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Integration of CAD and a cutting tool selection system

Y. Zhaoa, K. Ridgwaya, A.M.A. Al-Ahmarib,*

aMechanical Engineering Department, University of Shefeld, Mappin Street, Shefeld S1 3JD, UKbIndustrial Engineering, College of Engineering, King Saud University, P.O. Box 800 Riyadh 11421, Saudi Arabia

Accepted 31 August 2001

Abstract

This paper describes a novel concept for the integration of a CAD system and a knowledge based system of the

selection of cutting tools and conditions for turning operations (EXCATS). This integrated system (CADEX-

CATS) is capable of processing CAD data and automatically generating the component representation le for

EXCATS using the IGES neutral format and a feature recognition approach. The workpiece representation model

is capable to describe sophisticated turned components using Prolog facts and other operational linked keywords.

In addition, CAPP related features are effectively incorporated into the CADEXCATS system. A set of rules is

established for the automatic determination of set-up, detection of complex geometries, recognition of grooves and

other important features. Illustrative examples are presented to test and validate the developed system. q 2002

Elsevier Science Ltd. All rights reserved.

Keywords: Computer aided design/computer aided manufacturing; Computer aided process planning; Integration; Knowledge-

based system; Computer integrated manufacturing

1. Introduction

It is well recognised that computer aided process planning (CAPP) plays an important role in the

development of computer integrated manufacturing systems (CIM). The CAPP system provides a vitallink between computer aided design (CAD) and computer aided manufacturing (CAM). Therefore, therst step towards the total integration of CAD/CAM is the integration of CAD and CAPP systems.

The signicance of CAD/CAPP integration arises from the fact that CAPP relies on the data which isprovided by CAD to perform precise and consistence process plans. However, CAD and CAPP tend tohave different databases i.e. CAD databases are usually geometry-based, consisting of geometry

Computers & Industrial Engineering 42 (2002) 1734

0360-8352/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.

PII: S0360-8352(01)00061-4

www.elsevier.com/locate/dsw

* Corresponding author. Tel.: 1966-1-4676825; fax: 1966-1-4676652.

E-mail address: [email protected] (A.M.A. Al-Ahmari).


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primitives (e.g. points, lines, circles, etc.) whilst CAPP systems tend to be feature based (e.g. for turnedcomponent: faces, cylinders, grooves, etc.). Although, such a problem could be solved by developing a

feature-based CAD models to provide data direct to a CAPP system. This approach imposes limitation

on CAD models and requires process planning at the CAD stage. It is clear that the integration providesthe most attractive solution to the transformation of data between CAD and CAPP systems. By achieving

this, reproducible CAPP process can be guaranteed (Van Houten, 1992).There are currently two main integration approaches which address the data exchange problem, the

rst is the direct translator approach, and the second is the neutral format approach (Smith, 1987).Thai paper presents and demonstrates a new integrated system (CADEXCATS) which integrates a

commercial CAD system and EXCATS (Expert System for the Selection of Cutting Conditions and

Tools for Turning Operations). The EXCATS was developed at the University of Shefeld (Arezoo,1991; Arezoo, Ridgway & Al-Ahmari, 2000) as a generative type system to perform the selection of

cutting tools and conditions of turned components.

2. Review of previous work

Most commercial integrated CAD/CAM systems are only available at low level, which means thegeometric denition can be saved to create the NC code (from CAD to APT) (Kelta & Davis, 1989).However, a high level of integration, where CAPP forms an essential part, is currently being developed.

Because the data direct translation between CAD and CAPP systems lacks universal exchangeability,the neutral format approach is more actively researched, as presented by various researchers (Galan-

tucci, Picciallo & Tricarico, 1994; Kalta & Davies, 1994; Kim & Cho, 1994; Madurai & Lin, 1992 Zhao& Ridgway, 1994).

Dong and Soom (1986) rst established which is called Machine Process Oriented Data Format(MPODF) as a format to express most of the information required for process planning of rotationalparts. The main drawback of MPODF lies in its linear data structure. This means that the topological

relationship between the recognised turned features is linear and some information cannot be expressedusing this method. For example, when a dimensional or geometrical tolerance is related to more than onefeature. Wang and Chang (1987) and Wang and Wysk (1988) developed an algorithm to perform

automatic extraction of surface features from a 2D CAD database of symmetrical rotational parts.The algorithm, as the front end of a CAPP system, is an automated classication and coding system.Geometric entities can be extracted from a CAD system. The entities representing the upper prole of

the component are rst deduced and then the features are recognised. However, it is not clear from thework how the entities required are converted into the upper prole. Also, it is not capable of processing

threads and non-geometric information such as tolerances and component material. Li (1988) and Li andBedworth (1988)) generated an algorithmic intelligent system for part feature recognition which extractsturned feature from a 2D CAD database via IGES. The disadvantage of this work lies in its inability to

process threads. Furthermore, it is not clear whether the input is a true 2D technical drawing and how thetolerances are interactively added. Sahay, Graves, Parks, and Mann (1990) developed an algorithm to

recognise turned features, which is based upon a clear and unambiguous denition of features usinggeometric properties. The input to this algorithm is the geometric entities of an upper prole model as anASCII (IGES) le. However, the algorithm cannot process threads, llets and tolerances.

The EXCAP is a knowledge-based process planning system for turned components. To interface the

Y. Zhao et al. / Computers & Industrial Engineering 42 (2002) 173418


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This paper presents an integrated system (CADEXCATS) which avoids the limitations of the existingsystems. AutoCAD is selected to generate CAD models of typical turned components as case studies.

The layer properties of AutoCAD are utilised to provide effective data management. A set of complete

and straightforward guidelines are established based upon British Standard BS 308 to allow successfuland exible modelling. CADEXCATS is written in C and runs in turbo C11 Version 3.0.

3. Development of workpiece representation

The EXCATS depends upon component representation as data input. This input data was generatedand represented manually and thus presented an ideal case for the current integration study. Further, theEXCATS system was only capable of basic operations, although more advanced functions are under

development. This requires a more sophisticated workpiece representation model to be established. To

this end, such a model is rst identied and used to represent the workpiece and demonstrate theCADEXCATS integration system.

Among various workpiece representation approaches, the specically designed language approachstands out because it guarantees the complete representation of the all information required by a CAPPsystem. In this paper operation linked keywords are used to describe the workpiece, as Prolog facts,

which are capable of declaring objects and representing relationships between objects.

3.1. Procedural rules of workpiece representation

The CADEXCATS model, has been developed to include the following procedural rules:

1. The external and internal operations are represented separately;

2. The roughing and nishing operations are represented separately;3. The roughing geometries are so dened that the majority of material is removed to create a shape

near to the nal component prole;

4. The nishing geometries are the exact prole of the nal component;5. When representing the workpiece, the direction of the geometries features are dened such that the

related geometric proles from a continuous path, starting from the far right elements;

6. The external features are represented in a counter clock-wise manner, i.e. beginning from the farright element to the far left element nearest to the co-ordinate origin;

7. The internal features are represented in a clock-wise manner;8. The secondary turning operations only appear in nishing operations and are represented after

primary nishing operations;9. For nishing operations primary and secondary turning operations are represented separately;

10. The supplementary dimensional information and technological information for the component areincluded for the nishing operations.

The above rules are used because the CAD model of a turned component is presented with the normalright hand cartesian co-ordinate system and as a 2D upper prole.



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3.2. Machining geometry

A turned component is described by a combination of primary and secondary operations. The

`primary' or `basic' operations which can appear in both roughing and nishing operations, can begrouped into ten cutting actions as illustrated schematically in Fig. 1. In Fig. 1, the terms `in' and `out'

refer to the direction of the features relative to the centre line, and do not necessarily reect the truemachining action, which is determined by the subsequent CAPP process.

Complex geometric features, e.g. recesses and shoulders are further dened and indicated in the

component representation le because of their special signicance for cutting tool selection. Theyconsist of a group of neighbouring primary turning geometries, as illustrated by the dashed box inFig. 1.

Three typical secondary turning operations are considered, i.e. grooving, threading, and parting-off.Grooves are commonly seen in turned components to provide undercuts to facilitate subsequent opera-

tions, e.g. threading and to provide better tting or hold O-ring seals. They are usually created using aspecial forming tool in single or multiple cutting steps. The terms `groove' and `recess' are often

exchanged and it is difcult to differentiate between them. Since it is accepted that a recess is a complexfeature assigned to represent a combination of basic geometries which require a special set of tools tomachine this is seen as the main difference between a recess and a groove.

3.3. Geometric feature representation

The information structure follows a set of rules, consisting of Prolog predicates, related to the

component geometry through a sequential identity number and feature type, as shown below. Thebasic primary and secondary cutting actions required to create the desired geometry are represented

by terms such as: long_turn, face_in in_copy, etc. For each feature the complete information set isrepresented in the following specic order.

feature; no: N is_a cut-actionset-up-no;X1;X2; Y2:

where:

feature indicates the type of feature (operation and geometry); Ngives the identity number; cut-actionindicates the actual cutting action; set-up-no represents the set-up number; X1, Y1, X2, Y2 represents theco-ordinates of the start and end points respectively.

A component dened by cross-sectional drawings, as illustrated in Fig. 2, should have a component

Y. Zhao et al. / Computers & Industrial Engineering 42 (2002) 1734 21

Fig. 1. Various types of primary external turning operations for line cutting actions. The dashed box represents a shoulder,

consisting of one longitudinal and two facing features.


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representation le, as shown in Fig. 3. Hence, the longitudinal geometry with sequence No. 3 appears as:

ext_fin_geom no 3 is a long_turn1; 142; 26; 102; 26:

Secondary geometries can be represented, as demonstrated by the following examples:

A groove: ext_n_geom no 16 is_a groove(1, 86, 50, 76, 50, W is 10, D is 8) . Where the width, Wand

depth, D of the groove are additionally indicated; A thread: ext_n_geom no 17 is_a thread(1, 144, 24, 102, 24).

The parting-off: ext_n_geom no 15 is_a part_off(2, 0, 15, 0, 0).

Typical types of blank for turned components are solid bar, cast blank, pre-machined blank, and blankwith a pre-drilled hole. In the work described, only solid bars with and without pre-drilled holes areconsidered. Subsequently, the diameter and the length respectively of such a blank and the predrilled

holes are indicated in the component representation le as,

blank length is X; diameter is Y:

int_rough drill Xmin; Ymax; Xmax; Ymax:


Fig. 2. The technical drawings of a turn component (a) nishing and (b) roughing.


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3.4. Non-geometric feature representation

3.4.1. Supplementary dimensional information

The geometric information, given by the start and end points of individual features as describedabove, may not be sufcient for precise process planning during the nishing operation. In this case,

a representation including supplementary dimensional information is required, as demonstrated by thefollowing two examples:

In the case of a thread, the geometric information gives only the co-ordinates of the start and end

points. However, the crest diameter of an external thread or the root diameter of an internal thread andthe pitch are essential information for process planning. Such data is provided as supplementary dimen-

sional information. As a second example, the distance between two separated geometries needs to bespecied to ensure the quality of the manufacturing process. Here, such a specied length appears assupplementary dimensional information.

The following seven types of dimension are identied, which require supplementary dimensional


Fig. 3. The component representation le for the turned component shown in Fig. 2 based upon CADEXCATS workpiece

representation model.


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information, i.e. when associated with two geometries. (1) angular feature, (2) length and (3) width;when associated with a single geometry: (4) chamfer, (5) diameter, (6) llet, and (7) thread.

The exible `dimn' fact of Prolog is employed to represent the very versatile supplementary dimen-

sional elements, according to the following format:dimn_typefeature no: N1; no: N2; values:

Here the `type' indicates one of the above seven types; the `feature no. N1, no. N2' indicates thegeometric feature(s) which are related to the dimension. The `values' species the supplementary

dimensional information as further detailed in the following:

1. An angular element for an angle, A 608 between geometries (no 5 and no 6) will appear as:

dirnn_angular(ext_n_geom no 5, geom no 6, A is 60).2. The following length element is used to indicate a length, L 15 mm between geometries no 1 and

no 5:

dimn_length(ext_n_geom no 1, geom no 5, L is 15).3. The width element has a similar expression:

dimn_width(ext(n_geom no 1, int_n_geom no 1, W is 15).4. A chamfer with a length of 2 mm and a angle of 458 is expressed as:

dimn_chanfer(ext_n_geom no 2, 2x45).

5. A diameter element with a diameter, D 28 mm has the following expression:

dimn_diameter(ext_n_geom no 1, D is 28).

6. A radius element (for the arc or llet geometry) with radius, R 4 mm will appears as:

dimn_radius(int_n_geom no 8, R is 4).7. For a thread, M, with an crest of 120 mm and pitch of 1.5 mm together with a optional tolerance grade

of 6 g, the following expression is used:dimn_thread(ext_n_geom no 15, M is 120x1.5, 6 g).

3.4.2. General component information and manufacturing instructions

General component information includes the component name material code, batch size and surfacenish requirement for the whole component (when applicable). Manufacturing instructions can also be

specied including the heat treatment, polishing processes, etc. The representation of this informationtakes the following format:

componentTITLE : component0s name:

componentMATERIAL: material code:

component BATCH SIZE : component0s batch size:

component SURFACE FINISH : 0:6:

3.4.3. Tolerances

There are two types of tolerance information, i.e. the dimensional tolerances and the geometrical



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tolerances of form and position. Five types of dimensional tolerances are considered here, namely, (1)angular, (2) diameter, (3) length, (4) radius and (5) width. They are represented by `tol' fact in the Prolog

fact, which appears as,

tol_typefeature no: N1; no: N2; upper limit; lower limit:

as shown by the following example:

tol_lengthext_fin_geom no 6; geom no 9; 85:1; 84:9:

The geometrical tolerances are classied into two types: (a) single features and (b) related features.The former includes; (1) cylindricity, (2) atness, (3) prole of a line, (4) prole of a surface, (5)

roundness and (6) straightness, while the latter includes; (1) parallelism, (2) squareness, (3) angularity,(4) position, (5) concentricity, (6) symmetry and (7) run-out. Related feature tolerances, in comparison,involve two features, with the second one usually a reference datum. In the `tol' fact of Prolog, these two

types of tolerances are expressed as:

tol_typefeature no: N is tolerance value; and

tol_typefeature no: N1 to no: N2 is tolerance value:

Two typical examples are presented below:

tol_flatnessext_fin_geom 14 is 0:01:

tol_run_outint_fin_geom no 1 to ext_fin_geom no 14 is 0:3:

In association with the above related feature tolerance, surfaces used as the tolerance reference are

indicated as,tol_referencefeature no: N; reference identity:

where the reference identity is a capital letter used to label the reference surface, e.g.

tol_referenceext_fin_geom no 14; A:

3.4.4. Surface nish

Surface nish is expressed by the `tol' fact in Prolog using the following format:

tol_surf_finishfeature no: N is value:

as demonstrated by the following example:

tol_surf_finishext_fin_geom no 9 is 0:8:

3.5. CAPP Functions

Some CAPP functionalities are incorporated into CADEXCATS to enable advanced features, i.e. theautomatic detection of complex features, set-up number and geometric features that do not requirenishing operations, etc. All these would simplify the subsequent CAPP process.



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3.5.1. Set-up change

Duringmachiningoperations, more than one set-up may be requiredto machine the complete component.

The number of set-ups is determined by the surface prole, component size and technological constraints of

the component. The surface prole which has a dominant role in set-up determination can be generallyclassied into four types; i.e. constant, increasing, decreasing and mixed types (Kim & Cho, 1994) with

reference to the variation in the Ycoordinate of the prole in the direction of Xmin to Xmax.A set of rules guiding set-up change has been proposed for turned components, which require a

sophisticated CAPP process to implement (HInduja & Huang, l989). In the current work, a preliminaryset of rules are established as part of the CADEXCATS workpiece representation model and have beenincorporated to perform automatic determination of set-up change (Zhao, 1997).

CADEXCATS also allows for manual overriding and input of the set-up change. In such cases, a secondset up could be avoided, e.g. by creating a greater gap beyond the parting-ofine to accommodate the tool.

3.5.2. Minimum internal diameter

Additional information is provided to indicate the maximum allowable diameter of the boring tool-

holder which can be used for roughing and nishing operations, e.g. a maximum allowable diameter of20 mm for the bore nishing tool appears as;

dmin for int_fin_geoms is 20:

3.5.3. Complex features

The complex geometric features, such as recesses complicate the CAPP process and require a specialset of tools. Additional notation is given in the component representation to indicate the presence of

recesses. The sequential identity numbers of the primary geometric features, which form the recess

together with the depth of the recess, H, are shown in the following example:

noted : ext_fin_recessgeom nos 12; 13; 14; 15; H is 20:

3.5.4. Geometries that do not require nishing operation

For a turned component, it is possible that some parts of the prole can be adequately formed duringroughing operations, thus they do not participate in further nishing processes. The following four

conditions are established under which the nishing operation would be required for the speciccomponent feature:

1. If a surface feature involves secondary operation e.g. threading, grooving and parting-off;2. If a surface feature is related to a dimensional tolerance and the required dimensional tolerance is

#^0.6 mm (this value is the limit of roughing operation, Davis, 1989);

3. If a surface feature has a geometrical tolerance requirement;4. If a surface feature has a surface nish requirement with in 12.5 m (Davis, 1989).

Any surface feature not falling into at least one of the above conditions will not be assigned nishingoperations and will be noted as shown below, e.g. for geometry no 10,

ext_fin_geom no 10 finishing not required:



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3.6. Component representation

The CADEXCATS workpiece representation model can represent typical turned components, as

illustrated in Figs. 2 and 3. This model represents the data in the following sequences:

1. Blank size;2. External roughing features (including complex features);3. Internal roughing features (including complex features);4. External primary nishing features (including complex features);

5. External secondary nishing features;6. Internal primary nishing features (including complex features);

7. Internal secondary nishing features;8. External nishing features without further operations;

9. Internal nishing features without further operations;

10. General information about component;11. External supplementary geometric information;12. Internal supplementary geometric information;13. External dimensional tolerances;14. Internal dimensional tolerances;

15. External geometrical tolerances (including surface nishing);16. Internal geometrical tolerances (including surface nishing).

4. The integration approach

After establishing the workpiece representation model, the integration system (CADEXCATSsystem) is used to transfer the CAD database of turned components and generate the component

representation in a format which can be processed by the tool selection system EXCATS. The systemconsists of three essential parts, i.e. a CAD system for component modelling, the IGES neutral formatand pre-processor, and the CADEXCATS processor. The CADEXCATS processor further contains two

sub-processes respectively for processing IGES data and feature recognition. In this approach, a CADmodel of a turned component is rst generated and translated into an IGES protocol via the IGES pre-

processor. In the CADEXCATS process, data extracted from IGES is processed and nally, the featurerecognition approach is converted automatically into feature based component representation to provide

full information as direct data input to the EXCATS system.

4.1. Generation of CAD models

For each turned component, two separate drawings are generated for nishing and roughing geome-tries respectively, to guarantee clarity of information representation. The roughing drawing contains theroughing prole, nishing prole, and blank shape and size. The nishing drawing represents the exact

prole of the nal component, secondary geometries and contains further non-geometric informatione.g. supplementary dimensional and technological information. i.e. tolerance, surface nish, and generalcomponent information. It would be possible, at a later stage to combine nishing and roughing



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drawings (as partially demonstrated in the roughing drawing), when adequate space is available in thedrawing for a clear indication of rich technological information, e.g. by making the drawing to a larger

scale for small turned components.

Both projections and cross-sections are accepted for description of a turned component which mayhave both external and internal operations. The internal geometries are represented by dashed lines in the

projection drawing, while in the full cross-sectional drawing they are represented by solid lines with thesections hatched.

The layer structure of AutoCAD is utilised to facilitate the data management of CAD models. In thenishing drawing, for example, ve different layers are assigned respectively to the primary entities andpart-off in the main projection, internal geometries, which appear as dashed lines, secondary geometric

entities (e.g. threads and grooves), annotation entities (e.g. surface nish), and centre lines of allprojections. The roughing drawing differs from the nishing drawing only in that, layers 3 and 4 are

used for nishing geometry and blank, respectively.All supplementary dimensional information and technological information are modelled according to

British Standard BS 308 and appear in the main projection. Instead of symbols, two-letter strings areused to indicate geometrical tolerances and to simplify CAD modelling. These two letters are character-

istic of the geometric tolerance, e.g. the atness is indicated by `FL', roundness by `RD', etc. Similarly,surface nish is dened by `SF', e.g. `SF 0.2' stands for a surface nish of 0.2 mm.

4.2. IGES neutral format

Among various neutral format data standards, IGES is selected because of its wide acceptance and

sophistication (Owen & Bloor, 1987). In IGES, a product model is described as a collection of geometricand non-geometric entities, typically in ASCII format. All IGES le properties are effectively utilised in

CADEXCATS. For example, the layer identity allows for the utilisation of CAD layers for efcient datamanagement.

IGES is less efcient in representing non-geometric information, e.g. dimensions and tolerance. All ofthe non-geometric information is distributed in a group of IGES annotation entities, which implies acomplicated process for the extraction and re-construction of the related information into a singleelement. This problem, however, has been successfully addressed in the current work, as described later.

4.3. Processing IGES data

In CADEXCATS, the IGES data of a turned component CAD model is extracted and processed asgeometry based data. It is only at the nal stage that all the data are converted into feature based data

using feature recognition. A brief description is given in this section with full details presented in Section4.4. Firstly, all relevant information for the CAPP process is acquired from the numeric database of theIGES le and classied according to its functionality. Secondly, the true origin of the turned component

is located and the new co-ordinate system is established for the CAD model generated using the WCSsystem of AutoCAD. Thirdly, because of its central line symmetry, all data are converted into 2D upper

proles to simplify subsequent data processing. Fourthly, the geometric features are re-sequenced tofull the requirement of the CAPP application. Finally, a novel method is employed to automaticallyextract and construct supplementary dimensional information and technological information from theIGES neutral format and subsequently establishes their relationship to geometric features.



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Fig. 4. Rules for the turned features recognition based upon the upper prole drawing.

Fig. 5. Denition of rules for recognition arc features based upon the upper prole drawing.


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4.4. The feature recognition approach

The feature recognition approach has long been realised (Van Houten, 1992) as the key to reducing

ambiguity and providing consistency in product data interpretation, whilst offering exibility to CAD

modelling. Based on this approach 13 basic geometric features are dened to describe the geometry of aturned component, as illustrated in Figs. 4 and 5. During the recognition process, the co-ordinates of thestart and end points (and for an arc, the centre point) together with the direction of the entity are noted.The direction is dened such that the external and internal geometries form a continuous counter clock-

wise and clock-wise path respectively, in the 2D upper prole drawing.As discussed earlier, complex features such as recesses and shoulders require special consideration

during cutting tool selection. For example, a recess would usually require two opposite hand tools tomachine and the presence of a shoulder could signify a set-up change. For this reason, they are both

dened as complex features for feature recognition.


Fig. 6. The conguration of the integrated system.


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Supplementary dimensional information and technological information, such as dimensional andgeometrical tolerance, general component information and surface nish (which have been dened in

Section 3) are converted into feature based data via the feature recognition approach, as demonstrated inmore detail in Section 5.

5. CADEXCAT Structure

The CADEXCATS is a modular based system containing three main programmes (readcad1, read-

cad2 and connfct) allowing independent operation and future incorporation of new functions. Asshown in Fig. 6, the IGES les for nishing and roughing operations are parallel processed by readcad1

and readcad2 respectively to produce two les which are then merged by connect into the nalcomponent representation le. readcad1 is designed to process the IGES data for nishing operationsand comprises ve sub-routines. The readcad2 programme is used to process the data for roughing

operations and comprises two sub-routine programmes. The connect.c programme is used to merge theoutput les into one single le that represents the nal output of turned component obtained fromCADEXCATS.


Fig. 7. The technical drawing of the second example (a) nishing and (b) roughing.


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6. Illustrative examples

Two examples are presented in this section to demonstrate the operation of the system developed. In

the rst, the technical drawing is shown in Fig. 2. The automatically generated nal component repre-sentation le is in complete agreement with that shown in Fig. 3 which is, in fact, the componentrepresentation le based on the CADEXCATS workpiece representation model.

The technical drawings for the second example is illustrated in Fig. 7 shows and the corresponding

component representation le generated by the CADEXCATS system is shown in Fig. 8. The component


Fig. 8. The component representation le of the second example generated from CADEXCATS system.


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contains both external and internal geometries, which further comprise primary and secondary features.A recess and two llets are present in the external geometry. The external prole requires a second set-up

in this case. With a general surface nish requirement of l mm, nishing operations are necessary for the

whole turned component. Furthermore, the supplementary dimensional and technological information,such as general component information, dimensional tolerance and surface nish is included in the

component representation le.

7. Conclusions

A novel system, CADEXCATS, has been developed to integrate a CAD system and a generativesystem for cutting tools and condition selection for turned components. The system is based on the IGES

neutral format and feature recognition approach.As an integral part of the work, a novel workpiece representation model is developed by employing

operationally linked keywords. The model is capable of representing most primary and secondarygeometric features and supplementary dimensional and technological information. Further, a set ofpreliminary rules are established to identify CAPP related functions which could result in time savingduring subsequent CAPP processing.

The current integration concept demonstrates that a sophisticated workpiece representation model iscapable of completely representing turned components. It is in fact the rst step towards a successfulintegration between CAD and CAPP. By employing IGES, such integration provides independence from

commercial CAD systems and promotes its full exploitation.As shown in illustrative examples, CADEXCATS is capable of processing and representing sophis-

ticated turned components including nishing and roughing operations. In addition to the representation

of external and internal operations, which comprise primary and secondary cutting actions, the supple-mentary dimensional information and technological information are also included. In particular, further

information is provided for the automatic determination of set-up, complex features, surfaces requiringno nishing and blank geometry.

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