AUTOMATIC GENERATION OF PROCESS OUTLINES OF FORMING AND MACHINING PROCESSES (PROCESS PLANNING, CAM, COMPUTATIONAL GEOMETRY)

GAD ESHEL, Purdue University

Abstract

This thesis describes a method and a system for automatic generation of multi-technology process-outlines. A process outline is a sequence of operations leading from the raw workpiece to the required finished part. The method is applied to axisymmetric parts produced by a set of deep-drawing and machining processes. The method, the plan synthesis tactics and the forms of representation are based on the study and evaluation of the technological knowledge. The input is a CAD representation of the required finished part and the output is the highest priority process outline to manufacture the part. The process plan is developed, backwards, in two steps. In the first one a preform is designed and in the second a process plan to manufacture it is generated. The preform of a formable type, out of which the part can be machined, is produced by computational geometry heuristics. The deep-drawn preform is a uniform wall-thickness cup that circumscribes the required part while complying with recess radii constraints. The circumscription tactics can be expanded to non-uniform wall-thickness cups. The resulting preform is converted into a CAM representation and manipulated by the subsystem that generates forming process outlines. That system is a plan synthesis rule-based system that employs three mechanisms to generate the nodes along the most likely solution paths. These mechanisms define the system in abstract terms and make the deep-drawing and machining one instantiation of a more generalized method. The first mechanism is that main plan synthesis tactic, Generate & test and rectify. This tactic controls the automatic design of the preform and the generation of the deep-drawing process outline. Its basic premise is: If initial hypothesis fails the plan generator first attempts to rectify it. Regeneration of a new hypothesis is sought only if rectification also fails. The second mechanism is the hierarchical structure of rules. This structure stipulates that each technological rule is an instantiation of a higher level conceptual rule. The third mechanism, automatic construction of the inclusive test rule generates the "test" within the "generate and test" part. The appropriate test is tailored to each instance of material, geometries and sequence of forming processes. Both parts of the system are implemented in Prolog, under the UNIX operating system at Purdue University. Experiments demonstrate that the methods employed produce sound process plans for the specified domain.

Degree

Ph.D.

Subject Area

Industrial engineering

COinS