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Productivity improvement in the rubber roller industry

Productivity defined

Productivity originally is defined as resource consumption and the latter gets expressed in quantities like hours, kilos, pieces etc. The adding of monetary values is not genuine to the productivity discussion but it simplifies the judgement which resource combination is the cheapest (in the moment). The independence of quantities and prices leads us to the fact that the most productive way of manufacturing must not necessarily also be the cheapest and that the product costs depend not only on the resources consumed but also on the changes of the prices of the resources in question. So when we talk about productivity we always must take assumptions regarding the prices of the resources - at present and in the foreseeable future.

This is very difficult and normally we are wrong with our expectations: salaries do not always increase, raw material prices change heavily in every direction, interest rates develop unexpectedly, rents, rates and taxes rise or fall. In order to handle this problem in an acceptable way prices of resources normally are fixed and so is the relation between them. This procedure is valid whenever there is no predominant resource that influences the costs of the product far more than any other one does.

Costs in the rubber roller industry

In the rubber roller industry we have such a predominant resource: the rubber (or any other elastomers material); it determines between 25 and 30 % of the product costs. It is plain to see that price changes of the rubber often affect the calculation of a roller more than any other changes. It is often impossible to compensate this increase by improving the productivity of labour, machine usage, the volume of the work in progress and so on.

So even if we don't know the future pricing of rubber, we can argue that the least possible rubber consumption probably always is advantageous to any other solution. Knowing this we fix the actual pricing structure for all the resources and we assume that their relation will not change heavily in the future.

Reducing rubber consumption and costs

Our behaviour in re-covering rubber rollers would be estimated by any visitor from outer space to be a little bit strange: first we put a lot of expensive rubber on the roller, then we vulcanise it with expensive energy and after that we take at least 30 - 50 % off by cutting and grinding - and sometimes grooving. More strangely: when we start the recovering process we hold a metal core in hand that was covered with rubber before which we took off completely though only roughly 50 % of this rubber was effectively worn down. In our proceeding our visitor will hardly detect any material saving strategy.

Maybe there never was any need to save rubber. But since we know that the price of oil in long terms will continue to grow we should acknowledge that in this business the most effective rubber usage would be the best strategy to meet the shortfall of oil that we have to face.

Reducing the rubber volume applied to the rollers does not necessarily mean increasing other costs. The latter would only happen if all simple methods of rubber saving had been realised and we would enter the world of the substitution of one resource by another. But normally we are far away from this point.

In nearly every rubber roller factory there are ways to save rubber without investment in machinery or labour.

Reducing 'overbuild' and material flow

The first approach can be to reduce the "overbuild" of rubber in diameter. The unnecessary overbuild is mostly caused by bad experience with the cylindrical characteristics of the roller after vulcanisation. But the, originally, cylindrical form does not forcibly change in the autoclave.

With the right curing programme we can both keep the shape of the roller and inhibit too much material flow to the ends, which is the second aspect for rubber saving. Thus the rubber consumption in average can be reduced by more than 20%, which equals 5 to 7% of the overall costs, with little or no additional investment.

Reducing rejection rate

Another important issue is the rejection rate of the production. If it happens to be 2 or even 4 percent then also the consumption of rubber is 2 to 4% too high. Unlike many other industries, in the rubber roller manufacturing a rejected piece always means the loss of all rubber and labour applied; nothing can be saved for a second attempt. So the management of the rejection rate is a major issue for the responsible persons and the target of a rejection rate of less than 1% is worth pursuing.

Improved rubber useage

The working layer of rubber normally is less than 6 mm thick. Nevertheless mostly we put on the core more than 10 mm of rubber and completely strip the metal core when it has to be recovered. 5 mm of rubber would be still usable.

A first step into an improved rubber usage is building up a hard rubber layer on the core that will not be removed in the recovering process. This layer serves as core protection and reduces the quantity of rubber needed as well. Though there are still (smaller) problems with the rubber-rubber-bondage this approach is promising and can contribute another 10 to 15% to rubber savings.

This is not the place to discuss the advantages and disadvantages of the alternative delivery forms of rubber and the cost differences in the differing manufacturing processes. Whether a batch of rubber in combination with an extruder is used or a calandered sheet is put on the core in a three-roll-building machine is not primarily a question of rubber consumption.

It is correct that scrap of batch material can be used again while this is mostly impossible with the off cuts of calandered material. But both methods lead possibly to the same diameter and material flow in the curing oven. So these two alternatives have to be discussed separately under the aspect of process optimisation and the price difference of the rubber has to be compared to differences in investment, set up time process time, and rejection rate. Without anticipating any results I can say that in most cases the covering with a simple building machine is faster, cheaper and can lead to less rejection.

Rubber cost savings

Prices of rubber and the delivery terms vary strongly. It is normal to reuse a rubber quality that has proved to meet the requirements of the customer and nearly nobody dares to question this quality and substitute it by a less expensive one. So after some time every roller manufacturer ends up to always utilising material, which is too good for the application it is used for; this is an expression of the normal human attempt of risk avoidance.

It is also merely human that this behaviour is further developed in all companies that produce their own rubber. At the interface between mixing department and roller production of one (!) company the readiness to rely on the assurances of colleagues is less developed than the readiness to believe the assertions of a third party supplier. So in the first situation people prefer to increase the demands on the rubber, in the second they are more willing to compare quality and price - and to shift part of the risk to the supplier.

So the "home-made" rubber tends to be over-engineered systematically while the third party rubber is only over-designed due to a lack of precision in communication and a certain pattern of the iteration process of finding an apt solution.

What we can say for sure is that every rubber used over a long period of time without trouble is over-designed and should be reviewed. The easiest way to do so is to try cheaper and more modern alternatives. This suggestion automatically leads to the necessity to use more than one rubber supplier - what I think is inevitable in order to keep competition and innovation alive in the field of rubber. We can expect that a consequent rubber redesign after a ten-year period will provide a cost reduction of more than 10% - under competitive circumstances.

Altogether we see a potential for productivity increase on the rubber side of more than 30%, even if some of the savings would compensate each other. Under consideration that rubber now comprises one third of all costs we expect an overall cost reduction of 10% or more.

Changing manufacturing processes

Rubber roller manufacturing is an old technique. The basics did not change remarkably during the last 50 years. While other industries got turned upside down, roller production is still covering, curing, cutting, grinding, and grooving. Even the processes in detail show an unknown stability; machines aged 50 years are still used and do an acceptable job. Sixty-year-old autoclaves are not exotic.

The used-machinery market in the roller world is lively and the prices are high. Innovation is rare and apart from the production of a few graphic rollers in big quantities the roller manufacturing is not apt to automation. It would be ridiculous to accelerate changes in a world that does not need them. So I openly want to express my conviction that the technical processes also in the future will remain mostly as they are now.

In other words: grinding will not be substituted by turning, vulcanisation under pressure and high temperature will not be replaced by vulcanisation under room temperature and without pressure. On the other side there is a permanent attempt to reduce process time and costs as well. But the poor results are the expression of the inability to shake off a major obstacle of this industry: small numbers of identical rollers, nearly no series production, no learning curves, and no economies of scale.

If there is no alteration in technique and no improvement in the individual process time, is there any possibility for productivity increase at all?

We would argue yes and that this increase could be substantial.

Benefiting from automation

Like any other industry, in the rubber roller manufacturing we use machinery and human labour. Mostly the machines define the time consumption of the single processes and the people manage and support the machine work, often by simple monitoring. In other words: As long as the machines run, the workers do a good job.

This thinking was correct as long as the machines needed assistance and control. Nowadays they are able to work alone: they set up themselves, they start the manufacturing processes on their own, they monitor the quality of their doing and they stop when the job is done. The workers could do something else in the meantime, but normally they don't.

This is the big field of manufacturing improvement in the rubber roller business, rearranging the production organisation with the target to optimise both machine and labour usage. As soon as we understand that machines and workers do not necessarily work in timed sequence but that they can work independently from each other and only adjust and merge their results, then we see a tremendous range of possible improvements. To find these reserves of productivity we have to review all machine processes, especially when a couple of them are combined in one machine.

Core preparation

One field of improvement is core preparation. What do workers do while cores pass through a steel-blasting machine? How long does it take them to apply the bonding to the core? Could the workers affect additional processes like putting end protection caps while a machine is running? Can we grease and degrease the bearing seats while something else happens at the same time?

Many questions... and trust me, there are a lot more even in such an unimportant area. Many manufacturers do not know the actual time consumption in the core preparation. For an average roller of 2000 mm length and 300 mm diameter it figures out to be between 5 and 15 minutes personal time and 2 to 7 minutes machine time. Both can be reduced by at least one third.

Covering is composed of a little bit of technique and a lot of philosophy. We will not compare and judge the alternatives in this article but we want to lead your attention to the fact that conventional covering of a 1500 mm / 150 mm roller wrapped with a calandered sheet of rubber can be effected in less than 5 minutes - including treatment of the ends and bandaging. (The average covering time for such a roller varies today between 10 and 15 minutes.)

It is mainly a question of cutting the whole process in adequate pieces of labour organisation, of the layout of the machinery and the preparation of the workplace. Self-evidently also the ranking of the orders (according to the size of the rollers and type of rubber) is important; nevertheless it is astonishing how much time can be saved by reviewing the workflow and optimising manufacturing processes in detail. Comparable improvements are possible when covering takes place in a strip extruder or a crosshead extruder.

Most of the production time of a rubber covered roller is spent after curing in the cutting, grinding, and grooving process. Our standard roller (2000 mm / 200 mm) consumes on average more than 40 minutes personnel time and also machine time for trimming and grinding - and sometimes up to another hour for grooving (both personnel and machine time).

In-depth analysis

Analysing this whole process will provide a lot of very interesting information. First: the mere grinding process (without polishing) can be achieved in less than 20 minutes machine time and less than 7 minutes personnel time. Second: Grinding (of rollers up to the "standard" size) should be separated from polishing and from cutting as well. So the machinery can be specialised and the process time can be brought down.

Third: experience taught us to grind rollers between points; for cutting and polishing rollers must not be fixed between points.

Fourth: Today manual work like painting the ends, degreasing the bearing seats, removing corrosion stains, wrapping paper around the roller, and labelling normally take place in an expensive machine - and hinders it to do another worthwhile job; freeing these machines of simple processes is a big step towards increasing productivity.

Fifth: Also in the grinding process productivity improvements can be achieved with little investment.

Sometimes it is possible to save up to 50% of the former production time by rearranging and optimising the whole process - under the condition that we have lots of at least 10 identical pieces; with small quantities time reductions of 25% are easily to realise. Facing such a huge potential the question arises why improvements did not take place in the past already.

Obstacles to cost savings

The answer to this is quite simple: There was no need to cut costs and capacity never was a bottleneck. Cost cutting discussions are created by price reductions in the market. Since the rubber roller market mostly is not price driven, also price reductions are the exemption and they occur mostly in the OEM-business, but not in the recovery business of the small roller manufacturers.

The second reason, machinery capacity, is more astonishing. It is remarkable that in nearly every roller plant (in Europe) there is a surplus of (machinery) capacity, though the companies mostly do not grow quickly, if they do at all. A likely explanation for this fact could be an alleged preference for additional capacity instead of a review of the production organisation - because these are the only alternatives.

As long as the profits are supple the decision for capacity seems to be the preferred alternative, only when profits decrease the possibility of reorganisation in taken into consideration. The fact that up to now most rubber roller companies choose additional capacity can be judged as a proof for their economic soundness.

Qualifying services

Living in a post-industrial service society forces every company to provide services that exceed classic production. Most companies did not decide to extend their offer by own deliberations but were forced to this step by their customers. Accordingly they did not do much planning and shaping but stumbled into a new field of activity. So it should be normal that the way these services are affected is not very professional - and in fact it is.

The rubber roller manufacturers are not an exception to this rule. More or less every company in this branch of industry nowadays provides logistic services, technical customer support, engineering services, trading services, and emergency help (for example during the weekend).

From the point of view of the roller manufacturer these services lack three crucial elements:

  • They are not organised professionally
  • Their costs are unknown
  • They cannot be charged to the customer

Regarding professionalism of the organisation of the services things can easily get improved. Normally it is sufficient to have a look at your procedures and apply a good portion of common sense and you will find a solution that is way above average.

In general the issue is not finding a solution, the issue is the awareness of the problem itself. Let's take an example: Many roller manufacturers offer a logistic service to pick up rollers at the customer and to bring them back when they got recovered. But nearly no one who provides such a service ever separated his corresponding costs, compared them to the costs of a third party carrier, tried to investigate the costs per roller brought in or sent out, optimised the daily routes, organised regular milk rounds, checked a multi-trailer system with few vans, calculated a return-box-system etc.

Whenever this issue is dealt with professionally interesting facts emerge to the surface; always the service can be improved without cost increase. Sometimes even the expenses can be cut down. Often an inter-company solution will be found, which enhances the service of all partners involved and does not inflict competition. The technical quality of the service can be raised and sometimes even a boxing system can brought up that provides marketing advantages.

The awareness of the problem mostly provides already acceptable solutions and always gives the necessary information regarding costs. To know them is a substantial condition for pricing, even for first price discussions with the customers. And we should always realise that it is rather easy to convince someone to pay an invoice if we can explain the costs and the value of the service.

The example of the logistic service can be extended to all other services. Everywhere are possibilities of improvement and cost cutting and often even completely new ideas regarding additional services are born out of the engagement with this issue. Many companies only realise the tremendous value of the services for their business when they start caring about them: It is the services that tighten the customer relationship and that are perceived as core competence. And it is the services that allow a company to change their nature: to become a service provider, who additionally produces rubber rollers.

On a final note

Finally I want to mention that also internal services contain a remarkable potential of productivity improvement. Hence it should be reviewed carefully to cut costs. Contrary to many others I am convinced that even a small company should have an appropriate EDP-system but not do bookkeeping and personnel administration on its own.

Many specialised companies provide the latter, who in their business are far more productive than a roller manufacturer ever can be. Completely different is the situation regarding order processing, material and production management: A good software system, designed according to the needs of this branch of industry can not only provide a good overview and an optimised order flow, but also assist the company when it grows. The structure is in place, growing is reduced to a quantity problem and not a quality issue. So spending money once for such software will reduce the daily organisation costs and the mess that inevitably occurs when a company is growing unprepared.

Altogether every rubber roller manufacturer has a huge potential for productivity increase and cost cutting. He should carefully plan corresponding activities and take his time to realise them. An overall review will need three to four years to be affected.

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