- Email: [email protected]
A product modeling system for constructing intelligent CAD and CAM systems
Robottcs & Computer-Integrated Manu[acturmg, Vol 4, No 3/4, pp 483-489, 1988
0736-5845/8853 00 + 0 00 © 1988 Pergamon Press plc
Printed m Great Britain
• Paper
A PRODUCT MODELING SYSTEM FOR CONSTRUCTING INTELLIGENT CAD AND CAM SYSTEMS H. SUZUKI,* M. I N U I , t F. K I M U R A t and T. SATA~ *Department of Graphics, College of Arts and Science, The University of Tokyo, 3-8-1, Komaba, Meguro-ku, Tokyo 153, Japan, tDepartment of Precision Machinery Engineering, Faculty of Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113, Japan and ~tRIKEN,The Institute of Physical and Chemical Research 2-1, Hirosawa, Wako-shl, Saitama 351-01, Japan It is essential for the achievement of intelligent manufacturing systems to properly encode manufacturing knowledge in computer systems. We propose a product modeling system that is a framework for representing and utilizing models of both design objects and design tasks. The key concept in the framework is that of constraint. Several prototypical CAD/CAM applications constructed on the framework are shown.
duct models, and describes the functional or physical properties of the object being designed. The product models are just schematic design proposals at the conceptual design stage, then they are gradually developed into detailed descriptions which are used for generating production plans and commands. The design process knowledge is concerned with design tasks themselves. It is knowledge about how to perform design tasks, how to solve design problems and so on. In order to realize the automation of design, we have to formalize the knowledge and implement it in computers as a design task model that simulates the designers' tasks. In other words, some design task model is partially involved in a system that takes the place of human designers, or that supports designers. The product model and the design tasks model together form an expert CAD system as shown in Fig. 1. Each design task model is constructed for each design problem and cooperatively proceeds on the design process with human designers. Design task models are sometimes just a interface between the designers and product models, and sometimes they do the whole design task for the designer. The design task model solves a design problem and generates a product model as a solution. This generated product model is utilized by subsequent design task
1. INTRODUCTION In recent years, the tendency has been observed to expand AI optimistically in the area of research and development of CAD and CAM systems. Actually, AI techniques have been proved useful in many manufacturing fields, such as robot applications, production scheduling, diagnosis, unmanned operation system, VLSI design, process planning and so on. Simple applications of AI techniques, however, cannot achieve the automation of a wider range of manufacturing activities than mentioned above, or realize intelligent manufacturing systems. There is no doubt that extensive research work, especially directed toward the problems on intelligent manufacturing systems, is demanded. Among these problems, it is essential to properly acquire a wide variety of manufacturing knowledge in computers. In this paper we propose a framework for representing manufacturing knowledge and show several CAD/CAM programs based on the framework. 2. MODELS FOR DESIGN OBJECTS AND TASKS
Manufacturing knowledge can be roughly classified into two major classes, design oblect knowledge and design process knowledge. The former class is otherwise labeled as design object models or pro-
Acknowledgement--This research work is partly supported by Product Modehng System's Development Pro-
ject of Japan Society of Precision Engineering. 483
484
Robotics and Computer-Integrated Manufacturing • Volume 4, Number 3/4, 1988 Designmg process .
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.
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.
Engineer .
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I
User interface
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.
Design and monufacturmg subsystems Product design
Process planning
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D~menslons Tolerances
CAD/CAM sytems f o r a spemflc purpose or expert CAD systems
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Form Features
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I // Kinematics
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Product modet
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Fig 1. Design task models and product models.
Ftg. 2 Engineering models in a product modeling system.
models to generate other product models. Production information is also generated by a design task model for manufacturing preparation. The product model performs physical simulation to determine the product's behavior which is used by the design task model to solve design problems. 3. MODELING FRAMEWORK Besides developing product models and design task models to solve particular problems, ~ve require appropriate modeling frameworks both for representing those kinds of knowledge in computers and for utilizing the knowledge. Several modeling frameworks have been proposed on a research basis, but most of them lack generality and formality as well. In order to develop a general framework, it is essential to have key concepts that would guide us to rationalize the problem domain. One such concept is that of constraints. In the following subsections, we introduce product modeling frameworks on the basis of the constraint concept.
3.1. Design object modeling on geometric constraints In design practice, designers present their ideas about designing objects by using concepts that are common to most designers. These concepts cover geometric shapes, shape features, dimensions, tolerances, assemblies, surface finish, material properties and so on. Conventional machine drawings, which designers use for representing their ideas, can be seen as a syntax to represent those concepts. It is important for a product modeling system to accept those concepts so that it can construct product models by capturing the designer's ideas or
specifications of the product. Hence, it can be assumed that the product model is comprised of models of those basic engineering concepts. We call these models engineering models (Fig. 2), and think that it is basically important to realize the engineering models. 2 The concept of constraints mentioned above is useful for treating the engineering models. It can be seen that those engineering models are naturally associated with geometry of the product. Furthermore, the main portion of these engineering models is considered to be constraints on the geometry of the products, that is, geometric constraints among primitive elements of the product geometry, such as surfaces. The most typical example is a dimension that defines a nominal shape of a product. Tolerances, shape features and assemblies are also geometric constaints. In order to represent the geometric constraints in computers, the shape of the product should be represented as geometric models. Then those geometric constraints can be represented as relationships among elements of geometric models. The problem of representing those relationships and elements (entities) is not specific to the product model. It is common to all data modeling systems including database systems, programming language, knowledge representation and so on. We evaluated several data models and found that most of those data models, by nature, stand on a directed graph structure and they are unsatisfactory so as to meet requirements from product modeling for several reasons. 6 We are developing a new modeling framework that is specially designed for representing those
Product modelling system for CAD/CAM systems
geometric constraints in a formal way, and that takes a multi-paradigm approach of first order predicate logic and an object oriented language. In this framework geometric entities are instances or objects of a certain class, in which object's properties are handled by methods. On the other hand, relationships among objects are in the form of ground literals of first order logic. Entities and relationships form a logical structure in the framework; this logical structure is manipulated by a set of formal operations, including creation/replication/deletion of entities/relationships. The framework comprises a Prolog-like system and an object oriented language, so it has a logical programming capability that is useful for building design task models discussed in the following subsection. Furthermore, the framework incorporates the solid modeling system GEOMAP-III (Fig. 3) for dealing with geometric properties, geometric calculations and graphical modeling interfaces.
Geometric reasonmg programs
GEOMAP Tl-r Solid modelling system
•
H.
485
SuzuKi et al.
duct specify the most functional constraints for the design solution. The constraints are modified to more attributive ones and finally converted to the detailed product description. In this process the designer's concern is to solve constraints, to refine constraints, to propagate constraints and so on. The design process thus can be seen as a process to manipulate design constraints (Fig. 4). This view of the design process in terms of design constraints gives a conceptual basis for a design task modeling framework, but it is not detailed or formal enough to be realized as a computer system. Though a proper modeling framework for design task models has not been implemented yet, we make several prototype systems as shown in the applications in the next section. These design task models employed in applications have their own specific reasoning mechanisms or procedures to manipulate the design constraints. Those mechanisms are realized based on the logical inference functions of the product modeling framework introduced in the previous subsection. Through these prototypes, we expect to reach a more formal and integrated framework for describing design task models.
Relationship Distance
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Fig 3. Product modeling framework.
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3.2. Design task modeling on constraint manipula-
tion Since there is no complete theory for the design process of human designers, it cannot be expected that there is a general framework for design task models, or knowledge of the possibility and limitation of functionality of design task models in general. However, design task models in some limited domain of design tasks can be tractable, for example, the domain of routine design and variational design where products are designed by using the similar products designed previously, and following some relatively fixed designing procedures. Those design activities are less creative but are substantial in industry. The concept of constraint is also useful for thinking about design task models. Generally in the design process, the initial requirements to the pro-
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Fig. 4. Design process m terms of constraints manipulation
486
Robotics and Computer-Integrated Manufacturing • Volume 4, Number 3/4, 1988
4. APPLICATIONS This framework is used for several C A D / C A M applications. All of the following systems are implemented in Lisp language and runs on Symbolics Lisp Machine. •
Parametric design system
Dimensions are represented as geometric constraints among face elements of solid models. When dimensional values are changed, a design task model preforms a geometric reasoning process to modify the solid models (Fig. 5). In this process, geometric constraints are propagated from one face to another to modify the shape.
|.-,-.,,.-,m.-==.-,,,.o
Pl ,I • -274.778. -,LIB?, - Z Z n ° -3SS° 0
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PS 4, -430. I;~$. -.Z2~,1. -~2,13,-47g.@ NO4
Fig 6. Robot fine motion generation system.
@ t"
Fig. 5. Parametric demgn system.
Robot fine motion generation system Assembly information is represented as constraints among form features, and these form features are treated as geometric constraints among face elements. Robot fine motion generation rules are applied to those constraints and the system determines a sequence of operations, robot's motion for each operation, parts grasping position, and so on (Fig. 6). Geometrical interference is also checked using solid models of the assembly and the robot.
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DisassemblabiIity test program
This program tests the disassemblability of an assembly and generates a plan to disassemble it, in the same manner as the robot fine motion generation system. Technological information about the fitness and surface finish are taken into consideration for determining disassemblability. Figure 7 shows a disassembling sequence of a disk spindle unit.
Fig 7 Disassemblablhty test program.
• Tolerance evaluation program for N C 3 In machine drawings, dimensional values are usually given dimensional tolerances. When production engineers calculate the NC cutter path to cut the contour out, they first replace the nominal dimensional value with an appropriate dimensional value
487
Product modeUmg system for CAD/CAM systems • H. SUZUKi et al.
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Fig. 8. Tolerance evaluation program.
by evaluating the tolerances. This program performs this task by employing the generation and test method. In Fig. 8, part (a) shows a toleranced contour and (b) shows the result. An EXAPT part program is produced from (b), and (c) shows a simulated cutter motion. •
Processplanning systems for machining operation
It is a rule-based process planning system where the relationships among machining operations and form features are described using production rules.
Those rules are applied to the product model, and make machining operation plans. During the plan generation, machining simulation using the product model is performed; its result is reflected to the plan generation. Using product models, it is possible to include various kinds of precise machining constraints in the production rules. Figure 9 shows an example machine part and its process plan. •
Processplanning systems for bending operations7 This system takes the same kind of approach as
Phase I Workplace: Y- Direction Machine: HORIZONTAL,MACHINING_CENTER
Op. 1.1: Op. 1.2 Op. 1.3 Op. 1.4 Op. 1.5 Op. 1.6 Op. 1.? OIx 1.8 Op. 1.9:
Ruting Face: OFO ROUGH FACE.MILLING=> (01~ OF4) OPEN_FACE ROUCH FACE_},/IIJJNG => (01;'3) OPEN_FACE FIN FACE.MILLING => (OF'-.'OF4) OPEN_FACE FIN FACE..}41LLING => (OF3) OPEN_FACE CENTEI~ORILIJNG => (HLI6 HLI?) HOLE ROUGH Di~IJJNG --> (HLI8 HLI.9) HOLE FIN END.J,/ILLING => (HLI8 HLI?) HOLE ROUGH END_},ilLLING => (GRVO) GROOVE FIN END_}JJLLING => {GRVO) GROOVE
Fig. 9. Process planning system for machining operation
488
RoboUcs and Computer-Integrated Manufacturing • Volume 4, Number 3/4, 1988
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Fig. 10. Process planning system for bending operation.
Fig. 11. Sheet metal part design system.
the previous system. The system receives a product model of a sheet metal part and generates bending sequence, tools, positions and positioning methods. The system uses bending planning rules in production system and takes into consideration ease of bending, tolerances, tool interferences and so on. Figure 10 shows a generated bending sequence.
5. CONCLUSION A concept of geometric constraints is introduced, which allows us to treat information about design objects. This concept is implemented in a multiparadigm modeling framework, combining first order predicate logic and an object oriented language. A geometric modeling system is also incorporated in the framework. Design tasks are thought of as processes which manipulate constraints. Several prototypical design task models have been built for C A D / C A M applications.
• Sheet metal part design system s In general, a shape of a machine part is determined in several ways. Some portion of the shape is determined to realize the product's function, in other words, this portion must be that shape. On the other hand some portion is determined as appropriate, in other words, this must not necessarily be that shape. This system solves a problem of the latter kind. In Fig. 11, the system is given contour (a) and automatically adds some portions to contour (a) and generates contour (b). The contour (b) is required to include all specified holes, to have no interference with other parts, and to keep some spaces around the holes. The system produces the initial contour satisfying these constraints and then refines it by applying refinement rules to the product model. In addition to the above applications, some simple experimental systems are also developed to examine how routine design tasks can be formalized as constraint manipulation processes using AI techniques. 5
REFERENCES 1. Suzuki, H., Klmura, F., Sata, T.: Treatment of Dimensions on Product Modelling Concept, Design and Synthests. Amsterdam, North-Holland. 1985, pp. 491-496. 2. Sata, T., Klmura, F., Suzuki, H., Fujita, T.: Designing machine assembly structure using geometric constramts m product modelling.Ann. CIRP 34: 169-172, 1985. 3. Kimura, F., Suzuki, H., Wlngard, L.: A uniform approach to &mensioning and toleranclng in product modelhng. Computer Applications in Production and Engineering, CAPE'86, Amsterdam, North-Holland. 1987, pp. 165-178. 4. Sata, T., Kimura, F., Hlraoka, H., Suzuki, H., Fulita, T.: Comprehenswe modelling of a machine assembly for off-hne programming of industrial robots. Off-Lme Programming of Industrial Robots, Amsterdam, North-Holland. 1987, pp. 19-33.
Product modelhng system for CAD/CAM systems • H. SUZUKIet al 5. Kimura, F., Suzuki, H., Sata, T.: Variational product design by constraint propagation and satisfaction in product modelling. Ann. CIRP, 35: 75-78, 1986. 6. Suzuki, H.: A product modelhng framework for integrating manufactunng information. Doctoral dissertation, The University of Tokyo, 1986 (in Japanese). 7. Inui, M., Suzuki, H., Kimura, F., Sata, T.: Generation and verification of process planning using dedicated
489
models of products m computers. Proceedings of A S M E W A M 1986, Symposium on Knowledge-Based Expert Systems for Manufacturing, December, 1986. 8. Kimura, F., Suzuki, H., Ando, H. Sato, T., Kinosada, A.: Variation geometry based on logical constraints and its applications to product modelling. Ann. CIRP (in press).
0736-5845/8853 00 + 0 00 © 1988 Pergamon Press plc
Printed m Great Britain
• Paper
A PRODUCT MODELING SYSTEM FOR CONSTRUCTING INTELLIGENT CAD AND CAM SYSTEMS H. SUZUKI,* M. I N U I , t F. K I M U R A t and T. SATA~ *Department of Graphics, College of Arts and Science, The University of Tokyo, 3-8-1, Komaba, Meguro-ku, Tokyo 153, Japan, tDepartment of Precision Machinery Engineering, Faculty of Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113, Japan and ~tRIKEN,The Institute of Physical and Chemical Research 2-1, Hirosawa, Wako-shl, Saitama 351-01, Japan It is essential for the achievement of intelligent manufacturing systems to properly encode manufacturing knowledge in computer systems. We propose a product modeling system that is a framework for representing and utilizing models of both design objects and design tasks. The key concept in the framework is that of constraint. Several prototypical CAD/CAM applications constructed on the framework are shown.
duct models, and describes the functional or physical properties of the object being designed. The product models are just schematic design proposals at the conceptual design stage, then they are gradually developed into detailed descriptions which are used for generating production plans and commands. The design process knowledge is concerned with design tasks themselves. It is knowledge about how to perform design tasks, how to solve design problems and so on. In order to realize the automation of design, we have to formalize the knowledge and implement it in computers as a design task model that simulates the designers' tasks. In other words, some design task model is partially involved in a system that takes the place of human designers, or that supports designers. The product model and the design tasks model together form an expert CAD system as shown in Fig. 1. Each design task model is constructed for each design problem and cooperatively proceeds on the design process with human designers. Design task models are sometimes just a interface between the designers and product models, and sometimes they do the whole design task for the designer. The design task model solves a design problem and generates a product model as a solution. This generated product model is utilized by subsequent design task
1. INTRODUCTION In recent years, the tendency has been observed to expand AI optimistically in the area of research and development of CAD and CAM systems. Actually, AI techniques have been proved useful in many manufacturing fields, such as robot applications, production scheduling, diagnosis, unmanned operation system, VLSI design, process planning and so on. Simple applications of AI techniques, however, cannot achieve the automation of a wider range of manufacturing activities than mentioned above, or realize intelligent manufacturing systems. There is no doubt that extensive research work, especially directed toward the problems on intelligent manufacturing systems, is demanded. Among these problems, it is essential to properly acquire a wide variety of manufacturing knowledge in computers. In this paper we propose a framework for representing manufacturing knowledge and show several CAD/CAM programs based on the framework. 2. MODELS FOR DESIGN OBJECTS AND TASKS
Manufacturing knowledge can be roughly classified into two major classes, design oblect knowledge and design process knowledge. The former class is otherwise labeled as design object models or pro-
Acknowledgement--This research work is partly supported by Product Modehng System's Development Pro-
ject of Japan Society of Precision Engineering. 483
484
Robotics and Computer-Integrated Manufacturing • Volume 4, Number 3/4, 1988 Designmg process .
.
.
.
.
.
Engineer .
.
.
I
User interface
I
I
.
Design and monufacturmg subsystems Product design
Process planning
\\
D~menslons Tolerances
CAD/CAM sytems f o r a spemflc purpose or expert CAD systems
\I
Assembty
Machining data g ene ratJ on
Form Features
ptanm ng
I // Kinematics
,
Product modet
AssembLy
/
- - Constraint - - AttrJ bute Geometric model
Engineering model
Fig 1. Design task models and product models.
Ftg. 2 Engineering models in a product modeling system.
models to generate other product models. Production information is also generated by a design task model for manufacturing preparation. The product model performs physical simulation to determine the product's behavior which is used by the design task model to solve design problems. 3. MODELING FRAMEWORK Besides developing product models and design task models to solve particular problems, ~ve require appropriate modeling frameworks both for representing those kinds of knowledge in computers and for utilizing the knowledge. Several modeling frameworks have been proposed on a research basis, but most of them lack generality and formality as well. In order to develop a general framework, it is essential to have key concepts that would guide us to rationalize the problem domain. One such concept is that of constraints. In the following subsections, we introduce product modeling frameworks on the basis of the constraint concept.
3.1. Design object modeling on geometric constraints In design practice, designers present their ideas about designing objects by using concepts that are common to most designers. These concepts cover geometric shapes, shape features, dimensions, tolerances, assemblies, surface finish, material properties and so on. Conventional machine drawings, which designers use for representing their ideas, can be seen as a syntax to represent those concepts. It is important for a product modeling system to accept those concepts so that it can construct product models by capturing the designer's ideas or
specifications of the product. Hence, it can be assumed that the product model is comprised of models of those basic engineering concepts. We call these models engineering models (Fig. 2), and think that it is basically important to realize the engineering models. 2 The concept of constraints mentioned above is useful for treating the engineering models. It can be seen that those engineering models are naturally associated with geometry of the product. Furthermore, the main portion of these engineering models is considered to be constraints on the geometry of the products, that is, geometric constraints among primitive elements of the product geometry, such as surfaces. The most typical example is a dimension that defines a nominal shape of a product. Tolerances, shape features and assemblies are also geometric constaints. In order to represent the geometric constraints in computers, the shape of the product should be represented as geometric models. Then those geometric constraints can be represented as relationships among elements of geometric models. The problem of representing those relationships and elements (entities) is not specific to the product model. It is common to all data modeling systems including database systems, programming language, knowledge representation and so on. We evaluated several data models and found that most of those data models, by nature, stand on a directed graph structure and they are unsatisfactory so as to meet requirements from product modeling for several reasons. 6 We are developing a new modeling framework that is specially designed for representing those
Product modelling system for CAD/CAM systems
geometric constraints in a formal way, and that takes a multi-paradigm approach of first order predicate logic and an object oriented language. In this framework geometric entities are instances or objects of a certain class, in which object's properties are handled by methods. On the other hand, relationships among objects are in the form of ground literals of first order logic. Entities and relationships form a logical structure in the framework; this logical structure is manipulated by a set of formal operations, including creation/replication/deletion of entities/relationships. The framework comprises a Prolog-like system and an object oriented language, so it has a logical programming capability that is useful for building design task models discussed in the following subsection. Furthermore, the framework incorporates the solid modeling system GEOMAP-III (Fig. 3) for dealing with geometric properties, geometric calculations and graphical modeling interfaces.
Geometric reasonmg programs
GEOMAP Tl-r Solid modelling system
•
H.
485
SuzuKi et al.
duct specify the most functional constraints for the design solution. The constraints are modified to more attributive ones and finally converted to the detailed product description. In this process the designer's concern is to solve constraints, to refine constraints, to propagate constraints and so on. The design process thus can be seen as a process to manipulate design constraints (Fig. 4). This view of the design process in terms of design constraints gives a conceptual basis for a design task modeling framework, but it is not detailed or formal enough to be realized as a computer system. Though a proper modeling framework for design task models has not been implemented yet, we make several prototype systems as shown in the applications in the next section. These design task models employed in applications have their own specific reasoning mechanisms or procedures to manipulate the design constraints. Those mechanisms are realized based on the logical inference functions of the product modeling framework introduced in the previous subsection. Through these prototypes, we expect to reach a more formal and integrated framework for describing design task models.
Relationship Distance
( A ~
/...,°
Attribute nominal =10
,
frn°:slthnel~:;~OUS ]
Geometrical calculotlons
\
Display funcOons
Fig 3. Product modeling framework.
] I " parts ..... llst
,I :Z:',::: <
J .
.
.
.
~
--
-
I
" o:"p<,.ttona~
5-AI~ p//
instruction ~
[
I
._o...
I
3.2. Design task modeling on constraint manipula-
tion Since there is no complete theory for the design process of human designers, it cannot be expected that there is a general framework for design task models, or knowledge of the possibility and limitation of functionality of design task models in general. However, design task models in some limited domain of design tasks can be tractable, for example, the domain of routine design and variational design where products are designed by using the similar products designed previously, and following some relatively fixed designing procedures. Those design activities are less creative but are substantial in industry. The concept of constraint is also useful for thinking about design task models. Generally in the design process, the initial requirements to the pro-
.o._o V _ _
__
*
tolerances
kinematics * geometric shaps *
°=.=...j
f D e s l g n Constrs£nts~
BASIC ENGINEERING MODEL
I
I DESIGN T A S K M O D E L S
I
I PRODUCTMODELS
Fig. 4. Design process m terms of constraints manipulation
486
Robotics and Computer-Integrated Manufacturing • Volume 4, Number 3/4, 1988
4. APPLICATIONS This framework is used for several C A D / C A M applications. All of the following systems are implemented in Lisp language and runs on Symbolics Lisp Machine. •
Parametric design system
Dimensions are represented as geometric constraints among face elements of solid models. When dimensional values are changed, a design task model preforms a geometric reasoning process to modify the solid models (Fig. 5). In this process, geometric constraints are propagated from one face to another to modify the shape.
|.-,-.,,.-,m.-==.-,,,.o
Pl ,I • -274.778. -,LIB?, - Z Z n ° -3SS° 0
MOJ.
PI 3 . ~ 3 4 . S U . - ~ 3 ~ . - ~ 3 4 . . S S 4 . @ ~3
PS 4, -430. I;~$. -.Z2~,1. -~2,13,-47g.@ NO4
Fig 6. Robot fine motion generation system.
@ t"
Fig. 5. Parametric demgn system.
Robot fine motion generation system Assembly information is represented as constraints among form features, and these form features are treated as geometric constraints among face elements. Robot fine motion generation rules are applied to those constraints and the system determines a sequence of operations, robot's motion for each operation, parts grasping position, and so on (Fig. 6). Geometrical interference is also checked using solid models of the assembly and the robot.
(a)
(b)
Q
•
•
0
©
4,
(d)
~
(c)
DisassemblabiIity test program
This program tests the disassemblability of an assembly and generates a plan to disassemble it, in the same manner as the robot fine motion generation system. Technological information about the fitness and surface finish are taken into consideration for determining disassemblability. Figure 7 shows a disassembling sequence of a disk spindle unit.
Fig 7 Disassemblablhty test program.
• Tolerance evaluation program for N C 3 In machine drawings, dimensional values are usually given dimensional tolerances. When production engineers calculate the NC cutter path to cut the contour out, they first replace the nominal dimensional value with an appropriate dimensional value
487
Product modeUmg system for CAD/CAM systems • H. SUZUKi et al.
k
I
,
I
!
/ _,/
~0
,I
,J
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-
~
- -
Fig. 8. Tolerance evaluation program.
by evaluating the tolerances. This program performs this task by employing the generation and test method. In Fig. 8, part (a) shows a toleranced contour and (b) shows the result. An EXAPT part program is produced from (b), and (c) shows a simulated cutter motion. •
Processplanning systems for machining operation
It is a rule-based process planning system where the relationships among machining operations and form features are described using production rules.
Those rules are applied to the product model, and make machining operation plans. During the plan generation, machining simulation using the product model is performed; its result is reflected to the plan generation. Using product models, it is possible to include various kinds of precise machining constraints in the production rules. Figure 9 shows an example machine part and its process plan. •
Processplanning systems for bending operations7 This system takes the same kind of approach as
Phase I Workplace: Y- Direction Machine: HORIZONTAL,MACHINING_CENTER
Op. 1.1: Op. 1.2 Op. 1.3 Op. 1.4 Op. 1.5 Op. 1.6 Op. 1.? OIx 1.8 Op. 1.9:
Ruting Face: OFO ROUGH FACE.MILLING=> (01~ OF4) OPEN_FACE ROUCH FACE_},/IIJJNG => (01;'3) OPEN_FACE FIN FACE.MILLING => (OF'-.'OF4) OPEN_FACE FIN FACE..}41LLING => (OF3) OPEN_FACE CENTEI~ORILIJNG => (HLI6 HLI?) HOLE ROUGH Di~IJJNG --> (HLI8 HLI.9) HOLE FIN END.J,/ILLING => (HLI8 HLI?) HOLE ROUGH END_},ilLLING => (GRVO) GROOVE FIN END_}JJLLING => {GRVO) GROOVE
Fig. 9. Process planning system for machining operation
488
RoboUcs and Computer-Integrated Manufacturing • Volume 4, Number 3/4, 1988
,--
1-1
1
DWsE3 0 ~-Other ports
(o)
1
=L
J
1
~
-Other ports
(b)
Fig. 10. Process planning system for bending operation.
Fig. 11. Sheet metal part design system.
the previous system. The system receives a product model of a sheet metal part and generates bending sequence, tools, positions and positioning methods. The system uses bending planning rules in production system and takes into consideration ease of bending, tolerances, tool interferences and so on. Figure 10 shows a generated bending sequence.
5. CONCLUSION A concept of geometric constraints is introduced, which allows us to treat information about design objects. This concept is implemented in a multiparadigm modeling framework, combining first order predicate logic and an object oriented language. A geometric modeling system is also incorporated in the framework. Design tasks are thought of as processes which manipulate constraints. Several prototypical design task models have been built for C A D / C A M applications.
• Sheet metal part design system s In general, a shape of a machine part is determined in several ways. Some portion of the shape is determined to realize the product's function, in other words, this portion must be that shape. On the other hand some portion is determined as appropriate, in other words, this must not necessarily be that shape. This system solves a problem of the latter kind. In Fig. 11, the system is given contour (a) and automatically adds some portions to contour (a) and generates contour (b). The contour (b) is required to include all specified holes, to have no interference with other parts, and to keep some spaces around the holes. The system produces the initial contour satisfying these constraints and then refines it by applying refinement rules to the product model. In addition to the above applications, some simple experimental systems are also developed to examine how routine design tasks can be formalized as constraint manipulation processes using AI techniques. 5
REFERENCES 1. Suzuki, H., Klmura, F., Sata, T.: Treatment of Dimensions on Product Modelling Concept, Design and Synthests. Amsterdam, North-Holland. 1985, pp. 491-496. 2. Sata, T., Klmura, F., Suzuki, H., Fujita, T.: Designing machine assembly structure using geometric constramts m product modelling.Ann. CIRP 34: 169-172, 1985. 3. Kimura, F., Suzuki, H., Wlngard, L.: A uniform approach to &mensioning and toleranclng in product modelhng. Computer Applications in Production and Engineering, CAPE'86, Amsterdam, North-Holland. 1987, pp. 165-178. 4. Sata, T., Kimura, F., Hlraoka, H., Suzuki, H., Fulita, T.: Comprehenswe modelling of a machine assembly for off-hne programming of industrial robots. Off-Lme Programming of Industrial Robots, Amsterdam, North-Holland. 1987, pp. 19-33.
Product modelhng system for CAD/CAM systems • H. SUZUKIet al 5. Kimura, F., Suzuki, H., Sata, T.: Variational product design by constraint propagation and satisfaction in product modelling. Ann. CIRP, 35: 75-78, 1986. 6. Suzuki, H.: A product modelhng framework for integrating manufactunng information. Doctoral dissertation, The University of Tokyo, 1986 (in Japanese). 7. Inui, M., Suzuki, H., Kimura, F., Sata, T.: Generation and verification of process planning using dedicated
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models of products m computers. Proceedings of A S M E W A M 1986, Symposium on Knowledge-Based Expert Systems for Manufacturing, December, 1986. 8. Kimura, F., Suzuki, H., Ando, H. Sato, T., Kinosada, A.: Variation geometry based on logical constraints and its applications to product modelling. Ann. CIRP (in press).