Earlier this year Woody developed CNC projects for inlays and, in the end, the result was very good... especially for a first effort (see March, 2018 journal).  Now I'm working on  programs that will take some of the shoulder work out of the guitar/ mandolin building processes. Like manually contouring the surface of the fretboard with a 12-inch radius sanding block. The CNC can rough cut ebony or rosewood quicker and better than my old shoulders. The luthier still has to smooth sand after the inlays are set. The final product doesn't necessarily come quicker, but it is better.  No flat spots from over sanding and a uniform radius improves the fret installation.

   Another convenient use of the CNC will be in rough-carving a mandolin top and back. I'm working up to that.

     Last week I worked on a program to inlay scrimshaw that I had an artist produce. The ivory is about 1/8" thick. Here are some photos that might give you the idea. On the right is a shot of the toolpath commands.  As you can see, it is primarily drop-down and select...no writing of code  (that's​ a good thing).    

October, 2018

Beginner Project on CNC

     Inlay Scrimshaw

     Cut out the Bridge

​     What the home-shop luthier needs are self-designed and programmed tool paths. Bottom line: It takes time and study to produce your first custom design. One has to accept that mistakes are common and you might as well get used to it.​  

Beginner Project (the bunny is extra)

    Today I am working on design and toolpaths for cutting out a guitar bridge.  Below is what I have so far on the design screen... pretty generic, huh? Again, notice the various design icons on the left...seems simple but these tools will only do what you instruct them to do. The process of design creation will make you think and observe more precisely.

     Now to open the toolpath screen and create the various toolpaths to cut out a guitar bridge...can o' corn.  Right?

Scrimshaw on ivory for inlay.

Vectric preview of routed inlay pocket.

    OK, it took about an hour to design the bridge in the top photo using the tools on the left. The effort is to layout the shape and get the vector lines smooth and symetrical.  Then it took less than 20 minutes to select the various tools to cut each vector path. 

     Now I need to save the toolpaths in a machine language that the CNC understands.  Select language (post processor) from a drop down list.  Of course, the machine uses the same language every time so I just have to select it once...when I create the first toolpath.  Then, in execution of the project on the CNC one must manually change the tool (router bit) after completion of each toolpath.  Toolpaths that use the same tool can be saved together and the machine will run one path after the other.

     Notice that the wings of the bridge are the same thickness as the center of the bridge.  This is because it's easy to take the wings down on a spindle sander later... or, I could CNC rout these areas down to the approximate thicknes and then take the bridge to the spindle sander to smooth out the  transition up to the top of the bridge.

     A final note: See the little tabs that are holding the bridge in the blank in the preview. You can see five of them in this picture. There are actually six.  These are to hold the bridge in place while the router bit continues around the work until it is completely through the stock. Without the tabs the bridge would snap free while the router is making its final passes and this NO GOOD! After the bridge and the router bit stopped fighting for territory one of them is going to fly who knows where and either or both will be badly damaged. Just hope that somebody is not in the line of fire.  Create the tabs and sand them off later.

   OK.  That's enough for now...gotta go make some wood chips.


Toolpaths created on Vectric software.

Peg head ornament.

Nice fit.

Routed inlay pocket in MDF.

Shark CNC practice

---------------------- about 2 inches --------------------

     Most of the month was spent developing new ways to use the Shark CNC to mill out guitar parts and inlays.  It's a tedious process with lots of study and learning (hopefully). It's not simple, primarily because it seems that each project is unique to guitar building. The designs and toolpaths are, therfore, not standard fare for home-shop CNC machining.  Most beginners start with making signs and carving figures from clip-art files.