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Help on Capability Study

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Viewing 11 posts - 1 through 11 (of 11 total)
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  • #31771

    Hemanth
    Participant

    Hi all,
    I know this may not be the right forum to ask this question. We are trying to solve quality problem on one of a subcontracted metal bracket. the part is a formed in a mechanical press, on which some injection molded relays are fitted.
    One question the team is struggling with is the appropriate tolerances for the bracket. It looks like we have very tight tolerances. Any suggestion on how should we move ahead on identifying appropriate tolerances?
    Secondly, what are the typical tolerances given on sheet metal components? Do you feel there could be any issue of assembling a sheet metal component (less controlled process)with an injection molded component (highly controlled process)?
    Any inputs would be greatly helpful.
    Thanks in advance
    Hemanth

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    #84131

    Sanjeev Verma
    Member

    Hemanth
    I am not sure if I understood your problem correctly. What is the problem with the tolerances ??
    1) Is it that you want less tolerance and the vendor you are talking to doesn’t have technology to support those tolerances?
    2) Or you are not able to know, whether the tolerances specified are GOOD ENOUGH or not?
    3) Or with what you thought are the right specifications for the tolerance, the product quality is still not being met with.
    Would appreciate if you could elaborate on THE PROBLEM.
    Regards
    Sanjeev
     

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    #84153

    Hemanth
    Participant

    Hi Sanjeev,
    You have understood the situation right..the problem is that we feel the designers have given a very tight specification for this part. We tried some parts which were out of spec and they went fine in the assembly, now the other parts are standard relay bases (injection molded). Team has been debating on relaxing the tolerances. Above this we have a huge measurement error (esp. reproduciblity) as well. Where should we go from here now..
    Thanks for your reply
    Hemanth

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    #84154

    Shree Phadnis
    Member

    pls contact me with details, If possible send drawing with current 15-30 readings on all the critical dimensions.I will help you with the tolerancing.my mail id is [email protected]

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    #84172

    Sanjeev Verma
    Member

    Hemanth
    I think, Shree will be helping you out with the tolerance specs. In fact, the whole process of fixing the tolerance specs will help you develop a strategy to reduce the errors……………
    Let me know if i still can be of any help
     
    Regards
    Sanjeev
     
     

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    #84174

    Hemanth
    Participant

    Dear Mr. Phadnis
    Thank you for your reply, I have just sent you the details. Do let me know if you need any information.Hemanth

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    #84175

    Hemanth
    Participant

    Thanks Sanjeev,
    I have sent him the details. However, what strategy do you use to fix tolerances? Is their a guideline, DFSS is something which will be difficult for us to follow I am looking for something simpler..Thanks againHemanth

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    #84182

    Sanjeev Verma
    Member

    Hemanth
    Though I don’t know your case specifically, but in general (meaning strategically) my approach towards tolerancing would be as follows
    1) What happens when the tolerances are as per your vendor, which is beyond the permissible limit – You may need to quantify the impact of increased tolerances in terms of a) Added costs b) increased obsolence c) impact on your customer orders etc
    2) Then you may need to quantify the numbers other way round – that is what do you gain by high-specing the tolerances limits – the monetary or the tangible benefits only
    3) Detailed process on “Which part or step of the process causes worry” and what are the practical feasible techniques to alter the tolerances and how much would they cost
    4) Numbers on 1), 2) and 3) can be compared on an ongoing basis and a call can be taken at any point in the future. You can take “Cost” as a basis of analysis or you can take “Cost & Ease of operations together” as the basis of analysis.
    I would recommend that lets wait for Shree’s analysis and then we can chart out the strategy aspect of it
    Regards
    Sanjeev
     

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    #84183

    Hemanth
    Participant

    Hi Sanjeev
    Thanks for your reply. I look forward to more discussion once we recieve reply from Mr Phadnis.
    RegardsHemanth

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    #84192

    Erik L
    Participant

    Hemanth,
    A quick answer here would really go back to understanding the relationship of the VOP to the VOC.  If you have data that shows the distribution of the process that you are focusing on and then have let’s say some guidance from management, suppliers, and benchmarking of appropriate levels of quality (e.g. yield, sigma-level, dollars in COPQ, etc.) you can then set what would be the appropriate specifications to get you there.  Once that is established you can compare what the pen and paper approach came up with to what is occurring in reality and then strategize how you get from here to there…
    Regards,
    Erik 

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    #84195

    Hemanth
    Participant

    Hi ErikThanks for your reply, this is the approach we are trying out but were not sure. Your reply, did boost my confidence.Thanks againHemanth

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