FRIDAY, APRIL 20, 2018
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Topic Mistake Proofing Solutions

Mistake Proofing Solutions

Home Forums General Forums Methodology Mistake Proofing Solutions

This topic contains 6 replies, has 4 voices, and was last updated by  Strayer 8 hours, 22 minutes ago.

Viewing 7 posts - 1 through 7 (of 7 total)
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  • #704940 Reply

    We make batch solutions which are sometimes diluted with IPA and sometimes with nPA. The batches are expensive and we had one diluted with IPA but it should have been nPA. The cost of this error is large enough to require mistake proofing, but we aren’t sure of a good method.

    Does anyone have a good method to ensure that the correct solution from a chemical supplier is used? Currently we do barcode scans on each component and have a green light indicate that the correct items were selected, but the wrong label was placed on the incoming bottle. We have also had the solutions mixed first and then the barcodes scanned after only to find out then that the solution was made wrong.

    Detection methods would be helpful if they are quick and robust, but we really should be making it so that this cannot happen.

    #704944 Reply

    As you know, mistake proofing (poke yoke) involves designing the process so that it can only be done correctly, or at least that mistakes are immediately detected and corrected. From what you say, your problem is mistakes made by your supplier. It’d be easy to say you need better detection methods but what you really need to do is to work with your supplier and help them to prevent making such mistakes. This might involve assigning a team to help them, or paying someone to help them and sharing the expense. Getting it right is good for both of you. If they resist cooperating maybe it’s time to look for a different supplier.

    #704947 Reply

    Laura Stolar
    Reputation - 35
    Rank - Aluminum

    Thank you for reading and responding @Straydog. I should clarify that the chemical from the supplier was correct and correctly labeled. An incorrect dilution was made from it and subsequently labeled with our internal barcodes. This was an internal mistake. We buy the chemical off-the-shelf, so there is not internal barcodes when received. It was the first internal process which made the incorrect barcode. Is it possibly uncommon to purchase off-the-shelf when there are high stakes for a smaller company?

    #704953 Reply

    Forgive me for making assumptions. So the product from the supplier is correct, and correctly labeled. You dilute it and relabel with an internal barcode which indicates the amount of dilution. The error is that dilution and internal barcode don’t match. So the question is how can you prevent that from happening. You might do an FMEA on this first internal process to understand how it can fail and where your internal controls are inadequate. Is there some way to automatically link measurements of the chemical and dilutant to generation of the barcode in order to eliminate human error?

    #704971 Reply

    No need to apologize @Strayer. Thank you for revisiting the question. You have summarized it appropriately that the first dilution was incorrectly barcoded.

    We can do verification after dilution and have the barcode print only if within specification.

    I was hoping for suggestions on preventative measures before mixing. Imagine if there was a safety hazard if the wrong chemicals were mixed. Detection would be obvious, but it would be best to never mix them together in the first place. We are not a chemical company, so I was thinking there may be examples of how chemical companies avoid these errors.

    #704973 Reply

    There is instrumentation you COULD use if you’re adding the material into a process line. Other options also if not.

    #704982 Reply

    @lausto Without knowing the details of your process it’s unlikely that any of us can suggest anything other than generalities. I stand by my previous recommendation that you do FMEA. If you aren’t familiar with Failure Modes and Effects Analysis you can find the template and guidance here and many other places via search. Basically you decompose the process into its elemental steps, identify the various ways each step could fail, evaluate each failure mode in terms of severity/probability/detectability to prioritize failure modes, then discover better controls to prevent or at least better detect failures. You’ll need to put together a team of people who are very familiar with the process commit to the time to do it. With the limited process you describe this might be a few hours or a day or two. I often recommend excluding managers, supervisors, and process engineers since they tend to be biased toward what they think is happening or is supposed to happen. You want people who know what actually happens. If you or no one in your company has done an FMEA you might do well to contract a consultant to facilitate the exercise. Since you’re dealing with a critical error this should be worth the expense. But beware of the consulting company game — Very often they’re more interested in getting a foot in the door and selling additional services so they only do enough to convince you that you need to pay for more.

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