Pneumatics at heart of bearing assembly system

Precision pneumatic controls from SMC Pneumatics are at the heart of innovative new automatic assembly systems, designed for Sarnatech BNL to make bearing assemblies

Precision pneumatic controls from SMC Pneumatics are at the heart of innovative new automatic assembly systems, designed for the world-leader in the design and manufacture of rolling element thermoplastic bearing assemblies, Sarnatech BNL, that are critical to the efficiency of new photocopying machines.

The novel and bespoke assembly equipment designed and manufactured by Precision Engineers, of Pontefract, for Sarnatech BNL, performs a range of complicated pick and place, and inspection manoeuvres, to manipulate the delicate bearing assemblies with complete precision.

The assembly systems produced by Precision Engineers have proved highly successful as systems engineering solutions, to improve assembly efficiency for Sarnatech BNL.

As the company produces between 40 million and 50 million bearings a year, the importance of the company's continuous improvement programme, together with its move towards increased automation can be clearly seen.

Each of the bearing assembly systems and the bearing cage assembly machines has been built with maximum flexibility in mind.

The main benefits of Sarnatech BNL's type of fully integrated bearing assemblies are that they have reduced weight and inertia, whilst being low on friction and lubrication free, they are corrosion and chemically resistant.

These attributes are important considerations for the international photocopier market where the dominant feature is the fact that product life cycles are short, usually between two and three years.

Therefore, Sarnatech BNL needs to have adaptable production systems for its assemblies to allow for the introduction of new photocopier model designs.

"By working in conjunction with SMC, Precision Engineers came up with a novel system that was specifically designed to enable us to maintain our position, at the forefront of bearing technology production and assembly.

We have a collaborative programme that enables us to work very closely with Precision Engineers and that commitment to a long-term relationship means we are able to jointly develop innovative ideas," said Sarnatech BNL's Manager, Technical Marketing, Viv Hallam.

As a result of this latest collaboration, Sarnatech BNL has been able to capitalise on a system that is delivering completely efficient production of bearing assemblies, 100 per cent reliability in quality control, increased production speeds and, vitally, complete repeatability.

The first system, designed in close co-operation with SMC by Precision Engineers, is a 12-station rotary assembly automatic machine, which has the ability to provide 100 per cent quality control.

It checks and double checks the ball bearing assemblies for very small ? approximately 3mm - ball bearings that might have escaped the assembly during the process.

This high level of inspection is made possible through SMC's controls enabling the machine to rotate the bearing housing in front of a sensor which can identify if balls are missing, whether the bearings are placed in a single housing or a double housing assembly.

Of great importance is the use of an SMC compact guide cylinder, which controls the automatic introduction and retraction of a grease gun into the rotary system, at a single point.

A precise amount of grease is applied to the bearings, to provide lubrication for silent performance when installed into a photocopying machine.

Exactly the right volume of compressed air (2.8 Bar) is required, to inject the correct volume of grease into the bearing housing, the gun has an exacting travel distance to and from the bearing housing, as it is held in SMC grippers at the grease gun station.

The time elapsed at the grease gun station was also exactly calculated by Precision Engineers as this was of great help in helping govern the volume of grease placed in the bearing.

The company also took a significant amount of time identifying the correct grease to use, as the bearings demanded a certain viscosity for them to operate correctly.

The assembly process begins with the plastic bearing inner race located onto a central pin fixture.

The cage is first fitted over the inner race and then orientated so that the ball pockets align correctly.

Steel balls are then inserted into each pocket to produce a cage assembly.

If a double row bearing is required, the second cage is rotated through 180 degrees and then filled with balls.

The cage assembly is transferred to the next station where the plastic bearing outer race is pushed over the cage to complete the bearing assembly.

At this point the housing is rotated in front of the inspection sensor, which detects if there are any missing balls.

If incomplete, the assembly is ejected using an SMC MHQ25D air chuck.

If the assembly at this stage passes inspection, it moves to the next station where an outer plastic bearing race is pushed over the cage to complete the assembly.

In selecting SMC as the pneumatic controls supplier and development partner in the creation of these new assembly systems, Precision Engineers were confident that they would be able to realise a step change in the production efficiencies of its customer.

As Precision Engineers Production Director and designer Mick Carey-Topping explained, the machines are designed to currently produce 1,200 housings per hour within a stringent operating environment.

"The SMC cylinders have to perform trouble free to a heavy cyclic pattern and their total repeatability and reliability is crucial.

In a typical shift there is a high volume of strokes on any single cylinder and that can impose a heavy repeated load on the nose and bearings of the cylinders, with a lot of strain also applied to the seals on each cylinder," he commented.

In addition, he has found an additional way of enhancing cylinder life, (and another safeguard), by incorporating floating joints where applicable at the different stations, on the rotary machines, allowing the cylinders to naturally self-locate without strain should there be any lateral movement or minor variance during the process.

As manufacturers of bespoke and tailor-made automated systems for a wide variety of applications, Precision Engineers highly values the close teamwork and support it receives from SMC's sales engineers and the technical specialists at its Milton Keynes UK headquarters.

Mick Carey-Topping totally embraces the partnership SMC provides his company as the market no longer has a need for off-the-shelf mass produced capital equipment but has needs which demand a focused approach to companies' individual issues.

"As an engineering designer I have to face a wide range of difficult technical problems and create the most efficient and reliable answer in the form of any type of machine that will deliver production efficiencies and complete reliability for the end user.

SMC has an immense range and I can turn to any area of their vast catalogue and find a product around which I can base detail designs to provide optimum solutions.

I know there is always something there for me and it is supported by a close inter-action and enthusiastic involvement in genuine problem solving," he emphasised.

And the importance of the close partnership between Precision Engineers and Sarnatech BNL within the overall quality partnership concept is vital to the success of Sarnatech BNL, as Viv Hallam emphasised.

"It is crucial to know that one of our partners is working with a company like SMC who clearly provide a high quality range of products that can be supported virtually anywhere in the world.

We strongly believe in a market as competitive as ours, where we always put the emphasis on quality and added value, that we operate an extended value chain with all our suppliers at every level.

Clearly with SMC through Precision Engineers, that value chain is very strong indeed," said Viv Hallam.

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