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Tandler Precision advises users on how to choose the most appropriate drives for their applications.

According to the company, electronic servo drives are ‘in fashion’ – for many design engineers, they are the preferred choice for systems that synchronise and co-ordinate the movement and position of fast-moving components.

However, while they have an important contribution to make, they are not necessarily the right choice for all applications.

A mechanical solution may not be as technically exciting, but in many cases it can be more reliable, more accurate and far more cost efficient in the long run.

Mechanical drives are often seen as old fashioned and low tech.

In truth, added Tandler, they are the subject of much development.

Mechanical drives are getting better and better, and those at the quality end of the scale are now able to deliver even greater accuracy and reliability.

Elements that have contributed to this improvement include the more accurate machining of components, more durable materials, higher-quality bearings, new methods of heat treatment and in particular vacuum hardening, which effectively eliminates any distortion.

The electronic drive is often sold on the basis of it being more accurate than its mechanical counterpart.

Mediocre-quality mechanical drives may be inferior, but those at the higher end of the quality scale can far exceed the accuracy of the electronic drive.

The main benefit of a largely mechanical system – one comprising line shafts and bevel gearboxes – is that its accuracy is maintained throughout the system.

Within one revolution, a mechanical drive will always repeat itself – it will always return to its original position.

The transmission error of a geared system must be considered, but this can be measured.

It is a known quantity for which compensation can be made.

In a multi-stage process driven by electronic drives, the relationship between the position of the product and various elements of the machine is fed back to the controller by a variety of peripheral sensors.

The system is therefore far more complicated, and often servomotors cannot respond fast enough to achieve the required degree of accuracy.

By its nature, an electronic drive system will only respond to where the product was in relation to the drive – not where it is.

There are, however, applications where a single electronic drive offers advantages over a single mechanical drive.

If the user needs fast response and if the application involves changes in motion, the electronic drive is the best choice.

It is suitable for replacing cams and for applications that require high torque for fast acceleration and braking.

However, if the whole system requires high torque, the electronic drive and motor will need to be large and may be expensive.

In this case, a motor/gearbox solution will produce high torque far more cost effectively.

Electronic drives are also limited when it comes to providing high torque at low speed; gearbox speed reduction is the only viable solution.

Electronic drives are often chosen for machines used to produce or process a number of different products.

Stored setup data can be quickly called up to reset the machine with changed parameters.

However, an electronic drive does not always have to be the foregone conclusion.

Speed modulation or phasing gearboxes are extensively used in packaging machinery.

These gearboxes allow adjustments to be made in machine setup to accommodate different product and package sizes at a much lower cost than having all components driven and controlled electronically.

Although the cost of servo drives is reducing, they remain expensive in relation to mechanical drives.

One of the main cost penalties is the programming back-up they require.

The majority of good servo-drive suppliers do offer this service, but help is not always readily at hand in the middle of the night shift.

Also, when problems occur in an electronically driven system, it can be difficult to know where to start.

A largely mechanical system is much more simple and user friendly – a problem is easier to track down.

Given the right application, there is no longer any reason for an electronic drive to be dismissed on the grounds of unreliability.

However, if maintained properly, a mechanical system can be highly reliable and can maintain the same level of accuracy over many years.

Again, it is important to remember that a mechanical drive will always accurately repeat itself per revolution and that its accuracy can be measured.

This assurance allows an OEM to predict its own product accuracy with confidence.

While the electronic drive has its merits, so does the mechanical drive, and a combination of the two in most multi-stage systems invariably provides the best solution.

In printing presses, many manufacturers have redesigned machines with the mechanical drives being replaced with servos.

Some are now moving back to high-quality geared drives, with line shafts and gearboxes for critical elements such as print units, while retaining servos for unwinds, rewinds and tension control.

The best machines will use a combination of mechanical and servo elements.

Tandler Precision

Tandler has been at the forefront of gear manufacturing technology for more than half a century. Wherever high-quality gearing is required, in industrial, aerospace, military and automotive applications, from one-offs to volume production, we can manufacture gears of all types to meet the most stringent quality requirements.

With the wide range of gearboxes from Tandler, and couplings and torque limiters from R+W, we are able to offer a wide range of power transmission solutions.

We prefer a consultative approach to determine the optimum solution to meet your requirements. We invite you to call us with your design challenges. It is through identifying your unique needs that we can be most helpful.

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