Metodología para dar soporte al proceso de planeación a través de grupos tecnológicos

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(1)INSTITUTO TECNOLÓGICO Y DE ESTUDIOS SUPERIORES DE MONTERREY CAMPUS MONTERREY DIVISIÓN DE INGENIERÍA Y ARQUITECTURA PROGRAMA DE GRADUADOS EN INGENIERÍA. METODOLOGÍA PARA DAR SOPORTE AL PROCESO DE PLANEACIÓN A TRAVÉS DE GRUPOS TECNOLÓGICOS. TESIS PRESENTADA COMO REQUISITO PARCIAL PARA OBTENER EL GRADO ACADEMICO DE:. MAESTRO EN CIENCIAS ESPECIALIDAD EN SISTEMAS DE MANUFACTURA. POR: FERNANDO PÉREZ MARTÍNEZ. MONTERREY, N.L. MAYO 2002.

(2) INSTITUTO TECNOLÓGICO Y DE ESTUDIOS SUPERIORES DE MONTERREY CAMPUS MONTERREY DIVISIÓN DE INGENIERÍA Y ARQUITECTURA PROGRAMA DE GRADUADOS EN INGENIERÍA. Los miembros del comité de tesis recomendamos que el presente proyecto de tesis presentado por el Ing. Fernando Pérez Martínez sea aceptado como requisito parcial para obtener el grado académico de Maestro en Ciencias con especialidad en:. SISTEMAS DE MANUFACTURA Comité de Tesis:. Arturo Molina. Ph. D. Asesor. Ciro Rodríguez. Ph. D. Sinodal. Horacio Ahuette. Ph. D. Sinodal. Aprobado:. Federico Viramontes Brown. Ph. D. Director del Programa de Graduados en Ingeniería Mayo 2002.

(3) Dedicatoria Quisiera agradecer a nuestro Señor todo lo que me ha dado. A mis queridos padres, Imelda y Noé, por todo su tiempo dedicado y por brindarme todos sus sabios consejos cuando más los necesitaba. A mis hermanos, Carlos Alberto y José Eduardo, por su apoyo incondicional. A mis abuelos, tíos, primos, por mostrarme siempre su cariño. A Jenny Ximena, por mostrarme siempre su apoyo y cariño. Y a todos mis amigos.. V.

(4) Agradecimientos Agradezco al Dr. Arturo Molina el haber aceptado ser asesor de este trabajo de tesis, así como por haber compartido conmigo sus comentarios y tiempo, que enriquecieron en gran medida esta investigación. Al Dr. Ciro Rodríguez, por sus comentarios y análisis que dieron forma final a esta tesis. Al Dr. Horacio Ahuette, por su retroalimentación sobre este trabajo de tesis. Al Sr. Antonio García y al Sr. Gerardo Ávila, por compartir sus conocimientos y ayudar en la elaboración del caso de estudio. Así como, por esos buenos momentos a la hora del almuerzo. A mis amigos del Laboratorio de CNC: Ricardo, Joaquín, Julián, Miguel, Pedro; así como al grupo "Clusters Virtuales" por todos esos bellos momentos compartidos dentro y fuera del área de trabajo.. VI.

(5) Resumen Los procesos de manufactura han sido un elemento que ha cambiado los requerimientos subjetivos de un cliente en productos llenando una necesidad específica. El negocio de una empresa manufacturera está enfocado en la transformación de materia prima a un producto requerido por un cliente. En la manera de llevar acabo dicha actividad, la empresa tiene que desarrollar una planeación, que es hecha en la mayoría de los casos por el experto de manufactura, quién reúne la experiencia y el conocimiento al momento de tomar las decisiones. La planeación consiste en organizar, controlar y dirigir las acciones a ser tomadas para producir un bien, ésta planeación es llevada acabo en tres niveles: Producción, Proceso y Operación. Cada uno de ellos cubre un aspecto específico de la planeación. Esta actividad requiere de gran conocimiento y experiencia concentrada en el experto de manufactura, de ahí que el problema de la planeación se convierta en algo muy complicado por que un gran conocimiento sobre los procesos, máquinas, herramientas es necesitado. Teniendo esto como antecedente, es indispensable para una buena planeación desarrollar una metodología que permita organizar, mejorar y documentar dicha actividad, capaz de ser manejada por cualquier persona relacionada con el proceso de manufactura, además debe incluir un sistema de automatización para acelerar la rutina de toma de decisiones. La tesis presentada se centra en el área de manufactura, desarrollando una metodología y un sistema automatizado para el proceso de planeación a través de Grupos Tecnológicos, que ayudará con el problema planteado. Dicha metodología fue aplicada en un caso de estudio realizado sobre una empresa manufacturera relacionada con el proceso de troquelado, tomado como ejemplo las aspas para ventiladores industriales. Los resultados obtenidos de este trabajo se pueden enmarcar de la siguiente forma: una metodología capaz de documentar y dar soporte a la planeación a través de Grupos Tecnológicos, un sistema automatizado para el proceso de planeación basado en Grupos Tecnológicos y caso de estudio para probar la funcionalidad y efectividad de la metodología y sistema automatizado..

(6) Index Figures list …………………………………………………………………………... XI Tables list …………………………………………………………………………. .. XII Chapter 1 Introduction ………………………………………………………………………… 1.1 Problem Analyzed ……………………………………………………………… 1.2 Objectives ………………………………………………………………………. 1.3 Scope …………………………………...……………………………………… 1.4 Hypothesis ……………………………………………………………………… 1.5 Methods and Methodology …………………………………………………….. 1.6 Thesis Structure …………………………………………………………………. 1 1 2 2 2 2 3. Chapter 2 Introduction ……………………………………………………………………………... 4 2.1 Production Planning ….……………………………………………………………... 4 2.1.1 Production Management Function ……………………………………………. 7 2.1.2 Methods involve in Production Problems ……………………………………... 7 2.1.2.1 MRP …………………………………………………………………… 8 2.1.2.2 JIT ……………………………………………………………………... 9 2.1.3 Automation of Production Planning …………………………………………. 10 2.2 Process Planning …………………………………………………………………… 11 2.3 Automation of Process Planning ………………………………………………..….. 14 2.3.1 Approaches of CAPP. Evolution …………………………………………….. 15 2.3.1.1 Variant ………………………………………………………………... 15 2.3.1.2 Generative ……………………………………………………………. 16 2.3.2 Implementation Techniques ………………………………………………….. 16 2.3.3 Recent work on CAPP ……………………………………………………..… 17 2.4 Operation Planning ……………………………………………………………….... 19 2.5 Group Technology ………....……………………………………………………..... 19 2.5.1 Classification and Coding ……………………………………………………. 21 2.5.1.1 Monocodes ….……………………………………………………….. 22 2.5.1.2 Polycodes ……………………………………………………………. 22 2.5.1.3 Mixed …………………………………………………………...…… 22 2.5.2 Family Formation …………………………………………………………….. 22 2.5.3 Part Family Formation methods ………………………………………...……. 23 2.5.4 Available Codes and Classification Systems ………………………………… 24 2.5.4.1 BRISCH System …………………………………………………...… 24 2.5.4.2 OPITZ System ……………………………………………………….. 25 2.5.4.3 CODES System …..…………………………………………………. 25 2.5.4.4 MICLASS System …………………………………………………… 25 2.5.4.5 Other Codes Systems ………………………………………………… 25 2.6 Chapter Conclusion ………………………………………………………………... 26. VIII.

(7) Index Chapter 3 Introduction ….…………………………………………………………………………. 27 3.1 Production Planning ...……………………………………………………………… 27 3.1.1 GT as Support of Production Planning …...…………………………………. 27 3.2 Process Planning …………………………………………………………………… 28 3.2.1 Route Cards …………………………………………………………………. 28 3.2.2 GT as Support of Process Planning …………………………………………. 29 3.3 Operation Planning ……………………………………………………………….... 30 3.4 Tools Supporting Group Technology …………………………………………….... 30 3.4.1 Code and Classification Systems ……………………………………………. 31 3.4.2 Part Family Formation In-house/ Commercial ……………………..……….. 32 3.4.2.1 Storing …………………………………………………………….… 33 3.4.3 Information Retrieval and Rationalization ………………………………….. 34 3.4.4 Selection ……...…………………………………………………………..…. 35 3.4.4.1 Process Planning …………………………………………………..… 35 3.4.4.2 Machines ……………………………………………………………. 36 3.4.4.3 Tools ………………………………………………………………… 37 3.4.4.4 Routing …...………………………………………………………… 38 3.5 Chapter Conclusion ……..………………………………………………………… 39 Chapter 4 Introduction …………………………………………………………………………..… 40 4.1 Methodology ………………………………………………………………….……. 40 4.1.1 First phase. Step 1. Group Technology ……………………………………... 43 4.1.1.1 Training on GT …………………………………………………….. 43 4.1.1.2 Do Code and Classification ………………………………………… 43 4.1.1.3 Family Formation ……...……………………………………….….. 43 4.1.1.4 Finding Tooling Formation …………...………………………....… 43 4.1.1.5 Explain Data Retrieval ………………...…………………………... 44 4.1.2 Step 2. Tooling Coding ……………………………………………...…….... 44 4.1.2.1 Inventory and Classification According Process …………….….…. 44 4.1.3 Step 3. Planning ………………………………………………………….…. 45 4.1.3.1 Production ……………………………………………………..…… 45 4.1.3.2 Process ………………………………...………………………..…. 45 4.1.3.3 Operation ……………………………...…………………………... 45 4.1.4 Step 4. Storing System …………………………………………………….… 45 4.1.4.1 Define Stored System and Accessibility …………………………… 45 4.1.5 Second Phase. Step 5. Planning Automation ……………………………….. 46 4.1.5.1 New Part Arrival ………………………………………………. 46 4.1.5.2 Codifying ………………………………………………………. 46 4.1.5.3 Searching …...………………………………………………….. 46 4.1.5.4 Recovery ………………………………………………………. 47 4.1.5.5 Editing and Release …...………………………………………. 47 4.2 Summary ...………………………………………………………………………… 47 IX.

(8) Index Chapter 5 Introduction …..………………………………………………………………………… 48 Methodology Applied ………………………………………………………………….. 48 5.1 First Phase. Group Technology …………………………………………………….. 48 5.1.1 Training on Group Technology ...…………………………………………… 49 5.1.2 Do Code and Classification ……...………………………………………….. 49 5.1.3 Family Formation ...…………………………………………………………. 50 5.1.4 Finding Tooling Families ...…………………………………………………. 51 5.1.5 Explain Data Retrieval ………...……………………………………………. 52 5.2 Tooling Coding …………………………………………………………………….. 52 5.2.1 Inventory and Classification Accord Planning …………...…………………. 52 5.3 Planning ……………………………………………………………………………. 53 5.3.1 Production ……………………...…………………………………………… 54 5.3.2 Process ………………………....……………………………………………. 55 5.3.3 Operation ……………………...……………………….……………………. 56 5.4 Storing System ……………………………………………….…………………….. 57 5.4.1 Definition of Store System and Accessibility ……….………………………. 57 5.5 Second Phase. Automation Planning …………………….………………………… 59 5.5.1 New Part Arrival ….…………………………………………………………. 59 5.5.2 Codifying ………….………………………………………………………… 60 5.5.3 Searching ………….…………...……………………….…………………… 60 5.5.4 Recovery …………..………………………………………………………… 60 5.5.5 Editing and Releasing ……………………………………………………….. 61 5.6 Summary …………………………………………………………………………… 61 Chapter 6 Introduction …………………………………………………………………………….. 63 6.1 Results ……………………………………………………………………………… 63 6.2 Conclusions ………………………………………………………………………… 64 6.3 Future Research ……………………………………………………………………. 65 Reference ………………………………………………………………………………. 66 Appendix A …………………………………………………………………………….. 69 Appendix B …………………………………………………………………………….. 70. X.

(9) List of Tables 1. Table 1. Production Planning …………………………………………….…… 55 2. Table 2. Process Planning ……………………………………………………. 56. XI.

(10) Lista de Figuras 1. Manufacturing Business Structure ……………….……………………..……. 4 2. Levels of Production Planning ………………….………………………..….. 5 3. Main Methods for Production Planning Problems …….…………………..…. 8 4. Types and Levels of Process Planning activity and their outcome ….……… 12 5. Process Planning Structure ………………………………………….………. 13 6. Link Between Design and Manufacturing …………………………………... 14 7. GT as Support of Production Planning …………………………….………… 28 8. GT as Support of Process Planning ……………………………….……….... 29 9. GT as Support of Operation Planning …………………………….………… 30 10. Tools Supporting GT ……………………………………………………….. . 31 11. Fulfillment of Requirements ……………………………………………….... 32 12. Examples of Components Coding ………………………………………….... 33 13. Storing Family Formation …………………………………………………... 34 14. Information Retrieval ……………………………………………………….. 35 15. Selection Criteria Process Planning ………………….……………………… 36 16. Machine Selection According to Specific Criteria ….………………………. 37 17. Tool Selection based on Machine Selection …….…………………………... 38 18. Generic Framework …………………………….…………………………… 40 19. Framework Concepts …………………………….………………………….. 41 20. Two-phase Methodology …………………………….……………………… 42 21. Sequence of Implementation (1st phase) …………….………………………. 42 22. Sequence of Implementation (2nd phase) …………….……………………… 46 23. Scheme of Code Developed ………………………………………………… 49 24. Coding Parts ………………………………………………………………… 50 25. Family Formation …………………………………………………………… 51 26. Finding Dies Families ………………………………………………………. 52 27. Dies and Tools Coding ……………………………………………………… 53 28. Example of Planning ………………………………………………………... 54 29. Core Operation Planning ……………………………………………………. 57 30. Data Base System …………………………………………………………… 58 31. Retrieving Action ……………………………………………………………. 60 32. Retrieval Information ……………………………………………………….. 61. XII.

(11) Chapter 1.Introduction. Introduction The business of a manufacturing company is focused on transforming raw material into a product demanded by a client. Through the years the manufacturing process has been the element that has helped in changing clients requirements into final products. To accomplish such activity the company must get into planning its actions in order to carry out any request, in many situations time and knowledge are key elements at the moment to take any decisions, frequently done by the manufacture expert. As a general concept Planning is concerned with the activity of organizing, managing, controlling and directing the actions to be taken in order to be able to produce a good by a manufacturing company. The Planning in a company is based on three major levels. These levels can be classified into Production, Process and Operation planning. Those levels provide information useful throughout the entire path by which raw material must go to be transformed in a product useful to a particular client. Each of them fulfill a specific aspect of planning. In Production Planning is important to establish the resources within a company focused on a useful activity to manufacture a product, even more; the information regarding to the product to manufacture is clarify; quantity to produce is established, possible process to follow are determined, machines and tools can be identified, material initial form is decided; all this information is the starting point to construct a plan or program in where sequence of activities are specified. For the Process Planning similar actions are taken in consideration, being more specific in the activities or operations of each process defined during Production Planning, final selection on machines and tools is accomplished, and some notes about specific operations are mentioned. Operation Planning is the final level in which the execution of what was planed before is carried out under specific conditions for each operation. An important concept to take care and that would be very helpful for the product organization of a company is the Group Technology concept. This concept can be mentioned as a way of working by grouping similar part types based on criteria selection such as geometry or process. Parts similar in geometry or shape can form a group or family, the same applies to parts similar in processes. There are some elements that conform the Group Technology concept, for example: code and classification, for this activity codes can be developed fulfilling specific necessities of a particular company or commercial codes can be used in order to start a classification. Another element is the family formation, once the coding and classification are done family formation is accomplished by grouping similar codes. As mentioned before this concept can be very helpful in organizing company products. 1.1 Problem Analyzed The problem of planning in a manufacturing company become very complicated, a deep and well understanding of the process, machines and tools in the company is necessary in order to perform a good planning, this activity is done by the manufacture expert in most. 1.

(12) Chapter 1.Introduction. of the cases, because he concentrates the knowledge and the experience needed. That is why a tool or methodology that is able to improve, organize and document such activity in a way that is easy and useful for anyone related to the manufacturing process is needed. This tool or methodology must involve a degree of automation to speed up the decisions making in the process planning time. 1.2 Objectives • • •. Creation of a Methodology able to document and support the planning through the use of Group Technology. Develop an Automate System to support the planning process using Group Technology. Test the functionality and effectiveness of the Methodology and the Automate System by means of a case study.. 1.3 Scope The scope of the research is to create a methodology able to document and give support to the planning using the concept of Group Technology. In addition, the construction of an Automate System to support the planning process by means of Group Technology is carried out. Finally, the exposition of a case study to prove both. 1.4 Hypothesis The planning in a manufacturing company can be developed by anyone related to the manufacturing process once a methodology able to document and support it is created to serve that purpose. In addition, the existence of an Automate System will improve the decisions making process because all the information will be structure. 1.5 Methods and Methodology In this thesis will be shown how the planning (Production, Process and Operation) in a manufacturing company can be supported through the use of Group Technology and how the Group Technology created can be used into an automated system developed in a generic tool helping in the quick decision making. The way of working of the variant approach will serve as reference for the proposed methodology. At this moment, the author of this thesis is working in a manufacturing company focused on the sheet metal process, and this experience will serve as a method to develop this work. To formulate the case study, a manufacturing company dedicated to the sheet metal process will be used as an example, in which the methodology created will be applied.. 2.

(13) Chapter 1.Introduction. As result of this thesis was obtained a methodology to support the planning through the use of Group Technologies, an automated system based on GT supporting the planning process and a case study to prove the way of working. In conclusion, the two-phase methodology created was easy to use, the automated system fulfilled the purpose of its creation and the case study proved the effectiveness and functionality of the methodology created. 1.6 Thesis Structure This thesis is structure as follow: In chapter 2, a review of the literature about Planning at its different levels, ways of planning automation and Group Technology is presented. The integration of different levels of planning with the concept of Group Technology and its tools is treated in Chapter 3. In chapter 4, the methodology needed as guide to formulate and apply Group Technology involving the planning is presented. In chapter 5, the methodology created will be used and applied, making a detailed description of each one of the activities involved. At the end, in chapter 6, the conclusions and results obtained from developing this thesis will be discussed; also, future research is recommended.. 3.

(14) Chapter 2. Literature Review Introduction In order for a manufacturing business to work it must have a structure that help it to accomplish its goals. This structure can be defined as the integration of the customer requirements and the fulfillment of their needs, for doing this; it is important to establish a well work planning that can be used as a guide to obtain desirable profit and survive as long as possible. Planning activities can be classified into three levels: strategic, managerial, and operational planning (Hitomi et al, 1985). As defined a manufacturing business is focused on the transformation of raw material into a finished product as a general concept, if it’s so; production planning is usually concerned with all three, as shown next. Fig 1. Further in this chapter will be discussed how the production planning and its components (Process and Operation Planning) form part of the execution and transformation of raw material into a finished product and the problems that are treated for each one, and how the concept of Group Technology can served as a tool to run production. A presentation of how working with those concepts will be made, making a difference within the manufacturing business.. Manufacturing Business Structure Market Demand Manufacturing Business Management. There are three levels of Planning - Strategic - Managerial - Operational. Customer Fulfillment and Shipment. Production Planning. Fig. 1. Manufacturing Business Structure.. 2.1 Production Planning What is it? Production Planning can be defined as the function of management, concerned with planning the physical means to be used by an enterprise, to produce the goods, or services, which it provides (Burbidge, 1971). In reference to the physical means of 4.

(15) Chapter 2. Literature Review production, five main types of plan required can be found: material form, production facilities, route, handling and storage, layout. It has to be stated that production planning is a function of Management and the responsibility falls into the manager. “A manager is a person who plans, directs, and controls the work of human beings towards a common aim (Burbidge, 1971)”. If all management tasks are divided into a common sequences of processes known as planning, direction and control; they can be achieved easily. Planning is the process by which plans are made about what should be done in the future. Direction is the process by which plans are caused to be implemented. Control is the process by which events are constrained to follow plans. All efficient planning is progressive or analytical, in other words it starts with a broad outline of a plan, and then gradually increases the detail in the plan at a succession of following planning stages or levels. In the case of Production planning are three levels: factory planning, process planning and operation planning.. Levels of Production Planning Factory Planning. Series of process Kinds of product items Quantities to be produced Possible machines to use. Process Planning. Series of operations to transformed raw materials Process routes are determined Define the work centre. Operation Planning. Executes operation determined Tooling Ana lize work centre. Time Period. Fig. 2 Levels of production planning. Factory planning also called production planning can be considered the first level of progressive production planning, it is related with the selection of the material form, the facility is plan based on the site, buildings, and types of processing plant. For the routing it is only considered the sequences of mayor process involved (metal founding, machining). It also important to determine the kinds of products and the quantities to be produced during a specific time period. As shown in Fig 2. Process planning at this level each process and department found during factory planning is examined in turn, the provision of facilities is planned in units of particular machines and equipment, the layout is taking care of their position. Something also important is the selection of the raw material for each item produced and the routing considers the. 5.

(16) Chapter 2. Literature Review sequence of work operations necessary to complete each process until a finished product is obtained, as shown in Fig. 2. Operation planning each work centre and operation found during process planning is studied in turn, for the provision of facilities is mainly concerned with the choice of tooling, and layout deals with the spatial arrangement of the machines and equipment forming each work centre. The choice of material form can only be varied by changing the stage of completion at which each operation starts, or by making special provision in earlier operations to provide features for production conveniences in later operations. Routing at this level affects the division of the operation into a series of planned work elements. As mentioned before, in order for the business to survive it must achieve certain goals and for doing so, it must sort some kind of problems, these problems have been classified by Hitomi as decision problems in his book Manufacturing Systems Engineering (Hitomi, 1979). The decision problem classification follows three groups, according with the levels marked in the production planning scheme (production, process, operation). Fig2. The referring for the production planning will be discussed (Hitomi, 1979): . . . . Optimal product mix: this determines an optimal combination of kinds of product items to be produced with the existing production capacity. If there is insufficient capacity to produce the entire amount of products demanded, such a demand cannot be sufficiently fulfilled, then an optimal product mix should be properly selected. In order to solve this problem it must focus on maximize the total profit obtained by production under the capacity constraint for doing so, some linear programming techniques can be used. Requirement analysis: this determines, in a specified time period, the quantities for the products which are decided to be produced by optimal product mix. Quantitative techniques, as linear programming, quadratic decision analysis is useful to assist decision-making for solving this problem. MRP plays an essential role in this field. Lot size analysis: helps to determine the optimal production quantities in intermittent production, where the demand rate for a product is small compared with the production rate for the product. For solving this problem a economic lot size and optimal production cycle are used to minimize the total production cost which are taken a the sum of set-up cost, manufacturing cost, inventory cost. Production smoothing: in some time periods, this determines, the production quantities of product items of fluctuated demand over a time period so that the level of production is even up. Management policies for this purpose are given for further information refer to (Gutenberg, 1955).. Those problems will be marked in a general form for two major concepts such as JIT (Just-in-time), MRP in further this chapter.. 6.

(17) Chapter 2. Literature Review 2.1.1 Production Management Function The general function of management read in management texts –organizing, planning, controlling, coordinating – is too generic to help understand the uniqueness of managing production against accounting or any other area, because of that the need to set specific function related to production, but also common to all production organizations, is indeed a great necessity. The origin of this functions is unclear and probably they come from the routine of managers, a first written description appear in the book by Oliver Wight, Production and Inventory in the Computer Area, 1984. Around five functions common to production management is how the book is organized; the following terms come from this book. Master Production Schedule (MPS) – the anticipated build schedule for those items assigned to the master scheduler. The master scheduler maintains this schedule, and in turn, it becomes a set of planning numbers that drives material requirements planning. It represents the production of the company in specific configuration, quantities, and dates (Cox & Spencer, 1998) Priority Planning – helps to determine what material is needed and when (Cox & Spencer, 1998). Capacity Planning – process focused on determining the amount of capacity required to produce in the future (Cox & Spencer, 1998). Priority Control – mean by which start and completion are communicated to the manufacturing department in order to execute a plan (Cox & Spencer, 1998). Capacity Control – process of measuring production output and comparing it to the capacity plan, determining if the variance exceeds pre-established limits, and taking corrective actions to get back on plan if limits are exceeded (Cox & Spencer, 1998). 2.1.2 Methods involve in the Production Planning After some readings it has been raised the conclusion that through the years, Production Planning has been solved by means of two major systems: JIT, MRP. See Fig. 3 JIT (Just-in-time), is considered a composition between level scheduling and Kanban philosophy, this concept was first used in Japan and focused on repetitive manufacturing environments. The history shows how the MRP (Material Requirement Planning) has evolved from a planning system for materials, to a system involving both capacity and material system, then to a manufacturing resource planning and finally, to a enterprise resource planning system.. 7.

(18) Chapter 2. Literature Review. Methods for Production Planning Problems. Decision problems Production Planning. Optimal Product mix Requirement Analysis Lot size analysis Production smoothing. Main solving systems JIT MRP. Fig. 3. Main Methods for Production Planning Problems.. 2.1.2.1 MRP By the mid-1960’s a new concept for planning and controlling the production was developed. Since then, its application has been a continuous practiced; the first real implementation of this concept was made to J.I Case Company (Orlicky, 1975) where the elements of MRP were developed in many different systems by many differing practitioners. If it is supposed to give a formal definition to this concept, it is “a set of techniques which uses bills of material, inventory data, and the master production schedule to calculate requirements for materials. It takes recommendation to release replenishment orders for material. Further, since it is time phased, it makes recommendation to reschedule open orders when due dates and need dates are no in phase…” (APICS Dictionary, pp. 50-51). Through the years the method became widely used in manufacturing and several modifications have been performed to the system, such that today the MRP is seen simply as a scheduling tool. The evolution of this system brought the creation of Manufacturing Resource Planning that has the same abbreviation (MRP) for that reason many practitioners use the term of MRPII to describe this multifunctional information systems. In our days the MRP is used around a set of interconnected computerized programs that host the production planning and control functions. Within an MRP system, the master production scheduling works taking as input the sales forecast and actual customer orders, the next step is to convert these input into materials and capacity requirements and measured against existing capacity and inventory levels. The master schedule is programmed in weekly time periods and can cover a horizon from 13 weeks to 78 weeks, depending on the management policies. Capacity planning works in conjunction with the master scheduling process in the MRP, that allows any change take a rapid adjustment to the levels of resources and material, 8.

(19) Chapter 2. Literature Review both functions are performed by the same planner at the time the master schedule is made. Priority planning is a function carried out by the MRP itself, in order to determine when the material is required to support the master schedule thanks to the lead time set as part of the internal logic of MRP. As planned orders are launch Priority control occurs taking in action and material is released to match the quantities on the now opened shop orders. The use of MRP systems with today’s complex products requires a computer to perform the job, other way would be very difficult to manage. 2.1.2.2 JIT Toyota automobile in the mid-1970’s appears with a new concept for the time for the Production Planning, under the name of Just-in-time. A formal definition can be obtained from de APICS Dictionary: “ a philosophy of manufacturing based on planned elimination of all waste and continuous improvement of productivity. It encompasses the successful executing of all manufacturing activities required to produce a final product, from design engineering to delivery and including all stages of conversion from raw material onward. The primary elements of just-in-time are to have only the required inventory when needed; to improve quality to zero defects; to reduce lead times by reducing setup times, queue lengths, and lot sizes, to incrementally revise the operation themselves; and to accomplish these things at minimum cost. In the broad sense, it applies to all forms of manufacturing, job shops and process as well as repetitive” (APICS Dictionary). Six key areas have been identified by Dr. Robert Hall (1991) concerning to the elements of the JIT: 1. 2. 3. 4. 5. 6.. Produce only what customer desires Produce only at the rate that the customer wants the product Produce the products with perfect quality Produce instantly with no lead times Produce with no waste of labor, material, or equipment Produce with methods that demonstrate a respect for people. Taking in count these elements, a brief reviewed of the functions of production planning and control will highlight the JIT method, starting the master scheduling function is customer driven through the use of actual orders, the time horizon is fixed for the first few months; then changes in volume are allowed in increasing steps as a percentages of the current capacity. The capacity planning function is performed as an integral part of the master production schedule development, if it’s point out a difference between MRP and JIT is the prohibition against adjusting manpower levels beyond a given level to establish a lower capacity; in the case of JIT does use temporary workers who are subject to layoffs, but uses layoffs as a last resort to adjust capacity.. 9.

(20) Chapter 2. Literature Review In the Priority planning function, material is only allowed to exist at the correct location by the design of the physical layout of the facility, operations are closely linked and space is simply not made available to hold idle work in process; a pull system is used rather than the creation of a formal schedule with due dates and start date. The removal of a piece of raw material may trigger the supplier to begin a replenishment cycle as well. The capacity control points to the schedule of almost 80% of total capacity, if necessary protective capacity is built and overtime is schedule if there is a need, but this situation is avoided by all mean because it would be considered a waste. The priority control function within the MRP system is limited, it means that if there is not a formal date scheduled, there is no way to measure against of the production, for this situation looked under the scope of a pull system, the lot sizes are quite small, and the lead times approach to zero, the replenishment is authorized only by the physical withdrawal of a previously finished piece. Mentioning that the above is how is supposed to work an ideal JIT, but in many cases not all is accomplished. 2.1.3 Automation of Production Planning Coding and Clustering of design and manufacturing features Production planning now counts with a new tool to be carried out. This tool is based on a feature modeling system using two types of features: design features and manufacturing features (Xue and Dong, 1997). This system is introduced for modeling these two product life-cycle aspects. In the case of design features, represented as mechanical components and mechanisms, are used for modeling design candidates to satisfy design functions. A design feature coding system is developed based on the analysis of design functions. A clustering algorithm is built to organize the large design feature library into hierarchical feature groups. Required design features are identified using graph-based search. A manufacturing feature is a geometric element to be produced. A manufacturing feature coding system is developed based on the analysis of product geometry and production operations. The introduction of a group technology-approach to organize components into groups according to their manufacturing feature codes using a clustering algorithm is presented. Production operations are optimized by a special optimization module. The two coding systems have been implemented in a feature-based, integrated concurrent design system for generating design candidates and planning production processes. Planning Group Technology For this concept, John Burbidge developed a methodology for the planning of Group Technology (GT). In his work “ The first step in planning Group Technology” is established that the essential first step in planning group technology (GT) is to plan a total division into groups and families, in which each group completes all the parts it makes. Such a division is always possible, and if it is based on the technique of. 10.

(21) Chapter 2. Literature Review production flow analysis (PFA), it is not difficult, time consuming, or expensive to plan (Burbidge, 1996). The possible savings from GT depend on finding groups which complete all the parts they make. With this methodology is intended and it must find such a division, expressed in practical terms of the machine numbers and part numbers in each group. It must show, in other words, that the conditions needed to obtain significant savings can be achieved. Later planning steps require consultation and discussion. 2.2 Process Planning The case of decision problems in the process planning can be mentioned as follow (Hitomi, 1979): . . . Process design (or work design) : this is a decision making which determines an overall process route for converting raw materials into products. It includes flowline analysis and selection of work station for each operation include in the work flow determined by means of operation process charts, routes sheets. Operation design (or job design): this decides the type of operation to be performed in each of the production process (content of each operation in the work flow) by means of man-machine charts. Layout planning: this is concerned with the spatial location of production facilities for material flow which has been established by process planning. Layout planning is usually made in a heuristic way, linear programming or can be used the method developed by R. Murther (1973) called Systematic Layout Planning. Analysis of optimum manufacturing conditions: is has to be done under the criteria of the maximum production rate, minimum production cost and the maximum profit rate, just to get an efficient and economic run of the manufacturing system.. For a normal way of saying process planning is the act of preparing detailed processing documentation for the manufacture of a piece part o assembly (Chang, 1990). This detailed processing documentation may include process selected, operation parameters, process sequences, setups, fixtures, etc. The outcome of the process planning may be affected by several factors, that is why they are classified in various levels according to the information provided. At the highest level, process planning may seek to select the most suitable technology for producing a feature, a part or a product (i.e. metal removing, forming or joining, etc), this is called generic o conceptual planning, from which is obtained a conceptual (abstract) plan. Getting deep into the levels, planning may concentrate only in one domain (eg. Assembly, sheet metal processing) or may consider several different applications and hence would be called multi-domain process planning (EI Maraghy, 1993). Forming a detailed analysis can gives us a view of a Macro-Planning (concerned mostly with. 11.

(22) Chapter 2. Literature Review sequencing) or Micro-Planning (concern with process parameters, setups, required tools, process time, resources, etc), for better understanding see fig. 4.. HIERARCHY OF PROCESS PLANNING PLANNING ACTIVITY LEVEL Generic Planning:. PLANNING OUTPUT General. High level. Manufacturing. Process Plans. Technologies/Process. Select Technology. Conceptual plans, Dfx analysis results. Rapid Process Planning 1. 4. Macro-Planning:. Routing. 3. 2. Multi-domain. (non-linear plans, alternate resources). 2.1. Detailed planning:. Detailed Process plans: 2.2. Single domain. (sequences, tools, resources, fixtures,……). 2.3. Single process (at a time) Micro-Planning:. Process/Operation. Optimal Conditions. Parameters (time, cost, etc… ). Machine instructions Detailed. More specific. Adapted from ElMaraghy. Fig. 4. Types and levels of process planning activities and their outcomes. In order to carried out the process planning the following activities must be involved: a) b) c) d) e) f). Selection of operations Sequencing operations Selecting tools Determining setup requirements Calculation of parameters Design of jig and fixtures. 12.

(23) Chapter 2. Literature Review. Process Planning Structure. Production Planning Input specifications. Select material size and conditions Select sequences and process parameters Select equipment, tooling, fixtures. Process Planning. Operation Planning. Select routing Determine time element for each process setup. Fig. 5. Process planning Structure. Within a process plan the degree of detail varies from industry to industry, and it will depend on the type of parts, production methods, and documentation needs. The process planner must have to perform these process planning activities (Chang, 1990): • • • •. Extensive knowledge of machines, tools referring to their capabilities related to a process. An understanding of the interaction between the part, manufacturing quality and cost The ability to analyze and understand part requirements Posses analytical capabilities. A task that help us to convert the materials into the forms required by the input specification is call routing, which involves the division of process into operations and the specification of the machines on which they are to be carried out (Burbidge, 1971). A document used to record the decisions made in routing is generally known as a route card. This card provide a brief description of all the operations necessary to complete a specific process for a particular part, in the sequence in which they have to be done, and that it also shows the work centers where the work is to be carried out. Something important to remark is that route cards can be seen as the mean of safeguarding company know-how; they also provide the basic record on which plant layout, production control and much of costing are based. The main problems involved in their preparation are: . Recognition of the final material form required. 13.

(24) Chapter 2. Literature Review . Division of the process into operations Consideration of the sequence of operations The choice of work centre for each operation. Difference with production planning which is concerned with the production environment as a whole, all the decisions made at the process planning stage are limited to a specific part only. For example, it can be said that production planning serves as a link between technical and non-technical planning; and the process planning serves as the critical link between design and manufacturing as seen in the figure 6. L in k betw een design and m a nufacturing IN P U T S P E C IF IC A T IO N S. P rocess P lanning Se lect m aterial size and co nditions Se lect seq uen ces and process. S hop O peration. Se lect equip m ent, toolin g and fixtures Se lect rou ting D eterm ine tim e e lem ent fo r each process set up. Fig. 6 Link between design and Manufacturing. 2.3 Automation of Process Planning Nowadays it has been proved that process planning is the crucial link in the manufacturing cycle, and can tell you how a product is going to be manufactured. Traditionally process planning is carried out manually, like in most industries, by experienced engineers who interpret engineering drawings of products and after they are able of determine the “best route” and manufacturing methods based on available materials, process, the time scale and cost restraints. Also it is known that planners can have different routes for the same part, which not always gives the optimal solution, that’s why a standardization for the best practice and company’s knowledge is necessary. As a solution computerization of process planning has evolved given as a result the CAPP. Computer-Aided Process Planning (CAPP) is a critical link between Computer-Aided Design (CAD) and Computer-Aided Manufacturer (CAM) (Hetem V et al, 1995). The CAPP Systems have been recognized as playing key within Computer Integrated. 14.

(25) Chapter 2. Literature Review Manufacturing. Even though the great efforts for developing CAPP Systems, the benefits in the real industrial environment are still to be seen. The beginning of this concept is presented by Neibel in his Ph.D. dissertation that in 1965 had the idea of using the speed and consistency of the computer to assist in the determination of process plans (Alting, 1988). Given the possibility to determine the operation and processing sequences from a part geometry, even though computer aided process planning was not took in research until the beginning of the 1970’s, that was probably for the fact that computer software and hardware were not too developed. But in 1976, a first system was built under the sponsor and direction of CAM-I (Computer Aider Manufacturing-International) by the same year other project was presented under the name of MIPLAN which was developed by the OIR (Organization of Industrial Research) at Houtzeel. Since then CAPP systems have begun to be widely pointed. From that moment until now CAPP has became an important tool in the integration of design and production plans. Based on the definition given by SME for process planning which states that “the systematic determination of the methods by which a product is to be manufactured economically and competitively”, a CAPP systems gives you the approach of having design and manufacturing together; its input can be determine by the product design and specification and its output is the production steps and instructions. This sequences of interpretation and planning consists of a series of work steps. With the interpretation being made on the product design data and materials, process activities are identified and sequenced. As mentioned this task is usually performed by an experienced planner but carried it out manually, with the help of computers this process can be automated. CAPP is a tool that frees the process planner from the many decisions which are required during the process planning task.. 2.3.1 Approaches of CAPP. Evolution 2.3.1.1 Variant It is basically to fill the information in a manual way, where a process plan for a new part is created based on remembering and identifying an existing plan for a similar part, many times called master part, doing some modification for the new part (Cay and Chassapis, 1997). For various variant systems parts are grouped into a number of part families, with some basic characteristics like manufacturing method or geometry. The idea is that for each part family, a standard process plan is created, with all the manufacturing process related to that family stored in the system. A difference from a manually process planning is that the variant approach will increase the information management capabilities. Also procedure can be standardized by incorporating a planner’s manufacturing knowledge and structuring it to a company’s specific needs. One of the main problems of this approach is the difficulty in maintaining consistency in editing practices and the quality of process plan still depends on the knowledge. 15.

(26) Chapter 2. Literature Review background of a process planner. An example of this kind of system is presented by (Alan et al, 2000) in their work entitled “Automate Process Planning for the manufacture of sliders”, in where a CAPP for injection mould components was developed searching the standardization of process planning and a reduction of lead time. The input to the system is a 3-D drawing, which the system typifies and refers to a standard process plan template; helping in selecting machines, tools, fixtures and cutting parameters, also the system includes a simulation of the process plan execution. Other example is presented by (Lin et al, 1999) which the objective of their work lies in developing a system to aide in the fabrication of aircraft components; process charts are the output of this system which includes operations illustrations to help machine operators in carrying out workshop machining task. 2.3.1.2 Generative In this case a process plan is generated through decision logics, formulas, technology algorithms, and geometry based data to perform uniquely the many processing decisions for converting a part from raw material to a finished state (Cay and Chassapis, 1997). When using this kind of system a specific process plan for a specific part can be generated without any involvement of a process planner. For generative systems, the input of data can be made through either as in text input where the user answer a number of questions or as a graphic input where the part data is obtained from a CAD module, the latter form is the most common used within enterprises. Examples of these types of systems are presented by (Younis and Wahab, 1997), whose works is limited to the manufacturing of rotational components using metal cutting operations. The model design is guided by tips provided for the different expert system classes, as well as relevant realizations from previous works, plus experimenting programming. A prototype system with a sample knowledge base is created as a result of this programming effort. The COMPLAN CAPP is another generative system developed by (Kruth et al, 1996), the Feature-based Computer Automated Process Planning application often suffer from exponential growth of the search space and thus CPU time, with increasing complexity of a part. In the research are explained some methods that were used to improve the response time of this newly developed CAPP system that is capable of generating net-shaped process plans, called non-linear process plans, containing several alternatives. 2.3.2 Implementation Techniques GT. Group Technology With the introduction of computer aided technologies and flexible manufacturing systems GT has become recognized and widely used in CAPP systems. Usually GT can be defined as the philosophy of studying a large population of apparently different items and then dividing them into group of items having the same o similar characteristics. The utilization of GT is in the part family concept where coding and classifying of the part are used. Several methods are used to classify parts, just to mention we have: Manual and. 16.

(27) Chapter 2. Literature Review visual search, Nomenclatures/functions, production flow analysis, classification and coding, mathematical programming. Classification and coding is the widely used.. The “the bottom-up This form develops CAPP systems by tracking the task of process planning from finished part to the raw material, because it is a conventional process planning method oriented to the variant approach. Even though, Marshall (1985) states that this form is simply use a computer as an arithmetic calculator. The “the top-down Like its name suggest, opposite to the one before, develops CAPP systems by tracking the task of process planning from top to bottom. This is an automated computer aided process planning method oriented toward the generative approach, where the computerized system works in the sequence determination of overall strategy and analysis. It’s look for the general rules of the manufacturing strategy to be built into algorithms which can operate on inputs data describing the geometric features and engineering requirements as they relate to individual component parts.. AI Techniques and expert systems The CAPP systems where AI techniques have been applied are call expert systems (ES) or Knowledge Based Systems (KBS), in that manner an expert system can be defined as a tool which has the capability to understand problem specific knowledge and use the process area knowledge to suggest alternative paths of action. By the case of process planning in the manufacturing area requires the human expertise, KBS is considered to have the largest potential for development of CAPP systems. As an example, it can be mention the R1(XCON) project which is an expert system for computer configuration and an expert system for job shop scheduling. Starting from that several expert systems have been developed. KBS basically consist of 4 components: 1) Knowledge base, 2) knowledge acquisition mechanism, 3) recognition –interface mechanism and 4) user interface. 2.3.3 Recent work on CAPP Knowledge-Based CAPP Research work in developing an automated computer-aided process planning system for a hot forging or blanking product by press working is presented by (Kim et al, 2001). This is a computer-aided process planning system written in AutoLISP on AutoCAD using a personal computer and in I-DEAS Drafting Programming Language on the I-DEAS Master Series Drafting with workstation in hot forging and blanking which requires many. 17.

(28) Chapter 2. Literature Review kinds of technical and empirical skills, supported by an approach based on knowledgebased rules; a process knowledge base consisting of design rules is built. Based on the investigation and collection of knowledge of the processes, is how this methodology is developed. This integrated computer-aided process planning system is composed of two main modules: hot forging and blanking modules. It is designed by considering several factors, such as the complexities of the blank geometry, the punch and die profiles, the availability of press equipment, and standard parts. Results obtained using the modules enable the designer and manufacturer of forging or blanking dies to be more efficient in this field. Feature-Based CAPP For this work the primary objective was to develop a prototype feature-based multiplealternative process planning system in which the process plan would be generated directly from design and available factory facility information (Yang et al, 2001). With this system an overall removable volume is generated by graphically comparing the 3D part and 3D workpiece blank, then the manufacturing features are decomposed into a series of general manufacturing features by using a mixed graph-based and rule-based algorithm. The multiple-alternative process plan generation is based on recognized manufacturing features and various production rules. After generating multiple process plans, each process plan is allocated the possible manufacturing scheduling time and the candidate process plans are retrieved based on the required due day. An example problem is presented to illustrate the functionality of the prototype system. Object-oriented CAPP In this research a specific emphasis is made about the importance of time, quality and information. Nowadays, in the current highly competitive international marketplace, these factors are especially crucial to the electronics industry. The system created based on an object-oriented model of a computer-aided process planning (CAPP) for the manufacturing of bare circuit boards is proposed (Law et al., 2001). Process constraints and planning knowledge are all represented and modeled by respective constraints objects. The system is then implemented for the automatic process planning of doublesided circuit boards. The performance of the system is then compared with that of experienced process planners. The advantages in the use of the constraint and knowledge objects approach in a computer-aided process planning system are revealed. GT & Expert Systems CAPP For this research the objective was to create a tool able to assist a machinist in determining an optimal process plan for prismatic components in the shortest time possible, explaining that expert systems managing prismatic components have not been developed (Jiang et al., 1999). Also describes the philosophy and design of an automatic process planning system (APPS) that is able to generate process plans rapidly from CAD drawings. The way of working is: APPS extracts the design features that are represented by a special code based on a new group technology (GT) classification coding scheme.. 18.