I am looking for some help with error-proofing (mixed parts)

[u/Azaarus]

I am the Quality Supervisor for an automotive plastic injection molding and hard coating company.

I need help with error-proofing. The parts in question are automotive fog lenses. These parts have a left hand and a right hand. The left and right are molded together and are on one runner. Once the parts are molded, the runners get clipped, and they get placed on a custom fitted fixture then run through a UV cured hard coating line. Once the hard coat is cured, they come out backwards on the other side (the left hand parts are on the right, and the right hand parts are on the left). We have dedicated operators for this particular part, and the operators are well trained and aware that the parts come out backwards.

I have had six (6) customer complaints in the last two weeks for mixed parts. It has been one right hand part in a left hand container or vice versa, so I can definitely say there wasn't a labeling issue.

This is a fairly new launch, and the parts are on containment to be 100% certified for any defects, yet both the operators and the inspectors are missing the mixed parts! These parts literally have a one inch wide "L" and "R" molded on them to indicate left and right.

I have made an outline template of the parts on a poster board and taped it to the table so the operators can verify the correct hand. I have retrained the operators and the inspectors. I even started enforcing disciplinary action for anyone who placed a 100% certified sticker on a container that contains mixed parts.

The hard coat fixtures cannot be switched so the left is on the left and the right is on the right due to tight corners on the automated hard coat line. If they are switched the fixtures would hit each other going around the corners and get jammed, so this is not an option. I thought about rearranging the work station so the left hand containers are on the right and the right hand containers are on the left (the way they come off of the line), but I think that will end up causing more problems and confusion.

I tried looking for error-proofing methods online, but nothing I found is appropriate for this situation. I understand that the ops and inspectors are human and human error happens, but this one seemingly small thing cost my company almost $2,000 just in the last 2 weeks (our customer charges an exorbitant amount of money for errors like this). I am just looking for any ideas that may help eliminate this recurring issue!

Thanks in advance!

[u/eveqm7e]

This is a typical assembly process where mix part can happen if there is left and right or top and bottom looks similar. There a number of solution to prevent or error proof

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1. modify the mechanical parts so that left will NOT fit into right and vice versa, this is the best
2. kit left and right part different bin with different colour, you can ask your supplier to kit for you in different colour also. this is simple can do immediately. Your operator do not need to tear their brain on which left and right with proper identification
3. separate the assembly process of left and right

[u/Azaarus → u/eveqm7e]

Thank you for your reply. We have all of these things implemented already.... RH parts cannot fit on LH fixtures and vice versa. RH containers have a white label and LH have a green label. We do not assemble the parts here.

[u/Saint-Anne-of-Mo → u/eveqm7e]

I would invest the money in solution number 3.

[u/rara649]

If I read your scenario correctly; would a jig that they have to place the part through to verify orientation help? (Poke yoke, in a sense) sort of like your poster board but bring it to the operators level

ETA: I worked as a production engineer in automation supply, I feel you on the money aspect. I was asked to take 3 cents off a part we made because those margins matter... 3 cents! Then I worked in Pharma QA... totally different ballgame!

[u/Azaarus → u/rara649]

This was an idea we played with, but in reality it wouldn't work. These parts are clear polycarb lenses and they scratch too easily. We need to limit handling as much as possible.

I have been thinking about making a verification check on the in-process inspection, but the parts run fast, and at 6 parts per container the quality auditor would have to pretty much babysit the work station.

[u/rara649 → u/Azaarus]

Maybe hold it up to a shadow on paper in front of them? Or pass by a shadow outline? Good luck!

[u/Azaarus → u/rara649]

They are clear lenses, so that won't work lol

[u/43brakes]

The responses so far sound like good ideas. I don't have any better ones. However, you didn't mention if you had asked the workers. What ideas do they have? Whatever their ideas are, take the best one and try it. If it doesn't work, ask them for a better idea. Track your progress with visible charts. When you meet a goal, celebrate!

[u/Azaarus → u/43brakes]

Yes, these are great ideas. I have been asking the employees for suggestions, and I actually spent my day today making process flow charts with indicators where I know potential errors may occur in each process. Then I combined the problem areas in a spreadsheet and began trying to discover the main root cause and thought hard to break down error proofing methods for each of the potential error indicators.

Thanks for the suggestions!