- Email: [email protected]
A traceability information model for CNC manufacturing
Computer-Aided Design 38 (2006) 540–551 www.elsevier.com/locate/cad
A traceability information model for CNC manufacturing Julio Garrido Campos *,a, Martin Hardwick b a
Department of Automation and System Engineering, Universidad de Vigo (Vigo University, Spain), E.T.S. Ingenieros Industriales, Campus Lagoas-Marcosende, 36200 Vigo, Pontevedra, Spain b Department of Computer Science, Rensselaer Polytechnic Institute, Troy, NY, USA Received 12 April 2005; accepted 24 January 2006
Abstract This paper proposes an information model for tracing CNC manufacturing operations. The objective of the model is to assure that traceability data is comprehensive and available for every CNC machined product, independent of the relationship between the subcontractor and the contractor. The prominent feature of the model is a link between CNC report data for a product instance, the CAD design and the CAM data. This link enables users to browse the traceability data and understand the relationships between the manufacturing process, the CAD design and the CAM data. The link is independent of the systems used to build the CAD and CAM data, and allows the users to be sure the manufactured product contains the required characteristics. Then if a product instance fails, this linkage will make possible to analyze the trace data and identify any exceptions or unusual conditions in the manufacturing process. q 2006 Elsevier Ltd. All rights reserved. Keywords: Traceability; Product characteristics; STEP; CAM; ISO 10303 AP238
1. Introduction Contractual relationships are often temporary, especially those linking a primary contractor (assembly company) with its subcontractors (supply chain companies). For many products, there is a traceability requirement that must be met by documenting the steps taken in the manufacturing process, so the data can be analyzed if a failure. When the manufacturing is performed internally, the process can be documented using systems that can be assumed to be available in the event of failure [1]. When manufacturing is performed externally issues can arise if the systems are no longer available or comprehensible. In order to contract more manufacturing tasks, industrial companies need to extend their ability to trace the execution of external manufacturing processes. One method is to require the partner company to use the same systems and procedures as the contractor company. This is, however, cumbersome and expensive, and therefore only practical when there is a lot of business between the companies. Another approach is to develop methods that can be used across an industry. Examples * Corresponding author. Tel.: C34 986 812610; fax: C34 986 814014. E-mail address: [email protected] (J. Garrido Campos).
0010-4485//$ - see front matter q 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.cad.2006.01.011
can be found in the automotive [2], aerospace [3], and pharmaceutical [4] industries. This paper describes a traceability model for CAD/CAM and Computer Numerical Control (CNC) machining domains. The primary purpose of the model is to support the flow of traceability information across these domains, so a company can trace the processes used to make a product even if it has been machined by different partners. The new model addresses two key problems of supply chain traceability: data understandability and data availability. The hypothesis of the model is that: by linking CNC report data, CAD design data and CAM process data, an efficient traceability data set can be developed. This former is system independent, and allows the partner companies to assure the quality of the manufacturing process at the time of manufacture and also in the event of a product failure. The new model is built on top of existing STEP (Standard for the Exchange of Product Data, ISO 10303) [5,6] models for CAD (AP-203 [7] and AP-214 [8]) and for CAM (AP-238 [9]). Most CAD systems can export AP-203 or AP-214 data, and many CAM systems are considering adding an AP-238 (STEPNC) export option. All STEP models are extensible and designed to support the product life cycle. The traceability model described in this paper extends these CAD and CAM models into the maintenance phase of the product life cycle for CNC machined products. Section 2 gives some background on the models used to build the traceability model. Section 3 describes an
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
541
Fig. 1. STEP-NC demonstration scenario.
experimental traceability system. Section 4 summarizes the modeling requirements determined from this experiment and Section 5 details the experiment implementation. Section 6 summarizes and proposes future research directions. 2. Background on STEP-enabled manufacturing and STEP-NC Flexible product data interchange is one of the critical success factors for many industrial collaboration scenarios. One of the objectives of STEP is to enable product data interchange [10]. STEP has defined a framework for depicting a complete representation of product data through its life cycle [11]. It defines, among other basic infrastructures, an object oriented information modeling language (EXPRESS, STEP part 11 [12]) and a file transfer format (STEP part 21 [13]). Using Application Protocols, STEP addresses many industrial data exchange requirements. There are protocols for drawings and for 3D geometry to use in many contexts, and protocols for specific kinds of products such as boats, buildings, and electronic circuit boards that are largely limited to their respective industries. One of the newest application protocols, AP-238, defines a model for exchange CNC machining data between Computer Aided Manufacturing and Computer Numerical Control systems [14,15]. AP-238 is a structured featured-based representation of process plans for manufacturing processes such as milling, turning, etc. and it is based on the geometric information of APs, such as AP-203, AP-214 and AP-224 [16]. So the use of AP-238 avoids CAM systems to redefine the product geometry because involved STEP APs share the same geometry data (shape and features). The CAM system just adds process information (manufacturing feature and tool path data) to the CAD data so the CNC has enough input to make the part. Fig. 1 shows how STEP-NC project [17] is applying AP-238 to supports CAM and CNC applications [18]. In this AP-238 prototype scenario, a CAD system makes an AP-203 data file describing the part geometry. A CADD system (Computeraided Drafting and Design) adds design requirements as Geometric Dimensions and Tolerances (GD&T). The CADD exports this data as AP-203 Edition 2, or as AP-224 file if the detailing also includes the definition of features. The CAM system adds process information (e.g. assigns tools and process
parameters for each feature) and exports the data to a CNC controller as an AP-238 file. Fig. 2 shows the generic structure of the AP-238 information model. An AP-238 file includes product geometric information as well as process information. The file is organized into a sequence of manufacturing operations called workingsteps. Each workingstep defines an operation performed on one or more features by a CNC machine tool. These workingsteps provide the basis for the workplan to make the product, and are generic descriptions, not linked to a specific format or code. AP-238 changes the focus of machining from axis path motions (ISO 6983 [19], known as G&M codes [20]) to volume removal operations applied to machining features. It provides and object oriented data model for CNCs, with a detailed and structured data interface that incorporates featured-based programming [21]. One benefit of this new organization is that it provides a framework for adding meaning and intelligence to machining programs. In STEP-enabled manufacturing [22], besides AP-238, new APs are being developed to get rapid and cost-effective manufacturing of quality parts: AP-240 [23] for macro process planning and Computer Aided Process Planning (CAPP) tools, AP-219 [24] for STEP-enable analysis, simulation and tolerance inspection through Coordinate Measure Machines (CMM) [25], etc. However, manufacturing traceability has not yet been considered from a global STEP manufacturing perspective, but just defined to support AP specific requirements, as for instance in AP-223 for casting [26]. This paper AP238 major concepts & relations Project
WorkPiece
WorkPlan
WorkStep
Feature
Tools
Fig. 2. AP-238 general structure and Integrated Resources.
542
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
Fig. 3. STEP-NC demonstration scenario updated with traceability proposal.
explores traceability in an AP-238 working scenario, but from the perspective of a further integration with other STEP manufacturing APs. 3. CNC traceability system overview Fig. 3 shows the STEP-NC project pilot demonstration scenario updated to include the manufacturing traceability system proposal described in this paper (new A1/A3 modules at the CAD/CADD/CAM side, and new A2 module at the CNC system side). In this scenario, an integrated CAD/CADD/CAM system settles traceability requirements (A1 module). As a result, a file specifying the traceability configuration is created and sent to the machining company with the CAM design data (AP-238). A traceability system at the CNC shop-floor registers traceability data for the machining process following the instructions given in this configuration and creates a new traceability data file for each machined part (A2 module). Finally, the product and its traceability data file are sent back to the designer company, where data is reviewed and audited to check if it is correct and it is complete (A3 module). 4. CNC traceability information model Fig. 4 shows EXPRESS-G [27] information modeling definitions for the main traceability data objects. Information contents of the model can be grouped in: (A) Traceability Header Data, (B) Manufacturing Operations Data and (C) Product Characteristics Data. Part A covers the information needed to establish links between traceability data, the CAM process data and the manufactured product instance. Parts B and C cover traceability data for manufacturing operations and product characteristics. In what follows, more details are given for each of the parts. 4.1. Traceability header entity Traceability data files are organized around a header TRACE_PROJECT entity (Part A in Fig. 4). The
‘identification’ attribute (TRACEABILITY_IDENTIFICATION_RELATIONSHIP entity) specifies the traceability code of the product instance (e.g. a serial number). Links between external CAM data and traceability data are defined in two relationship entities: TRACE_MANUFACTURING_ OPERATION_RELATIONSHIP entity and TRACE_CHARACTERISTIC_RELATIONSHIP entity. The ‘data source’ attribute specifies the AP-238 file name to resolve the references to AP-238 objects. Fig. 5 shows an example of these links. In this figure, a manufactured product instance with serial number ‘362KW3’ is linked to its CAM product definition (AP-238 workpiece identity). The ‘data_source’ attribute references the AP-238 file (url://server/AP238.stp). Also in the figure, traceability objects for each manufacturing operations are grouped in a ‘traced_operations’ list (‘milling 1’, ‘drill 18’, etc). 4.2. Tracing CNC-machining operations Mostly driven by safety considerations, often regulatory, different industries have different traceability requirements. In aerospace manufacturing, for instance, traceability means recording everything that went on to make a part. In automotive assembly, it is common to trace just the most important components such as the chassis, motor, airbags, transmission, keys, etc. Irrespective of the industry a distinction can be made between two types of manufacturing traceability data: ‘static’ data about ‘resources’ and ‘dynamic’ data about the ‘sub-processes’ or ‘steps’ performed to make the product. The static data includes information to identify raw materials, tools, and human resources involved in the roles of supervisors, operators, etc. The dynamic data includes information about the manufacturing timings, and other data necessary to reproduce the manufacturing sequence. Tracing CNC machining processes means tracing the sequence of workingsteps. For each manufacturing operation object in the AP-238 file (e.g. a drilling operation), a new set of traceability objects
B MANUFACTURING_OPERATIONS
A TRACEABILITY HEADER .
TRACE_ PROJECT
data_Source
TRACE_OPERATION
integrated_cnc_schema.document_reference
Data_Entity_id identification
TRACEABILITY_ IDENTIFICATION_ REALTIONSHIP
traced_characteristics L[0:?]
ASSEMBLY_MANUFACTURING_OPERATION PROCESS_MANUFACTURING_OPERATION
tr_Person
Data_Entity_id traced_operations L[0:?]
tr_IDENTIFICATION
TRACE_ MANUFACTURING OPERATION_ RELATIONSHIP
TRACE_ CHARACTERISTIC_ RELATIONSHIP
INTEGER description
Manufacturing_Operation name
Data_Entity_id
INTEGER
MANUFACTURING OPERATION_DATA_ AND_RESOURCES
Operators L[0:?]
remakrs
STRING
used_machine time
tr_RawMaterial TRACE_ CHARACTERISTICS Characteristic_id
serial_number
used_Materials L[0:?]
RawMaterial_id
tr_timeStamp
INTEGER
supplier
start time
integrated_cnc_schema.DATE_ AND_TIME
end time
integrated_cnc_schema.DATE_ AND_TIME
integrated_cnc_schema.MEASURE_ REPRESENTATION_ITEM
time tr_timeStamp tr_Person
STRING
tr_TYPE
STRING
description
Operators L[0:?]
trace_type
tool_id
time
measure
tr_IDENTIFICATION
used_tool L[0:?]
tr_Tool
C PRODUCT CHARACTERISTICS
name
tr_Person
Characteristic
category
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
authorized_by
CNC_MANUFACTURING_OPERATION
INTEGER Product_Code
integrated_cnc_schema.PERSON_ AND_ORGANIZATION integrated_cnc_schema.DATE_ AND_TIME
Fig. 4. Traceability Information Model (EXPRESS-G).
543
544
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
Fig. 5. Product, CAM data and traceability data main relationships.
(MANUFACTURING_OPERATION_DATA_AND_RESOURCES) is created each time the operation is performed. These objects trace the specific resources (for instance a drill tool serial number, or a raw material lot number) and the specific process conditions (time, etc.). For instance, in Fig. 6, traceability data of the tool used to make a round_hole feature (no. 3664) and planned as a drilling operation (no. 1138), is in a tr_Tool object. These data include both tool identification (lot, batch, supplier etc.) and tool use time (the drilling operation starting and ending time). Time records can also be used for tasks such as productivity analysis, machine usage control, etc. 4.3. Tracing product characteristics measurements Product characteristic measurement is an important quality measurement process. Today it is performed using ‘statistical inspections’ and automated inspection systems. The proper function and assembly of mechanical parts depends on dimensional tolerances. These are in turn verified by dimensional measurements, but due to the large number of measurements required to verify the dimensional conformance of a part, the inspection is complex. This complexity may be overcome by automating the dimension inspection through
Coordinate Measurement Machines. AP-219 is being developed as a model for recording the results of a CMM machine. Product characteristics, as manufacturing traceability, are often defined by a design organization, registered by a different manufacturing organization, and communicated back to design organizations. Therefore, the traceability model defines characteristic to be measured and included in the trace file. To measure them, the controller program must track some defined points and register their values. The same characteristic data model may be also used for characteristics not directly related to a CAD/CAM defined object, for example, a characteristic that must be measured before the CNC machining begins or after its completion. Such scenarios may be predefined in ‘characteristic repositories’ and linked through an ‘identification’ code or they may be added to the traceability configuration file. As an example, Fig. 7 depicts how a traceability file traces a characteristic for a round_hole feature (no. 3664, linked to workingstep no. 974). A TRACE_CHARACTERISTIC entity links to its corresponding feature (no. 3664) through the TRACE_CHARACTERISTIC_RELATIONSHIP entity. In this example, the characteristic is a dimensional tolerance and
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
545
AP 238 WORKPLAN - Drill 18 #1683 WorkingStep - drilling #974
WorkingStep
WorkingStep - drilling #975
ID 3664
feature
Operation
round_hole
drilling
Traceability part 21 Trace_Manufacturing_Operation_RelationShip (List) WorkingStep #975
trace_Operation (#1138)
WorkingStep #974
trace_Operation (#1139)
CNC_Manufacturing_Operation Manufacturing_Operation_Data_ and_Resources
tr_ Tool
description used_tool (List) tr_RawMaterial (List) tool_id time
Fig. 6. Data model detail for manufacturing operations.
the recorded information includes: the characteristic identification (characteristic_id and name), the measure (measure attribute), time (starting an ending time of the measure process) and who did the measure (operators list attribute). 5. Current prototype implementation and future work A prototype implementation has been developed to verify the information model in an experimental scenario (Fig. 8). To test this scenario, a driver for StepTools STEP-NC Explorer was implemented. The driver, coded in CCC, uses STdeveloper tool-kit and STEP programming interfaces like STEP SDAI [28] and STEP STIX [29] to work with STEP data, and XML APIs to work with XML data. 5.1. Current prototype implementation: configuration In this prototype, the company which designs the product contracts CNC machining companies (suppliers) to make parts of the product. It defines the traceability configuration, as it is the responsible for the correct product behavior. Fig. 9 details the implementation of the traceability configuration module (A1 in
Fig. 8). Traceability configuration is performed over AP-238 data, browsed from STEP part 21 files or from a data repository provided by STEP NC-Explorer. The traceability configuration module can be decomposed into two blocks: A11 extracts the product geometry and A12 provides a graphical user interface to translate traceability requirements into traceability configuration data. These data are saved as STEP part 21 data (ASCII files) or as STEP part 28-compliant data (XML files) [30]. Fig. 10 shows how the graphic user interface (A12) allows setting the traceability requirements over the AP-238 CAM data visualization (workingsteps, features and tolerances). 5.2. Current prototype implementation: manufacturing During production, the traceability configuration data is browsed and used to control the updates to the traceability file with the manufacturing data. A traceability system (A2 in Fig. 8) coupled with the CNC-system performs this role on the shop-floor, although, in the prototype implementation, an automatic data generation application simulates this process. The result is a new traceability data file, one for each product
Fig. 7. Data model detail for product characteristics.
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
Fig. 8. Prototype implementation.
546
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
547
Geometry Schema [ISO 10303 Part 42] SDAI [Step Part 22,23] AP 238 STIX Interface Library
Step AP Physical Files
VIsualization Tool Step NC-Explorer ( StepTools )
Step AP Data Structures
A0
Geometric Kernel Data Structure Geometry, Features & Tolerances Extractor/Mapper
Physical File Format [ISO 10303 Part 21]
A11
XML File Format [ISO 10303 Part 28] Proposed CNC Traceability EXPRESS Schema Software
Software
STEP part 21 Traceability Configuration WorkingSteps Features List Tolerance List
Traceability Configuration Generation
Design Engineer
STEP XML part 28 Traceability Configuration
A12
Software
Fig. 9. Detailed traceability configuration module (A1).
instance. Finally, the traceability data files are sent back to the contractor company when the product instances are also sent. Fig. 11 is an example of a STEP part 21 traceability data file and a STEP part 21 AP-238 file. The figure details the traceability data for a drilling operation (workingstep no. 974). For this operation, the example highlights the information about the tool used (no. 824), and more specifically, the tool use time (no. 885). 5.3. Current prototype implementation: audit, check and verification In the last stage of the scenario, the responsible organization audits and stores the traceability data. During the audit, the data sent by the supplier company is compared with the original traceability configuration specification, to see if it is correct and if it is complete. A visual tool for data browsing and audit was implemented. This tool has options such as: ‘show/hide not traced configuration requirements’, ‘show/hide not traced
characteristic’; ‘show/hide failed characteristics’, etc. These options can help the responsible organization analyze the large amount of data coming back from the manufacturing units. Fig. 12 details the traceability report and visualization module (A3 in Fig. 8). Input data for this module are the traceability data files coming from the manufacturing process and the traceability configuration files. The traceability report and visualization module can be decomposed into functional blocks corresponding to audit, check and verification tasks. A33 block performs audits by comparing traceability requirements (configuration files) and traceability data files. A31 is a traceability data interpreter. It browses the input traceability data files, ASCII (STEP part 21) or XML (STEP part 28 compliant) and outputs XML formatted traceability report files. A32 provides a graphical user interface resolving the links between traceability data, the product geometry structure, and AP238 entities. It makes possible to browse traceability data through the product CAM graphic representation.
Fig. 10. Traceability data configuration application.
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
Fig. 11. Extract of STEP part 21 traceability data file.
548
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
549
Geometry Schema [ISO 10303 Part 42] SDAI [Step Part 22,23] AP 238 STIX Interface Library
Physical File Format [ISO 10303 Part 21] XML File Format [ISO 10303 Part 28] Proposed CNC Traceability EXPRESS Schema
STEP part 21 Traceability Data STEP XML part 28 Traceability Data
Geometry, Features & Tolerances Extractor/Mapper
XMLTraceability Report VIsualization Tool Step NC-Explorer ( StepTools )
XML Audit Report
A0
Visual Browse or Audit
Step AP Data Strucutures
A32
Quality Control Software Engineer
XML Traceability Report
Product Traceability Data Traceability Data Interpreter
Quality Control Software Engineer
Geometric Product Data
A31
XML Traceability Report
Physical File Format [ISO 10303 Part 21] Quality Control Software Engineer
XML File Format [ISO 10303 Part 28] Proposed CNC Traceability EXPRESS Schema
STEP part 21/28 Traceability Configuration
Traceability Data Validation
XML Traceability Audit Report
A33
Quality Control Software Engineer
Fig. 12. Detailed traceability report and audit module (A3).
The traceability data can also be used as the source for datamining processes (Fig. 13). For example, both contractor and subcontractor will have the possibility to check and compute the time employed by a specific machine to perform a manufacturing operation. The EXPRESS definition of the traceability model, a more detailed explanation of the current implementation, as well as some sample data files, are available for review and download at (http://www.aisa.uvigo. es/jgarrido/Etrace/Etrace.htm). 5.4. Future work Integration of the traceability model with STEP-NC is ongoing. New data definitions are being considered to support specific STEP-NC operations (e.g. turning, inspection, etc.). Concerns about product characteristics are under investigation
and more information may be needed to support traceability requirements. For example, whether to define specific dimensional characteristics or whether to reuse the tolerances already considered in AP-238 and AP-219. Two main strategies can be adopted for the future project development: (1) integrate the traceability information model into STEP, or (2) follow a parallel path without going through standardization. In the first one, a new information model will be required to be developed and published as a new Application Protocol. In the second one the traceability requirements are added to the STEP-NC model [31], resulting in a new STEP-NC unit of functionality (Fig. 14). Another ongoing objective is to support as much automation as possible. For instance, to measure dimensional characteristics, the machine controller code can be enhanced
Fig. 13. Traceability data report (workingsteps timings).
550
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
STEP-NC Model Project data model WorkPlan data model
Feature data model Operation data model
Core STEP Geometry
Working_step data model
NC_parameters data model Shape data model
Profile data model Traceability data model Fig. 14. Traceability model into STEP NC.
with extra ‘code lines’ to track and register them. This automation covers two objectives: (1) productivity and (2) data reliability. In case where the CNC controller measures data, then a communication protocol can be defined to allow it to communicate with upper-level traceability systems. Such a protocol can prevent the CNC from continuing to the next machining working step if a problem is detected. For example, the traceability layer stops the CNC control if any information that should have been traced (for instance, the ‘identification code’ of a new CNC tool), has not been registered. 6. Conclusions This paper has presented an information model for tracing spread manufacturing processes and shown how this model can be integrated with other product data models pertaining to CAD/CAM. A prototype system has been implemented to explain the new model. It shows the traceability data flow through the supply chain and different traceability processes along the product life cycle, specifically: 1. Traceability requirements are configured while designing the product. 2. The traceability configuration data is linked to the CAM data and sent to the supply companies. 3. A supply company uses the configuration to register the required data in a traceability file. 4. The contractor company reviews, audits and storages the traceability data. 5. If a product instance fails in the future, data is revised and used as a diagnostic tool to discover any exceptions or unusual manufacturing conditions. The key point for successful integration of the traceability data is the linkage between the manufacturing data and the CAD/CAM data. The linkage also provides an infrastructure to
create visual tools to develop Man/Machine Traceability interfaces. However, the main advantage is that it assures data understandability and availability, independent of future relationships between the supplier company and the contractor one. Formalizing traceability and characteristics information can help both contractor and supplier manufacturing companies. The contractor may have an electronic feedback describing the manufacturing data as well as the quality control data. The supplier may have a digital way to browse and understand traceability requirements. References [1] ECR-Europe. ECR-Using traceability in the supplier chain to meet consumer safety expectations [Available online: http://www.ecrnet. org/]. [2] ISO/TS 16949:2002. Quality management systems—particular requirements for the application of ISO 9001:2000 for automotive production and relevant service part organizations. Geneva, Switzerland: International Organization for Standardization (ISO TC 176). [3] Farris II MT, Wittman CM, Hasty R. Aftermarket support and the supply chain: exemplars and implications from the aerospace industry. Int J Phys Distrib Logist Manage 2005;35(1):6–19. [4] Parker BR, Lahr G. Pharmaceutical recall strategies for minimizing the damage. Drug Inf J 1999;33(2):541–56. [5] ISO 10303-1:1994. Industrial automation systems and integration— product data representation and exchange—part 1: overview and fundamentals principles. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [6] Fowler J. STEP for management exchange and sharing. Technology Appraisals Ltd.; 1995. [7] ISO 10303-203:1994. Industrial automation systems and integration— product data representation and exchange—part 203: application protocol: configuration controlled 3D designs of Mechanical parts and assemblies. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [8] ISO 10303-214:2003. Industrial automation systems and integration— product data representation and exchange—part 214: application protocol: core data for automotive mechanical design processes. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [9] ISO/DIS 10303-238. Industrial automation systems and integration— product data representation and exchange—part 238: application protocol: application interpreted model for computerized numerical controllers. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4); 2005. [10] Peng T, Trappey AJC. A step towards STEP-compatible engineering data management: the data models of product structure and engineering changes. Robot Comput Integr Manuf 1998;14(2):89–109. [11] STEP Application handbook [Available online: http://www.isg-scra.org/ STEP/]. [12] ISO 10303-11:2004. Industrial automation systems and integration— product data representation and exchange—part 11: description methods: the EXPRESS language reference manual. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [13] ISO 10303-21:2002. Industrial automation systems and integration— product data representation and exchange—part 21: implementation methods: clear text encoding of the exchange structure. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [14] Suh SH, Lee BE, Chung DH, Cheon SU. Architecture and implementation of a shop-floor programming system for STEP-compliant CNC. Comput Aided Des 2003;35(12):1069–83.
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551 [15] Albert M. Plugging into STEP NC. Mod Mach Shop 2002;75(2):80–5. [16] ISO 10303-224:2001. Industrial automation systems and integration— product data representation and exchange—part 224: application protocol: mechanical product definition for process planning using machining features. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [17] STEP-NC Pilot Demonstration. OMAC STEP–NC working group meeting, Orlando, FL; 2005 [Available online: http://www.isd.mel.nist. gov/projects/stepnc]. [18] Allen RD, Harding JA, Newman ST. The Application of STEP-NC using agent-based process planning. Int J Prod Res 2005;43(4):655–70. [19] ISO 6983-1:1982. Numerical control of machines—program format and definition of address words—part 1: Data format for positioning, line motion and contouring control systems. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 1). [20] Albert M. STEP NC—the end of G-Codes? Mod Mach Shop 2000;73(2): 70–80. [21] Young RIM, Bell R. Design by features: advantages and limitations in machine planning integration. Int J Comput Integr Manuf 1993;6(1&2): 105–12. [22] Xu XW, He Q. Striving for a total integration of CAD, CAPP, CAM and CNC. Robot Comput Integr Manuf 2004;20(2):101–9. [23] ISO 10303-240. Industrial automation systems and integration—product data representation and exchange—part 240: application protocol: process plans for machined products. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [24] ISO/CD 10303-219. Industrial automation systems and integration— product data representation and exchange—part 219: dimensional inspection information exchange. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [25] Legge DI. Off-line programming of coordinate measuring machines: integration of design, inspection and quality management systems; 1996. p. 19L [ISSN 0280-8242]. [26] The Step Manufacturing Suite. White paper. Version 3; March 2005. p. 60–8 [Available online: http://www.isg-scra.org/STEP/files/STEP_MfgSuiteWhitePaper.pdf]. [27] Schenck D, Wilson P. Information modeling: the EXPRESS way. New York: Oxford University Press; 1994. [28] ISO 10303-22:1998. Industrial automation systems and integration— product data representation and exchange—part 22: implementation methods: STEP data access interface. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [29] STIX. A STEP library for AP-238 [Available online: http://www. steptools.com/stix/].
551
[30] ISO/TS 10303-28:2003. Industrial automation systems and integration— product data representation and exchange—part 28: implementation methods: XML representations of EXPRESS schemas and data. Geneva, Switzerland: International Organization for Standardization, (ISO TC 184/SC 4). [31] Feeney AB, Price DM. A modular architecture for STEP. Proceedings of world automation congress; 2000 [Available online: http://www.nist.gov/ msidlibrary/doc/isoma-9977.pdf].
Dr. Julio Garrido Campos is an associate professor in the department of Automation and Systems Engineering of Vigo University (Spain), where he is leading research government financed projects about traceability formalization for manufacturing (MCYT DPI2003-01967). His current research interest includes industrial traceability for collaborative environments, traceability automation for CAD/CAM, shop floor data automation and Product Data Exchange and Sharing by STEP. He got his PhD degree (1999) at Vigo University, after being for one year (1995) a research assistant at Rensselaer Polytechnic Institute (Troy, NY).
Dr. Hardwick is a Professor of computer science at Rensselaer Polytechnic Institute in Troy, New York. He is the team leader of the ISO TC184/SC4 STEP Manufacturing group. Previously he was the deputy convenor of Working Group 7 of ISO STEP, the group responsible for implementation methods of the STEP standard. He lead the Model Driven Intelligent Control of Manufacturing program, known as the “Super Model” Project, which is supported by the National Institute of Standards and Technology (NIST). He is the author of numerous papers and articles on engineering database systems, STEP, PDES, and concurrent engineering, and he has worked on several high profile data integration programs. He is also president and CEO of STEP Tools, Inc. His research interest includes engineering database systems and manufacturing data modeling. He received a BS and PhD in computer science from Bristol University in England.
A traceability information model for CNC manufacturing Julio Garrido Campos *,a, Martin Hardwick b a
Department of Automation and System Engineering, Universidad de Vigo (Vigo University, Spain), E.T.S. Ingenieros Industriales, Campus Lagoas-Marcosende, 36200 Vigo, Pontevedra, Spain b Department of Computer Science, Rensselaer Polytechnic Institute, Troy, NY, USA Received 12 April 2005; accepted 24 January 2006
Abstract This paper proposes an information model for tracing CNC manufacturing operations. The objective of the model is to assure that traceability data is comprehensive and available for every CNC machined product, independent of the relationship between the subcontractor and the contractor. The prominent feature of the model is a link between CNC report data for a product instance, the CAD design and the CAM data. This link enables users to browse the traceability data and understand the relationships between the manufacturing process, the CAD design and the CAM data. The link is independent of the systems used to build the CAD and CAM data, and allows the users to be sure the manufactured product contains the required characteristics. Then if a product instance fails, this linkage will make possible to analyze the trace data and identify any exceptions or unusual conditions in the manufacturing process. q 2006 Elsevier Ltd. All rights reserved. Keywords: Traceability; Product characteristics; STEP; CAM; ISO 10303 AP238
1. Introduction Contractual relationships are often temporary, especially those linking a primary contractor (assembly company) with its subcontractors (supply chain companies). For many products, there is a traceability requirement that must be met by documenting the steps taken in the manufacturing process, so the data can be analyzed if a failure. When the manufacturing is performed internally, the process can be documented using systems that can be assumed to be available in the event of failure [1]. When manufacturing is performed externally issues can arise if the systems are no longer available or comprehensible. In order to contract more manufacturing tasks, industrial companies need to extend their ability to trace the execution of external manufacturing processes. One method is to require the partner company to use the same systems and procedures as the contractor company. This is, however, cumbersome and expensive, and therefore only practical when there is a lot of business between the companies. Another approach is to develop methods that can be used across an industry. Examples * Corresponding author. Tel.: C34 986 812610; fax: C34 986 814014. E-mail address: [email protected] (J. Garrido Campos).
0010-4485//$ - see front matter q 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.cad.2006.01.011
can be found in the automotive [2], aerospace [3], and pharmaceutical [4] industries. This paper describes a traceability model for CAD/CAM and Computer Numerical Control (CNC) machining domains. The primary purpose of the model is to support the flow of traceability information across these domains, so a company can trace the processes used to make a product even if it has been machined by different partners. The new model addresses two key problems of supply chain traceability: data understandability and data availability. The hypothesis of the model is that: by linking CNC report data, CAD design data and CAM process data, an efficient traceability data set can be developed. This former is system independent, and allows the partner companies to assure the quality of the manufacturing process at the time of manufacture and also in the event of a product failure. The new model is built on top of existing STEP (Standard for the Exchange of Product Data, ISO 10303) [5,6] models for CAD (AP-203 [7] and AP-214 [8]) and for CAM (AP-238 [9]). Most CAD systems can export AP-203 or AP-214 data, and many CAM systems are considering adding an AP-238 (STEPNC) export option. All STEP models are extensible and designed to support the product life cycle. The traceability model described in this paper extends these CAD and CAM models into the maintenance phase of the product life cycle for CNC machined products. Section 2 gives some background on the models used to build the traceability model. Section 3 describes an
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
541
Fig. 1. STEP-NC demonstration scenario.
experimental traceability system. Section 4 summarizes the modeling requirements determined from this experiment and Section 5 details the experiment implementation. Section 6 summarizes and proposes future research directions. 2. Background on STEP-enabled manufacturing and STEP-NC Flexible product data interchange is one of the critical success factors for many industrial collaboration scenarios. One of the objectives of STEP is to enable product data interchange [10]. STEP has defined a framework for depicting a complete representation of product data through its life cycle [11]. It defines, among other basic infrastructures, an object oriented information modeling language (EXPRESS, STEP part 11 [12]) and a file transfer format (STEP part 21 [13]). Using Application Protocols, STEP addresses many industrial data exchange requirements. There are protocols for drawings and for 3D geometry to use in many contexts, and protocols for specific kinds of products such as boats, buildings, and electronic circuit boards that are largely limited to their respective industries. One of the newest application protocols, AP-238, defines a model for exchange CNC machining data between Computer Aided Manufacturing and Computer Numerical Control systems [14,15]. AP-238 is a structured featured-based representation of process plans for manufacturing processes such as milling, turning, etc. and it is based on the geometric information of APs, such as AP-203, AP-214 and AP-224 [16]. So the use of AP-238 avoids CAM systems to redefine the product geometry because involved STEP APs share the same geometry data (shape and features). The CAM system just adds process information (manufacturing feature and tool path data) to the CAD data so the CNC has enough input to make the part. Fig. 1 shows how STEP-NC project [17] is applying AP-238 to supports CAM and CNC applications [18]. In this AP-238 prototype scenario, a CAD system makes an AP-203 data file describing the part geometry. A CADD system (Computeraided Drafting and Design) adds design requirements as Geometric Dimensions and Tolerances (GD&T). The CADD exports this data as AP-203 Edition 2, or as AP-224 file if the detailing also includes the definition of features. The CAM system adds process information (e.g. assigns tools and process
parameters for each feature) and exports the data to a CNC controller as an AP-238 file. Fig. 2 shows the generic structure of the AP-238 information model. An AP-238 file includes product geometric information as well as process information. The file is organized into a sequence of manufacturing operations called workingsteps. Each workingstep defines an operation performed on one or more features by a CNC machine tool. These workingsteps provide the basis for the workplan to make the product, and are generic descriptions, not linked to a specific format or code. AP-238 changes the focus of machining from axis path motions (ISO 6983 [19], known as G&M codes [20]) to volume removal operations applied to machining features. It provides and object oriented data model for CNCs, with a detailed and structured data interface that incorporates featured-based programming [21]. One benefit of this new organization is that it provides a framework for adding meaning and intelligence to machining programs. In STEP-enabled manufacturing [22], besides AP-238, new APs are being developed to get rapid and cost-effective manufacturing of quality parts: AP-240 [23] for macro process planning and Computer Aided Process Planning (CAPP) tools, AP-219 [24] for STEP-enable analysis, simulation and tolerance inspection through Coordinate Measure Machines (CMM) [25], etc. However, manufacturing traceability has not yet been considered from a global STEP manufacturing perspective, but just defined to support AP specific requirements, as for instance in AP-223 for casting [26]. This paper AP238 major concepts & relations Project
WorkPiece
WorkPlan
WorkStep
Feature
Tools
Fig. 2. AP-238 general structure and Integrated Resources.
542
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
Fig. 3. STEP-NC demonstration scenario updated with traceability proposal.
explores traceability in an AP-238 working scenario, but from the perspective of a further integration with other STEP manufacturing APs. 3. CNC traceability system overview Fig. 3 shows the STEP-NC project pilot demonstration scenario updated to include the manufacturing traceability system proposal described in this paper (new A1/A3 modules at the CAD/CADD/CAM side, and new A2 module at the CNC system side). In this scenario, an integrated CAD/CADD/CAM system settles traceability requirements (A1 module). As a result, a file specifying the traceability configuration is created and sent to the machining company with the CAM design data (AP-238). A traceability system at the CNC shop-floor registers traceability data for the machining process following the instructions given in this configuration and creates a new traceability data file for each machined part (A2 module). Finally, the product and its traceability data file are sent back to the designer company, where data is reviewed and audited to check if it is correct and it is complete (A3 module). 4. CNC traceability information model Fig. 4 shows EXPRESS-G [27] information modeling definitions for the main traceability data objects. Information contents of the model can be grouped in: (A) Traceability Header Data, (B) Manufacturing Operations Data and (C) Product Characteristics Data. Part A covers the information needed to establish links between traceability data, the CAM process data and the manufactured product instance. Parts B and C cover traceability data for manufacturing operations and product characteristics. In what follows, more details are given for each of the parts. 4.1. Traceability header entity Traceability data files are organized around a header TRACE_PROJECT entity (Part A in Fig. 4). The
‘identification’ attribute (TRACEABILITY_IDENTIFICATION_RELATIONSHIP entity) specifies the traceability code of the product instance (e.g. a serial number). Links between external CAM data and traceability data are defined in two relationship entities: TRACE_MANUFACTURING_ OPERATION_RELATIONSHIP entity and TRACE_CHARACTERISTIC_RELATIONSHIP entity. The ‘data source’ attribute specifies the AP-238 file name to resolve the references to AP-238 objects. Fig. 5 shows an example of these links. In this figure, a manufactured product instance with serial number ‘362KW3’ is linked to its CAM product definition (AP-238 workpiece identity). The ‘data_source’ attribute references the AP-238 file (url://server/AP238.stp). Also in the figure, traceability objects for each manufacturing operations are grouped in a ‘traced_operations’ list (‘milling 1’, ‘drill 18’, etc). 4.2. Tracing CNC-machining operations Mostly driven by safety considerations, often regulatory, different industries have different traceability requirements. In aerospace manufacturing, for instance, traceability means recording everything that went on to make a part. In automotive assembly, it is common to trace just the most important components such as the chassis, motor, airbags, transmission, keys, etc. Irrespective of the industry a distinction can be made between two types of manufacturing traceability data: ‘static’ data about ‘resources’ and ‘dynamic’ data about the ‘sub-processes’ or ‘steps’ performed to make the product. The static data includes information to identify raw materials, tools, and human resources involved in the roles of supervisors, operators, etc. The dynamic data includes information about the manufacturing timings, and other data necessary to reproduce the manufacturing sequence. Tracing CNC machining processes means tracing the sequence of workingsteps. For each manufacturing operation object in the AP-238 file (e.g. a drilling operation), a new set of traceability objects
B MANUFACTURING_OPERATIONS
A TRACEABILITY HEADER .
TRACE_ PROJECT
data_Source
TRACE_OPERATION
integrated_cnc_schema.document_reference
Data_Entity_id identification
TRACEABILITY_ IDENTIFICATION_ REALTIONSHIP
traced_characteristics L[0:?]
ASSEMBLY_MANUFACTURING_OPERATION PROCESS_MANUFACTURING_OPERATION
tr_Person
Data_Entity_id traced_operations L[0:?]
tr_IDENTIFICATION
TRACE_ MANUFACTURING OPERATION_ RELATIONSHIP
TRACE_ CHARACTERISTIC_ RELATIONSHIP
INTEGER description
Manufacturing_Operation name
Data_Entity_id
INTEGER
MANUFACTURING OPERATION_DATA_ AND_RESOURCES
Operators L[0:?]
remakrs
STRING
used_machine time
tr_RawMaterial TRACE_ CHARACTERISTICS Characteristic_id
serial_number
used_Materials L[0:?]
RawMaterial_id
tr_timeStamp
INTEGER
supplier
start time
integrated_cnc_schema.DATE_ AND_TIME
end time
integrated_cnc_schema.DATE_ AND_TIME
integrated_cnc_schema.MEASURE_ REPRESENTATION_ITEM
time tr_timeStamp tr_Person
STRING
tr_TYPE
STRING
description
Operators L[0:?]
trace_type
tool_id
time
measure
tr_IDENTIFICATION
used_tool L[0:?]
tr_Tool
C PRODUCT CHARACTERISTICS
name
tr_Person
Characteristic
category
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
authorized_by
CNC_MANUFACTURING_OPERATION
INTEGER Product_Code
integrated_cnc_schema.PERSON_ AND_ORGANIZATION integrated_cnc_schema.DATE_ AND_TIME
Fig. 4. Traceability Information Model (EXPRESS-G).
543
544
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
Fig. 5. Product, CAM data and traceability data main relationships.
(MANUFACTURING_OPERATION_DATA_AND_RESOURCES) is created each time the operation is performed. These objects trace the specific resources (for instance a drill tool serial number, or a raw material lot number) and the specific process conditions (time, etc.). For instance, in Fig. 6, traceability data of the tool used to make a round_hole feature (no. 3664) and planned as a drilling operation (no. 1138), is in a tr_Tool object. These data include both tool identification (lot, batch, supplier etc.) and tool use time (the drilling operation starting and ending time). Time records can also be used for tasks such as productivity analysis, machine usage control, etc. 4.3. Tracing product characteristics measurements Product characteristic measurement is an important quality measurement process. Today it is performed using ‘statistical inspections’ and automated inspection systems. The proper function and assembly of mechanical parts depends on dimensional tolerances. These are in turn verified by dimensional measurements, but due to the large number of measurements required to verify the dimensional conformance of a part, the inspection is complex. This complexity may be overcome by automating the dimension inspection through
Coordinate Measurement Machines. AP-219 is being developed as a model for recording the results of a CMM machine. Product characteristics, as manufacturing traceability, are often defined by a design organization, registered by a different manufacturing organization, and communicated back to design organizations. Therefore, the traceability model defines characteristic to be measured and included in the trace file. To measure them, the controller program must track some defined points and register their values. The same characteristic data model may be also used for characteristics not directly related to a CAD/CAM defined object, for example, a characteristic that must be measured before the CNC machining begins or after its completion. Such scenarios may be predefined in ‘characteristic repositories’ and linked through an ‘identification’ code or they may be added to the traceability configuration file. As an example, Fig. 7 depicts how a traceability file traces a characteristic for a round_hole feature (no. 3664, linked to workingstep no. 974). A TRACE_CHARACTERISTIC entity links to its corresponding feature (no. 3664) through the TRACE_CHARACTERISTIC_RELATIONSHIP entity. In this example, the characteristic is a dimensional tolerance and
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
545
AP 238 WORKPLAN - Drill 18 #1683 WorkingStep - drilling #974
WorkingStep
WorkingStep - drilling #975
ID 3664
feature
Operation
round_hole
drilling
Traceability part 21 Trace_Manufacturing_Operation_RelationShip (List) WorkingStep #975
trace_Operation (#1138)
WorkingStep #974
trace_Operation (#1139)
CNC_Manufacturing_Operation Manufacturing_Operation_Data_ and_Resources
tr_ Tool
description used_tool (List) tr_RawMaterial (List) tool_id time
Fig. 6. Data model detail for manufacturing operations.
the recorded information includes: the characteristic identification (characteristic_id and name), the measure (measure attribute), time (starting an ending time of the measure process) and who did the measure (operators list attribute). 5. Current prototype implementation and future work A prototype implementation has been developed to verify the information model in an experimental scenario (Fig. 8). To test this scenario, a driver for StepTools STEP-NC Explorer was implemented. The driver, coded in CCC, uses STdeveloper tool-kit and STEP programming interfaces like STEP SDAI [28] and STEP STIX [29] to work with STEP data, and XML APIs to work with XML data. 5.1. Current prototype implementation: configuration In this prototype, the company which designs the product contracts CNC machining companies (suppliers) to make parts of the product. It defines the traceability configuration, as it is the responsible for the correct product behavior. Fig. 9 details the implementation of the traceability configuration module (A1 in
Fig. 8). Traceability configuration is performed over AP-238 data, browsed from STEP part 21 files or from a data repository provided by STEP NC-Explorer. The traceability configuration module can be decomposed into two blocks: A11 extracts the product geometry and A12 provides a graphical user interface to translate traceability requirements into traceability configuration data. These data are saved as STEP part 21 data (ASCII files) or as STEP part 28-compliant data (XML files) [30]. Fig. 10 shows how the graphic user interface (A12) allows setting the traceability requirements over the AP-238 CAM data visualization (workingsteps, features and tolerances). 5.2. Current prototype implementation: manufacturing During production, the traceability configuration data is browsed and used to control the updates to the traceability file with the manufacturing data. A traceability system (A2 in Fig. 8) coupled with the CNC-system performs this role on the shop-floor, although, in the prototype implementation, an automatic data generation application simulates this process. The result is a new traceability data file, one for each product
Fig. 7. Data model detail for product characteristics.
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
Fig. 8. Prototype implementation.
546
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
547
Geometry Schema [ISO 10303 Part 42] SDAI [Step Part 22,23] AP 238 STIX Interface Library
Step AP Physical Files
VIsualization Tool Step NC-Explorer ( StepTools )
Step AP Data Structures
A0
Geometric Kernel Data Structure Geometry, Features & Tolerances Extractor/Mapper
Physical File Format [ISO 10303 Part 21]
A11
XML File Format [ISO 10303 Part 28] Proposed CNC Traceability EXPRESS Schema Software
Software
STEP part 21 Traceability Configuration WorkingSteps Features List Tolerance List
Traceability Configuration Generation
Design Engineer
STEP XML part 28 Traceability Configuration
A12
Software
Fig. 9. Detailed traceability configuration module (A1).
instance. Finally, the traceability data files are sent back to the contractor company when the product instances are also sent. Fig. 11 is an example of a STEP part 21 traceability data file and a STEP part 21 AP-238 file. The figure details the traceability data for a drilling operation (workingstep no. 974). For this operation, the example highlights the information about the tool used (no. 824), and more specifically, the tool use time (no. 885). 5.3. Current prototype implementation: audit, check and verification In the last stage of the scenario, the responsible organization audits and stores the traceability data. During the audit, the data sent by the supplier company is compared with the original traceability configuration specification, to see if it is correct and if it is complete. A visual tool for data browsing and audit was implemented. This tool has options such as: ‘show/hide not traced configuration requirements’, ‘show/hide not traced
characteristic’; ‘show/hide failed characteristics’, etc. These options can help the responsible organization analyze the large amount of data coming back from the manufacturing units. Fig. 12 details the traceability report and visualization module (A3 in Fig. 8). Input data for this module are the traceability data files coming from the manufacturing process and the traceability configuration files. The traceability report and visualization module can be decomposed into functional blocks corresponding to audit, check and verification tasks. A33 block performs audits by comparing traceability requirements (configuration files) and traceability data files. A31 is a traceability data interpreter. It browses the input traceability data files, ASCII (STEP part 21) or XML (STEP part 28 compliant) and outputs XML formatted traceability report files. A32 provides a graphical user interface resolving the links between traceability data, the product geometry structure, and AP238 entities. It makes possible to browse traceability data through the product CAM graphic representation.
Fig. 10. Traceability data configuration application.
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
Fig. 11. Extract of STEP part 21 traceability data file.
548
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
549
Geometry Schema [ISO 10303 Part 42] SDAI [Step Part 22,23] AP 238 STIX Interface Library
Physical File Format [ISO 10303 Part 21] XML File Format [ISO 10303 Part 28] Proposed CNC Traceability EXPRESS Schema
STEP part 21 Traceability Data STEP XML part 28 Traceability Data
Geometry, Features & Tolerances Extractor/Mapper
XMLTraceability Report VIsualization Tool Step NC-Explorer ( StepTools )
XML Audit Report
A0
Visual Browse or Audit
Step AP Data Strucutures
A32
Quality Control Software Engineer
XML Traceability Report
Product Traceability Data Traceability Data Interpreter
Quality Control Software Engineer
Geometric Product Data
A31
XML Traceability Report
Physical File Format [ISO 10303 Part 21] Quality Control Software Engineer
XML File Format [ISO 10303 Part 28] Proposed CNC Traceability EXPRESS Schema
STEP part 21/28 Traceability Configuration
Traceability Data Validation
XML Traceability Audit Report
A33
Quality Control Software Engineer
Fig. 12. Detailed traceability report and audit module (A3).
The traceability data can also be used as the source for datamining processes (Fig. 13). For example, both contractor and subcontractor will have the possibility to check and compute the time employed by a specific machine to perform a manufacturing operation. The EXPRESS definition of the traceability model, a more detailed explanation of the current implementation, as well as some sample data files, are available for review and download at (http://www.aisa.uvigo. es/jgarrido/Etrace/Etrace.htm). 5.4. Future work Integration of the traceability model with STEP-NC is ongoing. New data definitions are being considered to support specific STEP-NC operations (e.g. turning, inspection, etc.). Concerns about product characteristics are under investigation
and more information may be needed to support traceability requirements. For example, whether to define specific dimensional characteristics or whether to reuse the tolerances already considered in AP-238 and AP-219. Two main strategies can be adopted for the future project development: (1) integrate the traceability information model into STEP, or (2) follow a parallel path without going through standardization. In the first one, a new information model will be required to be developed and published as a new Application Protocol. In the second one the traceability requirements are added to the STEP-NC model [31], resulting in a new STEP-NC unit of functionality (Fig. 14). Another ongoing objective is to support as much automation as possible. For instance, to measure dimensional characteristics, the machine controller code can be enhanced
Fig. 13. Traceability data report (workingsteps timings).
550
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551
STEP-NC Model Project data model WorkPlan data model
Feature data model Operation data model
Core STEP Geometry
Working_step data model
NC_parameters data model Shape data model
Profile data model Traceability data model Fig. 14. Traceability model into STEP NC.
with extra ‘code lines’ to track and register them. This automation covers two objectives: (1) productivity and (2) data reliability. In case where the CNC controller measures data, then a communication protocol can be defined to allow it to communicate with upper-level traceability systems. Such a protocol can prevent the CNC from continuing to the next machining working step if a problem is detected. For example, the traceability layer stops the CNC control if any information that should have been traced (for instance, the ‘identification code’ of a new CNC tool), has not been registered. 6. Conclusions This paper has presented an information model for tracing spread manufacturing processes and shown how this model can be integrated with other product data models pertaining to CAD/CAM. A prototype system has been implemented to explain the new model. It shows the traceability data flow through the supply chain and different traceability processes along the product life cycle, specifically: 1. Traceability requirements are configured while designing the product. 2. The traceability configuration data is linked to the CAM data and sent to the supply companies. 3. A supply company uses the configuration to register the required data in a traceability file. 4. The contractor company reviews, audits and storages the traceability data. 5. If a product instance fails in the future, data is revised and used as a diagnostic tool to discover any exceptions or unusual manufacturing conditions. The key point for successful integration of the traceability data is the linkage between the manufacturing data and the CAD/CAM data. The linkage also provides an infrastructure to
create visual tools to develop Man/Machine Traceability interfaces. However, the main advantage is that it assures data understandability and availability, independent of future relationships between the supplier company and the contractor one. Formalizing traceability and characteristics information can help both contractor and supplier manufacturing companies. The contractor may have an electronic feedback describing the manufacturing data as well as the quality control data. The supplier may have a digital way to browse and understand traceability requirements. References [1] ECR-Europe. ECR-Using traceability in the supplier chain to meet consumer safety expectations [Available online: http://www.ecrnet. org/]. [2] ISO/TS 16949:2002. Quality management systems—particular requirements for the application of ISO 9001:2000 for automotive production and relevant service part organizations. Geneva, Switzerland: International Organization for Standardization (ISO TC 176). [3] Farris II MT, Wittman CM, Hasty R. Aftermarket support and the supply chain: exemplars and implications from the aerospace industry. Int J Phys Distrib Logist Manage 2005;35(1):6–19. [4] Parker BR, Lahr G. Pharmaceutical recall strategies for minimizing the damage. Drug Inf J 1999;33(2):541–56. [5] ISO 10303-1:1994. Industrial automation systems and integration— product data representation and exchange—part 1: overview and fundamentals principles. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [6] Fowler J. STEP for management exchange and sharing. Technology Appraisals Ltd.; 1995. [7] ISO 10303-203:1994. Industrial automation systems and integration— product data representation and exchange—part 203: application protocol: configuration controlled 3D designs of Mechanical parts and assemblies. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [8] ISO 10303-214:2003. Industrial automation systems and integration— product data representation and exchange—part 214: application protocol: core data for automotive mechanical design processes. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [9] ISO/DIS 10303-238. Industrial automation systems and integration— product data representation and exchange—part 238: application protocol: application interpreted model for computerized numerical controllers. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4); 2005. [10] Peng T, Trappey AJC. A step towards STEP-compatible engineering data management: the data models of product structure and engineering changes. Robot Comput Integr Manuf 1998;14(2):89–109. [11] STEP Application handbook [Available online: http://www.isg-scra.org/ STEP/]. [12] ISO 10303-11:2004. Industrial automation systems and integration— product data representation and exchange—part 11: description methods: the EXPRESS language reference manual. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [13] ISO 10303-21:2002. Industrial automation systems and integration— product data representation and exchange—part 21: implementation methods: clear text encoding of the exchange structure. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [14] Suh SH, Lee BE, Chung DH, Cheon SU. Architecture and implementation of a shop-floor programming system for STEP-compliant CNC. Comput Aided Des 2003;35(12):1069–83.
J. Garrido Campos, M. Hardwick / Computer-Aided Design 38 (2006) 540–551 [15] Albert M. Plugging into STEP NC. Mod Mach Shop 2002;75(2):80–5. [16] ISO 10303-224:2001. Industrial automation systems and integration— product data representation and exchange—part 224: application protocol: mechanical product definition for process planning using machining features. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [17] STEP-NC Pilot Demonstration. OMAC STEP–NC working group meeting, Orlando, FL; 2005 [Available online: http://www.isd.mel.nist. gov/projects/stepnc]. [18] Allen RD, Harding JA, Newman ST. The Application of STEP-NC using agent-based process planning. Int J Prod Res 2005;43(4):655–70. [19] ISO 6983-1:1982. Numerical control of machines—program format and definition of address words—part 1: Data format for positioning, line motion and contouring control systems. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 1). [20] Albert M. STEP NC—the end of G-Codes? Mod Mach Shop 2000;73(2): 70–80. [21] Young RIM, Bell R. Design by features: advantages and limitations in machine planning integration. Int J Comput Integr Manuf 1993;6(1&2): 105–12. [22] Xu XW, He Q. Striving for a total integration of CAD, CAPP, CAM and CNC. Robot Comput Integr Manuf 2004;20(2):101–9. [23] ISO 10303-240. Industrial automation systems and integration—product data representation and exchange—part 240: application protocol: process plans for machined products. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [24] ISO/CD 10303-219. Industrial automation systems and integration— product data representation and exchange—part 219: dimensional inspection information exchange. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [25] Legge DI. Off-line programming of coordinate measuring machines: integration of design, inspection and quality management systems; 1996. p. 19L [ISSN 0280-8242]. [26] The Step Manufacturing Suite. White paper. Version 3; March 2005. p. 60–8 [Available online: http://www.isg-scra.org/STEP/files/STEP_MfgSuiteWhitePaper.pdf]. [27] Schenck D, Wilson P. Information modeling: the EXPRESS way. New York: Oxford University Press; 1994. [28] ISO 10303-22:1998. Industrial automation systems and integration— product data representation and exchange—part 22: implementation methods: STEP data access interface. Geneva, Switzerland: International Organization for Standardization (ISO TC 184/SC 4). [29] STIX. A STEP library for AP-238 [Available online: http://www. steptools.com/stix/].
551
[30] ISO/TS 10303-28:2003. Industrial automation systems and integration— product data representation and exchange—part 28: implementation methods: XML representations of EXPRESS schemas and data. Geneva, Switzerland: International Organization for Standardization, (ISO TC 184/SC 4). [31] Feeney AB, Price DM. A modular architecture for STEP. Proceedings of world automation congress; 2000 [Available online: http://www.nist.gov/ msidlibrary/doc/isoma-9977.pdf].
Dr. Julio Garrido Campos is an associate professor in the department of Automation and Systems Engineering of Vigo University (Spain), where he is leading research government financed projects about traceability formalization for manufacturing (MCYT DPI2003-01967). His current research interest includes industrial traceability for collaborative environments, traceability automation for CAD/CAM, shop floor data automation and Product Data Exchange and Sharing by STEP. He got his PhD degree (1999) at Vigo University, after being for one year (1995) a research assistant at Rensselaer Polytechnic Institute (Troy, NY).
Dr. Hardwick is a Professor of computer science at Rensselaer Polytechnic Institute in Troy, New York. He is the team leader of the ISO TC184/SC4 STEP Manufacturing group. Previously he was the deputy convenor of Working Group 7 of ISO STEP, the group responsible for implementation methods of the STEP standard. He lead the Model Driven Intelligent Control of Manufacturing program, known as the “Super Model” Project, which is supported by the National Institute of Standards and Technology (NIST). He is the author of numerous papers and articles on engineering database systems, STEP, PDES, and concurrent engineering, and he has worked on several high profile data integration programs. He is also president and CEO of STEP Tools, Inc. His research interest includes engineering database systems and manufacturing data modeling. He received a BS and PhD in computer science from Bristol University in England.