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Work Order Concatenation occurs when two or more work orders are required to run together on the shop floor. To illustrate how the scheduler schedules operations on these orders, suppose we have three work orders: 1, 2 and 3. Let us further assume that their routings all have the following operations calling out the same respective machines: 10, 20, 30, 40, 50, 60, 70 & 80. If work orders are declared to be concatenated, the scheduler will schedule the same operation on all three of them when any one of them is picked. Let's suppose that the scheduler first chooses to schedule operation 10 of work order 3. When it schedules operation 10 of work order 3, it positions operation 10 for work order 1 and operation 10 for work order 2 immediately after it. The final result of scheduling all the 10 operations on one of these work orders produces concatenated sequences with operations 10-10-10 (work orders 3,1,2) scheduled together, operations 20-20-20 (work orders 1,2,3) scheduled together, operations 30-30-30(work orders 2,3,1) scheduled together, and so on. The order of the work orders within the concatenated sequence may vary from operation to operation. The above example is a rather simple one that shows basically how the scheduler groups the same operation from several work orders and positions a "concatenated" operation onto the machine which is common to all member work orders for that operation.
The two most common applications of work order concatenation are (1) serial effectivities, and (2) "odd-even" dash numbers. Serial effectivities are applied to a manufactured part, it often means that a work order is released for just one part, accompanied by traveler documentation that corresponds to that particular serial numbered part. It is quite often the case that several of these parts are required. Were it not for serial effectivity requirements, a single shop work order for the desired quantity might have been created. For example let's suppose that it is desired to make 12 parts of the same part number (and therefore having identical routings), using 12 work orders each with a quantity of 1. We assign an arbitrary 4-character concatenation code to each of the 12 work orders. This "concat" code, being the same for all 12 work orders, tells the scheduler they are a concatenated group. In this way the scheduler schedules the operations on these work orders much the same as if all 12 parts had been on one work order. The "odd-even" dash number case is where we have a work order for a "left-hand" part (with an odd dash number) and a work order for a "right hand" part (with an even dash number). Their respective routings are nearly identical, particularly with regard to the number of operations and the machine alternates called out to perform those operations. Physically the "left-hand" parts are the mirror image of the "right hand" parts. Many of the actual operations may be identical. But there might be some that are slightly different because of the left-right differences in the parts themselves. It is desired to run all the quantity of one work order first through an operation, then all the quantity of the other work order second. That is, you'll see the scheduler create schedules with a concatenated sequence (10-10) on the first machine, then (20-20) on the machine that is scheduled to perform the second operation, and so on. The "odd-even" dash number case occurs on a rather regular basis when detail parts are manufactured for airplanes. It is possible to concatenate work orders which have chained operations in their respective routing sequences. In these cases the scheduler will create schedules that have operation chains nested within concatenated sequences. |
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