Intelligent feature based process planning for five-axis mill-turn parts | |
| Author | Kriangkrai Waiyagan |
| Call Number | AIT Diss. no.ISE-09-01 |
| Subject(s) | Computer-aided design Machine-tools |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Design and Manufacturing Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ISE-09-01 |
| Abstract | This research proposes a new intelligent process planning system for five-axis mill-turn parts. This system focuses on practical machining knowledge and a new grouping of parts including both rotational and prismatic features defined as Prisronal parts. Prisronal parts are newly defined here as “parts having primitive shapes with one common centerline like cylindrical, cone or round shapes including other symmetric and/or asymmetric rotational machining features for example holes, faces, slots, grooves or pockets in different orientations”. The new system can be viewed as a hybrid Computer-Aided Process Planning (CAPP) combining variant with generative approach. The variant concept is applied in the sense of the machining features classification and a new group code system whereas the generative concept is applied in term of manufacturing knowledge and production rules for decision-making processes. The three main parts of the new system are as follows. a) A novel machining features classification based on machining processes and number of simultaneously controlled axes of five-axis lathe (1D-5D). Two hundred ten features of general and specific mill-turn parts are classified. In addition, a new group code named the Prisronal part code system is proposed for classification of prisronal parts and forms the basis for variant CAPP approach. The uniqueness of the developed code system is a hierarchical structure for defining features. Hierarchical levels are useful for generating process plans because they provide a feasible machining sequence and show precedence relations between features. This coding scheme is based on a survey of machined parts from many industries in order to estimate the frequency and type of machining features found in prisronal parts. b) Machining feature definition model with representation; this concept allows a user to define designed parts to the system for generating a process plan. The feature definition model not only includes geometric and manufacturing data in the open layer but also includes machining processes and technical knowledge in the hidden layer of machining features viewed as production rules of the expert system. Geometric data of regular machining features like a pocket, slot and hole etc. are specified by parameters corresponding to the geometry of features like length, width and depth, positions and orientations. A set of 4D/5D features is non-parametric freeform. Those 4D/5D features are defined by three controlled surfaces: drive surface, path surface and check surface. Modeling of complex 4D/5D prisronal parts using parameters is included. Manufacturing data includes properties of blank part, and technological data like tolerances and surface finish. c) Process plan generation model; process plan is generated based on machining features and rules. A user interactively identities and maps geometric entities to machining features by means of templates. Machining processes, types of cutting tools and essential rules requested for particular features are designed and built-in to each feature in the hidden layer. Therefore, process selection is done automatically when geometric entities have been mapped to machining features provided in the system library. To assist a user in selecting machining features under machining constraints, an algorithm for advising alternative machining features for sculpture surfaces and ruled surfaces based on accuracy, machining time and surface finish is integrated. Next, a list of machining processes is sent to the decision-making module. The inference mechanism executes auxiliary rules by using machine tools configurations and cutting tools data stored in database to make a process plan. The auxiliary rules currently include fifty rules for setup selection, precedence relation between machining operations, selection of cutting tools and tool path generation. Those rules can be updated and customized by user. Two case studies are included to demonstrate the developed system. The first case study focuses on a prisronal part including various regular turning features, positioning drilling and milling features. On the other hand, the second case study is shown by using a real industrial part (the gas swirl tip) with complex 5D features. This case study shows functions of the system step by step in details including input CAD file (STEP), defining the case study part with the prisronal code system, defining machining features, built-in machining processes, decision-making processes with applied auxiliary rules and the output list of process plan. Then, this created process plan is used as a guideline to generate tool paths by a commercial CAM system and translated into NC programs (G-code) for five-axis lathe. The pilot system is being implemented and programmed in Visual Basic and the expert system tool called Visual rule studio. The benefits of the system are: (1) fast and accurate process plan generation (2) corresponding process plans generated by the system and group code can be archived and used as a variant process planning system. |
| Year | 2009 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ISE-09-01 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Department of Industrial Systems Engineering (DISE) |
| Academic Program/FoS | Industrial Systems Engineering (ISE) |
| Chairperson(s) | Bohez, Erik L. J.; |
| Examination Committee(s) | Makhanov, Stanislav S.;Pisut Koomsap; |
| Scholarship Donor(s) | Prince of Songkla University, Thailand; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2009 |