Digitally enhancing the glass container forming process

Peter Firth* shares his thoughts on how innovations within digital technology could improve the glass container forming process in the future.

I was recently asked whether I think advances in digital technology will enhance the glass container forming process in years to come.

The person asking me the question was in particular thinking of digital incarnations such as robots/cobots and swabbing automation, as well as other digital automation systems.

I have been involved in the glass container manufacturing industry all of my working life, gaining a first-class honours degree in electronic systems and control engineering along the way.

I was introduced to the particular world of IS Machine Digital Control with a bang, as it was the first undergraduate project given to me by Redfearn National Glass’ Barnsley, UK plant (now Ardagh Group).

The task was to debug a real-time digital control system the company had invested in, as the in-house developer had left the business to pursue other opportunities.

This control system was one of the first systems to implement automatic rejection of ware after swabbing. It also tried to go further and simulated the warm-up of moulds to implement cold mould rejection and automatically turn off when the moulds were sufficiently hot.

It was based on an advanced programmable process control system developed by Hewlett Packard called the HP2250.

With many of the lines not working correctly and software being blamed, my challenge was to rectify this and fix the software.

There were very few explanatory comments in the programme to help. It seemed to have been coded direct from the programmatical thinking of the person who developed the system, straight into real-time computer code.

I therefore had to get into the thinking of that person who had programmed the system and work out what was going on.

This was a great introduction for me to the digitisation of ancillary IS machine controls at an early stage in my career.

Now, aged 57, I am in semi-retirement and enjoying consultancy work, mostly for Glass Futures in the UK, with a focus on the design of the St Helens Pilot R&D Plant.

Between that sobering introduction to IS machine digital control systems and now, I have had further exposure to specifying and using such systems to maximise production efficiencies.

I have witnessed the move from basic electronic timing systems to servooperated mechanisms and now into the era of intelligent vision-based systems and robotic applications.

These robots are known as cobots, as they work alongside human operators to achieve a better outcome than just human operators.

The answer to whether I think advances in digital technology will enhance the glass container forming process in years to come is a resounding “Yes”.

This trend has happened for years now and there is no reason to stop.

However, a caveat is will the investment costs required justify the benefits? It is a difficult question to answer regarding which automations are cost-justifiable and which are not.

The easiest justification for capital investment is when it delivers a direct saving in terms of reduced rejects, or it allows for increased production speeds. In both cases, these are increases in productivity.

Some accountants have muttered in the past that if we had actually achieved all the benefits being claimed, we have been running at around 110% efficiency (in reality it probably should be much more!).

I remember the 1 or 2% increases in speed or reduction in rejects added to the many capital expenditure applications I have signed off, or been involved in formulating, particularly when I was an Operations or Plant Manager in glass facilities.

The accountants view was this didn’t necessarily achieve the claimed efficiency improvements. The vital thing to remember is that when a plant runs more efficiently, production speeds can be increased as well. This speed increase then later reduces the output efficiency again. However, overall the output is increased in terms of volume, then the cycle starts again.

Therefore, we can run at an actual 110% increase in output based on efficiency improvements while still operating at present production efficiencies of 90 – 95%.

This needs to be understood to believe in the benefits of future digitisation developments in the forming process.

The question remains as to whether the current capital investment levels required for advanced digital forming technology will be cost-justified, or just bells and whistles that cost a lot of money but give no net benefit to the actual glass container business they are implemented in.

This to me is the real question to ask, and one of the questions I hope an independent like Glass Futures can answer by evaluating without any bias, commercial or product sales pressure, which many suppliers of such systems will face.

In other words, to consider whether digital technology will enhance the glass container forming process in years to come, one has to contemporarily and objectively assess the whole cost-benefit equation of each particular digital control or robot/cobot application.

Some digital control systems deliver a demonstrably better control capability on a machine process variable, but without any quantifiable improvement in the productivity or quality of the glass container.

In such situations, the forming departments notice this and put such systems into manual operation, or the technical departments don’t maintain them, yet the plant continues to perform well without these.

One particular application is blank temperature control. In reality, there are a range of operating temperatures before we are too hot or too cold on the blanks to produce good containers.

A control system can maintain these temperatures within a few degrees by monitoring the blank temperature and adjusting the cooling air to each half of each blank.

Such control is, however, beyond the requirements of the process for the product being made.

This is no problem if the technology to do this is inexpensive and easy to use or maintain.

But, if any of those points become a problem, such a control system might be more trouble for a glass plant than it is worth.

That is from a practical glass-forming point of view, rather than me speaking with my pure control engineering hat on, upon which I might argue differently from a naïve control-only viewpoint (where any improvement in the control of a process variable must be a good thing).

There is also the downward-cost development of the generic technology used and any change in ease of implementation to consider as well.

When the costs reduce and the ease of implementation increases, it might mean an application which was not worth it at one point in time, now becomes viable.

Finding the right time to adopt a particular technological application when such a reduction in costs and ease of implementation happens is the key to linking the use of technology with a cost-competitive glass business. To do this a competent technical appraisal that considers the costs of ownership or such systems as well as the capital investment costs is required.

Digital technology applications

Now let us consider some future digital technology applications.

With the feeder, we know we have already got flexible servo drives to the needles and shears that give such precise control that we can even deliver consecutive gob cuts of precisely differing weights.

This has enabled the production of differing production types on the same IS Machine and at slightly differing weights, easily within 10% or so.

The cost-justification for this technology is clear if you need this flexibility in the manufacture of your job mix. It is easy to justify, where it offers a production capability expansion benefit.

For many years we have had the capability of gob weight control in NNPB by feeding back the pressing positions of the plungers forming the parisons, and then adjusting the feeder needle height and tube height to give gob weight control within a gramme or so. This is together with a statistical standard deviation of much less than a gramme.

Recent advances in gob imaging technology have seen estimations of gob weight made simply from a gob image straight after it was cut, which provides automatic weight control in the BB and WMPB process (the above-mentioned control system for NNPB can also be used on WMPB of course).

Such accurate control of gob weight in the BB process is not always required but it helps maintain consistent capacity control of containers and therefore a better product. But this is something where it needs to be decided if the result justifies the equipment cost.

With NNPB the automatic weight control is non-negotiable, it has to be implemented due to the risk of critical defects without it.

The gob distributor is currently also advanced with servo implementations giving accurate motion control which ensure that the scoop is stationary and points at the next trough entry before gob arrival, even with large swings in sections delivered (such as from Section 2 to Section 7 for example). This helps get the best firing orders for the best conveyor dead plate times (with the most even dead-plate times being the best).

Improvements can be made during delivery of the gob into the blank and systems have appeared which help with this. Vision systems that monitor the gob loading into the blank can make adjustments (or should make adjustments) to the deflector loading position.

Of course, in an ideal world the deflector would not need to be moved, but try running a machine without doing that and you soon have zero output!

Although I support efforts on better deflector design to achieve a situation where no adjustment is then necessary, loading remains a weak point of the forming process and needs improvement. The symptoms of variation in gob loading alignment can be treated with the aid of current technologies, even if does not address the root cause of the variation itself.

Now the IS Machine robots and other systems have made it easier and less costly to monitor the blank temperatures (using mobile infra-red thermometers) rather than using expansive and unreliable cables and thermocouples, such as in the past and in some plants today.

Therefore, my comments about the blank temperature control system not being worth the net benefit considerations might now become of age when a reduction in cost and increase in ease of implementation make it a nobrainer to use.

I hope this illustrates the point about costs and ease of implementation, which is the general rule by which all new digital technologies should be assessed as regards whether or not they bring a net benefit to a glass container manufacturing operation or not.

The mechanism motions of the IS Machine sections have already been implemented with more accurate servo systems, although the original pneumatically operated mechanisms are still widely used.

Servomechanisms give more repeatable motions and enable more speed from a section as mechanism motions can be run closer to ‘crashing’ the process than with pneumatic systems, which need a wider window for variation in speed and precision of operation.

The costs of the servos and reliability and maintenance costs will be factors to assess if they benefit a business or not, particularly when assessing it with the benefits that these bring together with more repeatable mechanism motions. Ware handling in modern highspeed production should definitely be implemented with servo motors. For the ware push-outs, it is better to use 3-axis systems where the containers are on large high-speed machines, or where unstable ware is being made.

The 3-axis systems enable the ware to be placed on the IS machine conveyor without repeating ware handling problems and problems with conveyor ware spacing.

The servo drives for the main machine conveyor, ware transfer, and cross conveyor allow for accurate synchronisation with the machine.

On the machine conveyor there is still a requirement to manually trim the main conveyor drive speed to compensate for inevitable belt stretch, in order to maintain the same linear belt speed. This can be a problem if staff are not trained at how to do this, so automating this may help as it will reduce the chance of ware handling problems and related production losses.

Servo stackers have been in use for years, and there is an emergence of robotic systems carrying out the same function. However, at high speed, the simplicity of the traditional stacker bar remains king. Such systems still need close attention to set up for best possible handling to ensure the ware pushed into the lehr is done stably and giving best possible straight row alignment. There could be opportunities for further digital control improvements here to achieve ideal lehr stacking requirements.

We can be imaginative when we consider how all these parts integrate and what future additions we should expect. However, in terms of the basic integrations, where we have widely implemented servo systems, there can easily be more rapid set-up changes for job changes of course. That can be a major factor for some plants, but not so for others. Such servo integration allows for an easier future closed-loop adjustment based on glass product measurement and inspection feedback.

This brings us to how we monitor the product and the advent of hot end inspection. This topic is often covered widely so I will only summarise it here. There is a lack of use of that information in terms of deploying it for process adjustment. Therefore, the IS Machine remains a largely open-loop system. Closing that loop on feedback from the final product is the next major advance.

This is easier said than done. Hot end inspection is not as accurate as cold end inspection, but cold end inspection is carried out far too long after manufacture for closed-loop adjustment to ensure consistent glass container quality. This weakness needs to be resolved. How we do this is another matter and is potentially a great opportunity with some process technology suppliers already working on this.

Once the inspection information is received, which should include typical defect identification at the hot end as well as glass distribution and dimensional measurements for example, we can then act on changing the machine or a section event setup, but this can only be done with a largely servo-mechanism implemented machine.

It is difficult to make the adjustments using pneumatic operated devices, although there will be some exceptions to this I can easily envisage.

The first implementation of the robot was in automating swabbing. I was in the first technical meeting in Ardagh’s Moerdijk Plant where we decided to implement this in partnership with Fanuc robotic systems developer. It was a success and Heye International now sell the swabbing system as an option for its standard machine.

Many other similar swabbing robots have come to market, but when we had those first few technical meetings, I was not aware of any other such swabbing robot at that time.

The additional applications such a robot could take care of are the measuring of the blank and plunger temperatures as well as possibly the neck-ring as well.

In addition, the same or similar robot could change blank-side mould equipment, although I am not aware of this being done yet. It could also adjust the deflectors in response to monitoring the gobs loading into the blanks, to keep the loading central.

These are things anticipated to come to market soon, if not already implemented already somewhere in the world.

Any improvement in gob loading will be a system of interest to improve container manufacture performance as bad loading is one of the most common causes of glass container defects. This is the next largest benefit of robotic applications, although there might be solutions implemented with just digital control that might not require a robot as such.

Let us close the loop on loading somehow, or else eliminate the causes of gob loading variation (something we have failed to do since the inception of the IS Machine).

I hope that I have gone at least partway to answering the question of whether I think advances in digital technology will enhance the glass container forming process in years to come.

I have tried to answer the original question in a thoughtprovoking way, with a focus on the overall cost competitiveness benefits.

I hope too the work I am involved with at Glass Futures will help to answer some of the questions raised regarding the right time to deploy such technologies in the forming process. For the corporate members of Glass Futures that should be one less thing to worry about.

*Peter Firth, Glass Container Production Consultant, Working with Glass Futures on the GFL St Helens Project. Contact: Via LinkedIn Profile (search ‘Peter J Firth’) or email peterjfirth@gmail.com Glass Futures, St Helens, UK https://www.glass-futures.org