Greetings all. I, too, have found this forum to be very valuable in guiding me in my quality endeavors.
We are a manufacturing company that does most of our calibrations in house. We have a policy and procedure for rejected gages, but it doesn't seem to be very realistic or accomplishing very much. In fact, it trys to blend two different situations.
The first situation is when a gage is "rejected" during a manufacturing process. The parts are identified with a "Hold" tag until the parts can be checked with a gage known to be in tolerance. Then the parts can be marked "Good" and move along. However, my question has been:"How would a person on the floor be able to tell that a gage is out of tolerance in the first place?" (unless of course the gage was dropped, etc.)
The second senario is when we discover an out of tolerance gage in our calibration lab. Currently, we issue a "Gage Rejection Notification" to the gage owner that directs them to make certain no bad parts were made with that gage. It seems a difficult task, though. I don't think the person receiving the notice can determine which parts may have been checked with that one gage. Maybe it was one part... maybe thousands. It could have been months ago and the products are already with a customer! To worsen matters... gages from our tool crib are issued to various people/machines. We do track where the gages are going to from the tool crib and used on what part (i.e. model number), but to find which specific parts touched that gage... mission impossible.
Am I missing something obvious? How does your company handle rejected gages and the potential non-conformities?
Thanks in advance.

The first situation is when a gage is "rejected" during a manufacturing process. The parts are identified with a "Hold" tag until the parts can be checked with a gage known to be in tolerance. Then the parts can be marked "Good" and move along. However, my question has been:"How would a person on the floor be able to tell that a gage is out of tolerance in the first place?" (unless of course the gage was dropped, etc.)
You're correct; unless something obvious is at work, a gage out of calibration isn't likely to be detected in production. A policy for dealing with those situations is still necessary, however, and from your description, it seems that the policy might be lacking a complete "positive recall" requirement that covers all of the parts which might have been assessed with the gage in question...
The second senario is when we discover an out of tolerance gage in our calibration lab. Currently, we issue a "Gage Rejection Notification" to the gage owner that directs them to make certain no bad parts were made with that gage. It seems a difficult task, though. I don't think the person receiving the notice can determine which parts may have been checked with that one gage. Maybe it was one part... maybe thousands. It could have been months ago and the products are already with a customer! To worsen matters... gages from our tool crib are issued to various people/machines. We do track where the gages are going to from the tool crib and used on what part (i.e. model number), but to find which specific parts touched that gage... mission impossible.
Am I missing something obvious? How does your company handle rejected gages and the potential non-conformities?
Thanks in advance.
Part the reason for the process or systems approach (identifying process interactions, e.g.) is illustrated here. In general, the ISO standards require a method for identifying material that might have been approved using a substandard gage. In order to accomplish this, there must be deliberate interaction between the process of lot control on the production floor and calibration control in general. Thus if it's discovered on July 20 that a gage is out of calibration, your system should be designed such that the wherabouts of all the material that might have been checked with that gage since the last calibration can be identified. If your system can't do this, it means that your lot control system in production wasn't designed to interact efficaciously with your calibration control system.

"How would a person on the floor be able to tell that a gage is out of tolerance in the first place?" (unless of course the gage was dropped, etc.)


A tough question to answer as it depends on the situation. It may be feedback from a customer (internal or external). The operator may check the gage and find an OOT condition. An assembly problem may lead to an investigation of the gaging. It may be an ATP failure that leads to the investigation, etc.

How does your company handle rejected gages and the potential non-conformities?

Our Metrology procedure hands off to our C&PA process when a gage is found to be out of “tolerance” either during use or routine calibration. Relative to containment of the suspect parts, you have to assess the risks involved since technically, all parts that could have been accepted with that gage are suspect and could possibly need to be contained/recalled.

Worst case, everything may need to be contained and re-qualified.

Greetings all. I, too, have found this forum to be very valuable in guiding me in my quality endeavors.
We are a manufacturing company that does most of our calibrations in house. We have a policy and procedure for rejected gages, but it doesn't seem to be very realistic or accomplishing very much. In fact, it trys to blend two different situations.
The first situation is when a gage is "rejected" during a manufacturing process. The parts are identified with a "Hold" tag until the parts can be checked with a gage known to be in tolerance. Then the parts can be marked "Good" and move along. However, my question has been:"How would a person on the floor be able to tell that a gage is out of tolerance in the first place?" (unless of course the gage was dropped, etc.)
The second senario is when we discover an out of tolerance gage in our calibration lab. Currently, we issue a "Gage Rejection Notification" to the gage owner that directs them to make certain no bad parts were made with that gage. It seems a difficult task, though. I don't think the person receiving the notice can determine which parts may have been checked with that one gage. Maybe it was one part... maybe thousands. It could have been months ago and the products are already with a customer! To worsen matters... gages from our tool crib are issued to various people/machines. We do track where the gages are going to from the tool crib and used on what part (i.e. model number), but to find which specific parts touched that gage... mission impossible.
Am I missing something obvious? How does your company handle rejected gages and the potential non-conformities?
Thanks in advance.
Let me suggest the following:
Gage control is important.
(note - there is a difference between "calibration" (adjusting the gage to meet specs) and "calibration validation" (testing gage against a master to see it is in spec WITHOUT adjustment)

One form of control is to limit the use of one gage to a single product line with periodic checks against a master to assure the gage is still within calibration specification.
If any of the checks shows the gage to be out of calibration specification, it means all the parts checked since the last confirmation of the gage are now SUSPECT and parts declared nonconforming and conforming during that period should be resampled. The out of calibration gage could have just as easily rejected conforming parts as well as passing nonconforming parts.
Given (2) above, it makes sense to have an absolute policy to check the calibration of the gage each time it is dropped. It also makes sense to graph the calibration validation intervals to find an optimum time between calibration validations to the point where wear and tear put the gage out of spec. This will limit the number of parts which fall into the "suspect" category when a gage is found out of spec.
Item (1) can be performed either by the operator himself or by a roving technician according to a schedule.
Tracking which parts are checked by which gage is a matter of "system" by establishing lot or batch control of the parts being checked. Therefore, if a company is turning out parts on a screw machine, batches or lots could be on any basis ranging from hourly to shift to 24 hour day. If several machines are making the same part, it makes sense to segregate each machine's output into separate lots, but it may not be necessary to have a separate gage for each machine. That aspect is strictly an economic decision balanced against the cost of re-inspecting parts if gage is found to be out of calibration.
A further aid to tracking which some companies have adopted is to hold the sample parts which were gaged in segregation between checking the gage against the master. If the gage is found out of spec, it is a simple matter to go back to the same samples previously checked for rechecking rather than pulling new samples from the entire lot or lots under suspicion.
Given these tips, you should have a clue for formulating your own policy and system which will work in your organization.

Good advice, Wes, except,
(note - there is a difference between "calibration" (adjusting the gage to meet specs) and "calibration validation" (testing gage against a master to see it is in spec WITHOUT adjustment)
As has been pointed out in these forums before, calibration does not necessarily include adjustment. It is the act of comparing a device against a controlled standard. Adjustment may or may not be necessary. If you disagree, then you must also agree that all gages that are in use on a production floor that didn't require adjustment during the last calibration are not calibrated.
Look here, for example: NASA Earth Observatory Glossary (http://eobglossary.gsfc.nasa.gov/Library/glossary.php3?mode=alpha&seg=b&segend=d)

Good advice, Wes, except,
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As has been pointed out in these forums before, calibration does not necessarily include adjustment. It is the act of comparing a device against a controlled standard. Adjustment may or may not be necessary. If you disagree, then you must also agree that all gages that are in use on a production floor that didn't require adjustment during the last calibration are not calibrated.
Look here, for example: NASA Earth Observatory Glossary (http://eobglossary.gsfc.nasa.gov/Library/glossary.php3?mode=alpha&seg=b&segend=d)
You are correct, of course. In my haste to put down an answer before moving on to other matters, I was less detailed than I should have been.

My intent was that "calibration" involves either adjustment or noting the difference between the gage and the master in comparing the two. Therefore, if the CALIBRATION notation said the gage was "off" the master by an eighth of a turn (for a tapered thread gage, let's say), then the check would show the gage to be out of calibration if it were a quarter turn off the master and no adjustment would be done except by a calibration technician.

Thank you for bringing the lapse to my attention and thereby helping others who read the thread.

What I have seen for some companies when faced with an OOT of a gage is that they have an engineer or someone who has the technical expertise to analyze the OOT condition with the worst case situation of products that the gage could have been used to inspect or measure. This is usually documented on a special form or on a CAPA form. The review must include all parts that the tool could have been used to inspect. This evaluation needs to be done very quickly in case the OOT could have allowed acceptance of bad material. Whatever the decission is it needs to be documented and justified.

Calrich,

It appears you have two basic issues:

The first is the control of the internal calibration program. How the gages are controlled, and the calibration standards are controlled, and how the appropriate standards are identified are all pieces of that puzzle. May I suggest obtaining a copy of The Metrology Handbook, available from ASQ? It is a good reference work. You may also want to obtain a copy of ANSI/ISO 17025, available from NCSLI, and use it as a guide to implement the best controls for your situation.

The second is what is known as reverse traceability. That is, taking a gage and determining what items it is used to approve. There is unfortunately no easy one-liner solution for that. The best solution is to have the gage ID and due date entered on the record where the product is documented as passing final approval. Ideally that will be in a database program where search fields can be set up.

http://www.asq.org

http://www.ncsli.org

Hope this helps.

Hershal

Am I missing something obvious? How does your company handle rejected gages and the potential non-conformities?
Thanks in advance.

We classify gages to help with this. If a caliper on the casting deck is found OOT we have other opportunities to detect the potential problem during several up stream chekcks. The risk of a spill to the customer is small (there may be expensive machine line crashes however). We calibrate these gages every 6 months.

However, if our CMM is OOT and it is used for a final inspection, the risk is high. We "verify" them every shift for this reason.

Gages for final inspection need to be known to be good at all times. Could your operators use a check master? Measure a golden part? Or a gage block?

Hope this helps a bit.