Robotic spray paint application offers cost, environmental and safety advantages over manual spray paint application. The benefits derived from robotic paint application depend in part on the path the robot is programmed to follow. Robots can be programmed manually or automatically. Manual path programming is limited by the operators ability to visually judge what the optimum path might be. Manual programming also requires the production line be stopped while the path is programmed.

An algorithm is developed here for the generation of paint paths based upon a geometric model of the workpiece. The algorithms are applicable to planar workpieces defined by contiguous line segments.

The spray pattern is modelled as an ellipse with uniform paint distribution. The generated path is comprised of a set of parallel horizontal spray passes, starting from the upper edge of the workpiece and descending to the lower edge in equal increments. The endpoints of each individual pass are determined by the intersection of the pass center with a curve offset from the workpiece boundary.

A process cost model is developed to quantify the economic cost of spraying an individual workpiece. The model includes the cost of the paint itself, operating and maintenance costs of the painting system, and costs for filtration and disposal of waste paint.

An algorithm is presented for minimizing the process cost model. The algorithm illustrates that minimum process cost is obtained with the highest possible spray gun velocity, subject to the constraints of maximum paint flowrate and required paint thickness, and the spray pattern adjusted for minimum aspect ratio.

For general workpiece geometry an exhaustive search over the feasible range of spray pattern size and pass orientation is required. For the special case of rectangular workpiece geometry the minimum cost occurs for spray passes oriented either parallel or perpendicular to the base of the rectangle. For rectangular workpieces there also exists a set of spray pattern sizes that result in local minima of the process cost function. The global minimum can be found through comparison of the local minima.

For a given deposition profile the uniformity of paint thickness over consecutive spray passes is determined by the overlap between them. Three measures for paint thickness uniformity are presented. For the elliptical spray pattern used here the optimum uniformity occurs between 16-18 percent overlap, depending which measure of uniformity is used.

The algorithms presented here have been written in the 'C' programming language and can be executed within the AutoCAD environment