Cetim-Ctdec relies on partnerships in its developments. HBM is one of those partners, having played a key role in the MAAT (machine automatique à auto-adaptation technologique/self-adaptive automated machine) project developed in recent years. Like many Cetim-Ctdec research projects, the MAAT project involved the development of an advanced technology allowing French (or European, since this project benefits from a European financial contribution) bar turning companies to improve their competitiveness in relation to competitors. The stakes are high since the bar turning industry constitutes around 600 companies in France, with a workforce of 14,000 people.
The idea here is to optimize the cutting conditions in machining, helping machinists to reduce setup times during production startup and, consequently, prevent drifts or even automatically correct the cutting condition parameters of machines in operation. Ctdec has supported the project and was backed by various experts in machine building, tools, lubricants, vibration and measurement. The developments made in this project should be usable in existing machines, old or new.
"The objective of the study was to be able to determine scientifically the speed and feed rate of tools in an optimal manner, taking into account lubricant consumption and the tool's service life. The project was started in 2007 and industrial production was launched in 2010 with the assistance of HBM", says Patrice Laurent, head of the Mechatronics Division and Group Activities at Cetim-Ctdec.
Several approaches were investigated in order to ascertain a cutting condition. The simplest approach is to measure the electrical power consumed at no load and during machining. This yields an image of the cutting pressure, that is, the tool pressure on the material. However, this method is unclear and is only applicable in case of chip removal and relatively large chips. There was a need, therefore, to shift towards a technique based on a transducer mounted on the tool. The idea of using a quartz transducer was quickly abandoned because, though this type of transducer has the required accuracy, it is also fragile and relatively costly, and hence ill-suited to industrial conditions.
"In the end we opted for the development of a new tool that directly measures the strain between the cutting tool and the material. Thanks to the sensitivity of this transducer we can study the cutting conditions for different operations, both during rough turning (when a lot of material is removed) and finishing of final dimensions. This is the key element in determining the ideal speeds and feed rates", explains Roger Busi, project leader and cutting expert.
Clearly, if one manages to increase the speed and feed rate, the work on the piece is done more quickly, allowing the production of more pieces during the day and hence the reduction of production costs. With this improvement in competitiveness, companies are better able to fight low labor cost competitors.