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Solver not giving me optimal result. Need help setting up for Solver.

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    Solver not giving me optimal result. Need help setting up for Solver.

    Hello, I am trying to find the best width cut size that minimizes scrap loss. I have a Master Sheet that I need to cut into multiple sizes (various widths). I'm given a specific width that we need to buy that is cut from that Master Sheet but we also have other sizes we use out of that same Master sheet. I need Solver to tell me which of those cuts and how many of each cut I should make to minimize the scrap loss. First it must pick the cut part that I need then decide based on the highest usage what other sizes to cut to. The Master Sheets can be 48-58" wide and there is always a minimum scrap loss of 1".

    I've tried running Solver but it does not give me the minimum scrap loss possible. It's selecting one size and one cut giving me a huge scrap loss. Not sure what I'm doing wrong but I also need help in incorporating the usage % to hopefully pick highest usage parts first after my initial size is selected. Any help is appreciated!
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    Last edited by osugirl7; 01-08-2021 at 03:31 PM.

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    Re: Solver not giving me optimal result. Need help setting up for Solver.

    I'm struggling to understand the data.

    One cut of each of the widths in M8:M14 gives a total 75.2 which is more than the maximum 58 width. So how could they all be satisfied from one sheet.

    Does this boil down to trying different combinations of cuts with several sheets to minimise the waste. e.g.
    Taking say M8:M11 & M14 which total 47, and cutting them from a 48 wide sheet, with a loss of 1, then accepting M12 & M13 will be cut from a second sheet.

    Then checking all other combinations to see if the loss of 1 in this example could be further reduced.

    What part if any do the usage %s in L8:L14 play?
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    Re: Solver not giving me optimal result. Need help setting up for Solver.

    The various cuts in M8:M14 are all the cuts we make for PartA. It doesn't need to be every cut size listed, just needs to pick one or two or more different cut sizes based on the usage and minimal scrap loss.

    For example, I would have it cut PartA6125 for a number of cuts (could just be one cut for that size) and then I want solver to tell me which other cuts to make after that but it doesn't have to be all of them. I don't want to cut all my material to the PartA6125 because it's only used 6% of the time. So maybe it tells me I can get the minimum scrap loss by making 1 cut in the 6.125" and 11 cuts of the 4.656". Now that I'm thinking about it I think the number of cuts for PartA6125 will need to be specified upfront. So let's assume we need 1 cut in the 6.125" and the other cuts can be any combination of sizes.

    To answer your second question, it does boil down to different combination of cuts with minimizing scrap. However the size can be anywhere between 48-58. The 1" Scrap Std loss will always be 1". The Scrap Loss that I'm trying to minimize will either be 0 or some number. The usage is a little tricky, I'm not quite sure how to go about it but maybe the solver gives me multiple answers for each size and tells me what the scrap loss is.

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    Re: Solver not giving me optimal result. Need help setting up for Solver.

    I'm not sure I understand your request, anyhow, here is a workbook with a different setup.

    You can use Simplex, and you don't need binary variables, just integers.

    HTH,

    Francesco
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    Last edited by Hydraulics; 01-08-2021 at 03:42 PM. Reason: Removed personal infos
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    Re: Solver not giving me optimal result. Need help setting up for Solver.

    Thank you Hydraulics! The solver seems to be giving me an optimal answer. Now I just need to figure out the usage assignment and find a way to prioritize which other sizes it selects based on their usage but this gives me a good start!

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    Re: Solver not giving me optimal result. Need help setting up for Solver.

    Is there any way to say if one size has the highest usage (besides the part selected, PartA6125) that the # of Cuts should be >=1 for that size?
    Last edited by osugirl7; 01-08-2021 at 05:35 PM.

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    Re: Solver not giving me optimal result. Need help setting up for Solver.

    You could add a helper column with the formula

    =IF(E8=MAX($E$8:$E$14),1,0)

    and then use it as a constraint on the number of cuts.

    HTH,

    Francesco
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    Re: Solver not giving me optimal result. Need help setting up for Solver.

    That did the trick! Thank you!

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