Machine tool technology is set to change dramatically in response to demands of users faced with increas-ingly competitive global markets.
That is the message of Andy de Vicq, technical director of machinery research centre Amtri, based on a survey of worldwide trends in machine tool research and development.
De Vicq presented his findings to last week’s Machine Tool Technologies Association seminar, Sharing Tomorrow’s Technology Today, which brought together speakers from the UK and Germany at three locations around Britain to exchange ideas and discuss best practice.
Machine tool users, said de Vicq, face a global market characterised by fierce international competition. As a result they would increasingly demand higher economic and operational efficiency from capital equipment as they sought to meet demands from their own markets for rapid product evolution.
He said: ‘The global market will require simple user interfaces which can easily be translated into different languages, embedded information on training and maintenance, and the ability to maintain machines remotely.’
Users will need tools to help them reduce manufacturing costs and cut lead times. Future machine tools can be expected to have ‘novel configurations, modularity and digital interfaces for everything from CAD/CAM to duty logging and tele-maintenance’. They will offer ‘high availability, low cost of ownership, improved reliability and easier maintenance and diagnostics’.
As an example, de Vicq cited a high-speed five-axis milling machine developed in a European Brite research project and recently launched commercially by Sweden’s Modig. Rather than having the usual structure of three mutually perpendicular axes, it has a novel external structure. This doubles as a guard but also allows machines to be linked as modules to build up a working envelope of the required size.
The demands of high-speed production will require machine tools with high axis-travel speeds and capability for high acceleration and deceleration, as well as faster spindle speeds. Consequently there will also be a need to handle large volumes of swarf, as well as NC controllers capable of high data transfer rates to link with CAD systems.
High travel speeds will put increasing demands on positional measurement systems and there will be more need for thermal compensation because of the additional heat generated by higher cutting speeds.
High spindle speeds have implications for bearing technology, said de Vicq. ‘Non-contact bearings are better but most designers still use conventional ones,’ he said. But he predicted that as permanent magnet motors gained acceptance, there would be scope for combining the motor with a magnetic bearing in one unit.
He said new structures and configurations will radically change the appearance of machine tools. Examples are hexapod machines, which have six degrees of freedom in effect the ability to move linearly along the X, Y and Z axes and to rotate about each one. These have already been developed by companies such as Giddings & Lewis, Geodetic, and Ingersoll. In theory these could be simpler to make than conventional machines, so in principle could be cheaper if produced in volume.
Manfred Weck, professor of machine tools at the technical university of Aachen, and another speaker at the seminars, said: ‘Hexapods are expensive at the moment because of the cost of making high-precision ballscrews in small volumes, and their developers’ need to recover R&D costs.’
But he predicted a big future role for the hexapod: ‘If it works properly it will replace a transfer line.’
However, de Vicq said so far few hexapods are being used in industry because the maximum degrees of freedom needed in machining is five not six. ‘The true industrial applications [for machines with novel configurations] are tending to have a reduced degree of freedom to suit specific applications,’ said de Vicq.
Thus Hitachi-Seiki is developing a machine based on its Delta 4 robot, which shares the hexapod’s attributes of parallel kinematics and low moving mass, for high-speed drilling. It has only three degrees of freedom, all that is needed for drilling, but has the key advantage of being able to move quickly between holes.
‘The robot configuration is well proven in the food industry,’ he said. ‘In drilling, the problem is that a relatively short proportion of the total time is spent in the drilling operation itself. Being able to move fast between holes has a huge effect on overall process times.’
Another configuration finding favour in industry is the Tricept, an assembly robot configuration developed by Neos and Comau. It is being used in the automotive and aerospace sectors, fitted with a machining spindle to turn it into a five-axis machine tool.
Information integration will be another big area of development. ‘PC functions will merge with CNC controllers to provide low-cost multimedia for embedded maintenance,’ de Vicq predicted. Instead of having a separate maintenance manual, details would be built into the machine to be searched like a CD-rom encyclopaedia.
More and more companies are providing access to programming and production data via networks, allowing the machine to be linked with planning and scheduling software, with machining data for each job being downloaded as required.
Similarly, provision for machine suppliers to gain access over the Internet for maintenance and diagnostics is becoming increasingly important.
Modular construction will allow machines to be linked and processes to be integrated, simplifying transfer line construction and allowing automatic loading and unloading.
Conversely, processes will be modified to eliminate intermediate stages. There will be a trend to hard machining instead of machining parts from a softer grade of steel and hardening it with heat treatment. Such ‘near net shape’ techniques will be used especially in the mould and die market, where strong growth is expected as plastics use expands.
Amtri is involved with nine other machine tool related companies in a European funded research project, Shimm, for single-hit multifunction machine technology. Its aim is to develop machines capable of being configured from modules to allow complete manufacture of components at a single setting. The £5m project began in April 1996 and runs for four years. Prototypes are about to be built in Sweden and at Amtri in Macclesfield, Cheshire.
Other challenges face the industry in the area of micromachining. Work is going on in numerous technologies to control very small movements and machine nanometre-sized parts. The stress of holding a part in a conventional chuck can cause significant distortion of small parts, and ways of handling parts ‘the size of a speck of dust’ need to be developed, said de Vicq.
Finally, more sophisticated measurement and control systems will be developed, capable of fine resolution over large areas. Measurement systems will become increasingly sophisticated in compensating for errors caused by thermal expansion or the inherent flexibility of the machine structure, inputting correction factors to the control system in real time.