Mould Number Reader (MNR) = Basic Tool for Quality Control

Personally I am not a fan of DIY jobs.

In fact I try to avoid them at all costs. I prefer to pay to professionals who – for sure – can do the task much better than I will ever be able to. It is a question of personal taste and also much clumsiness.

But from time to time there comes the occasional emergency where I have to get my hands dirty.

In those rare occasions one thing that I have found at my own cost is that there is always the right tool for the task at hand.

If you try to use the not-so-OK- but- I- think-it-will-work-tool usually things won’t work.

Or perhaps they do, but it will cost you double of the effort and the final result will not be perfect.

Unless you are Portuguese…We proud ourselves to be very good at improvising.

In my opinion just an excuse for bad planning…but that it’s a different story…

Coming back to our analogy.

For the Quality Inspector in a glass container plant, the tool that cannot be missing is the Mould Number Reader (MNR).

It would be like that if your job was to hammer nails.

But...without having a hammer.

You can do it…but it will take you more effort (and time) and the final result will probably be a crooked nail.

The MNR is an equipment installed in the line inspection machines which reads a code engraved in the glass containers. This allows the recognition by the inspection machine of the mould number that is being inspected.

The code is usually engraved in the body of the container – dot code, placed in the heel area – or in the bottom – as an alphanumeric code. What determines if a dot code or alphanumeric code is used is the type of MNR reader that is installed on the inspection machines. The type of reader used will determine the engraving area and type of code.

The fact that the inspection machine “knows” what is the container mould number that is being inspected at all times has two important advantages.

First, it allows that the machine can be programed to reject systematically specific mould numbers.

When a defect is detected at the Cold Inspections or informed by the Hot End – from its inspections as well - it is the Quality Inspector responsibility to guarantee that the defective containers do not contaminate the packed product.

If in the “old days” it was admissible to have the Quality Inspector rejecting by hand at the annealing lehr exit the defective containers, nowadays with bigger and faster IS production machines that task is simply impossible and in fact not reliable. Simply put, there is no time to do it!

In our days, the Quality Inspector programs the MNR to reject specific mould numbers accordingly with the outcome of the inspections performed in the Cold End or Hot End.

This rejection is automatic and systematic regardless if the container actually has a defect or not. Remember that the occurrence rate of a defect in a specific mould is not always 100% (on the contrary!).

A second outcome is that it allows the collection of valuable information that associates defects to the mould number of the inspected containers.

Most of common process defects are mould/cavity related.

When an inspection machine inspects a container and detects a defect and rejects it, “knows” the container mould number. That number is collected, treated statistically and displayed on screen. This is key information for process correction.

But it is not all rosy!

The MNR must always be effective!

We have to have absolute sure that upon programing a mould number for rejection ALL containers with that very same mould number – from that point on - are rejected and are not packed in the palletizer.

That is when the reading efficiency comes into play.

Reading efficiency is the percentage of good readings: the ones which the machine identifies correctly the mould number of the container.

We are aiming for a 99% of reading efficiency. The standard that we see in many glass plants is 97% and above.

The reading efficiency of the MNR is a parameter that must be regularly monitored and actioned if the efficiency is not satisfying.

It is always possible to make absolutely sure that defects are not packed even though the reading efficiency is not at 99%.

We can program the inspection machine to reject the remaining percentage of mould numbers in which the machine cannot identify the mould number, regardless if they have defects or not.

Although guaranteeing the rejection we are prejudicing plant efficiency since some of the rejected containers are free from defects.

The reading efficiency is strongly hampered if the code engraving it is not clear and prominent. If the code starts to fade the Quality Inspector must report and ask for the necessary correction to its Hot End counterpart.

This is one of those occasions where we can test if there is real team workbetween Hot End and Cold End. They must work together for the greater good of always having a high mould number reading percentage.

For example, upon detection of a critical defect – always an unexpected situation - all procedures to undertake must guarantee without any reasonable doubt that the critical defect was rejected and did not reach the pallet.

It is easily understandable that in this situation it is of special importance rejecting the critical defect using the highest mould number reading efficiency.

In parallel – before using the MNR - the best practice advises to always test for repeatability: program mould number, test rejection X times, check total number of rejections; thus confirming that the MNR can be trustingly used.

The will and the way

“Where there is a will there is a way”

In one – or more … - of my previous posts I have mentioned that I think that what really makes the difference in a glass container plant – or in any organization for that matter - it is not so much technology but people.

I know…I almost can see the smile in your face…That’s what everybody else says!

From the biggest multinational group to the smallest of the family owned producer everyone seems to have embraced this motto.

In fact, written – explicitly or implicitly - in the company mission and/or in its vision statements and displayed in the shop floor in BIG letters, we see it everywhere: “People are our most valuable resource”.

But do they really mean it?

That is, does the organization understands and recognizes that its employees are really the ones that are “making the way”?

And what about their “will”?

How can the organizations foster a working environment where people go that “extra mile”?

Don’t take me wrong.

I come from a technical background and worked all my life in manufacturing plants (automotive, electronic, glass container) so I understand perfectly the role of technology in the success of industrial processes.

Although to tell you the truth I have always found technology to be a little bit boring and people much more interesting to deal with…

My point is that even with the best available technology installed in a glass plant, that it is not a guarantee of success.

I have witnessed several cases where technology fails shockingly despite – and sometimes because – of people.

By the other hand, having people with the right attitude can really make the difference and set the company in the path of success in an arguably “less intensive” technological environment.

This being said by someone who is been working for the last 12 years in an industry that is notoriously known for being conservative and cautious in implementing technical innovations (theme to be addressed for sure in a future post!).

Again, do not miss interpret me. I do not say that technology and people are mutually exclusive.

No.

Ideally they should go hand in hand and the optimum results are achieved when we have the best people with the most modern technology.

I am just trying to make the point that if I had to choose the critical factor for success – based in my experience – I would say it is people. It’s their will that makes the way.

Let’s take the example of a glass container plant and more specifically of the Cold End / Quality Control areas (area which I have more first-hand experience).

Glass container plants are a harsh working environment.

Notoriously high temperatures and high noise levels make it a place where naturally you do not want to be. Let alone work for an 8 hours shift.

If that work involves some degree of physical effort, concentration, reasoning; you will have to be motivated – a reason for being there, the will – in order to make a good job, the way.

Motivated persons are curious and inquisitive regarding all things concerning and around their job.

They usually take ownership of their line and treat all things related with it as if they were their own.

It is of the most importance that the persons that are in the shop floor making the Quality Inspections – for example – really understand how important their job is to the success of the organization.

Their function has a meaning. It is not just a set of procedures – tasks – performed accordingly with a schedule during the shift.

And then they just go home.

I have found it too often – and experienced it! – that key information does not flow down to the floor shop. It stays in the meeting rooms where “sit down and report” happens.

People in the line are left often to their own devices, clueless of the bigger picture.

What is the customer of the bottle (jar) that is being produced? What is the product that is being filled in it? What are the main quality concerns of the customer? What are the usual defects? Do you know we are being audited?

For those who are familiar with behavioral theories know that not the same motivational techniques work for different persons. One should adapt to the “psychological profile” of the intended person.

Selection of people with the right profile for the job is key (unfortunately we see too many casting errors in glass plants!).

And then it is all about training, training and more training!

So if the “recipe” is known why we do not see it applied more often?

Let’s talk about the way.

We see in glass plants a lot of firefighting going on. Not enough time is invested in establishing and committing to a strategy that if not immediately for sure at middle term will give its results.

The focus is too much on the oncoming issue. The short term, the day’s efficiency.

In glass plants – and all the others – there is always a balance of powers between Production and Quality. In glass plants the scale typically tilts towards Production.

This is a capital intensive industry where in relatively short time cycles there is the need of big investments (furnace reconstructions, line refurbishments). Between cycles, money has to be made. Thus, the focus on efficiency, profitability.

The usual pitfall is to consider efficiency and quality as mutually exclusive.

In fact nothing could be more wrong.

Greater efficiency is achieved with higher quality level and not at the cost of the quality level.

They go hand-in-hand.

We use to say that in the long run we all be dead. But the fact is that only sustained quality throughout the time is what will keep customers keep coming back to buy more of our glass.

That should be the way.

The art of follow up in glass container Quality Control.

Human manual inspections are an important part of the Quality Control plan in a glass container plant.

In the Hot End that type of inspection is performed with some limitations since at that process stage the glass container is not completely formed. By the other hand, the advantage in performing it at that moment is that the operator who inspects can immediately act on the process and undertake the appropriate corrections.

On the contrary, at the Cold End the inspection can be complete and thorough. The glass container is finished and can be handled securely. But once detected, the operator is not able to correct the defect. Its task is to give feedback to the ones who can do it.

In fact, put it in very simple terms we can say that in the Cold End everything is all about Quality Control. The value added by the Cold End to the product is “adding” Quality.

The action of the Cold End operators does not limit itself simply to: “rejecting defective units”. Like every other control performed at this stage, there are two important objectives to meet.

For sure, by one side, prevent - using all the available tools - that defective units reach the pallet and consequently are sent to the glass fillers (The Final Customer!).

And, by the other side, give accurate and timely information to the Hot End operator (the line counterpart), regarding the quality of the inspected product. As said previously – with the exception perhaps of the Cold End Coating – the Cold End operator does not perform process adjustments/corrections. But its action is pivotal in providing inputs for process correction upstream.

Human manual inspections performed at the end of the annealing lehr are an important step in the different Quality Controls made at the Cold End area. The two goals to meet – reject defective units and provide feedback – have here their specific procedures as well.

In this post I will focus the discussion on the some of the actions necessary for providing valuable feedback and following up defects in the inspection done at the end of the annealing lehr in the Cold End area of a container glass plant.

One of the most important advantages of Lehr inspection is that the results will show exactly what the quality level is before automatic inspection.

As the bottles come out of the Lehr and they are still stacked in a specific pattern, it is easy to select a specific mould from this pattern for inspection. Moulds will be stacked according to a set pattern, according to the I.S. Machine Timing.

While bottles are on the Lehr in a set pattern we can do effective and proper follow up. When the containers leave the Lehr exit they become a mixed population. When mould numbers are mixed, it is not possible to select each individual mould when taking a sample.

This is very useful when inspecting and doing follow up on cavity related defects. It is important to know that most of common process defects are mould / cavity related.

Recognised to be an important tool for defect follow-up, it is responsibility of all involved – and now I am specifically thinking in the Hot End personnel – to assure that the best regular container pattern (the possible that makes the job easier for the Cold End operator) – is achieved in the lehr.

Once the bottles come out of the Lehr and there are at least 10 or more rows without a break, the Quality Inspector must take and note on the stacking pattern board, or in some other kind of visual aid, of the full set of cavities by number. By picking up any mould from the Lehr, the problem mould can be traced immediately by utilizing the board.

Good practices:

• Making sure the board is kept up to date at ALL times.

• Regularly checking correctness of board.

• Check after any gap appears in the stacking pattern: IS machine cavity/section stopped. There should be a visual and dimensional verification to the concerned cavities before and after the interval. The cavities that are in the vicinity of the intervals should be visually inspected, looking especially for the detection of glass stuck inside the containers. Verification and follow-up should be maintained.

If a fault is informed by the Hot End the necessary follow-up must be done on the Lehr.

Immediately checking the cavities signalled with the defect and initiating the rejection if the defect is confirmed at the end of the annealing lehr. Reporting fault assessment to the Hot End with percentage of occurrence, begin, end of systematic rejection.

By the time the Lehr length is almost over, Hot End Operator should have checked another set and should have fixed the fault or changed the mould or blow it off at the Hot End.

If the defect it is not confirmed at the lehr, the inspection to the signalled cavities should be kept by a typical minimum period of time of the lehr time plus 30 minutes. Usually rechecked at five minute intervals. At least five bottles of each offending mould must be taken and inspected.

Identifying trends is a key aspect of the inspections:

• If the same mould runs with the same defect for three or more checks (Defect trend);

• If the same mould runs with various defects for three or more checks (Sectional trend).

• If a mould is found defective with the same defect for three or more checks throughout the shift. (It is a trend primarily because the problem was not successfully rectified in the first place.)

All of this constitutes valuable feedback for Hot End Correction.