Parametric Based Controller for Rapid Prototyping Applications

Abstract

A methodology aiming at reproducing in Rapid Prototyping applications, exact parametric curves from CAD data is presented. The approach consists of converting the space-based parametric curves from the CAD system into time-base, such that the equations of the curve in terms of time are then fed to a controller directly. Optimization is used to solve the problem, which has both Rapid Prototyping process and scanning constraints. With information such as the equation of the curve, its first and second derivatives with respect to time, a real-time trajectory controller can be designed. The trajectory displays an increase in accuracy over traditional approaches using STL files, which is ofthe order of the chordal tolerance used to generate tessellations. The system model involves electrical and mechanical dynamics of the galvanometers and sensors. The controller, which acts on two mirrors, deflecting the laser beam of a stereolithography machine in the x and y directions respectively, should be easily substituted for current systems. Application of the methodology to freeform curves shows acceptable tracking and can be improved by judicious selection ofthe equation representing the spatial parameter as a function of time.