A knowledge-based system for strip layout design

• ~ • ~' " 17;

ELSEVIER C o m p u t e r s in I n d u s t r y 25 (1994) 3 1 - 4 4

¢OBFIITIE|S IN INDUSTRY

A knowledge-based system for strip layout design

Bryan Ngoi Kok Ann, Chua Chee Kai * School of Mechanical and Production Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 2263

Abstract

Strip layout design is a task that is dependent on the experience of designers. It normally takes several years of exposure and on-the-job training in the tool and die industry before a fresh designer has acquired the basics of strip layout design and is competent in doing his own design. Once acquired, this valuable expertise, which is not found in literature or texts, can be easily lost or "taken away" when the designer leaves the industry. Hence, there is a need to capture and retain this knowledge for future application and development purposes.

This paper presents an experimental knowledge-based consultation system developed for the purpose of capturing strip layout design knowledge. The system is developed using Expertech's XI-Plus shell package for stamping processes like piercing, blanking, bending and trimming. The knowledge of these processes is acquired from interviews with experienced die designers. Besides standardization and documentation of design knowledge, the system also aims to train and aid new designers in doing their own design. A description of the system's basic framework necessary for representing the expert knowledge is given. The knowledge and design rules that are being used in the system are also illustrated and explained and finally a sample test run of the system is shown.

Keywords: CAD/CAM; Strip layout; Tool and die design; Knowledge-based system; Expert system

1. Introduction

Strip layout design involves laying out the material s t r ip-- r ibbon of metal or other material that is passed through the press in order to produce stamping--exactly as it will appear after all operations have been performed on its parts. It has been well recognized that strip layout design is an art or know-how by itself that involves designing in the light of the realities of a situa-

* C o r r e s p o n d i n g a u t h o r .

tion. It is the experience of designers that deter- mines the feasibility of the strip layout for use in the die for production of the sheet metal part.

The dependence on experience coupled with the mobility of designers in the tool and die industry have caused much inconvenience to the particular industry and many companies. There- fore, it is deemed necessary to capture knowledge and experience into a knowledge-based system so that they can be retained and used for future application and development purposes.

Many C A D / C A M systems have been developed to further automate the design process of s tamping/progressive dies but no substantial

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32 B. Ngoi Kok Ann, (\K. Chua / Computers in Industry 25 (1994) 31-44

work has been done on the research and development of design rules for strip layout design. Al- though some knowledge-based design systems focused on the tool and dies area, none of them directly addressed strip layout.

Hitachi Production Engineering Research Laboratory has been very active in CAD/CAM system development work for tool and dies design. Murakami and Shirai [1-4] have investi- gated the design process and the average design time required for progressive dies. It was found that highly empirical processes are utilized only in designing the strip layout and the die layout, and that their combined times constitute at most 10 percent of the total design time. They have developed a CAD/CAM system for progressive dies in which the designer performs the strip and die layouts and optimizes the stock utilization. Determination of the die part list and drafting of the assembly and part drawings are done by computer.

Nee [5-9] has developed some experimental packages which involve algorithms and evaluation functions. These packages can perform a complete analysis on press capacity, the use of coiled or strip stock and cost factors in order to solve for near-optimum layout and nesting/patterning problems for both sheet metal and metal stamping blanks. He has developed a PC-based computer aid in sheet metal working [9]. In his package, a blank layout program was first developed [9,10] followed by fiat patterning and design considerations of progressive dies. The program also incorporates a number of expert design rules and provides an automated solution for progressive die layout with the following features: automated blank layout, punch shape determination and optimization, automated staging and minimum die- opening separation, etc. All of his work focused on the general strip layout design process for blanking and the expert rules involved do not include other stamping processes like piercing, bending forming and trimming.

Many CAD/CAM companies [10-17] and re- searchers [18-20] have also developed several CAD/CAM systems which emphasize the overall design process of complete dies and are usually focused on drafting, die design evaluation and

general calculations. None of these incorporates detailed design process rules and manufacturing considerations, especially for strip layout design. It should be noted that most of the work attempts to extend CAD into the area of dies for high- speed and high-precision work.

Only a few research and development works on expert system (knowledge-based) applications to the tool and dies area have been found. Most of the works are concentrated on process planning for sheet metal forming and drawing [21-25] and no specific system has been developed for strip layout or die layout design.

The objective of the development work pre- sented in this paper is to concentrate on the automation of the strip layout design activity via an expert consultation system. It is aimed to promote standardization, aid in training new designers, ensure the continuity and documentation of the knowledge and experience involved, which will ultimately lead to significant increases in productivity.

The developed system uses a heuristic algorithm that is made up of rules to derive recommendations and answers to queries of the user. These rules are derived from the knowledge obtained from interviews and discussions with local industrial die designers, and design theories from appropriate text books [26,27]. The consultation approach used for the system mainly consists of two sections: (a) part orientation, which refers to the arrangement of parts on the strip in a most efficient manner, giving due considerations to production factors; and (b) sequence of operations, which gives the user stepwise instructions on how to layout the strip in accordance to the priority of the progressive operations required (these operations include hole piercing, blanking, simple bending and trimming).

Section 2 gives an overview of the system's architecture plus a description of the rules that make up the various modules and submodules of the system's consultation structure. Section 3 presents examples of design rules represented in the form of a decision table to illustrate the consultation process involved. In Section 4, a sample session is given to demonstrate the program developed.

B. Ngoi Kok Ann, C.K. Chua / Computers in Industry 25 (1994) 31-44 33

2. Strip layout knowledge base system

The knowledge base consultation system for strip layout design was developed using the knowledge gathered from industrial designers, literature research and design handbooks. The system's main function is to allow the user to obtain recommendations and know-how about strip layout design.

2.1. Overall structure

The system comprises mainly of the knowledge base (made up of rules), the inference engine and the user interface.

The knowledge base contains rules to strip layout design which can be categorized into two main modules: (i) Part orientation module; (ii) Sequence of operations module. In the XI-Plus shell system, these modules are defined as applications which contain their re- spective knowledge bases. These are illustrated schematically in Fig. 1.

The part orientation module is made up of rules for part arrangement stored under the knowledge base "Layout". The sequence of operations module is further divided into four smaller submodules which encompass the four types of operation of a progressive die--piercing, blanking, trimming and bending--in order of priority in accordance to the experience of die designers. Pilot hole piercing and trimming operations are always the first and the last operations, respectively, whereas blanking apd bending sequences are not fixed; under certain special situations their operation sequence may switch places. Rules to these submodules are stored in terms of their priority of operation, in four different knowledge bases defined as "First operation", "Second operation", "Third operation" and "Fourth operation" under the application "Operation".

Expert System Core I

Ii Part Orientation module i

(Appl ica t ion - 0 ~ ) I

-1 Kaowkdscbue - Layout "l

Sequence of Operation module q ( A p p l i c a t i o n - OperaK, on)

~ - ~ Kaowledgcba~ - First Operation t ~ 3

~ Kaowledgebwe -Second Operation [

J Kn°wlcdgebasc " / I ' ( ~ Ixrafi°n ] "1

~ Knowl~geb~-Fonrdant.. Ol~rSaon [

Fig. 1. Knowledge base structure for consultation system.

an initial layout of the part in the strip; and (b) providing recommendations about the most appropriate part orientation in a strip.

Currently, the part orientation consultation module is divided into four phases. During each phase, the user will be prompted to answer a set of questions put forth by the system. Answers to these questions will serve as facts for the rules in the knowledge base, thus allowing the system's inference engine to respond with recommendations and conclusions. This consultation process is illustrated in Fig. 2 and a brief description of each phase is given as follows.

2.2. Part orientation module

The part orientation module is developed with the objectives of: (a) serving to provide the user with essential design pointers required for doing

(i) Customer specification. This phase contains rules to check for any customer's specification to the orientation of the part on the strip. These orientations can be wide or narrow, slanted at a certain angle or aligned along the grain direction.

34 B. Ngoi Kok Ann, C.K. Chua / Computers in Industry. 25 (1994) 31-44

Under circumstances where no customer's speci- fications are given, the system will suggest the next step that the user should take, that is to perform material optimization for the part orientation chosen by the designer himself. In fact, algorithms to optimize strip material of a part layout (also called pattern nesting) have been developed for this optimization process [8-12].

(ii) Material optimization. This phase contains rules to check for an orientation (either wide, narrow or slanted at a certain angle) with a maximum material optimization value entered by the user. Following this, the system will suggest to the user to arrange the part according to the standard available in the industry to ensure strip rigidity. These standards deal with the part-to- edge and part-to-part distances. The user is also informed to give enough space allowance on the strip for symmetrical pilot hole locations as shown in Fig. 3. Under circumstances where there is no

Layout )

I I I

I I

Removal Method I I II IIII II

Strip Movement Through the I

Fig. 2. Consultation process for part orientation module.

~ ilot~ng holes

Fig. 3. Piloting holes on the strip layout.

material optimization for all three orientations, the system will also suggest that the best orientation to use is wide because: - fewer cuts are required to produce the strip; - feed of strip is shorter, which gives rise to

reduction of operating time; - more blanks can be produced per strip.

(iii) Type of end-product removal methods. This phase contains rules to check for the type of end-product removal methods employed to re- move the final part from the scrap strip. For each of the methods used, design considerations that the designer has to take note of will be given by the system. These are summarized in Table 1.

(iv) Smooth strip movement through the die. This phase contains rules to check whether the strip is rigid enough to move through the die smoothly without any obstruction due to collapsing of the strip. Subsequently, it will give a final recommendation about the best orientation to be used or inform the user to orientate the strip in a compromised orientation. In such a case, the part-to- part and part-to-strip edge gaps will have to be increased for more strip rigidity at the cost of increased material wastage.

Table l Design considerations for different methods of end product removal

Method of removal Design consideration

Removal by using incoming parts

Removal by blanking part out as slug

Arrange part so that the part is easily removed

Burrs will be found on strip between the part and the die


~ symmetriesd pilot holes

Fig. 4. Symmetrical pilot holes on strip layout.

side notches

Fig. 5. Side notches to provide strip guidance.

2.3. Sequence of operations module

The sequence of operations module is developed with the following objectives in mind: (a) it

,,+,

~ I = +bil.liSmm

/

Fig. 6. Hole location tolerance.

will provide the user with the essential design recommendations to take note of in terms of strip layout design for each of the four operations of progressive dies; and (b) it will recommend the user the steps to be taken with regards to layout design under each of the four operations of piercing, blanking, simple bending and trimming.

As in the part orientation module, this module will also prompt the user for certain facts or data that will allow the inference engine to recommend conclusions and actions to be taken. Each of the four submodules under the sequence of operations module is described in the following sections.

First operation There are altogether five phases to this sub-

module as follows:

(i) Piloting holes. This phase contains rules to check whether holes on the part can be used for piloting. If so, the system will recommend that these holes be pierced first. Pilot holes are best pierced symmetrically about the strip, as shown in Fig. 4. Besides piloting holes, side notches can be used as a means for strip guidance through the die, as shown in Fig. 5.

(ii) Hole location tolerance. This phase contains rules to check for hole location tolerances of two holes to be pierced against a given tolerance criterion (see Fig. 6). A tolerance range within ± 0.05 mm will cause the system to recommend

°I 8

dt~lce betweem closer edges Fig. 7. hole-to-hole distances.

V ol 8

centre to cen tre dlJtonce

36 B. Ngoi Kok Ann, C.K. Chua / Computers in Industry 25 (1994) 31-44

Table 2 Min imum hole-to-hole distance that will prevent weak die

Strip Diameter thickness D (mm) (mm)

Hole distance, a (mm)

Nearest Center distance to center between (minimum) hole edges

~< 2 ~< 5 1.5D 4 > 5 1.0D 4

> 2 ~< 5 2.0D 4 > 5 1.5D 4

that these holes are to be pierced simultaneously in a single station; otherwise they can be pierced individually in subsequent stations.

(iii) Distance between two holes. This phase contains rules to check for the distance between the closer edges of two holes to be pierced against a given criterion (see Fig. 7 and Table 2). If the holes do not meet the criterion, a weak die will result. From the checking process, a confirmation of the above recommendation to pierce the holes simultaneously or individually will be given.

(ic) Distance between hole and part edge. This phase contains rules to check for the distance between the part edge and the nearer hole edge against a given criterion (see Fig. 8). If the criterion is not met, a weak die will result. From this checking process, a recommendation to add an idle station between the piercing and edge blanking stations will be given.

(v) Distance between hole and bend portion. This phase contains rules to check for the distance between the edge of an inner bend to the nearer hole edge against a given criterion (see Fig. 9 and Table 3). Failing to meet the criterion will result in a distorted hole due to the bending operation. From this checking process, the following recommendations will be given as a solution to this problem: (1) to bend the portion first before blanking the hole or vice versa; (2) to blank extra supporting holes beside the blanked hole; or (3)

sta 2 cutoff

~ 2 cutoff

J'°° sta 1 pierce

weak die will occur

3 . Good prxcUce

/ II °!/

Fig. 8, hole-to-part edge distance and the inclusion of an idle station in the layout,

a

bendlng

e d z e ! /nunl lanmg hole

i ! i I i

Fig. 9. Hole distance to bend edge.

Table 3 Min imum hole-to-bend edge distance to prevent distortion of hole due to bending

Strip thickness Minimum distance a t (mm) a (mm)

< 1 5 > 1 7

a Min imum distance from the inner bend edge to the nearest hole edge.

B. Ngoi Kok Ann, C.I~ Chua / Computers in Industry 25 (1994) 31-44 37

sup snidng hole

Fig. 10. Supporting slot to prevent hole distortion.

0 I I Fig. 12. Blanking portion-to-portion distance.

L

to change the shape of the hole to an elliptical one if possible (Fig. 10).

Second operation This submodule is divided into five phases as

follows:

(i) Shape of blanking portion. This phase contains rules to check for a standard shape of blanking portions. A standard shape will require commer- cially available punches whereas non-standard shapes will require punches to be EDM or wire cut. In some cases, these non-standard shapes can be formed from standard ones, thereby re- ducing the cost of machining.

(ii) Location tolerance of two blanking portions. This phase contains rules that checks for the location tolerances of two blanking portions against a given criterion (see Fig. 11). A tolerance value within the range of + 0.05 mm will require the portions to be blanked simultaneously in one station so as ensure the accuracy of the blanking

sections. Otherwise, they can be pierced individually in sequence.

(iii) Distance between nearer edges of two blanking portions. This phase contains a rule that checks for the distance between the nearer edges of two blanking portions against a given criterion (see Fig. 12). Failing to meet the criterion will result in weak die blocks. From the checking process, the system will confirm its recommendation given in section (ii) of whether to blank the two portions simultaneously or individually with refer- ence to the criteria given in Table 4.

Or) Dimension tolerance of a single blanking portion. This phase contains rules that will check for the dimension tolerance of a particular blanking portion against a given criterion (see Fig. 13). For a dimension tolerance within the range of + 0.05 mm, the system will recommend that this portion be blanked last so that its dimensional accuracy will not be affected by other operations.

tol=+/-O.OSmm

Fig. 11. Blanking portions location tolerance.

Table 4 Minimum die

Strip thickness (mm)

portion-to-portion distance that will prevent weak

Common dimension of Distance between closest of two portions edges of two portions L (ram) a (ram)

< 2 < 5 1.5L > 5 1.OL

> 2 < 5 2.0L > 5 1.5L


tol (A,B)=+/-0.05mm

Fig. 13. Blanking portion dimensional tolerance.

grain dlrecUon

• g r l l m dlrectloa

Fig. 14. Bending edges and bending directions.

In addition, the system will also give a general blanking sequence of different portion types in order of priority as: (a) rough and small, (b) rough and large, (c) smooth and small, and (d) smooth and large. The larger portion is always blanked first because it is likely to cause distortion to other blanking portions whereas the smoother (critical) portions are blanked last to prevent it from being distorted by other blanking operations.

(v) Strip movement through the die. This module contains rules that will check for sustained strip rigidity throughout the progressive operations, because the strip should be able to move through the die without any obstruction due to strip collapsing. A recommendation for a weak strip is to blank smaller portions first to ensure that more material remains on the strip to provide rigidity. In addition, a general blanking sequence of different types of blanking portions will also be given as in the previous section on dimensional tolerance of a single blanking portion.

(ii) Number of bending directions. This phase contains rules to check for the number of bending portions required on the part. One- or two-direc- tional bending is to be done along the grain direction or along a compromised direction, respectively, as shown in Fig. 14.

(iii) Distance from bend portion to blanked hole edge. Here the same rules apply as in Section 2.3.1(iv).

Or) Bending edge in line with steps of the part. This phase contains rules to check whether the bending edge is in line with steps of the part, as shown in Fig. 15. If such a situation occurs, the system will inform the user of possible cracks occurring at the bending edge and subsequently recommend remedial actions of: (1) shifting the bending edge away from the steps by an offset, e, gretaer than or equal to the thickness of the strip; or (2) providing undercuts at these corners, as shown in Fig. 16.

Third operation This submodule is divided into five phases as

follows:

(i) Bending requirement. This phase contains rules to check for the requirement of bending operations on the part. If bending is required, the system will recommend that portions within a strip to be bent be blanked or lanced first.

adlq edge i

Fig. 15. Bending edge in line with part steps.

B. Ngoi Kok Ann, C.IC Chua / Computers in Industry 25 (1994) 31-44 39

I~'ovlde undercut s~ps

k ~

I 2 / / r beumn% edge

Prevlde an offset

ltdercuts steps ~ j

bending edge ~ H

Fig. 16. Providing undercuts or offset to prevent crack at bend edge.

(v) Occurrence of cracks at the bending edge corners. This phase contains rules to check whether there is the possibility of cracks occurring at the bending edge without the bending edge being in line with a step of the part. If such a crack occurs, the system will recommend a remedial action of providing an undercut at the edge of the bend.

Fourth operation This submodule is divided into four phases as

follows:

(i) Dimensional tolerance of trimming portions. This phase contains rules to check for the dimensional tolerance of trimming portions against a given criterion (see Fig. 17). For tolerance values within a range of +0.05 mm, the system will recommend that the portions be trimmed simultaneously; otherwise they can be trimmed individually.

(ii) Symmetrical trimming operation. Rules contained in this phase will check for the existence of symmetrical trimming being done on the part in

s~mmetrictl trimmin%

pot'flens

ult~ummetr~Jd Lrlmndmg porttom;misslipmeut wm Occur

Fig. 18. Symmetrical and unsymmetrical trimming portions on strip layout.

the strip, as shown in Fig. 2.18. If unsymmetrical trimming is done, the system will inform the user of the occurrence of strip misalignment due to the presence of only one single strip carrier by the side.

(iii) Rearrangement of trimming portions. This phase is a follow-up on (ii) as it will recommend possible solutions to the unsymmetrical trimming operation. One of the solutions is, if possible, to rearrange the part layout such that trimming is done symmetrically about the strip; otherwise, the designer has to provide adequate side strip carriers along the strip flow path.

(iv) Parting-off operation. This is the final phase of the submodule. It checks for the completion of all trimming operations and, subsequently, rec- ommends the last operation, the parting-off operation, to be done in a progressive die. One of the common methods for parting off is blanking, which removes the end product as a slug from the die.

3. The knowledge base

punches

~ ~t~l-+l...O,OOSnmz) Fig. 17. Critical trimming portions.

3.1. Rule-based design

Rules for strip layout design are contained in the knowledge base of the expert system. These rules are arranged according to the consultation structure as described in Sections 2.2 and 2.3. In order to give a detail description of the rule-based structure and the program flow in each of the


modules and submodules, decision tables used.

3.2. Decision table

are

Basically, a decision table shows in tabular form a function in which the value of a variable is determined and, based on this value, some action is taken. The upper rows of the table specify the variables and conditions to be evaluated and the lower rows specify the corresponding action to be taken when an evaluation test is satisfied. Hence, each column in the table represents a rule. An example of a decision table for the first submodule (first operation) of the sequence of operations module is given in Table 5 to illustrate the consultation process.

3.3. Knowledge representation

The experimental expert system is developed using Expertech's XI-Plus version 3.0 running on a DOS operating system on an IBM compatible personal computer. This is a shell system that uses the rule-based language as its programming tool.

Rules obtained are translated into conditional " IF . . . T H E N " statements for software imple- mentation. An example of this is:

IF product has holes AND thickness of strip ~< 2 AND minimum distance between hole edge and part edge ~> hole diameter T H E N first operation is complete

Table 5

Decision table for first operat ion submodule (Phase 4)

Conditions Response

Strip thickness ~< 2 mm Y Y Y Y N N N N

Strip thickness > 2 mm N N N N Y Y Y Y

Common dimension between the blanking hole and the part edge, L ~< 5 mm Y Y N N Y Y N N

Common dimension between the blanking hole

and the part edge, L > 5 mm N N Y Y N N Y Y

Distance between the part edge and the nearer blanking hole edge >/1.5L Y N . . . . . .

Distance between the part edge and the nearer

blanking hole edge < 1.5L - Y . . . . . . Distance between the part edge and the nearer

blanking hole edge ~ L - -- Y N . . . . Distance between the part edge and the nearer

blanking hole edge < L - - N Y . . . . Distance between the part edge and the nearer

blanking hole edge i> 2L . . . . Y N - -

Distance between the part edge and the nearer

blanking hole edge < 2 L . . . . N Y - -

Distance between the part edge and the nearer blanking hole edge >/1.5L . . . . . . Y N

Distance between the part edge and the nearer blanking hole edge < 1.5L . . . . . . N Y

Action a

Rule 1 x X X X Rule 2 x x x x

a Rule 1: No action is taken. Rule 2: Add an idle station so that hole piercing and part edge trimming operat ions are separated apart by one station.


The programs of each module and submodule have been written in a manner that facilitates future development, that is the addition of more rules to the knowledge base. This is achieved by dividing the program within a knowledge base into modules as described in Section 2.1. Within each program, ~his is further subdivided into smaller sections or phases by making use of the " W H E N DONE . . . T H E N CHECK" statement. An example of such an application is:

W H E N DONE best orientation1 T H E N CHECK best orientation2

When such a statement is used, the next submodule or phase can be assessed, making the consultation process continuous within the module.

.- 159.00 ; /

F- +4,- +4,.- - ~ 2 6 . 0 0

Im ÷ - * - - ' - ....... MI

; + + * + . . . . . . . . . . . . . . . . . . . . . . . . . . .

-

~- -+- ~- + -e- )-+- . . . . . . . . . . . . . . . . . . . . . . . . . .

- ~

~++ - . + -e- . . . . . . . . . . . . . . . . . . . . . . . . . .

-

~--~.-+- 4- + -e-

4. Sample session of the part orientation module

To demonstrate how the actual consultation process takes place, a sample test run is given here.

The sample strip layout used for testing of the system developed is given in Fig. 19. Before starting a consultation, the user has to select a particular application and load the required knowledge base. Selecting the "Start Query" option in the starting menu, a main menu will appear request- ing the user to select a pre-defined query. With this selection, the consultation process is initi- ated.

4.1. Phase 1

Beginning with this module, a screen menu as shown in Fig. 20 will appear to prompt the user to choose whether there is any customer specification with regard to the type of orientation: narrow, wide or slanted at a certain angle. A positive answer to this question will result in a recommendation that the part is to be arranged in accordance to the customer's requirement. As- suming that no customer specification is given, the last option "customer specification is sup- pressed" is chosen. With this information, a rec-

Fig. 19. Sample strip layout.

W h a t b t he c u s t o m e r ' s s ~ d m ?

r= I ~ r r o w

ESc c s n c d : C t r t + R m eml : R t b s ~ :

Fig. 20. Screen presentat ion for part orientat ion module (Phase la).

4 2 B. Ngoi Kok Ann, C.K. Chua / Computers in Industry 25 (1994) 31-44

Appncadon: Orientation Knowled lebase : l ayou t

ill ..... - - n ~l~a laOol for roll ~ types of orbtetaUo~:wlde, Barrow and slant at certain analgle

ESc crewel : Ctr l ÷ R t n end : R t n select:

Fig. 21. Screen presentation for part orientation module (Phase lb).

Application: Orien ta t ion Kt lowledgebDe: layout

A r r a n g e the part to allow symmetr ica l pilot hole locationw on the s t r ip

ESc cancel : Ctr l + R t n end : R t n select:

Fig. 24. Screen presentation for part orientation module (Phase 2c).

Application:Orientation I<atowlnd gebase: layout

~ m t t l m f o r slant st certalnl tnlll¢

ESc cancel : Ct r l + R t n end : R t n select:

Fig. 22. Screen presentation for part orientation module (Phase 2a).

ommendation to perform material optimization calculations for the three types of orientation is given, as shown in Fig. 21.

4.2. Phase 2

Proceeding with the consultation, the system prompts for an orientation of the sample which gives a maximum material optimization of the strip (Fig. 22). Assuming a maximum value obtained for the wide orientation (after completing the calculations), the two recommendations shown in Figs. 23 and 24 are given.

Application: Ol4mtadon K n e w l e d a p b M e : ~ t

II ES¢ cancel : C/ r l + R t n end : R / n select:

A r r l n a ~ b i ~ r t ~ r d l a g to lhe s~ndard given II

Fig. 23. Screen presentation for part orientation module (Phase 2b).

4.3. Phase 3

The next screen that appears (Fig. 25) asks the user for the end product removal method to be used for this particular sample.

4.4. Phase 4

Choosing the "other than blanking" option, the consultation proceeds with a screen (Fig. 26) prompting for the strip's ability to move through the die smoothly after the part has been arranged according to the standard given in the industry (as seen in the recommendation in Fig. 23). As- suming that the wide orientation chosen can move through the die smoothly, a confirmation of this orientation being the best one is given in Fig. 27.

Having decided on the orientation type to be used for the sample, the next consultation module is chosen to decide on the detailed layout design of the strip layout.

5. Conclusion

The expert consultation system for strip layout design can be easily used on a personal computer by any die designer. The heuristic algorithm developed in this paper considers the various re- quirements and design rules required for strip layout design for progressive dies. It is able to provide essential knowledge for both beginners and experienced die designers. Since there are many directions for further development, it is possible to enhance the capability of the system and further promote design standardization; one

B. Ngoi Kok Ann, C.~ Chua / Computers in Industry 25 (1994) 31-44 43

Aplalkttlen: 0 rlmtatlea ICaewlNIpha~:layem

I 1 ESc cancel : Ctr l+ Rtn end : Rtn me l t .


Applicatlon:O rlentation gnowledgehme:htyout

21 Stop movement through the die Is ] l

[ moo~ m*r ~ r n ~ e~ pm ] l[ Imelh dter trrmszlmZ die ~rt ~.ccordlnl to the shmdard ztvm

ESc cancel : Ctrl + Rtn end : Rtu xk.et:


Application:Orientation Knowledpbue:layout

Best orimtation is wide

ES¢ cancel : Ctrl + Rtn end : Rta select:

II Fig. 27. Screen presentation for part orientation module (Phase 4b).

such area of improvement is the incorporation of material optimization algorithms [5-9] into the knowledge base consultation package. The ulti- mate goal is to develop an effective expert strip layout design package with useful design decision supporting tools for the tool and die industry.

Acknowledgement

The authors wish to thank Shineishangyo (Pte) Ltd and EM Tools (Pte) Ltd for providing the necessary design knowledge and expertise in the development of this expert consultation system.

References

[1] H. Murakami, K. Shirai, O. Yamada and K. Isoda, "A CAD system for progressive dies", Proc. 21st Int. Mach. Tool Des. Res. (MTDR) Conf., 1980, pp. 587-591.

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i

Bryan Ngoi received his BEng degree from the National University of Sin- gapore in 1985 and his PhD from the University of Canterbury, New Zealand in 1990. He is presently a lecturer at the Nanyang Technologi- cal University. His research interests are: computer-aided tool and fixture design, computer-aided process planning, automated assembly, knowledge-based systems and intelligent object representations.

Chna Chee Kai is a lecturer at the School of Mechanical and Production Engineering of Nanyang Technologi- cal University, Singapore. He received his BEng(Mech) with First Class Honours and MSc(Ind) from the National University of Singapore in 1985 and 1989 respectively. He is a member of Working Group 5.3 (Com- puter-aided Manufacturing) of the In- ternational Federation for Informa- tion Processing (IFIP). His current research interests include reverse engi-

neering, CAD/CAM, geometric modelling, rapid prototyping and the use of heuristics in optimizing modern production processes and systems.

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