Manufacturing Technology

Transcription

1 ]nt J Adv Manuf Technol (1991) 6: Q 1991 Springer-Verlag London Limited The International Journal of Advanced Manufacturing Technology DESIGN FOR MANUFACTURE AND ASSEMBLY: CASE STUDIES IN ITS IMPLEMENTATION D. J. Gerhardt, W. R. Hutchinson and D. K. Mistry Ingersoll-Rand Company, Portable Compressor Division, Mocksville, North Carolina, USA This paper reviews the rapid and successful implementation of design for manufacture and assembly (DFMA) at Ingersoll-Rand. The relationship of DFMA to simultaneous engineering is discussed. Keywords: Design; Manufacture; Assembly; Productivity; Simultaneous engineering; Development teams; Training 1. Introduction Ingersoll-Rand is an international company with annual sales in excess of three billion dollars. Over employees work in manufacturing plants in 17 countries. The company is decentralised, with each division responsible for engineering and new-product development. A Central Corporate Technology Office promotes advanced technology programmes with the divisional engineering departments. This paper describes activity at the Portable Compressor Division, which has responsibility for operations in North Carolina and in England. DFMA techniques were first presented to Ingersoll-Rand divisional engineering and manufacturing managers on 8 May The introduction was presented by Sandy Munro of Munro Technical Services for Productivity at a conference on simultaneous engineering sponsored by Ingersoll-Rand Corporate Technology services. As a consequence of the enthusiasm generated by the four-hour overview, arrangements were made to conduct a two-day training class at the Portable Accepted for publication: 14 July 1990

2 132 D. J. Gerhardt et al. Compressor Division on 1-2 June Thirty-four designers, engineers and manufacturing personnel were trained by Sandy Munro in the Boothroyd Dewhurst manual techniques. An actual example, using a new radiator and oil-cooler design concept, was used for the training. The DFMA design reduced the number of parts from 80 to 29, and the assembly time was reduced from 18.5 minutes to 6.5 minutes. The new design went into preproduction during the last quarter of 1989 and full production during February As a consequence of the success with the initial application, DFMA software training was conducted in July 1989 and a DFMA facilitator appointed in August DFMA is now being implemented on all engineering projects and is a key reason for the success of simultaneous engineering at Ingersoll- Rand. 2. Simultaneous Engineering The Portable Compressor Division of Ingersoll-Rand has used various aspects of simultaneous engineering for the past ten years. The introduction of DFMA in June 1989 as a simultaneous engineering tool served as a catalyst that has produced dramatic increases in productivity and reduced new-product development times. DFMA has been an important tool in uniting the project teams from various departments into a cohesive group. We have been able to reduce our new-product development time from two years to twelve months while maintaining high quality standards. The ten most important items for the successful implementation of a simultaneous engineering programme are as follows: DFMA Team selection Detailed specifications Supplier involvement CAD/CAM computer network Advanced engineering analysis Training Rapid prototyping Formalised review process Advanced testing techniques 3. Design for Manufacture and Assembly Ingersoll-Rand was formally introduced to DFMA by Sandy Munro of MTS for Productivity on 8 May 1989 [1]. The presentation was made at a simultaneous engineering conference sponsored by Ingersoll-Rand Corporate Technology Services. A two-day training class using the Boothroyd Dewhurst DFMA

3 Design for Manufacture and Assembly 133 manual techniques [2] was conducted at the Portable Compressor Division on 1-2 June Thirty-four designers, engineers, and manufacturing and marketing personnel were trained by Sandy Munro. Two examples from a portable compressor were used for the training. One involved a new radiator and oil-cooler concept; the other was for a bumper design. The improvements that resulted from the DFMA analysis are summarised in Table 1. Actual parts were brought into the training room for analysis. Five teams were set up for the training, with each team having representatives from various departments. The DFMA training served as a catalyst for team building that has stimulated our simultaneous-engineering activity. The new designs developed in the June 1989 training session went into preproduction during the last quarter of 1989 and into full production during February The new designs on the Ingersoll-Rand Prestige Series Compressors were introduced at the American Rental Show on 12 February As a consequence of the success with the initial application, DFMA software training was conducted in July The "Design for Assembly Toolkit" PCbased software from Boothroyd Dewhurst Inc. was used. A DFMA facilitator was appointed in August The facilitator attended the SME "Design for improved manufacturability and profitability" Conference [3] during September 1989 as part of his training. The DFMA software provides the capability to analyse complex designs in a short period of time. An example for a control and instrument panel is summarised in Table 2. The old and new designs are shown in Figs. 1 and 2. Table 1, DFMA comparison for the oil-cooler and radiator assembly. Original DFMA DFMA design revision gain Number of parts % Number of fasteners 38 2(I 47% Assembly operations % Assembly time (minutes) % Table 2. DFMA comparison for the control and instrument-panel assernbly shown in Figs. I and 2 Original DFMA DFMA Design Design Gain Number of parts % Number of fasteners % Assembly operations % Assembly time (minutes) % 4. Team Selection The most important element in a successful DFMA and simultaneousengineering implementation is team selection. The team will either "make" or

4 134 D, J. Gerhardt et al. Fig. 1. The old design, which used separate control and instrument panels.

5 Design for Manufacture and Assembly 13 ~. Fig. 2. The new DFMA design, which incorporates controls and instruments into one panel, "break" the project. The team leader must have a sense of urgency and persistence; "people skills" are required in addition to technical skills for a successful leader. At the Portable Compressor Division of Ingersoll-Rand, the team leaders have come from engineering, marketing and purchasing. Future plans are to have team leaders from manufacturing, quality and accounting. We currently have six active new-product development teams, one of which has members from three countries. Two of the teams have representatives from four Ingersoll-Rand Divisions. A summary of the six teams is presented in Table Detailed Specifications Earlier commercial programmes at Ingersoll-Rand were initiated with a sevenpage Product Development Authorisation. Military programmes were often initiated with specifications that contained hundreds of pages. The optimum specification effort falls between past general industry requirements and military requirements. The typical specifications for new programmes now range from 10 to 75 pages, depending on the size of the programme. Specifications for future programmes include input from competitive evaluations, best-in-class surveys and quality function deployment (QFD) input [4].

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7 Design for Manufacture and Assembly 137 Table 3. The simultaneous-engineering teams. Team Team Engineers and Manufactnring Marketing Purchasing Other leader designers and assembly l Marketing Manager 2 Engineer Senior Engineer 4 Senior Engineer 5 Engineering Trainee 6 Purchasing Manager 6. Supplier Involvement Early supplier involvement provides benefits in many ways. DFMA analysis is done on components that interface to supplier parts. By working with a supplier and making simple changes to a part, the overall cost of the product can often be reduced while increasing the quality and performance. We invite our key suppliers to joint training on Geometric Dimensioning and Tolerancing, Statistical Process Control and DFMA. CAD drawings and 3D models are provided by many companies. This saves us the time and expense of entering drawing information into our CAD systems. We are relying on suppliers to take more of the design responsibility where they have the expertise. Examples include plastic fuel tanks and running gear. 7. CAD/CAM Computer Network Simultaneous engineering requires that up-to-date information be available 24 hours a day for all the team members. With the proliferation of new computers, it is important to have an effective network linking the computers and databases to obtain maximum productivity. Fig. 3 illustrates the computer network at the Portable Compressor Division. The present CAD/CAM system at the Mocksville, North Carolina facility consists of 18 Computervision workstations. Eight of these workstations are minicomputer based and ten are based on SUN Microsystems workstation technology. Eleven seats are presently being utilised in design engineering, five seats are utilised in tool design, and two seats are in sheet-metal production. All of these workstations are connected through an Ethernet network. All of our product design layouts are produced in 3D. This database is distributed

8 38 D. J. Gerhardt et al. via the network to detailing, tool and fixture design, and to manufacturing. We are producing layouts for fixtures and tooling direct from the design model, and are generating sheet-metal parts direct from the design model. Various programme-management software packages are used, including MacProject li and Harvard Project Manager. The IBM Copics system is used for bills of material and for production control. 8. Advanced Engineering Analysis Advanced engineering analysis techniques, such as solids modelling and finiteelement analysis, are used to expedite new-product development. ARIES software is available on SUN 4/60 hardware for preliminary analysis. Stress analysis of CADD models can be conducted with STRESSLAB on a SUN 3/160. For more complex finite-element analysis, ANSYS is used on a VAX Training Training is an important part of effecting positive change such as simultaneous engineering. We have provided extensive technical training for personnel for the past ten years. Beginning with SPC training in 1985, we have extended technical training to include all affected departments in order to support the team approach. In addition to SPC, this training has included DFMA, GD & T, QFD, design of experiments, and many other courses. During 1989, we initiated a master's level engineering programme with the North Carolina State University. The courses are taught at our Ingersoll-Rand engineering facility. One current course by Dr Carl Zorowski is on mechanical design for automation [5, 6]. In order to promote teamwork, the Virginia Polytechnic Institute is instructing all 600 Portable Compressor Division employees on creative process improvement. These two-day classes by Dr Paul Kemmerling and Dr Timothy Greene, from the Industrial Engineering Department, cover various areas that give each employee a better appreciation of the overall plant operation. The topics include production control, costs, goals, communication, planning, quality and industrial engineering techniques. 10. Rapid Prototyping Rapid prototyping is a technique that evolved in the software industry to get fast evaluation of software programs. Ingersoll-Rand first used it in 1984 for the development of microprocessor software for the control of compressors and engines [7]. We are now using the technique for mechanical systems. Prior

9 Design for Manufacture and Assembly 139 to rapid prototyping, engineering technicians would build prototypes six to twelve months into the programme from detailed drawings. With the new system, assembly personnel build concept prototypes within the first month. Having a concept prototype early in a programme generates many more ideas from customers, manufacturing, marketing, purchasing, service personnel and suppliers. 11. Formalised Review Process The following review processes have been found to be essential to reduce the product development time: Product-specification review and approval Development-plan review Weekly team meetings Preliminary-design review Technical reviews Safety review Serviceability review Critical-design review Product-performance review Document-readiness review Production-readiness review 12. Advanced Testing Techniques The shorter product development times require advanced testing techniques and accelerated durability-testing programmes. For the past three years we have been using design of experiments computer software to structure compressor dynamometer testing. We have been able to reduce our testing time by more than 50% while obtaining more useful data. Six mobile dataacquisition systems are used to test complete compressors. Statistical analysis has been used to shorten testing times on certain programmes. Critical compressor test data is kept in a computer database and is available 24 hours a day to Ingersoll-Rand divisions worldwide. Accelerated durability testing is done on components and on complete machines. Acknowledgement The authors acknowledge the contributions of the following personnel in implementing DFMA at Ingersoll-Rand and the preparation of this paper:

10 140 D. J. Gerhardt et al. J. Arzbach, G. Bauer, T. Flatt, B. Goehler, P. Johnson, R. Moore, J. O'Dell, M. Weir and K. Sutton. References l, S. Munro, MTS for Productivity, Troy, MI G. Boothroyd and P. Dewhurst, "'Product design for assembly", Boothroyd Dewhurst Inc., WakeIield, RI 02879, "Design for improved manufacturability and productivity", Society of Manufacturing Engineers, Dearborn, MI 48121, September , W. Eureka and N. Ryan, "'The customer-driven company, managerial perspectives on QFD", American Supplier Institute, Dearborn, MI, , G. Boothroyd, C. Poll and k. Murch, Automatic Assembly, Marcel Dekker, New York, M, Andreasen, S. Kahler, T. Lurid and K. Swift, Design/or Assernbly, Springer-Verlag, New York, D. Gerhardt and T. Sills. "'Microprocessor control for diesel powered equipment". Society of Automotive Engineers paper 87077, I987. Correspondence atul offprint requests to: D. J. Gerhardt, Ingersoll-Rand Company, Portable Compressor Division, 501 Sanford Avenue, Mocksville, North Carolina , USA.