Assignation of RPN rating (Detection) on Visual Inspection where subsequent operation

[GoKats78]

We have a process where we perform a visual inspection upon receiving material into the operation (verify tag information matches the lineup). We then subsequently perform a check of actual dimensions to verify the product matches the tag and lineup.
These are two different processes and have separate RPN numbers associated thereto. We have assigned a 5 in “Detection” to the visual inspection based on the subsequent measurement of the product. We Our customer is questioning our assignment of 5 – he is stating the “Detection” should be an 8 (control is achieved with visual inspection only).

Thoughts? Ideas?

 

[Jim Wynne]

You do a visual inspection for what criteria? How is the visual related to the dimensional? You're doing a visual verification and a "detection" value of 5 has been assigned as an RPN factor, and your customer says it should be 8? Please provide more details.

 

[GoKats78]

The Failure Mode is "Delivered Product does not match product being produced at Finishing Cell"

Potential Cause is "Incoming Product does not match product being produced"

We are verifying the information on the tag (dimensional data) matches the lineup. This check is done by the material handler. Upon receipt the operator verifies the dimensions of the product matches the tag, the lineup, and the product currently being produced.

 

[Claes Gefvenberg]

Thoughts? Ideas?

Assuming you're using the usual scale with 10 as max I think an 8 sounds very heavy (unless your operator is nigh on blind, and I have no reason to think so). Mistakes would be very common. Are they?

What exactly does a 5 and an 8 mean in your terms?

 

[Jim Wynne]

The Failure Mode is "Delivered Product does not match product being produced at Finishing Cell"
Potential Cause is "Incoming Product does not match product being produced"

But you haven't told us anything about the product. You still need to fill in some blanks here. What's the difference between "delivered product" and "incoming product"?

We are verifying the information on the tag (dimensional data) matches the lineup.

What's a "lineup"?

 

[GoKats78]

Incoming Product - product brought to a finishing cell (long length tube to be cut and end finished) to be processed at the machine

Delivered Product - finished product delivered to the customer

Lineup - Schedule in Business System which list material to be processed.3

Information verifed visually (by comparing tag to lineup) - Tube OD, Wall, Customer.

Information verifed by measurement - Tube OD and Wall

 

[Rea]

From page 53 of FMEA 3rd edition the table for detection states an 8 for visual inspection only.

Page 39 of the manual item 10) " However, in preparing the FMEA, assume that the incoming part(s)/material(s) are correct.

Is it really necessary to include incoming on your FMEA?

 

[Bill Ryan - 2007]

GoKats
What, specifically, is/are the Failure Mode(s) and Cause(s) (how stated in your PFMEA)?

Rea
If you have a processing "step" (action) that involves "incoming inspection" then - YES - it should be included in your PFMEA.

 

[Howard Atkins]

Assuming you're using the usual scale with 10 as max I think an 8 sounds very heavy (unless your operator is nigh on blind, and I have no reason to think so). Mistakes would be very common. Are they?

What exactly does a 5 and an 8 mean in your terms?

One of the reasons that the rank is so high is the possibility of the part not being inspected, an error in the flow. This added to the accepted 100% inspection is 80% effective brings the detection to 8.

As can be seen from the attachment the rankings are built to improve the system and make it more robust.
There are a number of issues here as I see it the real failure mode is misidentification and not incorrect performance of the previous station.
Rea is correct that the assumption is that the material produced by the previous station is correct but here the problem is of identification and process flow, not the performance of the previous station. Incoming inspection in general should be on the FMEA.

The customer is referring to the standard guidelines, which might have been mandated in his CSR or you might have to submit your definitions of rankings if you do not use the standard ones.

But remember that just because the detection is 8 does not mean that the RPN is large. If the problem is identification and process flow there are plenty of actions that can be performed to reduce the occurrence.

 

[Jim Wynne]

Incoming Product - product brought to a finishing cell (long length tube to be cut and end finished) to be processed at the machine

And I assume that the material has been verified via incoming inspection?

Lineup - Schedule in Business System which list material to be processed.I note that cosmologists are quite willing to abandon earthly physics to support their ends, but biologists are loathe to do the same.

The equivalent of a process router?

Information verifed visually (by comparing tag to lineup) - Tube OD, Wall, Customer.

This step serves to verify the "lineup" and not the material, it seems.

Information verifed by measurement - Tube OD and Wall

And this step verifies the material, which seems to be redundant if it's already been verified at incoming inspection, and the "lineup" has been verified to be correct.

Assuming my surmisals are correct, you should have a line in your PFMEA for receiving inspection, and it should list the potential failure modes of that operation. The assumption should be made that the state of the incoming material is unknown, and that it's possible for the material to be misidentified, mis-tagged damaged (in receiving inspection, not by the supplier or the trucker) or somehow misdirected. There should be Severity, Occurrence and Detection factors assigned to each possibility. The Detection factor assumes that something bad has happened, and predicts the likelihood that the problem will be detected before value is added to the product, or before the final product is shipped to the customer. A Detection value of 1 means that the probablility of the problem going undetected is negligible; a factor of 10 means that the problem is impossible to detect.

Once the incoming product reaches the finishing station, the tag is compared to the "lineup." Again, an RPN should be developed. The Detection factor should follow the same reasoning given above. Note that whether or not the requirement for this (or any other) step reaches the control plan depends on the outcome of the PFMEA. You might determine that special controls aren't necessary. Just because an operation appears on the PFMEA doesn't mean that there must be a corresponding control plan line item.

Finally, the tubing is measured at the finishing station before further processing takes place. I said above that this might be a redundant control, and perhaps redundancy is a good thing. It depends on the level of risk involved, which you have to determine based on experience. If you find that redundant controls are necessary due to upstream bungling, that's another problem, and one that's not likely to be driven to extinction by more inspection. Inspection shouldn't be used to solve personnel problems.