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Relation between production management and computer-aided design
Computers in Industry 19 (1992) 157-160 Elsevier
157
ATPMS '92
Relation between production management and computer-aided design Congchang Xiao Information Center, NORINCO(G), P.O. Box 84, 100823 Beijing, China Computer-aided design (CAD) is an important tool to improve product design and to support modern production management effectively. This paper systematically explores the relation between computer-aided production management (CAPM) and CAD, which is a product information source in CAPM. The paper, taking the integrated CAD/CAM system leAS as an example, clearly describes how the CAD module exchanges data with other functional modules.
Keywords: Production
management, CAD, Information source, Information flow, Product model.
enterprise. If CAD is not used, man can only input manually in the computer the original data needed by computer-aided process planning (CAPP) or production management (CAPM), for example, product code, bill-of-material (BOM), geometric and technological information and so Off.
2. T h e " s o u r c e " a n d " f l o w " i n p r o d u c t i o n
man-
agement
1. I n t r o d u c t i o n
Coming along with the technological advances and the increasingly sharp competition on the world market, the most important objectives being pursued at present are: - to reduce production costs; - to raise production efficiency; and - to strengthen marketing competition capacity. The relationship between product design means, product models, product information and production management is most significant. Modern equipment and management methods are being used, such as computers, numerical control (NC), manufacturing centers, robots and MRP-II, JIT, OPT and so on [1]. Modern production management and decision making need modern design means (for example CAD), and a completely computerized product model. In turn, modern design means and advanced design measures guarantee, by the product design, the implementation of modern management methods in an
From a systematic engineering view, in an enterprise the production system consists mainly of two parts: - t h e material production system; workmen, equipments, installations, tools, workpieces and so on; their flow is the flow of material and the material processing is the shaping; - the management control system: management decision making, production planning and machining control instructions and so on; they command and control the material production system to be in motion.
2.1. Material flow An important part of material handling is the motion and shaping of workpieces and the exchanging of cutting tools and clamping apparatus. The former refers to the process from the beginning of raw material and blanks to the end of product shipping. The latter has different types, depending on the type of production organization: assembly line, GT, FMS and so on.
0166-3615/92/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights reserved
158
A TPMS '92
Computers in Industry
2.2. Information flow In production management, management decision planning and commands with product information and process planning are transported in the form of information to workers, equipments and control system. This is the information flow in a production system. The management information comes from the head and the decisionmaking departments of an enterprise, and the information source of a product is the product design. The process planning of a workpiece is obtained from the product information with CAPP by reverse deduction. The dimensions, specifications and preprocessing of raw material and blanks are obtained from the material, dimensions and accuracy of the pror~ :cts. Then the product information is used for machining control, quality testing and customers consulting by positive deduction. Feedback information will be used for improving old products and the design of new products.
2.3. Flow of funds In an enterprise, profit is a most important objective. Therefore, the managers should attach great importance to the flow of funds and increase of the value of investment and turnover of capital, variations in the cost of semi-finished products, which are all dependent on the flow of material and information.
2.4. Product and its information In the production process, the semi-finished product in the material production system and its information in a management information system in the computer have a corresponding relation: like body and shadow they complement each
Congchang Xiao is senior engineer and deputy chief-engineer at the Information Centre, NORINCO(G), China. He was born in ShaanXi, China in 1941 and graduated from Beijing Institute of Technology in 1965 He is engaged in research on vehicle engineering. Since 1978 he has been working on computer applications such as FEM, CAD/CAM and CIMS. His current research interests are CAPM and enterprise management information systems.
other. In the traditional machining process, the body is the semi-finished product, the shadow is the product blueprints. In CAPM and CAD systems, the shadow is the model and data in the computer. Through analysis of the material flow, information flow and fund flow pictures one could clearly find the information source, information processing and their mutual relation. And one could see whether the three flows are unbroken or clogged and where the bottleneck is.
3. Product models
The object of production management is the product and the semi-finished product. The workpieces on a production line should correspond to the product model and data stored in the computer. The product information and technological information can be shown in more detail on a blueprint by drawing, dimensioning and specifying technical conditions, but all these cannot be reflected in a computer model, because the expression of a product in a computer depends not only on the intent of the people, but also on the product model and the methods of expression in the computer. Table 1 reflects the information that can be carried by various types of geometric modeling [2,3]. Simple models can be structured conveniently, processed quickly, but their automatic processing is inconvenient, because the model carries not enough information. The complete product model has enough information which is transferred to CAPP and CAM, but its data structure is very complex. At present, the focal point of CAD research is the representation of a product in a computer to meet the demands of CAM. However, the complex data structure increases the difficulty of storage, handling and exchange of data, and along with this the difficulty of the data interface will increase. Feature technology (FT) associates manufacturing data with geometric design data and it allows one data structure to meet the need of all design and manufacturing activities. Furthermore, it may facilitate the organization of the data flow in relation to CAPM and CIMS greatly [41.
Computers in Industry
C. Xiao / Production management and CAD
4. Relation between CAPM and CAD At present, due to strenuous competition of commodities and the shorter life cycle of a product, the traditional design method cannot meet the needs of product design and, out of the ordinary, cannot meet the needs of production, i.e. the demands of order of goods and the principle of no goods kept in stock. Therefore, one should attach great importance to the use of CAD in design, thus CAD takes an important position in CAPM: (1) A CAD system can be used for the conceptual design and detailed design of a new product; it can simulate and analyze statically and dynamically the function of the product; compare and opt for design schemes; improve the quality and speed of design; and reduce the design cost of a product. The product design and technological design themselves are the main links in production preparedness. They provide a foundation for increasing the quality of production management. (2) CAD is not only useful for the design of a new product, but also beneficial for reforming an old product whose drawing was stored in computer. (3) The model in the computer--2-D drawings, 3-D wireframe, 3-D solid modeling and feature technologymdirectly influences CAPM whether the product information in the computer is perfect or not. (4) The bill of material (BOM) and process planning formed by the product design plus the master production schedule (MPS) are the main
159
basis for implementation of MRP II (manufacturing resources planning), and the original data for MRP (material requirements planning) and CRP (capacity requirements planning) [5]. (5) CAD techniques can make the workpiece on the production line correspond with the product and technological information in the computer, i.e. the body (workpiece) corresponds with the shadow (model in computer). Thus CAD is convenient for production control, automatic testing of the machining quality and production statistics. (6) The production information, process planning, production schedule and so on in the computer create the conditions for integration of information and manufacturing--CIMS (computer-integrated manufacturing system). (7) CAD makes possible the quantifying and graphing of enterprise management and the automation of cost calculation.
5. Integrated CAD/CAM system lCAS iCAS is an integrated C A D / C A M software package developed on a SUN 3/160 C workstation and running on the UNiX operation system. ICAS mainly consists of functional modules: 2-D drawing, 3-D solid modeling, free curve and surface modeling, finite element nets generator and analysis, CAPP, NC programming, data managemerit subsystems, etc. and the corresponding data interfaces.
Table 1 Information carried by various types of geometric modeling Feature technology 3-D solid modeling
Topological,geometric,material, surface and main technologicalinformation Topological,geometric,material and surface info of 3-D solid model
Other technological information Technologicalinfo
3-D wireframe + surface modeling
Topological,geometricand surface info of 3-D wireframe model
Solid characteristics, technologicalinfo
3-D wireframe modeling
Topologicaland geometricinfo of 3-D wireframe
Solid characteristics, surface and tech. info
2-D drawing modeling
Topologicaland geometricinfo of 2-D projection
Space feature, surface and technologicalinfo
Modelingtype
Information carried in the model
Main informationnot entered in the model
160
A TPMS '92
ICAS has seven functional modules, each with a basic characteristic data structure. To guarantee regular ,:unning of the integrated system and the common sharing of data sources, integrated data management and data flow in a reasonable direction are necessary. Therefore, the data files or data blocks fo~-med by the various functional modules should be coded uniformly and should be processed suitably, in order to make data input/output in/from the database suitable for unifying management and also possible to be distinguished from each other. Thus, the data flow between various functional blocks should follow the principle of one-time input and multitime use, integrating and precision [6]. The system takes 3-D solid modeling as the original data generator, i.e. the data source. Basic topological and geometric relations of the body are produced by the 3-D solid modeling subsystem, and support the other subsystems according to the international standard PHIGS. CAPP is a bridge and a key of the integrated system. According to the principle of opposite deduction and based on the product information formed by CAD software, by GT (variable way) or decision table, decision trees and AI deduction (created way), CAPP produces the process routing, machining methods, chooses the machine tools and clamping apparatus, calculates the size, specifications and allowance of each processing procedure and produces the drawings of the processing procedure. Thus from blanks to finished products, the computer expression of in-process products and the demands of each process procedure are formed. Process routings are prepared in terms of product information. In lCAS the product geometric information is provided by 3-D modeling. The product geometric information is grouped and coded in terms of solid elements and combinations of solid elements, then offered to CAPP. But workpieces having the same shape are processed by different process routings, due to different processing dimensioning. In order to compensate for the defects of CAD solid elements,
Computers in Industry
CAPP looks to the solid element as a minimum unit with geometric and process information. Features of dimensioning methods and processes are being considered, solid elements being divided. ICAS can provide CAPM with enough information, thereby laying a foundation for modern management in an enterprise.
6. Conclusion
Product design is the first key link of production preparation and a starting point for overall planning, quality management and economic calculations. The design quality of a product not only directly influences the quality and function of a product but also decides whether the overall, integrated production management by modern means can be in process or not. Therefore, more and more importance has been attached to the research of the relation between production management and CAD. CAD, as the first key link of production management and the information source of a product, will push forward the advance of computer-supported production management. Modern production management techniques will surely put up higher requirements and supply broader application prospects for CAD.
References [1] Strategic Piannig for Computer Integrated Manufacturing, SEA! Tech. Publ., 1988. [2] H. Grabowski, "Stand der Technik und Entwicklungstendenzen yon CAD", 3rd CASCO Symp., 1987. [3] Xiao Congchang and Zhao Jiahui, "Evolution of the data structure and feature technology", Advances in CAD/ CAM, October 6-9, 1987. [4] Xiao Congchang, "Computer integrated manufacturing system and a new generation CAD", CAD & CG '89, Beijing, 1989. [5] Wen Yuntang, Manufacturing resources planning (MRP II) system, China, 1990. [6] Xiao Congchang and Yuan Kerang, "An integrated CAD/CAM system--leAS", Computer Application Conf., 1990.
157
ATPMS '92
Relation between production management and computer-aided design Congchang Xiao Information Center, NORINCO(G), P.O. Box 84, 100823 Beijing, China Computer-aided design (CAD) is an important tool to improve product design and to support modern production management effectively. This paper systematically explores the relation between computer-aided production management (CAPM) and CAD, which is a product information source in CAPM. The paper, taking the integrated CAD/CAM system leAS as an example, clearly describes how the CAD module exchanges data with other functional modules.
Keywords: Production
management, CAD, Information source, Information flow, Product model.
enterprise. If CAD is not used, man can only input manually in the computer the original data needed by computer-aided process planning (CAPP) or production management (CAPM), for example, product code, bill-of-material (BOM), geometric and technological information and so Off.
2. T h e " s o u r c e " a n d " f l o w " i n p r o d u c t i o n
man-
agement
1. I n t r o d u c t i o n
Coming along with the technological advances and the increasingly sharp competition on the world market, the most important objectives being pursued at present are: - to reduce production costs; - to raise production efficiency; and - to strengthen marketing competition capacity. The relationship between product design means, product models, product information and production management is most significant. Modern equipment and management methods are being used, such as computers, numerical control (NC), manufacturing centers, robots and MRP-II, JIT, OPT and so on [1]. Modern production management and decision making need modern design means (for example CAD), and a completely computerized product model. In turn, modern design means and advanced design measures guarantee, by the product design, the implementation of modern management methods in an
From a systematic engineering view, in an enterprise the production system consists mainly of two parts: - t h e material production system; workmen, equipments, installations, tools, workpieces and so on; their flow is the flow of material and the material processing is the shaping; - the management control system: management decision making, production planning and machining control instructions and so on; they command and control the material production system to be in motion.
2.1. Material flow An important part of material handling is the motion and shaping of workpieces and the exchanging of cutting tools and clamping apparatus. The former refers to the process from the beginning of raw material and blanks to the end of product shipping. The latter has different types, depending on the type of production organization: assembly line, GT, FMS and so on.
0166-3615/92/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights reserved
158
A TPMS '92
Computers in Industry
2.2. Information flow In production management, management decision planning and commands with product information and process planning are transported in the form of information to workers, equipments and control system. This is the information flow in a production system. The management information comes from the head and the decisionmaking departments of an enterprise, and the information source of a product is the product design. The process planning of a workpiece is obtained from the product information with CAPP by reverse deduction. The dimensions, specifications and preprocessing of raw material and blanks are obtained from the material, dimensions and accuracy of the pror~ :cts. Then the product information is used for machining control, quality testing and customers consulting by positive deduction. Feedback information will be used for improving old products and the design of new products.
2.3. Flow of funds In an enterprise, profit is a most important objective. Therefore, the managers should attach great importance to the flow of funds and increase of the value of investment and turnover of capital, variations in the cost of semi-finished products, which are all dependent on the flow of material and information.
2.4. Product and its information In the production process, the semi-finished product in the material production system and its information in a management information system in the computer have a corresponding relation: like body and shadow they complement each
Congchang Xiao is senior engineer and deputy chief-engineer at the Information Centre, NORINCO(G), China. He was born in ShaanXi, China in 1941 and graduated from Beijing Institute of Technology in 1965 He is engaged in research on vehicle engineering. Since 1978 he has been working on computer applications such as FEM, CAD/CAM and CIMS. His current research interests are CAPM and enterprise management information systems.
other. In the traditional machining process, the body is the semi-finished product, the shadow is the product blueprints. In CAPM and CAD systems, the shadow is the model and data in the computer. Through analysis of the material flow, information flow and fund flow pictures one could clearly find the information source, information processing and their mutual relation. And one could see whether the three flows are unbroken or clogged and where the bottleneck is.
3. Product models
The object of production management is the product and the semi-finished product. The workpieces on a production line should correspond to the product model and data stored in the computer. The product information and technological information can be shown in more detail on a blueprint by drawing, dimensioning and specifying technical conditions, but all these cannot be reflected in a computer model, because the expression of a product in a computer depends not only on the intent of the people, but also on the product model and the methods of expression in the computer. Table 1 reflects the information that can be carried by various types of geometric modeling [2,3]. Simple models can be structured conveniently, processed quickly, but their automatic processing is inconvenient, because the model carries not enough information. The complete product model has enough information which is transferred to CAPP and CAM, but its data structure is very complex. At present, the focal point of CAD research is the representation of a product in a computer to meet the demands of CAM. However, the complex data structure increases the difficulty of storage, handling and exchange of data, and along with this the difficulty of the data interface will increase. Feature technology (FT) associates manufacturing data with geometric design data and it allows one data structure to meet the need of all design and manufacturing activities. Furthermore, it may facilitate the organization of the data flow in relation to CAPM and CIMS greatly [41.
Computers in Industry
C. Xiao / Production management and CAD
4. Relation between CAPM and CAD At present, due to strenuous competition of commodities and the shorter life cycle of a product, the traditional design method cannot meet the needs of product design and, out of the ordinary, cannot meet the needs of production, i.e. the demands of order of goods and the principle of no goods kept in stock. Therefore, one should attach great importance to the use of CAD in design, thus CAD takes an important position in CAPM: (1) A CAD system can be used for the conceptual design and detailed design of a new product; it can simulate and analyze statically and dynamically the function of the product; compare and opt for design schemes; improve the quality and speed of design; and reduce the design cost of a product. The product design and technological design themselves are the main links in production preparedness. They provide a foundation for increasing the quality of production management. (2) CAD is not only useful for the design of a new product, but also beneficial for reforming an old product whose drawing was stored in computer. (3) The model in the computer--2-D drawings, 3-D wireframe, 3-D solid modeling and feature technologymdirectly influences CAPM whether the product information in the computer is perfect or not. (4) The bill of material (BOM) and process planning formed by the product design plus the master production schedule (MPS) are the main
159
basis for implementation of MRP II (manufacturing resources planning), and the original data for MRP (material requirements planning) and CRP (capacity requirements planning) [5]. (5) CAD techniques can make the workpiece on the production line correspond with the product and technological information in the computer, i.e. the body (workpiece) corresponds with the shadow (model in computer). Thus CAD is convenient for production control, automatic testing of the machining quality and production statistics. (6) The production information, process planning, production schedule and so on in the computer create the conditions for integration of information and manufacturing--CIMS (computer-integrated manufacturing system). (7) CAD makes possible the quantifying and graphing of enterprise management and the automation of cost calculation.
5. Integrated CAD/CAM system lCAS iCAS is an integrated C A D / C A M software package developed on a SUN 3/160 C workstation and running on the UNiX operation system. ICAS mainly consists of functional modules: 2-D drawing, 3-D solid modeling, free curve and surface modeling, finite element nets generator and analysis, CAPP, NC programming, data managemerit subsystems, etc. and the corresponding data interfaces.
Table 1 Information carried by various types of geometric modeling Feature technology 3-D solid modeling
Topological,geometric,material, surface and main technologicalinformation Topological,geometric,material and surface info of 3-D solid model
Other technological information Technologicalinfo
3-D wireframe + surface modeling
Topological,geometricand surface info of 3-D wireframe model
Solid characteristics, technologicalinfo
3-D wireframe modeling
Topologicaland geometricinfo of 3-D wireframe
Solid characteristics, surface and tech. info
2-D drawing modeling
Topologicaland geometricinfo of 2-D projection
Space feature, surface and technologicalinfo
Modelingtype
Information carried in the model
Main informationnot entered in the model
160
A TPMS '92
ICAS has seven functional modules, each with a basic characteristic data structure. To guarantee regular ,:unning of the integrated system and the common sharing of data sources, integrated data management and data flow in a reasonable direction are necessary. Therefore, the data files or data blocks fo~-med by the various functional modules should be coded uniformly and should be processed suitably, in order to make data input/output in/from the database suitable for unifying management and also possible to be distinguished from each other. Thus, the data flow between various functional blocks should follow the principle of one-time input and multitime use, integrating and precision [6]. The system takes 3-D solid modeling as the original data generator, i.e. the data source. Basic topological and geometric relations of the body are produced by the 3-D solid modeling subsystem, and support the other subsystems according to the international standard PHIGS. CAPP is a bridge and a key of the integrated system. According to the principle of opposite deduction and based on the product information formed by CAD software, by GT (variable way) or decision table, decision trees and AI deduction (created way), CAPP produces the process routing, machining methods, chooses the machine tools and clamping apparatus, calculates the size, specifications and allowance of each processing procedure and produces the drawings of the processing procedure. Thus from blanks to finished products, the computer expression of in-process products and the demands of each process procedure are formed. Process routings are prepared in terms of product information. In lCAS the product geometric information is provided by 3-D modeling. The product geometric information is grouped and coded in terms of solid elements and combinations of solid elements, then offered to CAPP. But workpieces having the same shape are processed by different process routings, due to different processing dimensioning. In order to compensate for the defects of CAD solid elements,
Computers in Industry
CAPP looks to the solid element as a minimum unit with geometric and process information. Features of dimensioning methods and processes are being considered, solid elements being divided. ICAS can provide CAPM with enough information, thereby laying a foundation for modern management in an enterprise.
6. Conclusion
Product design is the first key link of production preparation and a starting point for overall planning, quality management and economic calculations. The design quality of a product not only directly influences the quality and function of a product but also decides whether the overall, integrated production management by modern means can be in process or not. Therefore, more and more importance has been attached to the research of the relation between production management and CAD. CAD, as the first key link of production management and the information source of a product, will push forward the advance of computer-supported production management. Modern production management techniques will surely put up higher requirements and supply broader application prospects for CAD.
References [1] Strategic Piannig for Computer Integrated Manufacturing, SEA! Tech. Publ., 1988. [2] H. Grabowski, "Stand der Technik und Entwicklungstendenzen yon CAD", 3rd CASCO Symp., 1987. [3] Xiao Congchang and Zhao Jiahui, "Evolution of the data structure and feature technology", Advances in CAD/ CAM, October 6-9, 1987. [4] Xiao Congchang, "Computer integrated manufacturing system and a new generation CAD", CAD & CG '89, Beijing, 1989. [5] Wen Yuntang, Manufacturing resources planning (MRP II) system, China, 1990. [6] Xiao Congchang and Yuan Kerang, "An integrated CAD/CAM system--leAS", Computer Application Conf., 1990.