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Sheet Metal Variation Control

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  • #47325

    BB_HB34
    Participant

    I have been tasked with setting up an SPC program within a large sheet metal fabrication department. I am looking for some information on best practices and possible benchmarking opporotunities. Our data shows that our largest scrap and rework costs were originated from the brakes and rolls areas. These are the areas that I will initiate the program. Of course I am working with a culture that is tooling controlled, so changing to a culture of checking the dimensions of a part verses visually checking to the tool will be a full time project in itself.
     Does anyone know of a company where SPC is being succesfully utilized within their sheet metal department.  Thanks for you help.

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    #157740

    Dennis Craggs
    Participant

    Try a google search on the words “spc sheetmetal”. There are about 262,000 web pages. Some companies proudly advertise that they apply SPC in their manufacturing processes. You should find many examples.

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    #157742

    Chad Taylor
    Participant

    Start with a Paerto Chart of the deffects. Prove to your operators the need for control with this data. Another approach is perform a GR&R on the current visual inspection of the tooling. Visual can be a good gage if everyone does it the same and is trained on what to look for. You may be able to set up some run quantities for the tooling that will remove the tooling pre-failure or pre-scrap.
    I assume the brakes are manual from your post. Do you have control blocks or jigs made for individual set ups, and what is the frequency for checking the set up. This will have to be developed from the data you collect on the individual dimensions. A trend toward out of spec should be seen in the data.
    Don’t try to reinvent the wheel. Take it one step or one deffect at a time and move forward. Have a Goal and stick with it.
    Chad Taylor

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    #158031

    Mike in STL
    Participant

    You might want to look upstream somewhat from the brakes; I, too, continue to work with high scrap and rework from sheet metal defects. What I found out in my initial investigation is the material was coming in with some minor variation but our shear operation was introducing up to .016″ variation. Since our fabrication prints only allow for .015″ after forming, we were strangling the brake operators because we had used up all the tolerance with the first step in the process! It’s better now . . .
    BTW, I don’t work in a SPC-friendly environment although I use control charts in a couple of sub assembly areas for my own protection. We have a lot of short runs to make and a whisker chart or box and whisker would be what I’d use since we have a lot of variation along a single bend or finished dimension. Old, worn out pumps and presses!
    Good luck –

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    #158036

    Snow
    Participant

    In this situation, where would you start.  I understand the more obvious approach of the big bars in the pareto, but that doesnt sound optimal to me.  Wouldnt either at the beginning (improving and controlling input specifications) or the end (resolving defects closest to the point of sale so improvements are not absorbed by downstream incompetence) be  a better idea?….any thoughts? Thanks!

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    #158065

    Alderman
    Participant

    Interesting post! You can use SPC on many different dimensions and many different parts from 1 machine. All you have to do is use (0) zero for your target, meaning if you have to shear a piece at 12″ that being your target, when measuring your part is it +/- from that 12″? then plot that as it is. You will start to see what is happening and then act accordingly.At least that is how I have done it.

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