Driving optimised performance

02Jan

posted by: John Inskip, Siemens UK

Optimising the performance of machine drive systems is a must for manufacturers.

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Doing so will enhance improvements in quality, productivity, flexibility and operational efficiencies, all of which are critical for success within an increasingly competitive global marketplace.

Within the modern world of manufacturing, we are constantly bombarded with views and information concerning topics such as productivity, lifecycle, utilisation, and efficiency. For many, this leads to challenges around achieving positive results and measuring performance, as well as ensuring strategically important machine capital investments made in a business are ultimately working effectively.

Almost all machines have movement generated by either air, liquid or electricity. But, the most commonplace by far is electrical energy, with an electric motor utilised to convert this energy to mechanical motion. Electric motors are designed in various guises including A.C induction, Servo or DC motors and by linking an electric motor with a variable speed drive and mechanics, a drive system is created.

There are countless information sources looking at energy efficiency in motors and using variable speed drives to control and regulate the speed. These are well known and widely understood principles. But, what about optimisation or performance? How does this directly impact the performance of machinery and are there methods to improve overall performance on a drive system?

The common practice of ‘tuning’ a drive system has been used in the past to gain the most amount of response out of a drive system. This has used techniques such as ‘step response’, where a controlled step response is introduced into the drive system and the response measured. Another approach is the ‘Zeiger-Nicolas’ method, which uses an oscillation input and measurements taken when making adjustments so the output is measured.

Such approaches will certainly improve the response of a drive system, but there are limitations in terms of the quality of the machine’s performance. To further improve matters, additional information such as frequency response throughout the operating area must be recorded using tools such as fast Fourier analysis. This can record how the drive system responds over the frequency spectrum.

Some may ask why there is the requirement to go into such detail if the drive system is producing material and is healthy - is this not sufficient?

In short, no, especially in a modern production environment where quality and quantity are prerequisites for success and competitiveness. For example, when looking at a printing press machine, the resonant frequency of the machine can affect print quality and also the long-term reliability of mechanical components. What would be undesirable would be for the drive system to generate or add to these resonant frequencies. In this case, ‘tuning’ with frequency response is beneficial to avoid unwanted quality issues in the printed media.

Having an optimum gain and response also adds ‘stiffness’ to a machine. This is a requirement of performance-orientated machines, with dynamic movements and where high accuracies are paramount in robotics and machine tool applications. Being able to respond to changes in a manufacturing process in a controlled and responsive way is always desirable in converting and hoisting applications.

There is no definitive value or default values of parameters that work for every type of machine. This means a holistic approach should be taken and tailoring the drive system to each individual machine is required to reach the highest performance levels. This level of detail can be perceived to be a complex process involving a lot of knowledge. But, technical innovation means help is at hand.

At Siemens, we go into great detail to ensure the tuning tools embedded into commissioning software are user friendly, intuitive and deliver clear information to the end user. There are additional features such as ‘auto-tuning’, where the software can ascertain the default values based on the mechanical system. This feature makes reaching higher performance levels far easier and removes the need for costly specialist engineers or expensive tools.

Today’s manufacturing processes are placing increased levels of demand on machinery to reach ever higher levels of productivity and utilisation and it is more important than ever to attain better productivity levels to be competitive within a globalised competitive manufacturing environment.

Using the methods described will not only help with product quality, they will also support response, first time quality, performance and efficiency objectives. As the UK manufacturing sector strives for increased product levels, openness and flexibility by embracing digitised benefits and the overall strategy of Industry 4.0, the importance of getting the most from the machines and their drive systems should not be underestimated.

About the author:

John Inskip is Product Marketing Manager at Siemens UK & Ireland. Having joined Siemens over 15 years ago, John’s current role sees him responsible for marketing activities across the business’ Drives & Motion Control division.