The clean, efficient and safe alternative

In the face of tougher health and safety legislation and demands for improved process efficiency, Robert Caddick of Danaher Motion explains why the electromechanical solution is the best way forward.

Pneumatics and hydraulics have done the job of linear actuation in a huge range of applications for years.

In the face of tougher health and safety legislation plus demands for improved process efficiency, however, their shortcomings are becoming ever clearer.

Every day it seems that new European or international regulations come into force to govern some aspect of industrial activity.

The result is that almost every activity that goes on inside a plant - from initial laboratory analysis of raw materials to final waste disposal - is subject to numerous rules and standards.

Two of the most stringently regulated areas today are health and safety and energy efficiency.

So any area that intimately links the two finds itself under a number of regulatory spotlights.

One such area is the use of pneumatics and hydraulics.

Both come from a time when manufacturing was neither as sophisticated or as regulated as it is today.

Often they were providing a cheap and relatively simple method of automating production systems.

Today these technologies have developed and are far more sophisticated.

However, although they are present in almost every plant in the world, today they are often regarded as "dirty" technologies.

For example, it is not unusual for pneumatics and hydraulics to produce airborne oil particulates that in turn can cause health problems.

The contamination issue is also feeding through to customers who are creating their own pressures by imposing more stringent packaging criteria on manufacturers, particularly for products used in the food and medical sectors.

But airborne contaminants are not the only health and safety issue for workers using pneumatics and hydraulics.

Hydraulic oil is known to produce allergic reactions in some workers.

This means there is the need for protective clothing, which will also reduce worker efficiency to some extent.

Then there is the noise issue: another hazard and yet more protection needed.

However, recent advances in technology and design mean that electromechanical actuators offer a real alternative to conventional pneumatic and hydraulic cylinders - in almost every application.

Not only do they go a long way to solving the problems associated with airborne contamination, allergies and noise, but also they also have a dramatic effect on energy efficiency.

Companies are continually on the lookout for ways to boost efficiency.

So it is important to note that pneumatic and hydraulic systems also have a far lower overall efficiency rating than their electro-mechanical alternatives.

The point is well made in a new survey of industrial energy consumption carried out by the Delegation of Energy Supply in Southern Sweden (DESS).

The survey's main aim was to analyse the consequences of a Swedish nuclear plant shutdown.

However, after analysing its data, the DESS discovered that production machines driven by pneumatic systems had an overall efficiency rating of 5%.

Furthermore, it was estimated that if those same systems were using electromechanical solutions a saving of up to 90% could be made in electrical power consumption.

Pneumatic systems are not alone when it comes to scoring badly in efficiency surveys.

Hydraulic systems are routinely found to be as poor, and in many cases even worse.

And both have the disadvantage of generating large amounts of heat, a classic byproduct of inefficient operation.

By virtue of the way they work, both systems are prone to inaccuracies too.

In a pneumatic system, where cylinder actuation is driven by air pressure, there is no way to control the cylinder's subsequent acceleration.

As the air pressure in the pneumatic system is uniform, the speed and force exerted by a pneumatic cylinder varies according its bore, length and the load placed on it.

Put simply, if there are differing loads placed upon the cylinders in a system, the acceleration of those cylinders will also be different.

Sophisticated control systems can to a certain extent improve the function, but even with costly control systems the disadvantages are still there.

As a result, a disadvantage of both pneumatic and hydraulic actuation methods is the inability to provide good positional accuracy between the start and end positions.

For its part, the "electrical cylinder" is controlled in every stage of movement.

Acceleration, speed, positioning and force can all be programmed to meet a specific application.

Therefore an engineer can determine where and when actuation should start, along with the acceleration and retardation of the cylinder.

This same level of control can exist between differing positions within the overall stroke length of the cylinder.

In other words, all cylinder movements are under full control.

It is no surprise, therefore, that more and more companies are opting to make the change to electrical actuators.

Or that suppliers are constantly improving the power and cost effectiveness of what they offer.

A good example of this is the Danaher Motion T130 heavy-duty industrial actuator.

An industrial actuator application that is incorporated within an automation system is often required to undertake high duty cycle rates within harsh environments.

The T130 meets these specific requirements.

In designing the T130 the Danaher team quickly recognised that simply scaling up an existing, smaller product would be unsatisfactory.

So in late 2002 the company surveyed its customers in order to draw up a design specification for the new product.

Once this was designed, all critical components were tested against predefined performance data.

The prototype itself was built and Beta tests were made in demanding applications in the field, and tested with the help of the company's Danish partner AVN.

The resulting T130 design uses a 40mm ball screw with three different screw leads: 10, 20 and 40mm.

This makes for a very powerful actuator with a maximum dynamic load of up to 40kN.

It also has a maximum stroke up to 2m and speeds of up to 2m/s.

It is designed for a 100% duty cycle.

In order to ensure that the T130 can be used in a wide variety of applications a range of accessories have been produced.

These include a magnet sensor, a belt gear, mounting kits, and a range of motor/gear connection interfaces.

The belt gear has been designed to handle demanding applications.

The gear fits most common AC and servomotors on the market and can also be equipped with a clevis mount option.

Use of a belt gear is a very good solution for gear ratios in the range 1:1-3:1 and is a highly cost effective solution.

But there are many other reasons for specifying a belt gear too.

For example, the application may require a parallel motor configuration (shorter overall length) or there might be a need to reduce the input speed to the actuator ball screw.

Another reason could be that the application demands the use of a higher motor speed and a smaller motor size.

Engineers may also need to gear up the output torque from the motor in order to reach an acceptable inertia balance between motor and actuator.

The belt gear itself offers a host of features such as low noise and maintenance, play free operation, reliability, high duty cycle and a long life expectancy.

Engineers are also enthusiastic about the option for clevis-to-clevis installation.

The BGM80 belt gear is built on a base plate with two driving wheels and timing belt, all protected by a plastic cover.

The belt wheels are mounted directly on to the motor shaft and the shaft of the actuator.

Automation in general is getting more diverse than it was eight to ten years ago.

At that time a good production manager should try to fit as many arm robots as possible into his plant.

Today we know that a mix of arm robots, linear drive units and in some cases also semi automation where human resources are used, is the most efficient way to set up a production line.

This is where Danaher have its strength.

Danaher can provide the "grease" to the line.

This grease consists of actuators and linear drive units.

These products have also become a natural building block for the engineers developing machines with linear movements.

Danaher has 20 years experience in making linear drive units.

When first launched in 1995, Danaher's M50 linear drive unit won the US Plant Engineering Product of the Year Award for Power Transmission.

It was intended as a noncomplicated product for OEM applications where larger volume production would ensure more competitive pricing.

Seven years on and faced with an even greater demand for a cost-effective product of this size, the company redesigned it to give a unit which is easier to manufacture and has better performance than its predecessor.

At the same time, however, the new M50 remains fully compatible with its old design so that no major plant reshuffles are necessary.

Years of manufacturing experience, plus customer feedback, have ensured that the new design comes with a number of major improvements.

One example of this is that the saddle is now one single part rather than an assembly of several components.

Such parts are produced in high volumes for lower cost at a machining centre.

Another improvement is that the drive end has a new smart design for the installation of bearings and the drive shaft.

This has resulted in fewer parts and greater flexibility in the manufacture of customised shaft designs.

The redesign has also led to a more rigid, longer life product with the same or higher performance data.

As none of the important dimensions have altered, the new M50 can fit the same applications as the original model, too.

The company has achieved what it set out to do by consolidating the position of M50 as the leader in its market segment.

The company is also benefiting from the ability to be extremely competitive in terms of price when faced with demanding OEM applications that need large volumes of units.

Examples of these include scanning in printing equipment, scanning in paper/plastic film production, and cut-to-length equipment for the window industry.

As new and increased demands are being put on linear drives, particularly in automation, robot and handling applications, further advances are being made in technological development.

In the case of Danaher Motion's Movopart linear drive units, the design of its unique in-house screw support option has been updated to offer less noise, longer life, adjustment of the slide bushing play, and easier assembly.

The design of this screw support has been one of the driving forces behind 20 years of Movopart success.

Now the company can supply one of the longest screw-driven linear drive units on the market.

The function of the screw support is to limit the unsupported length of the screw.

This is important because the maximum speed of the screw depends on its free length.

When the screw is rotating it can only stand a certain speed at a certain length.

Exceed that speed and the screw starts to warp as it has reached the critical speed for that particular length.

The expression "double screw supports" is used when there are two linked pairs of support bearings moving independently of one and other.

In this case, with two support bearings on each side of the saddle, the free screw length will be divided into three equal parts.

The new screw support allows Movopart units the following stroke: M55, up to 3m; M75, up to 4m; M100, up to 6m.

To make the choice straightforward, Danaher provides sizing and selection software to let users know when screw supports are needed.

Screw driven units are often the best solution in applications with high force and low speed demands.

However, many companies today are still using belt driven units because they are not aware that long screw driven versions are available.

Nevertheless, as a result of these technological advances and in the face of increased health and safety legislation, many industries are turning to mechanical actuation solutions.

In particular, there is strong interest from the general factory automation market while the packaging, health and fitness sectors are actively converting to the technology now.

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