- Email: [email protected]
Computer aided process design in cold-former forging using a forging simulator and a commercial CAD software
Journal of Materials Processing Technology 95 (1999) 155±163
Computer aided process design in cold-former forging using a forging simulator and a commercial CAD software C.S. Ima, S.R. Suhd, M.C. Leeb,c, J.H. Kimd, M.S. Jounb,c,* a CAD/CAM Laboratory, Yonam College of Engineering, Chinju, Seoul 660-750, South Korea Department of Mechanical Engineering, Gyeongsang National University, Chinju, Seoul 660-701, South Korea c Regional Research Center for Aircraft Parts Technology, Chinju, Seoul 660-701, South Korea d Research and Development Laboratory, Central, Ltd., Changwon 641-315, South Korea
b
Received 24 April 1998
Abstract In this paper, a computer aided process design technique, based on a forging simulator and commercial CAD software, is presented together with its related design system for the cold-former forging of ball joints. The forging sequence design and its detail designs are generated through user±computer interaction using templates, design databases, knowledge-based rules and some basic laws. The forging simulation technique is used to verify the process design. The detail designs, including die set drawings and die manufacturing information, are generated automatically. It has been shown that engineering and design productivity is much improved by the presented approach from the practical standpoint of process design engineers. # 1999 Elsevier Science S.A. All rights reserved. Keywords: Cold-former forging; Process sequence design; Automatic computer simulation; Detail process design
1. Introduction For the mass production of small- or medium-sized mechanical parts, cold-former machines, sometimes called multi-station automatic cold-forging machines, are being used in a wide range of mechanical parts manufacturing industries. In cold-former forging, initial materials, cut from simple bars, are formed progressively to ®nal shapes by automatic and synchronized operations, including shearing, upsetting, forward and/or backward extrusion, piercing and the like. Usually, the number of forging sequences in coldformer forging is larger than that in conventional forging because of the mass-production purpose of this machine. Simultaneous operation and production automation are also important characteristics of cold-former forging processes. It is very dif®cult to carry out the process sequence design in cold-former forging because many aspects should be considered, including production economy as well as the proper distribution of plastic deformation, machine limitation, production automation and the like. In addition, the *Corresponding author. Tel.: +82-591-751-5316; fax: +82-591-7515316 E-mail address: [email protected] (M.S. Joun)
reliability of process design in automatic multi- station forging is of great importance since a design failure or an intermittent stop of the manufacturing line can cause a decisive increase in manufacturing and design cost and loss of opportunities. In order to reduce possible failures in process sequence design, several works [1±16] have been reported for developing design assisting environments such as expert systems and CAD/CAM techniques. However, in addition to the intrinsic nature of forging sequence design, which is very creative and empirical, complexity in plastic deformation and high correlation between design parameters in different stages have made it dif®cult to realize process design automation in cold-former forging. The automatic design system is usually composed of a process design module and a simulation or veri®cation module. Most conventional research has focused on process sequence generation in the former. Ehrismann and Reissner [15] emphasized the importance of the integration of a simulation system with a design or manufacturing assisting system in order to promote mutual understanding between simulation experts and design experts and reduce the engineering time and cost. A practical viewpoint of process designers that an automatic design system has to possess can be found in the work of Kim and Altan [6] . According to
0924-0136/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 4 - 0 1 3 6 ( 9 9 ) 0 0 2 8 4 - 8
156
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
their work, ®rstly a process design module should minimize routine work, including sequence design generation, satisfying volume consistency, modifying designs, checking basic design rules, making detailed drawings and generating die manufacturing information. However, they underestimated the importance of the simulation module, since computers in those days were not powerful enough for the forging simulator to play a main role in the design information and knowledge system. Based on the above considerations, a fully integrated design system is developed in this study, in which a forging simulator plays the core role in assisting forging sequence design. Cold-former forging of ball studs used as ball joint components is selected as an application example, since there are many different sizes of ball studs manufactured in a company and the related technical materials can be obtained. 2. Overall procedure of the developed design system Several researchers [1±16] have studied the process design automation of cold-former forging. Most research has been focused on automatic process sequence generation in the process design module based on knowledge-based expert systems or AI techniques. However, there are limited applications for the whole sequence design of a new process, since the sequence design itself is very creative and human experts have only narrow information, Of course, conventional research works can be used for the sequence design of the special process if the design databases have many similar processes and the related design information can be accessed easily and modi®ed with accompanying automatic detailed veri®cation. It should be noted that the most important activity in an automatic design system or in a design assisting system lies in the veri®cation of the design candidate, and such veri®cation capability should be the core of the design system from the standpoint of the process designer. Constraints on process parameters from either machine speci®cation or rule-based design speci®cation can be checked with relative ease. The most dif®cult problem arises in metal forming mechanics. The plastic deformation in cold-former forging is very delicate and dimensional tolerance is inherently very tight. Therefore, conventional approximate analysis approaches cannot avoid many limitations and obstacles. Recent enhancement in computer hardware technology makes it possible to use a ®nite-element-based forging simulator as the core veri®cation tool. It is now possible to obtain the whole solution of a multi-stage forging process within 1±3 h by a fully automatic forging simulator [17] with a recently announced PC, and the associated computational time is becoming progressively smaller. The simulator can be used to investigate the detailed effect of a process parameter on the process conditions and the product quality if it is integrated with a design assisting system. In this case, a forging simulation technique is the major part of the design
assisting system. Even though some approaches [9±16] employed a ®nite-element-based forging simulator as a veri®cation tool, the functions were not fully integrated and the computer simulation required quite a large amount of time due to the user interface as well as to the computational time. As a result, the simulator could not be an active design tool in the related systems. In this study, a process design assisting system, called DASFOR, has been developed using a PC-based forging simulator, AFDEX/2D [17], and a PC-based CAD software, AutoCAD. The system is composed of the process design module and the design veri®cation module. It assists the whole work in process design, including the generation of design and manufacturing information, process sequence generation, engineering calculation, detail design veri®cation, detail design drawing extraction and process design veri®cation. Fig. 1 shows the conceptual ¯ow chart of DASFOR. The basic approach is introduced in the following
Fig. 1. Conceptual flow chart of the present approach.
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
two chapters through an application example in the coldformer forging of a ball stud. This paper does not include the determination of the number of forging stages. 3. Process design module The process design module helps the process design engineer to carry out interactively the whole work in process design. The major capabilities of the process design module include the interactive generation of the process sequence, the detail design of the process, the generation of simulation
157
information, the modi®cation of designs, the generation of detail drawings and database management. Fig. 2 shows an example of the process sequence generated by DASFOR for the cold-former forging of a ball stud. The process sequence design is quite creative and is dependent deeply on the intuition and experience of process design engineers. It may be very helpful for process design engineers if design experience has been accumulated systematically onto knowledge databases and they can be easily accessed. In this study, a cold-former forging of a ball stud, of which suf®cient design information can be obtained, was selected as an application example. First of all, 30 unit processes used in
Fig. 2. A process sequence design.
Fig. 3. Templates for the process sequence design in ball-stud forging.
158
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
Fig. 5. Combinations of possible process sequence designs for ball-stud forging.
Fig. 4. Parameterized unit process template.
the related industry or found from the literature were parameterized and the database was constructed. Fig. 3 shows some of the unit processes, called unit process templates, which have been used with frequency in the cold-former forging of ball studs. Each template is represented by a few design parameters, as seen in Fig. 4. The user can construct a process sequence either by selecting unit processes from their templates or by restoring a successful process sequence design from the database. Basically, the process sequence design starts from the desired product and then proceeds to the initial workpiece. Fig. 5 show combinations of possible process designs that
has been generated from experience and material found in the literature and stored in the knowledge database, with their related design rules after design veri®cation for a typical example. Fig. 2 shows an example of a process design made with the help of the knowledge database. When the product geometry is given, some design parameters in the preceding stages are determined either from the requirement on safe mounting and loading and clearance or by some experience-based rules [18]. The other design parameters can be calculated by general design rules [1± 16,18,19] including volume constancy, formability limitations and process designers' experience. Separation of each unit process into two pieces should be made prior to carrying out detail design of the lower and upper dies or punches.With the separation, one can obtain a basic design information ®le as shown in Fig. 6, which is used to generate process geometries for both computer
Fig. 6. Basic design information.
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
Fig. 7. Assembly drawing of the process design.
Fig. 8. Detail drawing of the die set for the first stage.
159
160
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
Fig. 9. Detail drawing of the die set for the fourth stage.
Fig. 10. Detail drawing of the punch set for the fourth stage.
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
simulation and detail design. It is to be noted that it takes much time to make mechanical drawings of the process design because tens of mechanical drawings are necessary for one process design. Automatic generation of drawings is thus one of major capabilities that a process design assisting system should possess. In general, standardization of forging dies and automatic generation of their drawings are very dif®cult to be achieved. It is fortunate that many parts for die sets in cold-former forging were already standardized. Drawings of die sets can thus be generated in an automatic or interactive manner. The main factors affecting this drawing work are the machine speci®cation, the gap between the upper die or punch and the lower die and clearance or tolerance as well as the process design itself. Some detail drawings for the example are given in Figs. 7±10. If the process design is accomplished, design veri®cation should be made by the veri®cation module. Note that it is quite time-consuming to prepare the whole input data for computer simulation of the process design candidates. An automatic interface program in the process design module that generates the simulation information with minimum user interface was developed.
161
Fig. 11. Process geometries extracted from the process sequence design.
4. Design verification module Forging simulators are now being used in many industries. Several researchers have attempted to use them for veri®cation of forging process designs. However, they failed to imbed the simulation capability into the process design module because the forging simulators used lacked in simulation automation. This deteriorated the applicability of both the process design module and the design veri®cation module. In this study, automatic and intelligent forging simulation techniques [17] were developed for the purpose of process design in cold-former forging. The forging simulator can be run automatically by the input data obtained by the interface program without any user interface during simulating a whole sequence of multi-stage forging processes. In the interface program, the geometry information of material and dies is extracted from the process design database, whilst process conditions, including frictional conditions, are entered in an interactive manner. Fig. 11 shows an example of the geometry information extracted automatically from the process design database. With this capability, much time taken in preparing the input data of the simulators can be saved. Thus, the applicability of the simulators to process design can be much enhanced and many of the ambiguous experience-based design rules can be replaced by the simulation capability with the engineer's scienti®c evaluation of the simulated results including stress, strain, strain-rate, die pressure and die stress, forming load, damage, hardness, die wear and the like. Several simulation results for the example are given in Figs. 12±14.
Fig. 12. Simulation results of metal flow.
Fig. 13. Simulation results of forming load.
5. Conclusions In this paper, a computer-aided process design technique, utilizing a forging-simulator and commercial CAD software, was presented together with its related design system
162
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
Fig. 14. Simulation results of damage.
for the cold-former forging of ball joints. The forging sequence design was assisted by knowledge-based rules and some basic laws. The detail designs for a design candidate of the selected forging sequence were carried out in an automatic or interactive manner by considering design constraints and experience-based laws. From the detail designs, all of the forging simulation information was extracted automatically and the whole forging process was simulated without any user interface. Successful detail designs, including die set drawings and die manufacturing information were obtained by user±computer interaction. It has been shown that the engineering and design productivity are much improved by the present approach from the practical standpoint of process design engineers. References [1] P. Bariani, W.A. Knight, Computer aided cold forging design: determination of machine setting conditions, Ann. CIRP 34(1) (1985) 245±248. [2] P. Bariani, W.A. Knight, Computer-aided cold forging process design: a knowledge-based system approach to forming sequence generation, Ann. CIRP 37(1) (1988) 243±246. [3] P. Bariani, E. Benuzzi, W.A. Knight, Computer aided design of multistage cold forging process: load peaks and strain distribution evaluation, Ann. CIRP 36(1) (1987) 145±148.
[4] M.T. Gokler, T.A. Dean, W.A. Knight, Computer aided die design for upset forging machines, Proceedings of the 11th NAMRC, 1983, pp. 217±223. [5] W. Makosch, K. Lange, Application-orientated CAD system for multi-stage tooling design for cold forging, Proceedings of the 16th NAMRC, 1988, pp. 63±70. [6] H. Kim, T. Altan, Computer-aided part and processing-sequence design in cold forging, J. Mater. Process. Technol. 33 (1992) 57±74. [7] K. Sevenler, P.S. Raghupathi, T. Altan, Forming-sequence design for multistage cold forming, J. Mech. Work. Technol. 14 (1987) 121± 135. [8] T.P. Davison, W.A. Knight, Computer aided process design for cold forging operation, Adv. Technol. Plast. I (1984) 551±556. [9] A.A. Badawy, P.S. Raghupathi, D.J. Kuhlmann, T. Altan, Computeraided design of multistage forging operations for round parts, J. Mech. Work. Technol. 11 (1985) 259±274. [10] K. Osakada, T. Kado, G.B. Yang, Application of AI-technique to process planning of cold-forging, Ann. CIRP 37(1) (1998) 239±242. [11] G.B. Yang, K. Osakada, An expert system for process planning of cold forging, Adv. Tech. Plast. 1 (1990) 109±115. [12] D. Glynn, G. Lyons, J. Monaghan, Forging sequence design using an expert system, J. Mater. Process. Technol. 55 (1995) 95±102. [13] P. Bariani, G. Berti, L. D'Angelo, M. Marengo, A. Rossi, An integerated CAD/CAE system for cold-forging process design, Adv. Technol. Blast. 1 (1990) 7±12. [14] H.S. Kim, Y.T. Im, Expert system for multi stage cold-forging process design with a re-designing algorithm, J. Mater. Process. Technol. 54 (1995) 271±285. [15] R. Ehrismann, J. Reissner, The integration of simulation techniques in expert systems, Adv. Tech. Plast. 1 (1990) 197±202.
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163 [16] Q.C. Hsu, R.S. Lee, Cold forging process design based on the induction of analytical knowledge, J. Mater. Process. Technol. 69 (1997) 264±272. [17] Users' manual of AFDEX/2D 2.1, Metal Forming CAE Laboratory in Gyeongsang National University, 1998.
163
[18] M.S. Joun, C.S. Im, M.C. Lee, Development of automatic process design program for cold-former forging of ball studs, Technical Report, Research Center for Aircraft Parts Technology, Gyeongsang National University, 1996±1997. [19] Metal Handbook, Forming and Forging, Am. Soc. Metals (1988).
Computer aided process design in cold-former forging using a forging simulator and a commercial CAD software C.S. Ima, S.R. Suhd, M.C. Leeb,c, J.H. Kimd, M.S. Jounb,c,* a CAD/CAM Laboratory, Yonam College of Engineering, Chinju, Seoul 660-750, South Korea Department of Mechanical Engineering, Gyeongsang National University, Chinju, Seoul 660-701, South Korea c Regional Research Center for Aircraft Parts Technology, Chinju, Seoul 660-701, South Korea d Research and Development Laboratory, Central, Ltd., Changwon 641-315, South Korea
b
Received 24 April 1998
Abstract In this paper, a computer aided process design technique, based on a forging simulator and commercial CAD software, is presented together with its related design system for the cold-former forging of ball joints. The forging sequence design and its detail designs are generated through user±computer interaction using templates, design databases, knowledge-based rules and some basic laws. The forging simulation technique is used to verify the process design. The detail designs, including die set drawings and die manufacturing information, are generated automatically. It has been shown that engineering and design productivity is much improved by the presented approach from the practical standpoint of process design engineers. # 1999 Elsevier Science S.A. All rights reserved. Keywords: Cold-former forging; Process sequence design; Automatic computer simulation; Detail process design
1. Introduction For the mass production of small- or medium-sized mechanical parts, cold-former machines, sometimes called multi-station automatic cold-forging machines, are being used in a wide range of mechanical parts manufacturing industries. In cold-former forging, initial materials, cut from simple bars, are formed progressively to ®nal shapes by automatic and synchronized operations, including shearing, upsetting, forward and/or backward extrusion, piercing and the like. Usually, the number of forging sequences in coldformer forging is larger than that in conventional forging because of the mass-production purpose of this machine. Simultaneous operation and production automation are also important characteristics of cold-former forging processes. It is very dif®cult to carry out the process sequence design in cold-former forging because many aspects should be considered, including production economy as well as the proper distribution of plastic deformation, machine limitation, production automation and the like. In addition, the *Corresponding author. Tel.: +82-591-751-5316; fax: +82-591-7515316 E-mail address: [email protected] (M.S. Joun)
reliability of process design in automatic multi- station forging is of great importance since a design failure or an intermittent stop of the manufacturing line can cause a decisive increase in manufacturing and design cost and loss of opportunities. In order to reduce possible failures in process sequence design, several works [1±16] have been reported for developing design assisting environments such as expert systems and CAD/CAM techniques. However, in addition to the intrinsic nature of forging sequence design, which is very creative and empirical, complexity in plastic deformation and high correlation between design parameters in different stages have made it dif®cult to realize process design automation in cold-former forging. The automatic design system is usually composed of a process design module and a simulation or veri®cation module. Most conventional research has focused on process sequence generation in the former. Ehrismann and Reissner [15] emphasized the importance of the integration of a simulation system with a design or manufacturing assisting system in order to promote mutual understanding between simulation experts and design experts and reduce the engineering time and cost. A practical viewpoint of process designers that an automatic design system has to possess can be found in the work of Kim and Altan [6] . According to
0924-0136/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 4 - 0 1 3 6 ( 9 9 ) 0 0 2 8 4 - 8
156
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
their work, ®rstly a process design module should minimize routine work, including sequence design generation, satisfying volume consistency, modifying designs, checking basic design rules, making detailed drawings and generating die manufacturing information. However, they underestimated the importance of the simulation module, since computers in those days were not powerful enough for the forging simulator to play a main role in the design information and knowledge system. Based on the above considerations, a fully integrated design system is developed in this study, in which a forging simulator plays the core role in assisting forging sequence design. Cold-former forging of ball studs used as ball joint components is selected as an application example, since there are many different sizes of ball studs manufactured in a company and the related technical materials can be obtained. 2. Overall procedure of the developed design system Several researchers [1±16] have studied the process design automation of cold-former forging. Most research has been focused on automatic process sequence generation in the process design module based on knowledge-based expert systems or AI techniques. However, there are limited applications for the whole sequence design of a new process, since the sequence design itself is very creative and human experts have only narrow information, Of course, conventional research works can be used for the sequence design of the special process if the design databases have many similar processes and the related design information can be accessed easily and modi®ed with accompanying automatic detailed veri®cation. It should be noted that the most important activity in an automatic design system or in a design assisting system lies in the veri®cation of the design candidate, and such veri®cation capability should be the core of the design system from the standpoint of the process designer. Constraints on process parameters from either machine speci®cation or rule-based design speci®cation can be checked with relative ease. The most dif®cult problem arises in metal forming mechanics. The plastic deformation in cold-former forging is very delicate and dimensional tolerance is inherently very tight. Therefore, conventional approximate analysis approaches cannot avoid many limitations and obstacles. Recent enhancement in computer hardware technology makes it possible to use a ®nite-element-based forging simulator as the core veri®cation tool. It is now possible to obtain the whole solution of a multi-stage forging process within 1±3 h by a fully automatic forging simulator [17] with a recently announced PC, and the associated computational time is becoming progressively smaller. The simulator can be used to investigate the detailed effect of a process parameter on the process conditions and the product quality if it is integrated with a design assisting system. In this case, a forging simulation technique is the major part of the design
assisting system. Even though some approaches [9±16] employed a ®nite-element-based forging simulator as a veri®cation tool, the functions were not fully integrated and the computer simulation required quite a large amount of time due to the user interface as well as to the computational time. As a result, the simulator could not be an active design tool in the related systems. In this study, a process design assisting system, called DASFOR, has been developed using a PC-based forging simulator, AFDEX/2D [17], and a PC-based CAD software, AutoCAD. The system is composed of the process design module and the design veri®cation module. It assists the whole work in process design, including the generation of design and manufacturing information, process sequence generation, engineering calculation, detail design veri®cation, detail design drawing extraction and process design veri®cation. Fig. 1 shows the conceptual ¯ow chart of DASFOR. The basic approach is introduced in the following
Fig. 1. Conceptual flow chart of the present approach.
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
two chapters through an application example in the coldformer forging of a ball stud. This paper does not include the determination of the number of forging stages. 3. Process design module The process design module helps the process design engineer to carry out interactively the whole work in process design. The major capabilities of the process design module include the interactive generation of the process sequence, the detail design of the process, the generation of simulation
157
information, the modi®cation of designs, the generation of detail drawings and database management. Fig. 2 shows an example of the process sequence generated by DASFOR for the cold-former forging of a ball stud. The process sequence design is quite creative and is dependent deeply on the intuition and experience of process design engineers. It may be very helpful for process design engineers if design experience has been accumulated systematically onto knowledge databases and they can be easily accessed. In this study, a cold-former forging of a ball stud, of which suf®cient design information can be obtained, was selected as an application example. First of all, 30 unit processes used in
Fig. 2. A process sequence design.
Fig. 3. Templates for the process sequence design in ball-stud forging.
158
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
Fig. 5. Combinations of possible process sequence designs for ball-stud forging.
Fig. 4. Parameterized unit process template.
the related industry or found from the literature were parameterized and the database was constructed. Fig. 3 shows some of the unit processes, called unit process templates, which have been used with frequency in the cold-former forging of ball studs. Each template is represented by a few design parameters, as seen in Fig. 4. The user can construct a process sequence either by selecting unit processes from their templates or by restoring a successful process sequence design from the database. Basically, the process sequence design starts from the desired product and then proceeds to the initial workpiece. Fig. 5 show combinations of possible process designs that
has been generated from experience and material found in the literature and stored in the knowledge database, with their related design rules after design veri®cation for a typical example. Fig. 2 shows an example of a process design made with the help of the knowledge database. When the product geometry is given, some design parameters in the preceding stages are determined either from the requirement on safe mounting and loading and clearance or by some experience-based rules [18]. The other design parameters can be calculated by general design rules [1± 16,18,19] including volume constancy, formability limitations and process designers' experience. Separation of each unit process into two pieces should be made prior to carrying out detail design of the lower and upper dies or punches.With the separation, one can obtain a basic design information ®le as shown in Fig. 6, which is used to generate process geometries for both computer
Fig. 6. Basic design information.
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
Fig. 7. Assembly drawing of the process design.
Fig. 8. Detail drawing of the die set for the first stage.
159
160
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
Fig. 9. Detail drawing of the die set for the fourth stage.
Fig. 10. Detail drawing of the punch set for the fourth stage.
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
simulation and detail design. It is to be noted that it takes much time to make mechanical drawings of the process design because tens of mechanical drawings are necessary for one process design. Automatic generation of drawings is thus one of major capabilities that a process design assisting system should possess. In general, standardization of forging dies and automatic generation of their drawings are very dif®cult to be achieved. It is fortunate that many parts for die sets in cold-former forging were already standardized. Drawings of die sets can thus be generated in an automatic or interactive manner. The main factors affecting this drawing work are the machine speci®cation, the gap between the upper die or punch and the lower die and clearance or tolerance as well as the process design itself. Some detail drawings for the example are given in Figs. 7±10. If the process design is accomplished, design veri®cation should be made by the veri®cation module. Note that it is quite time-consuming to prepare the whole input data for computer simulation of the process design candidates. An automatic interface program in the process design module that generates the simulation information with minimum user interface was developed.
161
Fig. 11. Process geometries extracted from the process sequence design.
4. Design verification module Forging simulators are now being used in many industries. Several researchers have attempted to use them for veri®cation of forging process designs. However, they failed to imbed the simulation capability into the process design module because the forging simulators used lacked in simulation automation. This deteriorated the applicability of both the process design module and the design veri®cation module. In this study, automatic and intelligent forging simulation techniques [17] were developed for the purpose of process design in cold-former forging. The forging simulator can be run automatically by the input data obtained by the interface program without any user interface during simulating a whole sequence of multi-stage forging processes. In the interface program, the geometry information of material and dies is extracted from the process design database, whilst process conditions, including frictional conditions, are entered in an interactive manner. Fig. 11 shows an example of the geometry information extracted automatically from the process design database. With this capability, much time taken in preparing the input data of the simulators can be saved. Thus, the applicability of the simulators to process design can be much enhanced and many of the ambiguous experience-based design rules can be replaced by the simulation capability with the engineer's scienti®c evaluation of the simulated results including stress, strain, strain-rate, die pressure and die stress, forming load, damage, hardness, die wear and the like. Several simulation results for the example are given in Figs. 12±14.
Fig. 12. Simulation results of metal flow.
Fig. 13. Simulation results of forming load.
5. Conclusions In this paper, a computer-aided process design technique, utilizing a forging-simulator and commercial CAD software, was presented together with its related design system
162
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163
Fig. 14. Simulation results of damage.
for the cold-former forging of ball joints. The forging sequence design was assisted by knowledge-based rules and some basic laws. The detail designs for a design candidate of the selected forging sequence were carried out in an automatic or interactive manner by considering design constraints and experience-based laws. From the detail designs, all of the forging simulation information was extracted automatically and the whole forging process was simulated without any user interface. Successful detail designs, including die set drawings and die manufacturing information were obtained by user±computer interaction. It has been shown that the engineering and design productivity are much improved by the present approach from the practical standpoint of process design engineers. References [1] P. Bariani, W.A. Knight, Computer aided cold forging design: determination of machine setting conditions, Ann. CIRP 34(1) (1985) 245±248. [2] P. Bariani, W.A. Knight, Computer-aided cold forging process design: a knowledge-based system approach to forming sequence generation, Ann. CIRP 37(1) (1988) 243±246. [3] P. Bariani, E. Benuzzi, W.A. Knight, Computer aided design of multistage cold forging process: load peaks and strain distribution evaluation, Ann. CIRP 36(1) (1987) 145±148.
[4] M.T. Gokler, T.A. Dean, W.A. Knight, Computer aided die design for upset forging machines, Proceedings of the 11th NAMRC, 1983, pp. 217±223. [5] W. Makosch, K. Lange, Application-orientated CAD system for multi-stage tooling design for cold forging, Proceedings of the 16th NAMRC, 1988, pp. 63±70. [6] H. Kim, T. Altan, Computer-aided part and processing-sequence design in cold forging, J. Mater. Process. Technol. 33 (1992) 57±74. [7] K. Sevenler, P.S. Raghupathi, T. Altan, Forming-sequence design for multistage cold forming, J. Mech. Work. Technol. 14 (1987) 121± 135. [8] T.P. Davison, W.A. Knight, Computer aided process design for cold forging operation, Adv. Technol. Plast. I (1984) 551±556. [9] A.A. Badawy, P.S. Raghupathi, D.J. Kuhlmann, T. Altan, Computeraided design of multistage forging operations for round parts, J. Mech. Work. Technol. 11 (1985) 259±274. [10] K. Osakada, T. Kado, G.B. Yang, Application of AI-technique to process planning of cold-forging, Ann. CIRP 37(1) (1998) 239±242. [11] G.B. Yang, K. Osakada, An expert system for process planning of cold forging, Adv. Tech. Plast. 1 (1990) 109±115. [12] D. Glynn, G. Lyons, J. Monaghan, Forging sequence design using an expert system, J. Mater. Process. Technol. 55 (1995) 95±102. [13] P. Bariani, G. Berti, L. D'Angelo, M. Marengo, A. Rossi, An integerated CAD/CAE system for cold-forging process design, Adv. Technol. Blast. 1 (1990) 7±12. [14] H.S. Kim, Y.T. Im, Expert system for multi stage cold-forging process design with a re-designing algorithm, J. Mater. Process. Technol. 54 (1995) 271±285. [15] R. Ehrismann, J. Reissner, The integration of simulation techniques in expert systems, Adv. Tech. Plast. 1 (1990) 197±202.
C.S. Im et al. / Journal of Materials Processing Technology 95 (1999) 155±163 [16] Q.C. Hsu, R.S. Lee, Cold forging process design based on the induction of analytical knowledge, J. Mater. Process. Technol. 69 (1997) 264±272. [17] Users' manual of AFDEX/2D 2.1, Metal Forming CAE Laboratory in Gyeongsang National University, 1998.
163
[18] M.S. Joun, C.S. Im, M.C. Lee, Development of automatic process design program for cold-former forging of ball studs, Technical Report, Research Center for Aircraft Parts Technology, Gyeongsang National University, 1996±1997. [19] Metal Handbook, Forming and Forging, Am. Soc. Metals (1988).