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Operational Qualification for Injection Molding

zagwyn

Involved In Discussions
#1
I am working on a Validation Plan for an injected molded plastic part (for a class 3, medical device) in which I am setting the OQ requirement to be =/>1.33 Cpk (sample size for each is >30) for High, Low and Nominal setting. The supplier and some of my internal PMs are stating that it is an unreasonable expectation. Please provide your thoughts and experiences.

Thank you
 

Ajit Basrur

Staff member
Admin
#3
I am working on a Validation Plan for an injected molded plastic part (for a class 3, medical device) in which I am setting the OQ requirement to be =/>1.33 Cpk (sample size for each is >30) for High, Low and Nominal setting. The supplier and some of my internal PMs are stating that it is an unreasonable expectation. Please provide your thoughts and experiences.

Thank you
I find it strange that your supplier is telling Cpk values of 1.33 or greater as unreasonable expectation; these are industry benchmarks. Cpk of 1.33 is closer to 4-sigma and considering a Class 3 medical device, I would definitely want to have a capable process to prevent issues.
 

AgnieszkaSz

Involved In Discussions
#4
We apply criterion Cpk of 1,66 for OQ phase and 1,33 for PQ phase. This is for medical decive component, criteria are set by our customer. Cpk indices are calculated for each cavity output (difficult to obtain Cpk of 1,33 for whole tool output). If your supplier of injection molded parts complains, I suspect the tools are not in mint condition.
 

zagwyn

Involved In Discussions
#5
Ajit, They do not have a problem with a Cpk of 1.33 at nominal, they are questioning why I ask for it at the High and Low settings of OQ.
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#6
The very point of OQ is to validate that the process as it will be run is capable. If the min and max are allowed as material, equipment and/or process settings then capability must be established at all levels.
 
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