computer aided process planning and cost estimation
- 1. Introduction to Computer Aided Process Planning
- 2. Computer Integrated Manufacturing (CIM) • Computer Aided Design (CAD) – 2D – 3D – Concurrent Engineering • Computer Aided Process Planning (CAPP) – Variant – Generative • Computer Aided Manufacturing (CAM) – CNC – Robotics – Material Handling – Just in Time (JIT) – Group Technology – Flexible Manufacturing Systems
- 3. What is process planning? • Recipe/Algorithm/Step-by-step instructions • Fast Food Chain • Same taste everywhere from NY to New Delhi • How do they do it? • Customization in formal dinner restaurant
- 4. Manufacturing Environment • Role of the master machinist in small batch manufacturing • Manufacturing is more complex than cooking yet the planning for it is similar • Job shop: group machines which perform same operation together • Routing of parts through the various departments • Process plan defines the route • Reduction in the necessary skill of operator can be achieved by using a detailed process plan
- 5. Formal Definition “Process planning can be defined as an act of preparing processing documentation for the manufacturing of a piece, part or an assembly” • depending on the production environment can be – Rough – Detailed • When process planning is done using a computer : “Computer Aided Process Planning”
- 7. • Manufacturing a part to meet design specs. – Selection of initial block – Sequence of operations – Selection of machine, process • Surface finish • Quality • Tolerance • Hardness • Life • Cost
- 8. A Rough Process Plan
- 9. A Detailed Process Plan
- 10. Components of Process Planning • Selection of machining operations • Sequencing of machining operations • Selection of cutting tools • Determining the setup requirements • Calculation of cutting parameters • Tool path planning and generation of NC/CNC programs • Design of Jigs/Fixtures
- 11. Process Planning in different environments • In tool-room type manufacturing – “make part as per drawing” is sufficient • In metal-forming type operations – The process planning requirements are embedded directly into the die. – Process planning is fairly trivial • Job-shop type manufacturing requires most detailed process planning – Design of tools, jigs, fixtures and manufacturing sequence are dictated directly by the process plan.
- 12. Requirements for process planner • Must be able to analyze and understand part requirements • Have extensive knowledge of machine tools, cutting tools and their capabilities • Understand the interactions between the part, manufacturing, quality and cost
- 13. Traditional process planning • Experienced based and performed manually • Variability in planner’s judgment and experience can lead to differences in the of what constitutes best quality • Problem facing modern industry is the current lack of skilled labor force to produce machined parts as was done in the past • Hence Computer Integrated Manufacturing and Computer Aided Process Planning
- 14. Advantages of CAPP • Reduces the demand on the skilled planner • Reduces the process planning time • Reduces both process planning and manufacturing cost • Creates consistent plans • It produces accurate plans • It increases productivity
- 15. Approaches to CAPP • Variant • Generative • Automatic
- 16. Variant Process Planning “based on the valid conjecture that similar parts will have similar process plans” Preparatory stage • GT-based part coding – Families of similar parts are created – Family matrix • A process plan is to manufacture the entire family is created
- 17. Variant Process Planning Production Stage • Incoming part is coded • Part family is identified • Process plan is edited to account for the different needs of the part Salient points of variant process planning • Easy to build, learn and use • Experienced process planners are still required to edit the process plan • Cannot be used in an entirely automated manufacturing system without additional process planning
- 19. Generative Process Planning “a system which automatically synthesizes a process plan for a new component” Requires • Part description – Part to be produced must be clearly and precisely defined in a computer compatible format (OPITZ,AUTAP) • Manufacturing databases – Logic of manufacturing must be identified and captured – The captured logic must be incorporated in a unified manufacturing database
- 20. Generative Process Planning • Decision making logic and algorithms – Decision trees – Expert Systems: – AI based approaches
- 21. Automatic Process Planning “ generate a complete process plan directly from a CAD drawing” Requires: • Automated CAD interface – Take a general CAD model ( 3D for unambiguous data) and develop an interface to develop a manufacturing interface for this model : Feature Recognition of CAD – Design the parts with available manufacturing features : Feature based CAD – Dual: useful features of both approaches • Intelligent (computer based) process planner
- 23. SUMMARY • CAPP is a highly effective technology for discrete manufacturers with a significant number of products and process steps. • Rapid strides are being made to develop generative planning capabilities and incorporate CAPP into a computer- integrated manufacturing architecture.
- 24. SUMMARY • The first step is the implementation of GT and coding. • Commercially-available software tools currently exist to support both GT and CAPP.
- 25. SUMMARY • As a result, many companies can achieve the benefits of GT and CAPP with minimal cost and risk. • Effective use of these tools can improve a manufacturer's competitive advantage.
- 26. References Systems Approach To Computer Integrated Design and Manufacturing • Author: Nanua Singh • Publisher: John Wiley & Sons Expert Process Planning For Manufacturing • Author: Tien-chien Chang • Publisher: Addison-Wesley Publishing Company