Parametric Solid Modeling Software for Stringed Instrument Design

by R.M. Mottola

Originally published in American Lutherie #87, 2006



Most folks are awed when first witnessing a Computer Numerical Control (CNC) machine shaping an instrument part. Since such a demonstration makes the advantages of using this technology immediately obvious, a number of people look into acquiring these tools for their own use. A substantial portion quickly loses interest when finding out the depth of complexity of the tools needed to design and build in this manner. Computer Aided Design (CAD) software must be mastered in order to draw the parts. Computer Aided Manufacturing (CAM) software must be mastered in order to specify how the drawings will be utilized in the machining process and to control the CNC machine. And the details of the CNC machine itself must be comprehended before real work can be performed. All of this conspires to lead all but the highly technical and/or highly motivated to the conclusion that these technologies need to be made a lot simpler and more accessible before they can be widely exploited in the industry. Adaptation and use of these technologies can be considered analogous to that of the automobile. When first introduced, the car was something only accessible to those who could understand all of the details of the machine (and repair all the parts, too), but eventually it evolved into a more commodity-like device that is usable with little or no knowledge of its inner workings.

This article is an introduction to Parametric Solid Modeling (PSM), an existing second-generation CAD technology that offers potential to bring the benefits of CAD/CAM/CNC to a wider user base. A comprehensive library of parametric models of instrument parts and subassemblies could go a long way toward making these technologies generally accessible. The availability of such a library could render a number of aspects of instrument design to sequences of preparing simple drawings and filling in values in forms. No such library currently exists, but it is possible and likely that one could be developed. Folks working with PSM software in this industry undoubtedly have developed such models for their own use. I have some of my own and will use one as an example of how this technology works.