World in motion

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Aerotech`s motion control products have been used throughout photonics for more than 40 years, as Warren Clark discovers

Aerotech has been involved in motion control technology for more than 40 years, having been founded in 1970. Based in Pittsburgh, Pennsylvania, the business began by specialising in servo technology for the military and aerospace sectors.

Simon Smith, European director of sales and marketing at Aerotech, says: ‘At the time of the company’s inception, one just couldn’t buy servo motor technology – it was all stepper motors.’

Servo motor technology gained acceptance fairly quickly, though, and Aerotech’s first major move was to introduce closed-loop control technology. ‘Traditionally a stepper motor would have been open-loop,’ says Smith. ‘That is, a command would be issued to the stepper controller to move a certain distance, but there would be no way of knowing if that move had been carried out; this is known as open-loop. With closed-loop, there is a feedback device on the system that guarantees that the required movement has been made. Today, closed-loop technology offers constant monitoring of the current position, enabling the constant correction of disturbances from target position.’

Simon Smith, European director of sales and marketing at Aerotech

Among the innovations that Aerotech introduced to the market were differential screws for manual stages, which were used for small electro-optic positioning systems. ‘Our product range has gradually increased year by year,’ adds Smith. ‘We generally invest about 10 per cent of our revenue back into R&D for new product development.’

One example of a past development is the introduction of direct drive technology. ‘Here, the motor is directly coupled to the load it is driving,’ says Smith. ‘It cuts out the mechanical leverage between them, which would otherwise be a ball screw or a worm and wheel gear. Instead, it is driven by magnetic circuits. The purpose of this is to improve throughput, provide better dynamics and generally enable better performance of the system.’

There are plenty of photonics applications for Aerotech’s technology. ‘Essentially, we provide a motion positioning solution,’ says Smith. ‘Whatever the market, there is a general trend for smaller and smaller items, and dynamic performance is becoming critical. From an accuracy perspective, we are now working in the micron and below region.

‘From very early on in the company’s history, we’ve had some unique features for the laser industry. We’ve used G-code, which is an industry-standard CNC programming technique often used with laser systems, from very early on. Our sealed stages are particularly suited to laser processing, as they prevent ingress of dust into the optical feedback systems, for example.’

Elsewhere in photonics, motion control is used to position either the laser beam or the item that’s being processed directly under the laser beam. ‘Some substrates being used are very sensitive to the amount of laser power that goes into them,’ adds Smith. ‘So, one of the challenges we solved fairly early on was the ability to deliver a pulse based on the position of the axes and the speed of the motion. This means that, when motion slows down as the laser beam approaches a corner cut, for example, the laser power will be adjusted to avoid damaging the product. This, combined with look-ahead functionality, effectively means that the machine programmer has a slide adjustment with which they can balance cut quality with speed, but only have to make one parameter adjustment. It drastically reduces set up time and optimisation time.’

Within optics, motion control is used to move plasma sources around for use in finishing and polishing. ‘On top of that, you need to be able to have the ability to measure the surface finish and the circular characteristics of the optics,’ says Smith. ‘That process requires the surface to be moved very accurately under some sort of white light interferometer, or other such sensor, and being able to confirm when one is in a particular position.

Manufacturing, polishing and measuring large optics is something that the UK is particularly good at, so we see a lot of business here.’

Aerotech has recently introduced a closed-loop galvo system. ‘This has a very high resolution feedback device on it,’ says Smith. ‘Typically, whatever is being marked or cut is within the view of the galvo. The smaller the area on which the galvo operates, the more accurate the results – but, with something like flat-panel displays, you might have a very large area over which you need to work. This system allows you to use a large-axis, linear stage to move across the large area, and then use the galvo for the high-dynamic, small parts of the process. The main advantage of Aerotech’s Nmark CLS is the infinite field-of-view capability.  This enables the user to program the geometry of the part they want to machine, and then the controller splits this profile between the long axes motion and the galvo motion to optimise the overall process time automatically.’

Smith points out that the accuracy of systems on the market is expressed in two very different ways: ‘A lot of our competitors talk about static accuracy value, but we are more interested in dynamic accuracy value – that is, how accurate the system is when it’s on the move. For the customer, dynamic accuracy is much more important.’

Aerotech’s strength is its capability to provide a complete motion-control system, according to Smith. ‘We manufacture our motion controllers; we own our own motor technology; we own our own IP with regard to how the stages are put together; we put together all the electronic components in house; we have our own surface mount lines and metrology equipment; and we develop all our own software.

‘Because we do everything, it’s very easy for us to customise and optimise the technology according to what the customer needs. We have a large range of standard building blocks and can help engineer them into custom systems. Our goal is to ensure that the process the customer is trying to achieve happens as quickly and accurately as possible.’

With headquarters in Pittsburgh, and offices in China, Germany, Japan, Taiwan and the UK, the company employs around 350 people. In most territories, sales and support is handled directly by Aerotech. ‘One of the main reasons customers come to us is the quality of our support,’ says Smith. ‘Everyone on the support side of the business is an engineer of some sort, so has a very good technical understanding of what the customer wants to achieve. We offer good, honest advice, and aren’t just trying to sell a product.’

Looking ahead, there are plenty of new technologies ahead. ‘We’re always asking: how can we provide better solutions that settle quicker, that enable customers to move faster, and that enable better dynamic performance? Also, we’re always looking for niches that don’t have a good solution right now – and, from a geographical perspective, we’re looking to move into areas, such as Russia, where we don’t yet have direct sales and support.’