汽车专业毕业设计-翻译-中英文(全)lean-remanufacture-of-an-automobile-clutch.doc

LEAN REMANUFACTURE OF AN AUTOMOBILE CLUTCHTony Amezquita* Assistant Professor, corresponding author.andBert Bras* Remanufacturing Engineer. Saturn CorporationSystems Realization LaboratorySpring Hill, TennesseeWoodruff School of Mechanical EngineeringGeorgia Institute of TechnologyAtlanta, Georgia 30332-0405AbstractIn the history of manufacturing there have been three production systems, namely, craft production, mass production, and lean production. In many automotive remanufacturing operations, craft production and mass production systems are used as the basis for remanufacturing processes. The lean production system has proven to be more effective in the manufacture of automotive parts and it has allowed manufacturers who use it to produce in much greater varieties, with higher quality levels, and with lower costs. Hence, if used in remanufacturing, it would greatly enhance it. In this paper, a current remanufacturing process of an automobile clutch is analyzed, and a lean remanufacturing process is developed and compared to the as is process. Our findings indicate that the lean remanufacturing process provides a more robust process with lower costs when compared with the current clutch remanufacturing process that utilize craft and mass production practices.1Our Frame of Reference Remanufacture in the Automotive IndustryRemanufacturing is the most economically sustainable form of reuse and recycling of manufactured goods, and it can be defined as the industrial process where worn out products referred to as cores, are brought back to original specifications and condition. In some cases, especially in the remanufacture of OEM automotive parts, remanufactured products exceed original specifications. The reason is that the latest engineering design and specifications, coupled with failure mode countermeasures derived from failure analysis, are used instead of the original specifications. The benefits of remanufacturing are many, but the most salient are:1)Remanufacturing salvages the material, energy, capital, labor, and emissions that went into the manufacture and material processing of products. 2) The resulting production costs can often be lower than manufacturing, allowing remanufacturers to sell their units for 25 to 50% less than manufactured units with equivalent or better quality levels.These two benefits are the result of the fact that parts are reused and the embedded utility in the parts are maintained. Hence the resulting production costs, which should be considerably less than in manufacturing, allow remanufacturers to pass the savings on to consumers. Remanufacturing in the automotive industry can be divided into two groups; independent remanufacturers and Original Equipment Manufacturer (OEM) remanufacturers. Both of these activities in the domain of automotive products constitute the largest remanufacturing consumer market segment in the United States and Europe. In 1978, Kutta and Lund documented a survey capturing some of the issues important to remanufacturers (Kutta and Lund, 1978). However, we discovered in surveys and interviews with remanufacturers that many changes have occurred in the industry since then (Hammond, et al., 1996, Hammond, 1996). Major changes have been the restructuring of automotive companies into platforms and the trend towards mass customization of products. Especially the latter has resulted in what remanufacturers have termed “Parts Proliferation”, which refers to the practice of making many variations of the same product - differing only in one or two minor areas. However, these differences (such as electrical connectors) are distinct enough to prevent interchanging these similar products. The focus in this paper is on independent automotive remanufacturers, because they remanufacture component parts from most of the automobile manufacturers in the world, and for a very large number of model years. This being the case, independent remanufacturers are faced with a parts proliferation problem which cannot be successfully handled with their current production practices, that consist of a mixture of mass production and craft production practices. As described below craft production practices maintain production costs high regardless of volume, and mass production practices are not compatible with large product varieties. Consequently independent parts remanufacturers are loosing market share to aftermarket parts manufacturers, and in some cases, remanufacturers are being forced out of the market, as in the case of clutch remanufacturing. For example, in 1989 the price difference between remanufactured and manufactured clutches was 50%. In 1994 the difference dropped to 20%, and now a large number of clutch remanufacturers are getting out of clutch remanufacturing altogether. It is our belief that the trends in mass customization and parts proliferation will not decrease and the small to medium sized independent remanufacturers seem to suffer most from these trends. Our surveys also point out the differences and sometimes hard “us versus them” attitude between independent remanufacturers and Original Equipment Manufacturers (OEMs), leading us to believe that the sharing of design information between OEM and remanufacturer is not a feasible solution and/or option in many cases. Hence, the only way we can help increase the remanufacturability of those products is by improving the remanufacturing processes. In this paper, we present some of our findings which, interestingly enough, indicate that the introduction of lean production techniques (which are one of the main causes of part proliferation and product diversity) in the remanufacturing industry, and hence creating lean remanufacturing processes, can lead to significant process improvements and savings compared to the current remanufacturing processes which are heavily batch oriented. In this paper, a solution to the parts proliferation problem of independent automobile parts remanufacturers is developed by transforming a current remanufacturing process of an automobile clutch into a lean remanufacturing process. This lean clutch remanufacturing process has been developed in great detail in (Amezquita, 1996). In this paper, we will discuss the as-is process, followed by a discussion on how to convert this process into a lean remanufacturing process. It should be stated up-front that although the proposed lean process offers substantial savings, it has not been implemented by the company who supported this case study. First, however, we will provide the necessary background on craft, mass, and lean production systems.2Craft, Mass, and Lean ProductionIn the 1800s, automobile manufacturing was the domain of the skilled craftsmen who controlled most of the activities on the manufacturing floor. These skilled craftsmen designed and built customized vehicles by making and fitting each part by filing it down until it mated with the other vehicle parts. Even if craft producers could make 10,000 identical cars, the price per car would not have dropped by much, because each car was essentially a prototype. The biggest benefits of this craft production system in the automotive industry were that: customers were able to obtain products which specifically met their needs, andworkers were satisfied, proud, and fulfilled, and their goal was to hone and perfect their skills and one day become independent owners.At the turn of the century, Frederick Taylor removed the control of the manufacturing operations from the hands of the skilled craftsmen by creating divisions of labor. This was the first step towards the development of mass production, which was fully implemented by Henry Ford. Taking the developments of Taylor, Ford added the standardization of the production of parts, which led to complete parts interchangeability, which in turn led to the simplification of parts assembly. In 1908, an assembler was spending 514 minutes (8.56 hours) assembling a large portion of the car before moving to the next car (Womack, et al., 1991). To reduce the cycle time of assemblers (period of time spent with each vehicle by each employee), Ford had each assembler perform a single task and move from vehicle to vehicle in the assembly hall. The cycle time per vehicle was reduced from 8.56 hours to 2.3 minutes (Womack, et al., 1991)! Finally, the simplification of assembly tasks allowed Ford to utilize the moving assembly line to bring the cars to the assemblers and eliminate all the walking previously done. In addition, the moving assembly line enforced a faster and even work pace. Fords implementation of the moving assembly line, which brought the car past the stationary worker, cut cycle time even further from 2.3 minutes to 1.19 minutes (Womack, et al., 1991).Ford discovered that his new system reduced the amount of human effort needed to assemble a vehicle, and with the same number of people, equipment, etc., the more standardized vehicles he produced, the more the cost per vehicle dropped (economies of scale). By the time Ford reached volumes of two million identical vehicles per year, he had slashed the real cost to the consumer by an additional two thirds from the time he started production of the Model T in 1908. Consequently, a production system which most closely resembles the mass production system can bring substantial savings to a remanufacturer, and is often advocated. However, this system runs aground when confronted with a large variety of parts, which is the current situation many independent automotive remanufacturers are facing. Most automotive parts remanufacturers (and other remanufacturers) still rely on craft production systems to handle the variability in the number of parts to be remanufactured and the variability inherent in refurbishing operations due to wear differences. However, as noted already by Henry Ford, craft production system has two main drawbacks:1)Production costs remain high regardless of volume (economies of scale are not possible, e.g. Ferrari Automobiles).2)Quality, consistency, and reliability are poor due to the lack of standardization.Thus, a different approach to remanufacturing which uses elements of the mass and craft production systems may prove to be more suitable for automotive parts remanufacturing.Lean production takes the best elements of the craft and mass production systems. This system was developed by the Toyota Motors Corporation, and later is was implemented by all Japanese automotive manufacturers. Lean production can be defined as an entire production system with the following fundamental characteristics:1)Economies of scale (from mass production),2)Production of large varieties of products (from craft production),3)Elimination of non-value added resources and activities, and4)Integration of all production system elements and functions to obtain long term functional relationships.Compared to the lean production system, the traditional mass production system can be fundamentally defined as having the following characteristics:1)Economies of scale,2)Very limited range of product varieties,3)Non-value added resources and activities are perceived as necessary, and 4)Division of all production system elements and functions to obtain specialization resulting in short term strained relationships. Given the fact that the lean production system is most suitable for the production of large varieties of products, and it allows the attainment of economies of scale, it would seem that using this production system as a basis for remanufacturing processes would provide better results than the ones currently obtained, which are forcing independent parts remanufacturers away from remanufacturing. In the remainder of this paper the remanufacturing process of an automobile clutch at one of the largest independent automotive parts remanufacturers is used as a case study. 3Automobile Clutch Remanufacturing at RaylocThe Rayloc Company is a division of the Genuine Parts Company which provides aftermarket replacement parts at 6,500 NAPA Auto Parts stores nationwide. Rayloc is one of the largest automotive parts remanufacturers in the world, and they remanufacture parts such as alternators, starters, drive shafts, brake master cylinders, calipers, wiper motors, window lift motors, rack and pinion units, steering boxes, power steering pumps, brake shoes, disc brakes and clutches. The focus of this paper is placed on the remanufacturing process of clutches.The clutch remanufacturing process at Rayloc was analyzed for six months at one of the remanufacturing plants. The process material flow is represented schematically in Figure 1.Figure 1 - Current Clutch Remanufacturing Process Material Flow With BatchingIn this process cores are supplied by customers, and are accumulated randomly in drums without identification at the NAPA jobbers or retailers. Cores (c1, c2, etc., see Figure 1) are then identified and sorted by part number and manufacturer, and are again accumulated in a core warehouse at the Rayloc plant. Based on a forecast, cores are removed from a core warehouse and processed in a batch. Batches of the same part number are randomly mixed and the reusable components are assembled together with replacement component parts. Non-reusable components are recycled after work has been done on them. The remanufactured cores (rc1, rc2, etc., see Figure 1) are placed in a finished goods warehouse to start the cycle over again after a customer buys the remanufactured clutch. The assumption behind this remanufacturing process is that identical cores can be easily collected into economic batches and together they can be disassembled, cleaned, inspected, refurbished, and reassembled. The process is distinguished by having large enough volumes to obtain some form of economies of scale. The practice of batching in remanufacturing was adopted from mass production, but batching is also done in remanufacturing for the purpose of cannibalizing reusable parts and reduce the need to purchase new manufactured replacement parts. Purchasing manufactured replacement components is for the most part more expensive than cannibalizing cores. In fact, a fundamental principle of economic remanufacturing is the maximization the reused content in finished remanufactured products. After the completion of the study, the clutch remanufacturing process was characterized using the criteria as shown in Table 1. The characteristics of this process reflect the problems and issues independent auto parts remanufacturers face, and are not indicators that Rayloc is poorly run. In fact, Rayloc is one of the most efficient remanufacturers in the U.S.A. with a proven track record exe