0.1mm. Since I’m using a 6mm flat bit, Fusion360 decided to use 5.7mm as overstep. That SHOULD be enough to make a clear face, but in practice this just doesn’t work out that way. All lose bits and pieces are more likeley to ‘tear off’ later and leave possible ‘scars’ on the guitarbody. So before I started the bottom job I already changed the stepover to 5mm for the facing strategy. Improvement #1: use smaller stepovers for the facing job. Also, I like to minimize toolchanges but this process can be faster by using a bigger bit. I do have a 25mm flat bit, so the stepover would be something like 24 mm. This would save a few minutes (although it’s only 9 minutes with the 6mm bit).

The CONTOUR strategy cuts out the rough shape all around. I do this in two passes, so a big gap appears between the stock and the guitar body. This way I avoid the dreaded ‘red lines’ in simulation (indicating warnings like:”hitting stock too hard”). These red lines notify you that SOMETHING is not right. By making the gap wider this is less likely to happen. The contour strategy though, only cuts half of the bodyheight and the other half when I do the other side. The result is a visible line halfway on the side. I can remove this by sanding it down, but I rather not sand at all 🙂
So improvement #2: contour the whole body height in one go and create 4 tabs which hold the body into place. How to exactly do this is project in itself. If I find the answer, I’ll be sure to let you know.

The PARALLEL strategy gives the body its perfect shape. In the video I’m using an overstep of 1 mm for timesake. But it could easily be done with 0,5mm or even smaller; it takes more time but the upside is that the result is much smoother. The result now shows small ‘steps’ in the wood which must be sanded down. I start with a very rough 40grit paper, and end up using a 320grit paper. Very smooth finish, but I need to very carefully sand down to remove these ‘steps’.
Improvement #3: Instead of using a flat bit 6mm, 32mm long, I might better use a 6mm ballnose. This in combination with smaller oversteps is likely to produce a smoother result with the parallel strategy. Also, I’m running this strategy both ways now, but could achive more even results probably if I would use ‘one direction’ passes. Smaller steps would also make it possible speed up the process, I’m now running at 3000mm/min but this could also very well be done with 5000mm/min.

UPDATE: after trying to fit the neck onto the body I found out that the cutout for the neck was +/- 0,8 mm overall too narrow. So I ran a test where I cutout a testpiece where the ‘neck’-part would exactly fit the ‘body’ in the design. As expected now, the actual fit is too tight. Then I made a test piece where the neckjoint was 0,5mm wider on all sides and the neck still had the designed dimensions; there is just a tiny space visible on the drawing (0,5mm on all sides of the neckjoint) but makes a nice snug fit when the part is actually fitted.

I might have forgotten a thing or two to mention here. But if you think I could improve on something else, or maybe you have a question, please let me know. Comments can be placed under the video or email me. Cheers!

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