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Machinery equipment for rubber roller production

Introduction

When it comes to rubber roller production, the equipment in use surprises most people. And we don't just mean the age of the machinery - where a lifetime of 20 or even 30 years is the norm rather than the exception. It's more the fact that the machines often do not fit together regarding aptitude, manufacturing quality, and capacity.

Although it is not unheard of within industry, for working equipment to lack innovation and investment, usually the equipment a company needs to do its job fits together and achieves a certain quality and quantity of products.

Yet in the rubber roller world things are a bit different. Here we normally find:

  • Surplus capacity
  • Low quality
  • An environment struggling with the conditions of quality assurance

Quantitative capacity

It is quite astonishing to see the average surplus of capacity in the average roller manufacturing plant, compared to other industries.

Yes, we know that the rubber roller business is not merely industry and that service is key, but we must obey the laws of providing services: quickness, flexibility, interaction with demanding customers, and the ability to react precisely to the needs of the markets.

All these requirements are only to be matched with machinery, which, on average, is not intensively used and thus provides free capacity for sudden orders, quick shots, or emergency services.

This should be common practice but, what we see in our rubber roller world, is not only flexibility assuring capacity but a surplus of machinery which covers any incapability of organising the work flow, any potential demand of any customer even if the last order dates back 15 years, and any other occasionally occurring situation.

The provision of this surplus of capacity has never been planned. It simply happens: new machines are bought and the old ones kept in reserve. With enough space the machinery grows and grows and gives you the good feeling of being able to fulfil any order immediately. However, in this world two facts are not considered sufficiently:

  • Depreciation/cost of the machines
  • Difference in quality between machines

Old versus new

Machines cost money and we make a big mistake believing that an older machine, bought on occasion, costs less than an expensive new one. Correct accounting always forces us to calculate the machine as if it was new and to depreciate it endlessly at 10 to 15% per year. Yet this is not feasible in practice as it would lead to costs that cannot be invoiced to the customer.

The second reason that explodes this myth is that most of these "occasions" or old machines work far less productively than new ones. They cause more time, energy, and material consumption and result in more rejects. These costs match with the price of the goods only if machine costs are neglected.

Machines of a different age may also differ in terms of quality. Yes, we know that customers often show a lot of patience with our quality (and even with the lack of it) but we should be aware that low quality has become a risk for every manufacturer.

In the neighbourhood there is - or will be - a competitor who has better skills, better machines or better productivity and in the long term he or she will win the business. It is a fact that quality is not everything; but without quality everything is lost.

You may say that even with an old worn-out machine a skilled worker can produce better quality than a poor worker with a brand new machine. True. But not one worker in this world can modify his personal approach to his job, in the sense that if he is carefully, correctly, and slowly working with old machines in the morning he will do the same with new ones in the afternoon - and never use them to their full potential.

What we urgently want to bring to mind is the risk of running machines of different quality in one single factory. The results are high costs, dependency on a few workers, lack of productivity, and self-deceit regarding your true costing level.

The situation, as described here, can be found in nearly all grinding departments in nearly all rubber roller manufacturing plants. Also it is often seen in the core preparation and sometimes even in the covering department.

Forward thinking for better planning

The advice, to all members of our industry, is to reduce and specify clearly your range of products and develop a long-term strategy with regards to investment in machinery. We would urge you to take away old and worn-out equipment - or at least to gather this equipment in a specific building with a specific staff. If you follow this advice we're sure you will soon see that there is no real cost advantage in maintaining these old machines.

Such an approach will lead to further improvement. By reducing the capacity available for good quality manufacturing, it will force you and your organisation to enhance your planning; improving the organisation of workflow, the production control, and order processing.

By being forced into a review of operational procedures we are confident that you will find many ways to reduce delivery times, assure quality and change the individual process steps so that they provide a better fit to ergonomic needs and repetitive precision.

Qualitative capacity

In this section, we no longer compare machinery of identical purposes like grinding or covering; now we have to look at the integration of the different departments within our factories.

We need to compare the preparation of the roller cores with the covering, the covering with the curing, the trimming, the grinding, grooving and the final assembly. If, in your factory, you also provide additional services like core manufacturing, balancing, rubber compounding and so on, these must be included in the thinking.

It may be a well-worn cliché but it is certainly true that a chain is only as strong as its weakest link. In comparison, the quality level of a rubber roller manufacturing plant will never surpass the quality level of the weakest department.

Many people all over the world may not consciously acknowledge this fact but all of them feel it and act accordingly. This can be seen in the behaviour of buying sophisticated goods and producing only the simple ones themselves. (Considering this, you will easily find out that a company buying goods and manufacturing the simple ones at the same time will never have competence in this respect and should buy all items needed from third party.)

Variety in quality

The quality levels, of the different steps of rubber roller manufacturing, vary remarkably in nearly every factory within our industry.

And apparently there is no pattern in this variation. Sometimes it is the core preparation which is poor, sometimes it is the covering, often it is the trimming and grinding. It's probably safe to say that the competence in curing is usually good and that the competence in grooving is mostly below average.

Sometimes rubber roller manufacturer have an expensive steel blasting capability for core preparation and afterwards wrap rubber sheets on to the core in an old lathe without any quality assurance and poor productivity.

In another you'll find strip extrusion or even cross-head extrusion in a covering department which hands over the rollers, after curing, to a grinding facility which seems to belong to the 19 th century.

It's even possible to come across numerically controlled grinding machines sitting side-by-side with grooving machines, which should be dedicated to a museum. We've even found a remarkable degree of mechanisation in transport and handling and then seen people disassembling and reassembling rollers manually with no other tools than hammers and pliers.

This list could go on and on and I'm sure every worker in our industry could tell his or her own story.

Improving quality

Speaking from experience, these situations are rarely planned, they simply occur by investing in new technology or even only in more capacity. Unfortunately, people are not aware of what they are creating; they are convinced that they will improve the quality level of the whole factory by improving one process step - and this is a wide spread illusion.

The quality level can only be raised by widening the qualitative bottleneck. Yet this seldom occurs, usually due to a lack of knowledge about where this bottleneck actually is. So many companies invest in more capacity and modern capacity and forget to look around the corner into the next or previous production department. After a certain period of time, they check the productivity and they are convinced that it was successful, and we admit they are - to a certain small extent.

Let's have a look at an example: A rubber roller manufacturer has a bottleneck in grinding; the travelling speed possible is less than 60 mm/minute (diameter 120 mm), therefore the machine produces approx. 36 meters of rollers in a two-shift regime, giving a set-up time of 25%. Investing in a new grinder doubles his capacity and once he must invest he decides to improve grinding, too. He invests in a grinder with a (fast turning) rubber hog, a second support for trimming the ends of the rollers, with the capability to crown the rollers and with an increase of the travelling speed to - 80 mm/minute. All over this investment is a big leap forward for our roller manufacturer. And he can prove this within a short period of time.

What he did not see was the reason, why the travelling speed was so poor: was it the grinder, the grinding stone, the rubber quality, was it the over-build due to a poor covering method or the risk of deformation during the vulcanisation?

No matter what it was, this company did not improve the whole process; it only hid the existing problems with new machinery.

More effective ways of working

This example also gives an indication of what should have been done: Check the whole process of manufacturing rubber rollers and find ways to improve all production steps from the very beginning to the end and not the other way round - backwards!

Look for alternatives to reshape, to simplify and to stabilise every single process. This should begin with the roller coming in, continuing with stripping the old rubber off, activating/roughening the surface, applying the bonding agent and covering it. It is incredible how many possibilities of productivity improvement you will find simply by checking these steps carefully in great depth.

Normally you will find out that with little money you can enhance your capacity and at the same time gain a higher quality level by reshaping the first steps of manufacturing - not the last. Normally you will find that by doing this, your expensive grinding capacity will be growing automatically without any need for further investment.

Determining the quality level

Before starting with the first steps according to the process flow, you should reconsider the overall quality level you are aiming at. Rubber roller covering is not just about rubber roller covering.

There is a wide range of possibilities in this business and for each of them there is a market. Given a good quality of rubber compound, which matches the customers' requirements in every respect, the roller manufacturer can:

  • Simply put the rubber on, try to create a more or less cylindrical shape and a surface quality which will not bother the customer
  • Put the rubber on, provide good bonding and a correctly cylindrical (or crowned) shape and a surface quality as requested
  • Check the metal/carbon fibre core, repair it if needed, advice the customer which rubber to take, guarantee perfect bonding and cylindrical/crowned shape, provide a surface quality which he can prove will match the customer's needs and life cycle expectations and offers grooving competence for any pattern.

The three quality levels are achievable only with completely different equipment - from the very first process step to the very last.

Without question, you will be able to reach the first level with used machinery, which is partly worn-out and provides low tolerances. You simply need an old lathe with a grinding belt attachment to strip and roughen the roller, the application of bonding agent can be achieved manually, the covering needs another old, slowly turning lathe, the curing can take place in a self-made autoclave, which is able to heat up to 145° C and 4 bar.

The trimming of the ends, the pre-grinding and the finish grinding can be done in a few more old lathes, to which little grinding stones are attached. Job done. The whole investment will cost you less than 150.000 €, even if you take first steps towards dust removal, lifting equipment and other workflow support items.

Yet, you will not achieve the second quality level by only buying one new grinding machine! This is the crucial point. This new level forces you to improve nearly all steps in order to reach a situation where all processes can be monitored and repeated in exactly the same way.

While the first level was typical for craftsmanship, this second one is already typically industrial. And the typical industrial characteristics are repetitiveness, defined and stable quality and the ability to check and monitor this quality.

In order to monitor quality of any process step, the input to this step must be precisely defined, which obliges the previous step to provide a well-controlled result. This type of result requires a certain type of machinery, which differs remarkably from the used equipment necessary for the first quality level. So it is unavoidable that you must change all (!) your equipment, unless you had a qualitative surplus of machinery already in your first level production - which rarely occurs.

Although the second quality level already is typically industrial, it is not yet modern in a way that the machinery is highly productive, perfectly fitting together, providing high tolerances combined with flexibility and is working in a rather clean environment.

Modern industry - a new approach

All these aspects interact intensively and cannot be achieved in isolation, so productivity will be a good indicator for this quality level.

The easiest way to measure productivity is time consumption: both personal time and machine runtime. (The ratio of machine runtime to personal time is another indicator for high productivity: every figure beyond 1.5 is estimated to represent a modern factory.)

The average over all (personal) time consumption for a roller 2000 mm wide and 250 mm in diameter in quality level one is roughly 1.5 to 2 hours. In level two-time consumption can be reduced to 1 hour. In level three it must be manufactured within 35 to 40 minutes. At the same time, the quality rose dramatically. Now it should be evident that this third quality level and the shortened manufacturing time cannot be obtained with the old machinery and just another effort of the working staff.

A completely new approach is needed with new machines fitting to each other quality-wise and additional training of the personal.

When in such a situation one or two old machines remain in usage they immediately become qualitative bottlenecks and prevent the company reaching the targeted quality and cost level. It goes without saying that the exchanging of all the machinery cannot take place in one step, but it should be planned and executed over time. When you replace the normal disorder regarding qualitative capacity with fitting machinery the success will only be a question of time.

The fitting environment

Operating poor machinery in a shabby building is often considered acceptable. Old machines, working on a poor quality level don't require an even, clean floor. The removing of grinding dust is as redundant as the cleaning of the machines from old rubber part and pieces.

The fact that small particles get pressed into the rubber with bandaging and get applied to the surface with the wrapping paper after grinding will not bother anybody - it is part of the working environment at level one.

Viewing rubber roller manufacturing from this angle also explains the indifference towards corrosion on the bearing seats, dirt on the flanks of the cores, stains in the rubber, little failures in the bonding and so on. Nobody is perfect and that includes the rubber roller manufacturer.

Changing the attitude to quality level two requires substantial improvements to the environment: first rate floor, dust removal system and a clean building. Level three additionally requires clean machines, clean and pretty rollers, no rust stains, no grease on the core after grinding, bright working places etc.

Building, machines, tools, and products on this level have to fit together with regard to their appearance. Investment in cleanliness is needed and, in the long-term it will pay dividends.

Conclusion

Not every rubber roller manufacturer needs a factory, which is comparable to food processing. Neither does every manufacturer need first-rate machinery. There are markets for all three quality levels and thus factories with ill-fitting machinery will survive.

The important statement of this article is that within your chosen quality level you should ensure that all machinery (and tooling as well) should fit and understand that any qualitative surplus is useless; your customers will not pay it for.

On the other hand be aware that the next quality level cannot be reached by purchasing just one or two crucial machines. All of your equipment must fit, not just parts of it. And it is not only the machinery: The third level cannot be obtained in an ugly building with a dirty floor and a messy workflow.

Whatever quality level you need or want to reach, try to obtain it from the first process step to the last and avoid any self-deceit along the way that you hope your products will not realise that they have been manufactured with second-rate equipment. Be sure, that they will.

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