A Comparison Of Group Technology & Process Layout (3)
A Comparison of group technology & process layout using a model of an actual shop<br />Presented by:-<br />Anish Garg<br />
introduction<br /><ul><li>Process layout:- process layout group machine of same type together in a machine center.</li></ul>There are as many machine centers as there are type of machines. <br />The machines are interchangeable.<br />Queue of waiting batches of part will form at the machine center.<br /><ul><li>Group Technology layout:- group technology groups parts into family of parts which are similar in physical appearance .
Machine which are needed to produce each family of parts are grouped together and is called manufacturing cell.
As many manufacturing cell as there are families of parts.
Machine in the cell are dedicated to working on only certain parts.
Queue may form at every machine because of its dedication.</li></li></ul><li>0verview<br /> This study used a computerized job shop simulation of actual shop to compare group technology with process layout. The shop was a computerized model of the shop at Extrusion Dies, Inc. manufacturer of dies. The shop at EDI contain:-<br /><ul><li>38 machine of those 12 functionally similar.
Each type contain between 1 and 5 major component.
Routing sheet for these component contain between 17 & 42 operation.
Time required for these operation varies between one and half hour to 22 hour.
3 type of material handling equipment are used.
All parts are produced in batches of I at EDI.</li></li></ul><li>Type of layout examined in this study<br />Process layout developed using craft, where each group of similar machine were considered as a department by craft.<br />Grptec layout group of different type of machine were dedicated to commonly occurring sequences of operation. Craft was used to arrange the machine within each cell and to arrange the cell relative to each other.<br />Indmec layout used craft on an individual machine rather than group it arrange 38 dedicated machines relative to each other. And resulting layout was similar to Grptec layout<br />Last the Proded layout was identical to the process layout, except that the machines were dedicated to commonly occurring sequences of operation, rather than being interchangeable.<br />
Four distributions of demand for product<br />The EDI distribution was the same as the average distribution of demand between product at EDI. It was biased toward 2 of the 6 product.<br />The MST distribution was biased toward those products which require the most operations.<br />The LST distribution was biased toward those product which require the least operation.<br />The last FLT assume the equal demand for all the six products.<br />
Ten variable<br />Average time per setup<br />Average distance per move<br />Average no of products completed per year<br />Average machine utilization<br />Average queue length<br />Average waiting time per queue<br />Average flow time per batch<br />Average work-in-process inventory<br />Longest average queue length<br />Longest average waiting time.<br />
Results<br />Average setup time was greater in process model<br />Average distance per move was longer, on the average, in process and proded models. And shorter in the grptec model<br />For the average no of products completed per year there were no significant difference between the model<br />Average utilization should be larger in process model, due to the longer setup time.<br />Average queue length was shortest in the process model and this is true for average waiting time too.<br />Move time tended to longer in process and proded model<br />Average run time were very similar in the four model.<br />The big difference between the models occurs in the amount of time which a batch spent waiting for machines to become available. So much shorter average flow time was in the process model <br />
Result by distribution<br />There were not many significant difference between the distributions, where significant difference occurred is just the EDI distribution.<br />Average setup time was shorter in the EDI model<br />The average machine utilization rate was lowest in LST distribution and higher in EDI distribution.<br />There was no statistically significant difference between the distributions in term of average queue length <br />
conclusion<br />So it is very interesting that, even though more time will be spent moving batches and setting up machines in shop which using process layout, the flexibility of the machines in this shop lead to overall advantages. So longer setup time and move time have little meaning if the product are completed in less time. So group technology may not be the panacea which it may appear to be in the literature. Although there may be some situations in which group technology will be the most appropriate method of shop organization, it is clear that there are some potential problems with its use.<br />
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