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Anonymous Poster

Tolerance Stack-up Analysis Techniques

10/17/2006 10:23 AM

Hello all,

I work in the medical device field, and I am looking for some information that is difficult to find. As many of you may know, there are multiple techniques available for analysing tolerances. My problem is that I need objective evidence to show that the method I am using is accepted for use with medical devices.

More specifically I would like to see an ISO standard that says this method is an accepted way of doing a tolerance stack. The method I'm using is called the Root Sum Square (RSS) method. I am aware that this method can be used in conjunction with 6 sigma approaches, but I'm not sure if RSS can be used by itself.

Rather than explaining what methods are better or worse, I would like to find objective evidence as to what method is appropriate for the medical device industry. Does anyone know of a resource where I can find such an iso standard.

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Join Date: Oct 2006
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#1

Re: Tolerance Stack-up Analysis Techniques

10/18/2006 1:24 PM

As a mathematical method of combining components, RSS can be applied in many instances, including medical device mfg-ing; this really depends on your application and the mathematical model describing it. Tolerances (maximum permissible errors) may not be combined using RSS.

The document that comes in mind is NIST TN 1297 which uses RSS method to calculate the combined standard uncertainty. An international document using the same method is abbreviated GUM for Guide for Uncertainty in Measurement, issued by five international organizations including ISO.

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Join Date: Oct 2006
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#2

Re: Tolerance Stack-up Analysis Techniques

10/18/2006 3:56 PM

Iwould sugest that you go to a university closest to you and prensent this problem to their machanical facilty and see what they have to say. The other alternative is to contact the agents for the equipment in concern and dicuss it with then . One thing you must bear in mind is that working on medical equipment is a extremly high specalised field and most manufactures enforce the hospitals and doctors to send the equipment back to them for service and most important of all is the calibration.

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Anonymous Poster
#3

Re: Tolerance Stack-up Analysis Techniques

12/18/2007 9:56 AM

I too am researching the best and approved tolerance analysis methods used in the medical field/industry. I would like to hear what you discovered. Maybe we can compare notes. If you want to contact me at mgiordano@ceatechnologies.com and leave your contact information, I'll contact you and we can discuss.

Regards,

Mike

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