SoftwareErrorCompensationofRapidPrototypingRP.pptVIP

Software Error Compensation of Rapid Prototyping (RP) Kun Tong, Sanjay Joshi, Amine Lehtihet Department of Industrial and Manufacturing Engineering The Penn State University DIMACS CAD/CAM Workshop Rutgers University, October 8, 2003 Rapid Prototyping (RP) A fabrication method in which parts are built by depositing material layer by layer under computer control. Dimensional Accuracy Main Error Sources in RP Processes: Positioning error of the tool tips (the laser beam focus or the depositing nozzle) Material shrinkage/expansion due to physical or chemical changes during prototyping CAD model ? STL file approximation error Staircase Effect due to finite layer thickness … Accuracy Studies for RP Focused on different aspects of process planning for RP STL File Correction Algorithms (van Niekerk (2000)) Slicing Algorithms (Kulkarni (1996), Tata (1998)) Tool Path Planning (Wah (2001)) Support Structure Generation Methods Parametric Tuning (Lynn(1999), Onuh(2000), Zhou(2000)) Build Orientation Optimization (Alexander(1998), Nee(2001)…) Limitation: The best-tuned system still has considerable systematic error. Software Error Compensation Software Error Compensation Approach This concept has been applied to Coordinate Measuring Machines (CMM) and machine tool systems. Three-step procedure: Build a Mathematical Machine Error Model—to write the components of the volumetric error (dx, dy, dz) as functions of the coordinates x, y and z. Develop a method of measurement to determine the coefficients in the model. Implement the error model in the machine control for compensation. How to Build the RP Error Model? Mechanistic Model or Statistical Model? RP machine is a complex system. It is very hard, if not impossible, to build a mechanistic model. Statistical model will introduce a lot of predictors which might not be significant and have no physical meaning. Solution: Build an approximated mechanistic model using the Parametric Errors Functions and Rigid Body