Minimizing Scrap...

**ozdemir** · 03-11-2009, 08:18 PM

Hello. I have a question that I am faced with answering to minimize our scrap by utilizing the available inventory to come up with my current demand. Here is the scenario:

I have the following lengths at the following quantities:
89 @ 1
92 @ 2
97 @ 1
107 @ 1
138 @ 7
149 @ 0
154 @ 2
164 @ 3
175 @ 8
185 @ 11
195 @ 25
206 @ 6
225 @ 0
228 @ 6
235 @ 15
245 @ 4
255 @ 2
257 @ 2
268 @ 15
351 @ 7

My demand is as follows:

92 @ 12
93 @ 12
99 @ 8
100 @ 12
105 @ 6
108 @ 24
116 @ 8
127 @ 6
161 @ 6
172 @ 12
183 @ 6

It is a must to use the shorter lengths first and save the longer lengths, if possible. For example, each 351 inch piece can be cut and made into 3 pieces of 118 with 3 inches of scrap. But, having a piece that is 351 inches means i can use that when an order comes in for that long. Its not often to have a continuous piece at the longer lengths, so we try to save those for when demand calls for the longer pieces.

Thus, i am thinking that there may be multiple solutions, depending on how i choose to accept the solution (i.e. minimized scrap by using longer lengths, or using shorter lengths and saving the longer pieces but not necessarily minimized scrap). I hope this makes sense.

I was thinking of using Solver, but my pea-sized brain cannot figure this out. We are a growing company and before we got as busy as we are today, the numbers were easy to figure out because the quantities were so low, and the inventory was low as well.

Any and all help is greatly appreciated. I am looking for a long term solution so that I can apply this over and over as my inventory changes. Thanks all.

Cihan

**shg** · 03-11-2009, 08:31 PM

As a practical matter, I think this will require code (there's a challenge

). I also think a rigorous solution would be complex, but I'd take this approach for an approximation:

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**Leith Ross** · 03-11-2009, 08:38 PM

Hello ozdemir,

Solver can used as part of the solution, but will not provide you with the complete solution. You need need to create a histogram based upon the frequency of each length and then use solver to find the best combination of lengths from a single length. Depending on your operation, other factors may need to be taken into consideration, such kerf (the amount of material lost during a cut). You may want to consider purchasing a program. In the long run it will save you time and money. What you develop today maybe obsolete in a year. If your company is growing fast, do you really have the time to devote to software development and maintenance?

**ozdemir** · 03-11-2009, 11:54 PM

Well, i don't necessarily think i need a sophisticated program. I am pretty sure that if i think long enough about the different iterations that can be done while accounting for the reduction in inventory, i can find out the answer. i just thought maybe there was a way to use solver. let's assume that i don't have another constraint related to keeping the longer lengths intact. couldn't i just assume the quantity is zero for those and if my demand is not met with the available inventory, then add them in slowly? and yes, kerf is taken into account. i really need lengths that are approximately 3/8 to 5/8 shorter than the rounded inch. i just round so that i can have room to play. anyhow, i will think about this problem more tomorrow. most likely will figure it out manually. with my mechanical and eraser! unless someone overnight figures this out!!!! thanks.