ME 538 AEROSPACE MANUFACTURING METHODS

1. ME 538AEROSPACE MANUFACTURING METHODS MANUFACTURING SUPPORT SYSTEMS Asst.Prof.Dr. Oğuzhan YILMAZ http://www.gantep.edu.tr/~oyilmaz Office: Room 319

2. Manufacturing support systems • Manufacturing is concerned with the effective use of technology, management and their integration to achieve added value and superior performance. • The modern concept of manufacturing stretches from product design, manufacturing planning and processing, to supply chain and end-of-life considerations. • To achieve world-class manufacturing performance it is essential to have an understanding of the holistic view of manufacturing systems as well as key components of the manufacturing process chain.

3. Manufacturing support systems • Process Planning • Concurrent Engineering • Product Design & CAD/CAM • Just-in-Time (JIT) • Computer Integrated Manufacturing (CIM)

4. PROCESS PLANNING • Two important areas in the life cycle of a product are design and manufacturing. Process planning serves as an integration link between design and manufacturing. • Process planning consists of preparing a set of instructions that describe how to fabricate a part or build an assembly which will satisfy engineering design specifications.

5. PROCESS PLANNING The resulting set of instructions may include any or all of the following: • operation sequence, • machines, • tools, • materials, • tolerances, • cutting parameters, • processes (such as how to heat-treat), • jigs, • fixtures, • time standards, • setup details, • inspection criteria, • gauges, • graphical representations of the part in various stages of completion.

6. PROCESS PLANNING CAM CAD Process design Process planning (CNC codes) Tool selection Facilities management Conceptual design Mathematical analysis Geometric data (graphical representation) CAPP COMPUTER AIDED PROCESS PLANNING

7. PROCESS PLANNING Some typical benefits of automated process planning include: • 50% increase in process planner productivity • 40% increase in capacity of existing equipment • 25% reduction in setup costs • 12% reduction in tooling • 10% reduction in scrap and rework • 10% reduction in shop labor • 6% reduction in work in process • 4% reduction in material

8. PROCESS PLANNING If the process planner’s productivity is significantly improved: • More time can be spent on methods, improvements and cost-reduction activities. • Routings can be consistently optimized. • Manufacturing instructions can be provided in greater detail • Preproduction lead times can be reduced. • Responsiveness to engineering charges can be increased.

9. PROCESS PLANNING The development of process plans involves a number of activities: • Analysis of part requirement • Selection of raw workpiece • Determining manufacturing operations and their sequences • Selection of machine tools • Selection of tools, workholding devices, and inspection equipment • Determining machining conditions and manufacturing time

10. PROCESS PLANNING ANALYSIS OF PART REQUIRENTS: The part requirements can be defined as: • part features • process determination • steps of processes • dimensions • machine tool size • tolerance specifications • machine tool capability • CNC code generation

11. PROCESS PLANNING DETERMINING MANUFACTURING OPTIONS AND THEIR SEQUENCES: • selection of processes • availability • accuracy requirement • suitability • cost • sequence of operations • work holding method • cutting tool availability

12. PROCESS PLANNING SELECTION OF MACHINE TOOLS: • work piece related attributes • part features • dimensions • dimensional tolerances • raw material form • machine tool related attributes • process capability • size • mode of operation • manual • semiautomatic • automatic • CNC • tooling capabilities • type of tool • size of tool • tool changing capability • manual • automatic • production volume related information • production quantity • order frequency

13. PROCESS PLANNING SELECTION OF TOOLS, WORKHOLDING DEVICES, AND INSPECTION EQUIPMENT: • Tools • tool material • shape • size • nose radius • tolerance

14. PROCESS PLANNING Workholding devices The primary purpose of a workholding device is to position the workpiece accurately and hold it securely. • manually operated devices • collets • chucks • mandrel • faceplates • designed devices • power chucks • specially designed fixtures and jigs • flexible fixtures used in flexible manufacturing systems • Inspection equipment • - on-line inspection equipment • - off-line inspection equipment

15. PROCESS PLANNING • DETERMINING CUTTING CONDITION AND MANUFACTURIN TIMES: Machining conditions • cutting speed (m/min), V • feed rate(mm/rev), f • depth of cut(mm), d V= .D.n / 1000 Object is to set the cutting conditions in such a way that theeconomically best production state is achieved.

16. PROCESS PLANNING What is the economically best production state? It is : 1- Minimum production cost or 2- Maximum production rate

17. PROCESS PLANNING • CHOICE OF FEED Finishing cut: Proper feed rate to provide desired surface quality (relatively low) Roughing cut: Feed rate is not effective as cutting speed over tool life, therefore, feed should be set to maximum possible value limitations: maximum tool force that the machine or the tool can stand and themaximum power available

18. PROCESS PLANNING CHOICE OF CUTTING SPEED Cutting speed is set to provide the optimum tool life. High V : low tool life high tool cost high production rate short production time Low V: high tool life low tool cost low production rate long production time

19. PROCESS PLANNING THE PRINCIPAL PROCESS PLANNING APPROACHES: • Manual experience-based process planning method • Computer-aided process planning method

20. PROCESS PLANNING MANUAL EXPERIENCE-BASED PROCESS PLANNING METHOD: • most widely used method • time consuming • inconsistent plans • requires highly skilled, therefore, costly planners

21. PROCESS PLANNING COMPUTER-AIDED PROCESS PLANNING METHOD: • it can systematically produce accurate and consistent process plans • it can reduce the cost and lead time of process planning • less skilled process planners may be employed • it increases the productivity of process planners • manufacturing cost, manufacturing lead time and work standards can easily be interfaced with the CAPP system

22. PROCESS PLANNING

23. PROCESS PLANNING There are two basic methods used in computer-aided process planning: • Variant CAPP method • Generative CAPP method

24. PROCESS PLANNING The Variant CAPP Method: • process plan is developed for a master part which represent the common features of a family of parts • a process plan for a new part is created by recalling, identifying, and retrieving an existing plan for a similar part and making necessary modifications for the new part • to use the method efficiently, parts classifying coding system must be used

25. PROCESS PLANNING Advantages of variant process planning: • efficient processing and evaluation of complicated activities and decisions, thus reducing the time and labor requirements • standardized procedures by structuring manufacturing knowledge of the process planers to company’s needs • lower development and hardware costs and shorter development times

26. PROCESS PLANNING Disadvantages of variant process planning: • maintaining consistency in editing is difficult • it is difficult to adequately accommodate various combinations of • material, • geometry, • size, • precision, • quality, • alternative processing sequences, • machine loading • The quality of the final process plan generated depends to a large extent on the knowledge and the experience of the process planners

27. PROCESS PLANNING The Generative CAPP Method: In a generative approach, process plans are generated by means of • decision logic • formulas • technology algorithm • geometry based data to perform uniquely the many processing decisions for converting a part from raw material to a finished state

28. PROCESS PLANNING There are basically two major components of generative process planning system: • a geometry based coding scheme • process knowledge in the form of decision logic and data

29. PROCESS PLANNING Geometry Based Coding Scheme: The objective is to define all geometric features for all process-related surfaces together with feature dimensions, locations, and tolerances, and the surface finish desired on the features. The level of details is much greater in a generative system than a variant system.

30. PROCESS PLANNING Process Knowledge in the Form of Decision Logic and Data: In this phase, part geometry requirement is matched with manufacturing capabilities in the form of decision logic and data. Selection of • processes • machine tools • tools • jigs and fixtures • inspection equipment • sequence of operations are achieved. Finally, operation instruction sheets(for manual operations) or NC codes (for CNC) machines are generated.

31. PROCESS PLANNING FUTURE TRENDS IN COMPUTER-AIDED PROGESS PLANNING: • One of the major strategies for reducing cost and lead time is to integrate various functional areas such as design, process planning, manufacturing, and inspection. • There are a number of difficulties in achieving the goal of complete integration.

32. PROCESS PLANNING • Other challenges include; • automated translation of the design dimensions • tolerances into manufacturing dimensions • tolerances considering process capabilities • dimensional chains, • automatic recognition of features, • making the CAPP systems affordable to the small and medium-scale manufacturing companies. • Artificial intelligence integrated CAPP systems

33. CONCURRENT ENGINEERING Definitions: • "Concurrent engineering is a systematic approach to the integrated, concurrent design of products and their related processes, including manufacture and support. • Typically, concurrent engineering involves the formation of cross functional teams, which allows engineers and managers of different disciplines to work together simultaneously in developing product and process design. • The applications of tools, techniques, methodologies, and behavioral, initiatives used to minimize product development timescales by maximizing the degree of overlap of design activities.

34. Concurrent Engineering

35. Concurrent Engineering

36. Concurrent Engineering • Serial engineering: • Control of twoparameters • ConcurrentEngineering: • Attempttocontrol of allthreeparameters

37. Concurrent Engineering Concurrent engineering • Has to be supported by top management. • All product development team members should be dedicated for the application of this strategy. • Each phase in product development has to becarefullyplanned before actual application. • New product’s lifecycle has to fit inthe existingproduct program lifecycles in a company.

38. Concurrent Engineering Benefits of Concurrent Engineering • Reduces time from design concept to market • launch by 25% or more • Reduces Capital investment by 20% or more • Supports total quality from the start ofproduction with earlieropportunities for continuous improvement • Simplifies after-sales service • Assembly in the Context of ProductDevelopment • Increases product life-cycle profitabilitythroughout the supplysystem

39. Concurrent Engineering

40. Computer aided design (CAD) & computer aided manufacturing-machining (CAM) In engineering practice, CAD/CAM has been utilized in different ways by different people. Some of the applications of this technology are: • production of drawings and design documents; • visualization tool for generating shaded images and animated displays; • engineering analysis of the geometric models (finite element analysis, kinematicanalysis, etc.); • process planning and generation of NC part programmes.

41. CAD/CAM

42. CAD/CAM • The CAD process is a subset of the design process. Similarly, the CAM process is asubset of the manufacturing process. • Once a conceptual design materializes inthe designer’s mind, the definition of a geometric model starts via the user interface providedby the relevant CAD system. • The choice of a geometric model to CAD is analogous to thechoice of mathematical model to engineering analysis. • For example, FEA might require adifferent model than kinematic analysis

43. CAD/CAM • Thegeometric model developed during the CAD process forms the basis of the CAM activities. • Various CAM activities may require various CAD information. • In case of process planning,features that are utilized in manufacturing (e.g., holes, slots, etc.) must be recognized to enableefficient planning of manufacturing. • NC programmes, along with ordering tools and fixtures,result from process planning. • Once parts are produced, CAD software can be used to inspectthem. This is achieved by superposing an image of the real part with a master image stored inits model database. After passing inspection, CAM software can be utilized to instruct robotsystems to assemble the parts to produce the final product.

44. CAD/CAM The link between CAD and CAM must be a two-way route. CAD databases must reflectmanufacturing requirements such as tolerances and features. Designers must think in termof CAM requirements when finalizing their designs. On the other hand, CAD databasesand their limitations must be conveyed to manufacturing engineers who plan to utilizethem in process planning and other manufacturing functions. It should be pointed out thatnot all manufacturing processes are, or need to be, computer driven.

45. Just-in-time • Just-in-time (JIT) is defined in the APICS dictionary as “a philosophy of manufacturing based on planned elimination of all waste and on continuous improvement of productivity”.  • It also has been described as an approach with the objective of producing the right part in the right place at the right time (in other words, “just in time”).  • Waste results from any activity that adds cost without adding value, such as the unnecessary moving of materials, the accumulation of excess inventory, or the use of faulty production methods that create products requiring subsequent rework.  • JIT (also known as lean production or stockless production) should improve profits and return on investment by reducing inventory levels (increasing the inventory turnover rate), reducing variability, improving product quality, reducing production and delivery lead times, and reducing other costs (such as those associated with machine setup and equipment breakdown).  • In a JIT system, underutilized (excess) capacity is used instead of buffer inventories to hedge against problems that may arise.

46. Just-in-time • JIT applies primarily to repetitive manufacturing processes in which the same products and components are produced over and over again.  • The general idea is to establish flow processes (even when the facility uses a jobbing or batch process layout) by linking work centers so that there is an even, balanced flow of materials throughout the entire production process, similar to that found in an assembly line. To accomplish this, an attempt is made to reach the goals of driving all inventory buffers toward zero and achieving the ideal lot size of one unit. • The basic elements of JIT were developed by Toyota in the 1950's, and became known as the Toyota Production System (TPS).  JIT was well-established in many Japanese factories by the early 1970's.  JIT began to be adopted in the U.S. in the 1980's (General Electric was an early adopter), and the JIT/lean concepts are now widely accepted and used.

47. Just-in-time • Some Key Elements of JIT • Stabilize and level the MasterProduction Schedule (MPS) with uniform plant loading: • create a uniform load on all work centers through constant daily production and mixed model assembly • Meet demand fluctuations through end‑item inventory rather than through fluctuations in production level.  • Use of a stable production schedule • 2. Reduce or eliminate setup times: aim for single digit setup times (less than 10 minutes) or "one‑touch" setup ‑‑ this can be done through better planning, process redesign, and product redesign. 

48. Just-in-time 3. Reduce lot sizes (manufacturing and purchase): reducing setup times allows economical production of smaller lots; close cooperation with suppliers is necessary to achieve reductions in order lot sizes for purchased items, since this will require more frequent deliveries. 4. Reduce lead times (production and delivery): production lead times can be reduced by moving work stations closer together, applying group technology and cellular manufacturing concepts, reducing queue length (reducing the number of jobs waiting to be processed at a given machine), and improving the coordination and cooperation between successive processes; delivery lead times can be reduced through close cooperation with suppliers, possibly by inducing suppliers to locate closer to the factory.

49. Just-in-time 5. Preventive maintenance: use machine and worker idle time to maintain equipment and prevent breakdowns. 6. Flexible work force: workers should be trained to operate several machines, to perform maintenance tasks, and to perform quality inspections.  In general, JIT requires teams of competent, empowered employees who have more responsibility for their own work.  The Toyota Production System concept of “respect for people” contributes to a good relationship between workers and management.

50. Just-in-time 7. Require supplier quality assurance and implement a zero defects quality program: errors leading to defective items must be eliminated, since there are no buffers of excess parts.  8. Small‑lot (single unit) conveyance: use a control system such as a kanban(card) system (or other signaling system) to convey parts between work stations in small quantities (ideally, one unit at a time).  In its largest sense, JIT is not the same thing as a kanban system, and a kanban system is not required to implement JIT (some companies have instituted a JIT program along with a MRP system), although JIT is required to implement a kanban system and the two concepts are frequently equated with one another.