Plastic Resin designated as Significant Characteristic

K

kyeng

Our product launch team designated the plastic resin used in our injection molding process as a significant characteristic (for a new assembly). Has anyone else used this approach for the resin? The resin is important, but no more than our other existing parts.

Our procedure says that an SC must achieve a 1.67 Cpk, use a poka yoke or have 100% process monitoring. Could we achieve the process monitoring by logging the lot certification for the resin batch?
 
V

vinny

Our product launch team designated the plastic resin used in our injection molding process as a significant characteristic (for a new assembly). Has anyone else used this approach for the resin? The resin is important, but no more than our other existing parts.

Our procedure says that an SC must achieve a 1.67 Cpk, use a poka yoke or have 100% process monitoring. Could we achieve the process monitoring by logging the lot certification for the resin batch?
Unless I misunderstand the question, the resin as an SC makes no sense to me. A characteristic of the resin (MFI or something else) could make sense as an SC. Beyond assuring that the correct resin is loaded into the press hopper, what is there to monitor as the SC unless you move to a material characteristic. That is like identifying the tool as an SC. The AIAG APQP and Control Plan manual states on p. 21 "In addition to drawing and performance specifications, material specifications should be reviewed for special characteristics relating to physical properties, performance, environment, handling, and storage requirements. These characteristics should also be included in the control plan>"
 

kuyakut

Involved In Discussions
I agree with the above post , Resin as a general does not fall into a category of special characteristic. it would be appropriate that the MFI will be considered as SC. How can you obtain a Cpk if the resin itself is not measurable. So the best is to put resin MFI as a SC.
 

somashekar

Leader
Admin
Plastic resin (including the make, grade, order number) can be a significant characteristic depending upon the product and application. Your product launch team may know why and have chosen it to be significant. Hence no change allowed, so ...
Could we achieve the process monitoring by logging the lot certification for the resin batch?
YES you can...
 
K

kyeng

I have been unsuccessful in getting an answer to "Why is it a significant characteristic". Then I usually follow up with "it makes no sense to make this an SC" and "do you realize we will need to create additional procedures / processes to accomplish this?".
I am okay with implementing new procedures to ensure we are using the correct material. I just don't like doing something if it's not value added.
 

Ronen E

Problem Solver
Moderator
I have been unsuccessful in getting an answer to "Why is it a significant characteristic". Then I usually follow up with "it makes no sense to make this an SC" and "do you realize we will need to create additional procedures / processes to accomplish this?".
I am okay with implementing new procedures to ensure we are using the correct material. I just don't like doing something if it's not value added.

There are situations where the specific grade and maybe even a specific supply chain are important, e.g. when it's a biocompatible grade for a medical device or when the client requires a specific source (supplier).

Whoever designated the resin a significant characteristic should be able to track it back to the design inputs. If it's not linked to any requirement in the design input or to a specific risk mitigation then it's not critical, IMO.
 

Bev D

Heretical Statistician
Leader
Super Moderator
Ronen and others are correct. 'The resin' can't be a special characteristic because resin is an entity not a characteristic.

If the person who designated the resin as a SC can't tell you what characteristic of the resin is critical, then there is nothing logical you can do. (other than record the CoA as you proposed and wait for some auditor to come in and say the same thing - perhaps they will carry more wait than simple logic)

I also have designated certain characteristics of resin to be critical...
 
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