New ground is being broken in the design of positioning tables

Linear motion and its associated systems don’t always get the attention they deserve. However, that does not mean there aren’t some fascinating innovations and applications out there.

One of these is in the field of linear tables. These are used in the most diverse fields of application. Due to their compact design consisting of guide and drive system, they can be used economically and efficiently in many areas. And anyone who wants to manufacture with precision should also be able to position precisely, because precision machining starts with an exact positioning. The motion control specialist Aerotech has developed a completely new series with the IGM motion platform in order to get away from rigid positioning systems.

The new linear tables are significantly more flexible and scalable than conventional positioning tables.

The development was initiated by Norbert Ludwig, managing director of Aerotech GmbH in Fürth. Aerotech has revived a concept already contemplated before. The Integrated Granite Motion Systems (IGM systems) are a scalable alternative to conventional positioning tables with a granite substructure. “The idea behind IGM is as simple as it is effective: We no longer position a complete linear adjuster on granite, but its individual components, so that the guide, drive and measuring system are mounted directly on the granite and not via the detour of a complete adjuster”, says Aerotech´s managing director, explaining the design and layout of the motion platform. “We are thus offering motion components as a product group for the first time and no longer as a purely special solution for the customer as we have done so far.” In this way, tailor-made IGM linear tables meet all requirements of different applications. And the advantage for customers in the European market: the positioning systems are configured to customer specifications at the German location in Fürth.

In the classical design, linear adjusters are screwed onto a flat granite base as a counter mass, in order to be able to safely accelerate and move large masses. Although IGM motion platforms have already been manufactured in special production, due to the flexible component concept, Aerotech applies this one-off production characteristic variably to the series and, using the components, assembles and application-specific positioning table according to customer requirements.

Compared to conventional positioning tables with granite substructure, the new IGM linear tables offer higher rigidity with reduced overall height and

consequently, increased flexibility in design. Depending on the special application, travelling distances, payload and dynamic performance, for example, can be adapted to suit. This ultimately leads to higher positioning accuracy and better dynamic performance.

In addition, IGM systems are often more compact due to the better integration of the machine components into the granite structure. Different versions with mechanical or air-bearing axes are available. For the drives, ball screw and linear motor are available as options. In addition, various feedback options are available, ranging from simple encoders to laser interferometers. Finally, additional motion elements such as rotary axes, lifting devices, piezo nano-positioners or even galvanometers can be integrated into the IGM axes – all components can be controlled centrally via Aerotech´s A3200 machine control.

“Nevertheless: IGM must not be understood as a finished product, but as a concept to show how customer-specific motion systems can be constructed flexibly”, admits Norbert Ludwig. “We can, for example, show how the axes and guide rails can be arranged in order to design the system according to the customer´s requirements.”

For discrete adjustment systems which are not available from the standard product portfolio, a designer needs all individual adjusters in a special design. This significantly increases the time and effort required for the processes from design to production. Mechanical processing must also be redesigned, including the creation of new machine programmes. This takes time, of course. The IGM, however, does not require a new design for every linear adjuster. For example, a 1200mm x-axis with 800mm y-axis can be quickly implemented once the design of the granite plate has been determined. Within certain limits, the design can be adapted quite well to the conditions of the designer. Nevertheless, you should not ignore that a high flexibility also has disadvantages, because the design is fixed in this case. For example, the y-axis cannot simply be extended in retrospect, because this would result in a new design. And because of the installation, the service can only be carried out on-site at the customer´s premises – the customer cannot replace any components on their own.

Usually, customer applications can be found in precision measuring and machining technology with adjustment ranges of up to 2 metres. If, for example, standard adjusters are no longer able to work at a length of 1 metre, because the milling machines can only process longer profiles with a great deal of effort, this would not be a problem for an IGM system. You can build any length, 1.50m, 1.80m etc. – without having to redesign it again.

“Our new IGM systems, for example, can be used in micromachining, but this is not necessarily a core area”, explains Brian O’Connor, product manager at Aerotech. “We support machine tool suppliers with solutions at the component level, such as motors, controls or drives, and also with high-precision positioning systems.”

Norbert Ludwig adds: “Although we have customers for our rail-on-granite platforms from the watchmaking industry, among others, the flexible positioning systems for various industrial applications can also be designed for mechanical engineering and the automotive industry, for example in the fields of measurement technology, testing and inspection.”