Int J Adv Manuf Technol (2001) 17:39–53 2001 Springer-Verlag London Limited

Integration Planning Model of IDEF0 and STEP Product DataRepresentation Methods in a CMM Measuring System

Z.-C. Lin and J.-J. ChowDepartment of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan

The measuring process using a CMM involves a large amountof data. It is necessary to understand and clearly define thedata required by the measuring process and the relationshipsof these data before incorporating automation into a CMMsystem. This paper uses the IDEF0 model to analyse themeasuring function requirements for solving the problem ofambiguous internal information flow and material flow duringthe measuring process. A data module for the CMM measuringsystem was developed using the EXPRESS language in STEP,to support the IDEF0 function process module. An informationflow design model was also established, which integrated theIDEF0 process requirement analysis model and the EXPRESSdata module. The objective is to enhance the efficiency of thedevelopment of measuring systems by system designers, and toprovide a basis for future development of measuring infor-mation systems using STEP data formats.

Keywords: CMM; Data representation; IDEF0; STEP

1. Introduction

In recent years, the introduction of CAD and CAM has dramati-cally improved product design and manufacturing capabilities.To improve product quality, high-precision machining equip-ment becomes essential. Precision measuring instruments arerequired for inspection to ensure product reliability and pre-cision. To support automation procedures in a manufacturingsystem, the measurement technologies must meet the require-ments of accuracy, reliability and flexibility. A coordinatemeasuring machine (CMM) possesses the capability of measur-ing in 3D space, of computer control of operations and of dataprocessing. In addition to improving the speed of the inspectionprocess and labour productivity, it also provides accuracy andflexibility. Therefore, the CMM has become an extremely

Correspondence and offprint requests to: Professor Z.-C. Lin,Department of Mechanical Engineering, National Taiwan Universityof Science and Technology, 43 Keelung Road, Section 4, Taipei,Taiwan 106. E-mail: zclinKmail.ntust.edu.tw

important measurement tool in the field of computer-integrated manufacturing.

The incorporation of a CMM system into a manufacturingsystem often suffers from poor integration after the measuringsystem is established. There is often a lack of understandingby participants of the entire measurement process. The planningof the measurement system is often not carried out with theoverall picture in mind. This is especially crucial in the analysisand design of the overall framework of the measurementsystem, in the establishment of system data standards and inthe confirmation of system requirements, all of which mustaim at achieving the maximum operability. The incorporationof computer-integrated manufacturing relies on the approachof top-down planning and bottom-up implementation. Thus,the first task of planning a measurement system is to investigateand study the information flow and material flow requirementsand the actual manufacturing conditions of the entire system.The goal is to search for possible solutions and the carry outassessment and optimisation. This procedure is called systemanalysis (SA). The outcome of SA is then used as the standardfor system design (SD). The analysis and design of a CMMmeasurement system are highly complex tasks. To give parti-cipants a better understanding of the relations among varioussubsystem devices, SA and SD use a graphical description [1]to present clearly a complex system so that they can achievethe objective of integrating the measurement system with theentire manufacturing system.

Among the studies in the field of CMM measurement plan-ning, Medland et al. developed a CAD and CMM integratedmeasurement system, which located the features of measuredobjects from CAD data and then produced automatic measure-ment planning. The planning includes feature identification,probe selection, and the establishment of the minimum numberof probe replacement and measurement directions [2]. Forstudies of the design of entire measurement systems, Reimannand Sarkis in 1994 applied a CAM planning developmentframework for workpieces. They used the IDEF0 method torepresent their system flow [3].

The above studies have currently solved the problem ofautomatic measuring planning (including such strategies asprobe selection, measuring sequence [4] and selection ofmachine model). However, systematic analysis of the CMM

40 Z.-C. Lin and J.-J. Chow

measuring process (including planning of workpiece measurementand measurement execution) is still lacking. In more complexmeasuring planning issues, an SA method must be adopted torepresent the detailed functional requirements of a systembefore the measurement system can be designed and developed[5]. The internal operational behaviour is the key to systemintegration. Gu and Chan presented an object-oriented measure-ment planning system using the representation of data model,which had received the STEP certification of ISO 10303.The system includes inspection procedure planning (IPRP) andinspection path planning (IPAP). Results obtained from IPRPare entered into IPAP to produce the complete object-orientedmeasurement sequence planning [6].

This study uses the IDEF0 model to analyse the measurementfunction requirements to solve the problems of ambiguousinformation flow and material flow in the measurement process.This enables the measurement planners and system designers tounderstand clearly the measurement procedures for workpiecesmachined by lathes and machining centers. To implement theapplication of the IDEF0 function requirement analysis of aCMM system in the design of a measurement system, weintegrated a CMM system data module constructed using theEXPRESS language of STEP and an IDEF0 model to producean information flow design model. This model enables systemdesigners and program developers to understand the detailedinformation flow of a measurement system and to develop asuitable CMM measurement system based on this model. Atpresent, both SA and SD put the emphasis on the planning ofmanufacturing machining units [7]. Detailed and precise plan-ning standards are yet to be developed for system analysisand design of a CMM. This paper is an attempt to remedythis deficiency.

2. IDEF0 Model of CMM Measurement

2.1 IDEF0 Model

IDEF0 uses a top-down dissection approach in systems analy-sis. It forces the sharing of interactions and data amongfunctional members. A graphical representation turns it into ahierarchical and structural functional model as shown in Fig. 1.

In an IDEF0 model, there is a node number on the bottomright hand corner of the diagram. This number tells whichhierarchy of the entire model this diagram belongs to. Anode index and node tree provides an overview of all theconnected diagrams.

The uppermost diagram of an IDEF0 model is called theA-0 diagram. This diagram contains only one activity box,whose title represents the subject of the IDEF0 model. The A-0 diagram also defines the scope and direction of this model.The various diagrams after dissection of the A-0 diagram mustremain within this scope, otherwise, another model must beestablished. The purpose of establishing a model must be givenin the A-0 diagram stating the intention and viewpoint of themodel builder.

As an IDEF0 model is dissected downward, the ICOMstructure elements inherit the dissected sublayers. If the arrowsof the ICOM elements appear only in the drafts of a certain

Fig. 1.Hierarchical structure of IDEF0.

hierarchy, instead of inheriting the sublayers, the arrow trianglecan be put in (), as shown in Fig. 2. If the ICOM elementsare not defined in the parent layer but appear in the sublayer,then the arrow line can be put in (), as shown in Fig. 2.These two arrow signs are called tunnelled arrows.

2.2 Establishment of the Initial Layer of the IDEF0Model

The first layer, in establishing the measurement planning model,is called the A-0 layer, which is the initial layer of the entiremodel. All system analysis activities start to be decomposedfrom this initial layer. There are two important indicators inestablishing the A-0 layer: one is “viewpoint” and the otheris “purpose”, as shown in Fig. 3. These two are crucial factorsin the decomposition from the A-0 layer toward the followinglayers. “Viewpoint” refers to the position of the model builderin the system. Given the same system, different model buildersmay have different system concerns in terms of functions.Therefore, the viewpoint of the builder should be indicated. Inthis paper, the model of measuring functions for a machinedworkpiece on a lathe was established from the viewpointof the “CMM system planning engineer”. The layers afterdecomposition can be said to use a “micro” perspective toexpress the functional aspect of the CMM system. The higherup the layer, the more abstract are the drawings. The purposeof the model established in this study is in understanding how

Integration Planning Model 41

Fig. 2.Example of tunnelled arrow.

Fig. 3. Initial layer of the IDEF0 model during the production process.

to plan the information flow direction and material flow direc-tion in the CMM measuring process. It is an attempt to expressclearly the relationship between all the detailed activities ofthe entire measuring system through system decomposition,inheritance and association so that the system flow process canbe accurately described. The subfunctional models of the Alayer are shown in Fig. 4.

2.3 A5 Node Model – CMM Measurement

The A5 node represents the major functions required by “CMMmeasurement”. The A5 activity box is dissected into threesubfunctional modules, namely “draft data extraction – A51node”, “planning of measurement environment – A52 node”,and “workpiece measurement execution – A53 node”. Thesethree functions can be further dissected into more refinedfunctions to describe the actions of these nodes. Figure 5shows the model of this node.

The purpose of measurement environment designation isfor making preparations before measuring, including the selec-tion of measuring hardware, fixture planning and path plan-ning. All information requirements of these tasks must bespelled out in the A5 node so that system designers understandthem clearly.

The A52 node is “planning of measurement environment”.Its input requirements are part code and part engineeringdraft. The relationship between the planning and execution ofmeasurement can be seen at the A5 node. All preparationsfor the environment planning must be completed before the

42 Z.-C. Lin and J.-J. Chow

Fig. 4. Subfunctional models of the A0 layer IDEF0 model during the production process.

measurement task can be executed. Hence, a “planning com-pletion message” is used as the control information of“execution of workpiece measurement”. The planning form andmeasurement path data are entered into the activity box of“execution of workpiece measurement (A53)”.

Draft Data Extraction – A51 Node

When designing the part engineering draft, design engineersusually mark the geometric tolerance and dimensional toleranceon the draft. Since the draft is stored in CAD, the problembecomes how to extract tolerance and dimensional data fromthe design draft for use in planning the measurement environ-ment and executing workpiece measurement. Therefore, thetask of extraction must be completed before the two majortasks of planning and execution.

The subsystem of data acquisition [8] in this study adoptsthe drawing function of AutoCAD and AutoLISP to constructthe function menu.

Planning of Measurement Environment – A52 Node

In this section, the planning of the measurement environmentis divided into four subfunctional modules, namely, “selectionof CMM type (A521 node)”, “decision on probe use (A522node)”, “planning measuring points and path (A523 node)”and “decision on measuring fixture (A524 node)”. Figure 6shows the model of A52 node.

Selection of CMM Type – A521 Node

The mechanism in the activity box for executing the selectionof the CMM model is the planning engineer and the selectionprogram of the coordinate measuring machine type. Control ofthis function includes the CMM types and the learning knowl-edge extraction model, which will be further discussed in thesubsystem sections. The output of this function is “selectedmachine type code”. The selected machine type code is storedin the “designated data of measuring environment”. This desig-nated data becomes the preparation basis for the execution ofworkpiece measurement.

Integration Planning Model 43

Fig. 5.Subfunctional modules of the A5 node model.

Decision on Probe Use – A522 Node

The use of a measuring probe involves the workpiecemeasuring direction, the measuring of workpiece features andsimultaneous multiprobe designation conditions. The currentavailability status of the probe selection in the factory has tobe examined. Hence, it is necessary to decide first on theCMM type, then determine the probes that can be used forthe CMM type which also meet the needs of workpiece to bemeasured. Therefore, probes suitable for the CMM type areused as the control information for probe selection. The outputof this function is “probe code”.

Planning Measuring Points and Path – A523 Node

Before planning the part measuring points, the measuring facesmust first be determined. After the part “measuring pointanalysis” is completed, the “measuring point positions” arederived, which are entered into the “planning of measuringsequence” to produce the optimal measuring sequence. Therelations are illustrated in Fig. 7. The optimal measuring

sequence is a sequencing issue. The purpose is to obtain theshortest measuring time. To decide the optimal measuringsequence, all factors affecting measuring time during the entiremeasuring process must be considered.

For measuring points whose measuring sequence is alreadyplanned, the path between one measuring point and anothermust be entirely without obstacles. Path planning is still neces-sary to plan a suitable path. For this part, the data to beentered include “measuring point position”, “measuring pointaxial vector”, and “measuring point normal vector” beforecollision-free paths are planned.

Decision on Measuring Fixture – A524 Node

The fixture planning subsystem [9] can automatically searchfor a suitable fixture support point and decide on suitablefixture devices. These capabilities save time spent in selectinga fixture and deciding on fixture support points. The decisionon the measuring fixture is subject to “measured workpieceshape features” and “fixture availability status”. The output of

44 Z.-C. Lin and J.-J. Chow

Fig. 6. Subfunctional modules of the A52 node model.

this action includes “fixture group code” and “fixture allocationcode”. Figure 8 shows the model of this node.

Workpiece Measurement Execution – A53 Node

In a manufacturing facility, the measuring planner and theCMM operator are rarely the same person. Thus, there are anumber of communication interface issues between planningand execution. This section describes the standard executionactions and internal information flow and material flow duringexecution. Figure 9 shows the subfunctional modules of A53node model.

Workpiece and Fixture Setting – A531 Node

First, obtain the fixture group code and fixture allocation codefrom the measurement environment designation form. Let theplanning engineer install the fixture on the CMM table. Loadthe workpiece by a robot arm or manually. Enter the workpiececode of this loaded workpiece to record its measuring status.

Measuring Environment Designation – A532 Node

This subfunction requires the input of the probe code, whichcan be obtained from the measurement environment designationform. The other input required is the basic face. By enteringthis data, a basic face on the workpiece, such as theXY face,YZ face or theZX face, has been selected, and the CMM hasbeen informed. This designation is necessary before conductingautomatic workpiece measurement for the first time.

Designating Compensated Coordinate System – A533Node

The actions in the A531 and A532 nodes must be completedbefore proceeding to the A533 node. This action must becompleted by manual intervention by the CMM operator. How-ever, it is needed only for the first workpiece measurement.During the measuring process for the same type of workpiece,the designated compensated coordinate system can be stored

Integration Planning Model 45

Fig. 7. Subfunctional modules of the A523 node model.

in the software memory, and later on read directly for automaticmeasurement after the next workpiece is loaded.

Measurement Execution – A534 Node

The information flow output of this section includes “statisticmanufacturing process control” and “inspection status infor-mation”. The former records data of the measurement resultat a certain period of time, from which one can discern themanufacturing trend when manufacturing this part. This allowsus to adjust the manufacturing process and produce productswhose specifications can approximate to the general designvalues. The inspection status information records whether theworkpiece passes inspection. This information tells us whetherthe measured workpiece is of good quality or is defective. Theoutput end of the material flow shows the machined workpieceto be a “product” or “defect”. Products that have passed theinspection can be stored in a warehouse for assembly orpackaging and delivery later on. The deviation of the defectiveproducts can be assessed to determine the possibility ofremachining.

3. Express Data Module of a CMMMeasuring System

3.1 Introduction of STEP

A large amount of data is generated for a product from itsfunctional requirements, design analysis, manufacturing, inspec-tion and quality control. Often due to different organisationalstandards or different computer systems, these data cannot beshared effectively by the personnel in product developmentand those in the machining process. Hence, it is necessary toestablish a common data conversion format that allows com-plete conversion and consistent description among differentcomputer systems. The International Standard Organization(ISO) is an international standard for computer data interpret-ation and product data exchange [10].

Framework and Contents of STEP

STEP consists of many parts. Each part provides a preciserepresentation and format for product information exchange for

46 Z.-C. Lin and J.-J. Chow

Fig. 8. Subfunctional modules of the A524 node model.

describing the entire life cycle of a product. This format isindependent of any specific computer system and covers alarge number of application fields and systems. Its frameworkcan be summarised into the following six major parts:

1. Description method.2. Implementation methods.3. Conformance testing methodology and framework.4. Integrated resources: these resources can be further divided

into generic resources and application resources.5. Application protocols.6. Abstract test suites.

The hierarchy of this framework is shown in Fig. 10. Itshows that part description is based on the EXPRESS languagewhich describes product information, and establishes integrateddata. The applications listed in the application protocols areexecuted through the implementation method, and supportedby conformance testing through abstract test suites. This is thebasic framework of the entire STEP product model.

Model Implementation Language – EXPRESS

The basic part of the STEP product model is the productdescription method, in which the EXPRESS language is usedas the standard language for describing product models [11].In the description method, this language is used as the formalmodular language for STEP product model development. It isused to describe information to be contained in a productmanufacturing cycle. It is a conceptual language and providesthe product information definition with conformance. Thischaracteristic guarantees understanding by users, and readingand execution by computers. It also possesses the characteristicof object-oriented hereditary. However, it is not equipped withthe function for establishing user interfaces containing inputand output usually found in programming languages in general.Consequently, an implementation method is required to store,retrieve, operate, and use the product data defined by theEXPRESS language. In the parts for integrated resources andapplication protocols in the STEP product model, this languageis used to define the product data structure. The description

Integration Planning Model 47

Fig. 9. Subfunctional modules of the A53 node model.

method also specifies a data model graphical representationmethod called EXPRESS-G language. The graphical represen-tation allows easier and clearer understanding of the definitionof the entire product data structure.

3.2 The Express Data Module

The schema to be represented can be divided into three datamodules: part data module, resource data module and inputdata module, defined as follows:

1. Part Data Module

This data module contains the part entity, part measuringfeature entity and measuring path data entity

ENTITY part;id :identificationFno;name :STRING;feature :SET [1:?] OF meas-feature;drawFfile :STRING;

maxFvol :REAL;material :STRING;NCFfile :STRING;tolerFfile :STRING;maxFaccuracy :REAL;

UNIQUEurl :id;

ENDFENTITY;

The part entity is defined as the basic data for a part. Attributeid denotes the part code, representing the identification numberof the part. This id number is the object identifier (OID) in theobject-oriented database. Every object has one, and only one,OID. That is, the relation equation for different objects allowsreference to be made directly to other objects through the idnumber. The OID has many other advantages. It can storesynthetic objects using the least storage space; it can directly andrapidly store and retrieve objects; it allows the system to storecorrectly and retrieve an object even after the contents of theobject are altered because OID is independent of object contents[12]. Name denotes the part name. The attribute feature defines

48 Z.-C. Lin and J.-J. Chow

Fig. 10.The framework of the STEP product model [10].

which basic element features constitute a part. Material definesthe part material. TolerFfile denotes the file name of part geometricand dimensional tolerances data. This file produces an ASCII fileby extracting data from the draft, which is used as the basic dataof the measuring points. Attribute NC file is the NC file nameof the part. The NC program is produced by the CAM subsystemof the manufacturing system.

ENTITY meas-feature;id :identificationFno;probeFno :Probe;partFid :identificationFno;style :styleFtype;dimension :REAL;tolerFtype :tolertype;tolerFvalue :REAL;normalForient :UnitFvector;reqFpts :INTEGER;feaFseqFno :INTEGER;

UNIQUEurl :id;

ENDFENTITY;

TYPE tolertype=ENUMERATION OF (Straightness, Flatness,Circularity, Sphericity, Cylindricity, Conicity)ENDFTYPE;

TYPE styleFtype=ENUMERATION OF (Plane face, Cylinderface, Cone face, Sphere face)ENEFTYPE;

ENTITY unitFvector;a,b,c :REAL;

WHERElengthF1 :a**2+b**2+c**2=1.0;

ENDFENTITY;

Each part has more than one measuring feature such asplanes and holes. Each measuring feature requires one probeto complete the measurement of all measuring points. Itsattribute is the feature id, i.e. its OID. The part id defines thecode number of the part, probe number is probe-no, featureface is style, required dimension is dimension and tolerancetype is toler-type which refers to the geometric tolerance. Thetolerance value is tolerFvalue, feature face normal vector isnormalFvector, required number of measuring points is regFptsand feature face measuring is sequence is featureFseqFno whichdefines the measuring sequence number of feature faces.

ENTITY meas-data;featureFid :identificationFnoptFseqFno :INTEGER;ptFcoord :point;refFpt :point;pFaxis :unitFvector;pFnormal :unitFvector;

ENDFENTITY;

ENTITY point;x :REAL;y :REAL;z :REAL;

ENDFENTITY;

This entity defines the measuring point data after measuringsequence and path planning. The attribute is featureFid, whichdefines the feature face OID, measuring point sequence numberis ptFseqFno, measuring points coordinates is ptFcoord, measur-ing point normal vector is pnoraml, measuring point axialvector is paxis and reference point of the measuring pointis refFpt.

2. Resource Data Module

This module contains the entity, measuring fixture entity, meas-uring probe entity, measuring environment designation entityand fixture allocation entity.

ENTITY cmm;id :identificationFno;xFrange :STRING;yFrange :STRING;zFrange :STRING;resolution :REAL;accuracy :dim;cmmFdim SET[1:5] OF probe;holderFid

UNIQUE;url :id;

ENDFENTITY;

ENTITY dim;length :REAL;width :REAL;depth :REAL;

The CMM entity defines the basic data and functions ofCMM. Its attributes include the CMM type id, defining themachine id number; xFrange, yFrange, zFrange, defining themeasuring range ofx, y, andz, respectively; resolution, defining

Integration Planning Model 49

machine sensitivity; accuracy, defining machine precision;cmm†dim, defining machine dimension. The data type is entitydim. Holder id denotes the probe number, whose data type isthe entity probe set.

ENTITY fixture;GTFcode :BINARY;name :STRING;spec :dim;usage :STRING;status :STRING;

ENDFENTITY;

The measuring fixture is coded by planning engineers inadvance, it is then used as the resource database by ancomputer-aided fixture-planning system. This entity defines thebasic data of measuring fixture, whose attributes include GTcode, name, specifications, usage, and status of the fixture.

ENTITY probe;id :identificationFno;diameter :REAL;srpportFCMM :SET [1:?] OF;status :STRING;

UNIQUEurl :id;

ENDFENTITY;

The entity probe defines the probe data and current usagestatus. Its attributes include probe id, probe diameter, suitableCMM type (supportFCMM) and probe status.

ENTITY measFsetup;planFid :identificationFno;partFid :identificationFno;cmmFno :identificationFno;planner :person;planFstatus :STRING;

UNIQUEurl :planFid;

ENDFENTITY;ENTITY person;

name :STRING;id :identificationFno;

ENDFENTITY;

Each part has a measuring environment designation entity.Attribute planFid is its OID; partFid defines the part OID of theenvironment designation; cmmFno defines the CMM type’s OIDsuitable for this environment designation. This OID is selectedby the CMM type selection program. The planFstatus defines thecontrol inspection number before workpiece testing. Testing iscarried out only after inspection planning is completed.

ENTITY fixture-config;planFid :identificationFno;useFfixture :SET [1:?] OF fixture;configFno :identificationFno;cmmFno :identificationFno;

ENDFENTITY;

For measuring environment designation, a part requires manymodules of a fixture to achieve a secure fixturing in most

cases. Attribute config†no is the part OID; planFid defines theenvironment planning id of the fixture allocation entity;cmmFno defines the OID of the CMM machine used by thisfixture allocation entity; useFfixture defines the fixture used bythis entity.

3. Input Data Module

This module contains the manufacturing order entity, manufac-turing order detail entity, workpiece measuring informationentity and part modification record entity.

ENTITY mfg-order;ABSTRACT SUPERTYPE OF (order);

id :identificationFno;startFdate :data;finishFdata :data;

UNIQUEurl :id;

ENDFENTITY;

ENTITY date;day :INTRGER;month :INTRGER;year :INTRGER;

ENDFENTITY;

This entity defines the information of the machined work-piece. The attributes include machined workpiece part id, startdate and finish date of an entire batch of machined workpieces.Its data type is the entity date.

ENTITY m-oirder-detail;SUBTYPE OF (mfg-order);

partFid :identificationFno;finisgFqty :INTEGER;startFstatus :STRING;finishFstatus :STRING;reqFqty :INTEGER;

ENDFENTITY;

Most manufacturing orders have more than one workpiece.The manufacturing order detail entity inherits the manufacturingorder entity. Its attributes include the code number of the part,partFid; the finished quantity, finishFQTY; the status of startingmeasuring, startFstatus; the status of finish measuring,finishFstatus; and the required quantity, reqFQTY.

ENTITY lot;lotFid :identificationFno;partFid :identificationFno;mfgForderFid :identificationFno;QCFstatus :STRING;measureFdata :data;setupFstatus :STRING;

ENDFENTITY;

The workpiece measuring information is used in on-siteworkpiece measurement. Workpiece id is a workpiece number.Each workpiece has one, and only one, workpiece id. A pieceof workpiece measuring information states the measuring statusof a machined workpiece. Its attributes include the code number

50 Z.-C. Lin and J.-J. Chow

of the part lot, lotFid; the code number of the part, partFid;manufacturing order id, mfgForderFid; status of quality control,QCFstatus; the date of measuring, measureFdata; and the statusof set-up part, setupFstatus.

ENTITY history;partFid :identificationFno;modifyFdata :data;modifyFperson :person;modifyFcontent :STRING;

ENDFENTITY;

A part may undergo a number of modifications between theplanning and the measuring process. This entity defines thepart modification information for the purpose of informationmaintenance. Its attributes include part id and modify date.The data type of the modify data is the entity date and thedata type of modify person is the entity person.

4. IDEF0 and STEP Integration Model

This section discusses the supporting relationship between theICOM (input, control, output, and mechanism) elements of anIDEF0 system functional requirement analysis and the entityand attribute of the EXPRESS data modules. In a nutshell, theICOM elements of IDEF0 can be fully supported by the threeEXPRESS data modules of output, control, and input, asshown in Fig. 11. In the figure, “measurement environmentdesignation” is the activity box of the IDEF0 functional require-ment analysis, whose node is “A52”; part number and plannernumber are the input information of the activity box. Availablesystem resources for the control information: planning com-

Fig. 11.A schematic diagram of the IDEF0 and EXPRESS data modules for the measuring system.

pletion message, planning record data, measuring path andpoint data constitute the output information. Part, history, meas-setup, meas-data, fixture, and probe are all entities ofEXPRESS.

Take the integration between part number and part as anexample. The part number is integrated with the attribute “id”of entity “part” by a corresponding approach. It is alreadyknown during design that the information of “part number”must be entered for functional analysis of “measuring environ-ment designation”. The attribute “id” of entity “part” allowsprecise identification of the position and data type of “partnumber” in the database. The “planner number” correspondswith the attribute “person” of “history”; “available systemresources” corresponds with the “status” of “fixture” and the“status” of “probe”, respectively; “planning completion mess-age” and “planning record data” correspond with attributes“planFstatus” and “planFid” of “measFsetup”, respectively; and“point data of measuring path” correspond with “measFdata”.

This integration model possesses the following advantagesfor system designers using the IDEF0 model for analysis:

1. Designers can understand what information is needed in aparticular function.

2. Data formats are clearly and completely defined by theEXPRESS object language. In addition to its object-orienteddata packaging and inheritance concepts, it further possessesthe capability of integrating schemas from different sourcesand systems.

3. It possesses both the functions of functional requirementanalysis and software information flow analysis.

4. System specifications are very precise, which promotesunderstanding of the detailed information flow of a measur-

Integration Planning Model 51

ing system by software coding personnel. The integrationof the IDEF0 model of a modelling measuring system andthe EXPRESS model fulfils the functions that cannot berealised by individual models. In addition, owing to theobject-oriented concept of the EXPRESS language, themeasurement data module developed by the language maybe used for reference in future development of an object-oriented measuring information database.

A brief example is described in the following. Table 1 givesthe integration report of IDEF0 and EXPRESS, the input valuesof the operations are shown in the righthand column in Table1. Among them, reference coordinate, measuring point normalvector, measuring point axial vector, and measuring pointposition are all vectors or coordinate values. The rest denotedata values, sequence number, or file names.

5. Development Flowchart of aMeasurement Information System

The eventual purpose of STEP is to establish a universalcommon data standard, which can represent product data duringthe product cycle [13]. The aim is to allow a free interchangeof engineering data, which originate from CAD, CAM, CAE,CIM, and logistics systems, among different work platforms.In the STEP standard, EXPRESS is a modelling language. TheEXPRESS model data must be written into a STEP file laterso that the STEP file can be converted to a real programminglanguage (e.g. C++, ObjectStore).

The STEP entity file is an ASCII code text file, whichbegins with ISO-10303-21 and ends with END-ISO-10303-21.The contents can be divided into two major sections: headersection and data section. For example, Fig. 12 shows the fileformat of a STEP entity file, such as title, data and origin.

The procedures of creating a STEP file are as follows:

1. A measuring system data module defined by theEXPRESS language.

Table 1. Integration report of IDEF0 and EXPRESS.

IDEF0 ICOM EXPRESS entity EXPRESS attribute Input value

Workpiece and fixture setup finish status LOT setupFstatus O.K.Workpiece lot number LOT lotFid 87-001-321Fixture allocation code FIXTURE-CONFIG configFno 1102100QC status LOT QCFstatus passedReference coordinate and original point MEAS-DATA refFpt (X, Y, Z)Probe code PROBE probeFno pH9CMM type code number MEAS-SETU cmmFno Ao1Fixture group code number FIXTURE-CONFIG GTFcode 1102100Measuring planning finish status MEAS-SETUP planFstatus O.K.Measuring point normal vector MEAS-DATA ptFunv (u, v, w)Measuring point axial vector MEAS-DATA ptFuav (u, v, w)Measuring point position MEAS-DATA xFcood (X, Y, Z)Measuring point sequence MEAS-DATA ptFseqFno P1 → P2 → % Pn

Part engineering draw PART drawFfile A003.dngGeometric and dimensional tolerance PART tolerFfile T-A003.datAccuracy requirement PART maxFaccuracy 0.01 mmPart maximum volume PART maxFvol 32.000 mm3

Fig. 12.The file format of a STEP entity file.

2. Use the EXPRESS translator to create a C++ class.3. Develop C++ programs to create STEP objects.4. Store STEP objects in an object-oriented database.

For the measuring information system discussed in thispaper, its eventual purpose is to establish the neutral databasestructure for a measuring information system independent ofother system structures. This structure acts as a bridge betweendifferent systems. As long as the data in a specific system canbe converted into this structure, they can be converted intodata that can be processed by other systems.

As mentioned earlier, we first established the IDEF0 pro-cedural module of CMM and then its EXPRESS data modulefor support. After that, a STEP file in the ASCII format iscreated for conversion into a real object-oriented programminglanguage. Figure 13 shows the information conversion pro-cedures of the CMM measuring information system in theSTEP environment. In the figure, the software tools used duringthe process of converting data into the STEP format include:EXPRESS language, C++ programming language, express2c++translator included in the ST-Developer software, ObjectStoredatabase and the ST-ObjectStore translator software.

52 Z.-C. Lin and J.-J. Chow

Fig. 13.The information conversion framework in a measuringinformation system.

The express2c++ included in the ST-Developer is applied inthe object classes of the C++ language converted from theEXPRESS data definition structure. Then, the information issent to the ObjectStore database. The STEP/OS translator inthe ST-ObjectStore translator software tools converts objectsin the ObjectStore into the STEP file format. In this fashion,we can further establish the measuring control information ofscheduling and the various fixtures required by the measuringsequence. The information obtained by actual measurement forreverse transmission to, and use in measuring control, can alsobe acquired. Therefore, the method recommended in this paperis applicable for measuring system information transmission inboth directions.

ObjectStore is an object-oriented database managementsystem developed by Object Design Inc., and used as anapplication tool in information operations. It has the follow-ing characteristics:

1. It is a data definition language (DDL), i.e. the class planningof C++.

2. It is a fully developed function database for informationoperations. Conventional data manipulation langrage (DML)is no longer necessary.

3. It provides an object id code, multiple inheritance and awide variety of data types.

4. It follows the principles of C++ data packaging.5. STEP files read or written by a system can be directly

converted by the ST-ObjectStore data converting softwaredeveloped by the STEP Tools International Inc., and storedas data with the help of ObjectStore.

The above characteristics demonstrate the fact that inaddition to the merits of an object-oriented database manage-ment system, using ObjectStore in integration also makes iteasier for combining with the C++ program. It is thus asuitable choice for system development.

6. Conclusion

A manufacturing environment equipped with a CMM systemnot only increases the manufacturing efficiency but alsoimproves product quality. However, owing to the system’scomplexity, compatibility problems often ensue after systemincorporation. This often prevents the realisation of theexpected effectiveness in the manufacturing system. This studyuses the IDEF0 system to analyse the functional requirementof measurement and to describe the correlation among varioussubfunctions. The objective is to solve the problems of ambigu-ous information flow and material flow during the measuringprocess and provide some help in practical applications.

Technologies related to measurement planning have beenmaturing in recent years. It is the right time for proposing anintegration model for the IDEF0 planning procedural modeland the EXPRESS data module of STEP. The purpose is toprovide an object-oriented measuring information flow designframework so as to increase the efficiency of system designersin developing measuring systems.

The objectives that can be achieved by this study of themeasuring functional requirement analysis of a machined work-piece can be summarised as follows:

1. It can plan, in a top down approach, the CMM measuringfunctions of a machined workpiece in a manufacturingframework. It also provides understanding of the effect ofmeasuring functions on the entire product manufacturingprocess and vice versa from the analytical model.

2. It can describe precisely the information flow and materialflow in the measuring planning and the execution of amachined workpiece.

3. The hierarchic analysis helps personnel of different levelsto focus their attention on a particular part of the measuringplanning process.

The study can also achieve the following objectives in theinformation flow design of a measuring system:

1. It can establish an information flow design framework fora measuring system and provide the development method

Integration Planning Model 53

for measuring information systems suitable for manufactur-ing systems.

2. The adoption of a design model of information flow inte-gration enables system analysis to be more efficiently usedin system design.

3. It can provide a reference for the future development ofmeasuring information systems using the STEP internationalstandard data format. This standard format is a neutraldatabase structure of a measuring information system, whichis independent of other system structures. This structureplays the role of a bridge between different systems. There-fore, as long as the data in a certain system can be convertedinto this structure, they can be converted into data that canbe processed by other systems.

References

1. K. Mandel, “Graphical process description – views and diagrams”,International Journal of Computer Integrated Manufacturing, 3(5),pp. 314–327, 1990.

2. A. J. Medland, G. Mullineux, C. Butler and B. E. Jones, “Inte-gration of coordinate measuring machines within a design andmanufacturing environment”, Proceedings of the Institution ofMechanical Engineers, B: Journal of Engineering Manufacture,207(B2), pp. 91–98, 1993.

3. M. D. Reimann and J. Sarkis, “Design for automating the inspec-tion of manufacturing parts”, Computer Integrated ManufacturingSystems, 7(4), pp. 269–278, 1994.

4. Z. C. Lin and S. C. Chen, “Measuring sequence planning dynamicprogramming”, International Journal of Computer Integrated Manu-facturing, 8(4), pp. 100–115, 1995.

5. J. Sarkis and Li Lin, “An IDEF0 functional planning model for thestrategic implementation of CIM systems”, International Journal ofComputer Integrated Manufacturing, Vol. 7 of ProductionResearch, 29(11), pp. 2239–2257, 1991.

6. P. Gu and K. Chan, “Generative inspection process and probepath planning for coordinate measuring machines”, Journal ofManufacturing Systems, 15(4), pp. 240–255, 1996.

7. G. J. Colqugoun and R. W. Baines, “A generic IDEF0 model ofprocess planning”, International Journal of Production Research,29(11), pp. 2239–2257, 1991.

8. Z. C. Lin and S. C. Chen, “The study of design data extractionfrom design drawing with application in measurement”, Inter-national Journal of Advanced Manufacturing Technology, 10, pp.99–109, 1995.

9. Ren Qing Huang, “Fixture planning of modular fixtures”, Thesisfor Master of Science, Department of Mechanical Engineering,National Taiwan University of Science Technology University,1994.

10. M. D. Chen, “Structure information system analysis and design”,Unalis Corporation, 1984.

11. Kun Jue Chen, “An integrated IDEF methodology for developingdatabase application models under client/server environment”, The-sis for Master of Science, Department of Mechanical Engineering,National Taiwan University of Science Technology University,1995.

12. David. A. Taylor, “Object-oriented information system”, Planningand Implementation, New York, John Wiley, 1992.

13. A. J. Medland, G. Mullineux, C. Butler and B. E. Jones, “Inte-gration of coordinate measuring machines within a design andmanufacturing environment”, Proceedings of the Institute of Mech-anical Engineers, B: Journal of Engineering Manufacture, 207(B2),pp. 91–98, 1993.