Design principles of reconfigurable machines

438built for its customers. The team investigated this corebuilder’sfunctionality and tried to understand its limitationsand improve them.The study led to the conclusion that the productivity ofthe existing core-builder is constrained by elevatedchangeover and cycle times. Therefore, the goal was tominimize changeover time and hence reduce the idle stateof the system. The constraint to productivity formed by thechangeover time can be addressed effectively by makingthe machine reconfigurable. As previously stated, RMs arespecifically designed to handle changes within a partfamily. Their modular design significantly contributestowards the reduction in changeover time. The changeoversin RAM are reduced to the interchanging of modulesinstead of the many adjustments needed in the existingassembly machines, when assembling different products.The first step in the design of a RM is a clearidentification of the part family. Using our industrialpartner’s products catalog, 398 radiators were classifiedand grouped. Combinations of product features werestudied in order to establish a relationship between theproduct characteristics. The information for this studyconsisted of product features such as model, length, width,height, number of rows and car that uses it. Theserelationships were utilized to define part families dependingon the characteristics that are more imperative tomachine architecture. The study of these relationshipsconcluded that the length and the width are the mostimportant parameters that affect the reconfigurability of themachine to the greatest extent.As a result of this study [38], three main subgroupsdefine the RAM part family, and a few rejected productswere identified as listed in Table 2. With the newlystructured part family, the number of required modules hasreduced to three; each of them takes care of one sub group,whereas still more than 90% of the product range wascovered. If the design of the modules is based on this partfamily definition then the resulting machine will handlechanges within product sub group without requiringchangeover at all, and if the change is across a part familythen the changeover will be restricted to a change of amodule. Hence, extended changeover time that leads tolarge downtimes, can be avoided. The easy changes acrossthe part family represent a good example of design forconvertibility. The design principles and the study of RAMwere not validated experimentally since the machine wasnot built.6 Summary and conclusionsThis paper outlines the importance of design principles forRMs. Based on the design principles presented in thispaper, the ideas presented in the RMT and RIM patents [25,29] were realized. Each of the full-scale RMs wasexperimentally tested for the validation of reconfigurationprinciples as well as for sound functional performance. Theprototypes described in the paper currently serve asresearch platforms.The main contributions of this paper are as follows:– The RMS vision was refined into concrete machinedesign principles for the design of RMs that can beused in a manufacturing system.– The generality of application of these principles wasdemonstrated in various manufacturing domains suchas machining, assembly and metrology.– The importance of the aforementioned design principleswas validated for RMs.– Studies that demonstrate reconfigurability and goodperformance of the RMs that used the design principlesfor RMs were presented.The conclusions of our study are as follows:– RMs represent a new class of machines that aredesigned mainly for high-volume production applications.They bridge the gap between the flexiblemachines and the dedicated machines.– Not all design principles presented in this paper mustbe reflected in the design of each specific RM.However, the principle of a machine that is designedaround a part family is a necessary condition andshould be reflected in the design.– The design principles were demonstrated in the designof reconfigurable machining, inspection and assemblymachines; however, this philosophy is general and maybe applied to other domains of machine design.– The design principles of RMs and RMS follow asimilar philosophy.– RMs enable production of different products thatbelong to the same part family by allowing rapidand efficient pre-designed changes of a machine’sconfiguration.– The design principles of RMs are focused mainly onthe functionality of these machines and are importantin the phase of conceptual design. The detailed designof a RM follows concepts similar to any other machinedesign.– The suggested design principles do not contradict anytraditional design principles related to the goodpractice of machine design.Acknowledgements The author would like to thank Prof. Y. Korenfor his RMS vision and his remarks to this paper and to the teams ofresearchers and graduate students who participated in the RMT, RIMand RAM projects. The author would like to thank V. Srivatsan, J.Duphia and Dr. P. Spicer for their feedback and remarks to this paper.The author also gratefully acknowledges the financial support of theNSF Engineering Research Center for Reconfigurable MachiningSystems (NSF Grant EEC95-92125) at the University of Michigan.References1. Mehrabi MG, Ulsoy AG, Koren Y (2000) Reconfigurablemanufacturing systems: key to future manufacturing. J IntellManuf 11(4):403–4192. Altiok T (1996) Analysis of manufacturing systems. Springer,Berlin Heidelberg New York