机械制造专业毕业设计外文翻译--制造分析

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1、MANUFACTURING ANALYSIS:HOW MUCH FLEXIBILITY? In addition to production systems that fabricate very high quality products,at low cost,and with ultrarapid delivery,many strategic planners and economists point to the need for flexibility. Publications from Japan(Yoshio,1994；Ohsono,1995)express a simila

2、r view,and the more recent J.D.Powers comparative surveys on automobiles indicate thatnow that others are closing the quality gap,the Japanese have to compete in other areas(see Rechtin,1994；and the annual J.D.Powers report series).Emphasis is thus place on these combined factors of quality,cost,del

3、ivery,and flexibility(QCDF).The ability to react to smaller lot sizes and the quest for ultrarapid delivery are major conconcerns,culminating in the possbility of a three-day car(Iwata et al.,1990_. In an ideal situation,once the various market sectors have been established,production will settle in

4、to a groove and be constantly refined and improved but with no major upheavals.Unfortunately,in recent years,manufacturers have not been able to rely on long periods of uninterrupted production because events in the world economy have forced rapid changes in consumer demand and the range of consumer

5、 preferences. Henry Fords favorite aphorism-that his cutomers could have any color of car they wanted as long as it was black-is in sharp contrast to todays range of consumer preferences.This has led to the proposal by some academics that manufactering can be built for customized mass production.Thi

6、s sounds nice on first hearing.Howerver,for products like automobiles,the degree of customization can go only so far for a given batch size and price point.Only hyperwealthy CEOs and movie stars can get precise customization in products like automobiles. Nevertheless,an ability to be prepared for an

7、y sudden market shifts is becoming more of an issue.As new equipment is purchased,manufacturing companies must decide between harware that is dedicate to only a few tasks and is thus relatively inexpensive,and more costly but more versatile equipment that might perform unforeseen tasks in the future

8、.The methodologies for analyzing capital expenditures,returns=on-investment(ROI),and depreciations are given in many texts (see Parkin,1992). these can be used to analyze the ROI for new machinery that has been identified as useful and is therefore about to be purchased.However,since todays market t

9、rends are so uncertain,such analyses do not help to predict the specific systems to install in the firt place.The hope is that some of the engineering solutions will provide much more flexible machinery for only a modest increase in cost(Greeenfeld et al.,1989).In this way,the investment dilemna mig

10、ht be less critical. The preceding discussions emphasize that flexibility is a main challenge for the continued growth of a mew company.The main question is:Can a design and fabrication system that is first set up to respond to one market sector be quickly reconfiqured to respond to the needs of ano

11、ther market sector,or even another product,and be just as efficient? Today,the answer to this question isprobably not.For example,if a machine shop is well equipped with lathes but has no vertical boring machines,there will be a natural limit on achievable tolerances.It is unlikely that it will be a

12、ble to suddenly jump from truck transmissions to helicopter teansmissions.And even in the reverse scenario,if a shop has dedicated itself to precision boring.it is unlikely that the equipment and the craftspeople will be able to br quickly redeployed in a cost-effective manner to routine production

13、procedures and less demanding tolerances；their competitive advantage would be lost.These same comparisons can be made for semiconductor manufacturing.Manufacturers who are currently focusing on the high-volume production of memory chips will not readily switch to application-specific devices or vece

14、 versa.The general conclusion may be drawn that todays manufacturing tools-specifically manufacturing systems-are still too dedicated to specific machine tools, robots,and manuvacturing systems-are still too dedicated yo specific market sectors and are not flexible enough. This general need for flex

15、ibl,reconfigurable manufacturing systems was of course a key aspect of CIMi its original xonception.Merchant(1980)led a number of industy forecasts between 1969and 1971 that refined the details and needs of the CIM philosophy.However,theseforecasts overestimated the rate at which flexible manufactur

16、ing systems ang related technology would be asorbed into factories.During the 1970s and 1980s,machines exchanged”handshakes”when tasks were completed.If these tasks were completes properly and on tim,then a flexible manufacturing system(FMS)continued to operate satisfactorily.However,if the machines

17、 went seriously out of bounds,then the communicaations broke down and too frequent human intervention wasneeded to make the FMS efficient.Duringthis era,the experiences of several research and development groups showed that the inadequacy of cell communication software was probably the key impedimen

18、t to the industrial acceptance of CIM(Harrington,1973；Merchant,1980；Bjorke,1979).Of interest was that by the late 1980s.the review articles on CIMwere advocating much smaller FMSs of only three or four maxhines as the most efficient way of utilizing the cell concept.Allthese trens suggestes more sop

19、histicated computer-and sensorbased techniques at the factory floor.as described later. 2.6.1Design for Flexibility(Reuse) Design for flexibility in the automobile industry can pay off in a bigway if there is some reusability of fixture families.The automated assembly lines where the frames, doors, and chassis are asembled with robots and welded together are obviously intensely expensive.These are suall two_story-high lines as big as many football fields where