Let’s talk about something that it is not controversial!
And then, there are those things that are not controversial (confused with this beginning? Please check my previous post).
Those things that everyone agrees upon. Those topics that generate a broad consensus.
In a glass container plant, one of those – rare… - subject’s, concerns Critical Defects.
The definition of critical defect does not leave any doubt: “defects that could or are likely to result in hazardous or unsafe conditions for individuals using the glass container or be injurious to their health, under normal conditions of use as defined between the glass manufacturer and the filler.”
Or in other words: “A defective condition on the bottle (or jar) which can/may cause physical injury or even death to the consumer or our direct customer during normal use/operating conditions. Based on judgment and experience indicates that it could likely result in a substantial Customer or Consumer complaint.”
Bottom line: when they are detected every effort must be made to avoid that the defective units reach the pallet and are shipped to the customer- at all costs!
The examples of defects that are considered to be critical are not even arguable:
-Bird swing, spike (any plunger pull on the container inside surface), over press/wire edge finish, flanged finish (horizontal glass projection at guide ring and neck ring match area), chipped finish, internal stuck glass; internal loose glass; internal soft blister, sharp external stuck glass, sharp (or could be broken to become sharp) seam, etc...etc.
Basically we are referring to any defect that could result in a substantial Customer or Consumer complaint.
Off course there are some less obvious.
Here I would include for instance defects that can affect the sealing surface of the glass container and therefore cause the loss of vacuum and ultimately spoil the filled product (being that the case).
Upon detection, or even the suspicion of occurrence, actions must be undertaken immediately both in the Hot End and the Cold End.
The secret about any defect is to make sure we are in control, not the defect.
As long as we know when it happened and then can TRACE/TRACK it effectively, we will never have problems.
The most important is to immediately eliminate risk (reject at Hot End) and make decisions in CUSTOMERS’ favor.
A detailed report, as per procedure, should be required for each and every CRITICAL DEFECT we identify during production.
Independently if the defect is detected in the Hot End or in the Cold End the procedures usually establish redundant mechanisms.
These mechanisms usually imply that some final product is rejected – just to be safe – even though it is reasonably admitted that no critical defected was packed.
We find small variations in these procedures between glass manufacturers but we can safely say that the final goal in all is to make absolutely sure that no critical defect is packed and unintentionally sent to customers.
From my experience there are two situations of great concern in what regards the management of critical defects:
ON and OFF situations (the defect occurs intermittently);
The critical defect runs in the production (more of what is in the Lehr at time of detection).
Now this is a REAL issue when the defect is of difficult visual detection and the inspection machines struggle to reject it…
Let me give you the following analogy (with the courtesy of a very good friend of mine).
Let’s imagine that the plant floor is a football pitch (soccer pitch if you are in the US).
The operator that is the Hot End in the IS machine is the striker and the operator that is the Cold End (the Quality Inspector so to speak) is the goalkeeper.
The goalkeeper has the objective of stopping all the balls (defects) that the striker shoots at him preventing that they reach the goal (the final pack) - preventing a goal of being scored.
I have to say that off course the objective of the Hot End operator it is not to produce defects. It does not want to score a goal. This is just an image to illustrate a specific situation.
If the striker does not shoot too many balls at the goal keeper at the same time the goalkeeper can defend its goal and prevent the score.
But if the striker starts shooting various balls simultaneously in different goal directions the goalkeeper just it is not able to stop them all. Some will relentlessly go into the goal.
The best way to break down a system is to overload it!
Basically this means that while the Hot End works on the critical defect, it must be simultaneously rejected at Hot End.
And that rejection only must be stopped when we have absolutely sure that the critical defect root cause was found and corrected!
In the Hot End it is better to not jump to conclusions too early and allow sometime for confirmation.
Follow-up in the Cold End – after the defect was declared fixed - is critical!
