Current machine tools are complex mechatronic structures full of sensors and drives where control laws are implemented. However, in these systems the measurement and action points are usually far from the cutting zone and frequently the actuation bandwidth is not wide enough to avoid self excited vibrations and assure a proper dynamic behavior. DYNXPERTS project has overcome these limitations introducing actuators and sensors as close as possible to the machining point.
With this objective in mind, DYNXPERTS project has focused on the development of a new generation of plug and produce adaptive components. These components are able to improve the dynamic behavior of machine tools in several aspects and increase their productivity introducing new features in existing machines.
• A new concept of spindle head for heavy roughing operations: “The 5F Active Inertial Spindle Head”. With this head is possible to obtain the dynamic properties of the machine in all working area, to monitor the state of the mechanical components of the head, to change the spindle speed to avoid unstable cutting conditions, to introduce active damping using an inertial drive, and improve the motion control introducing acceleration signals in the control loops. The dynamic stiffness has been increased 150% applying smart functions and the material removal rate has been quadrupled with this new spindle head. A patent has been submitted protecting the concept.
• An innovative spindle head for High Speed Machining: “The 5F Magnetic Active Spindle Head”. It makes use of magnetic bearing technology and features the aforementioned 5 functionalities of the new roughing head. In this component the actuation to calibrate the machine and to avoid self-excited vibrations have been made using the capability of the magnetic bearings to induce a force in the shaft. The damping ratio has increased more than 40% and the material removal rate has increased 8 times taking advantage of the new five functions. The spindle head has been presented in a workshop to important aerospace aluminum part manufacturers.
• New smart fixturing devices have been developed in the project based on an active damper and advanced clamping system. The damping has been implemented with magnetorheological elastomers and eddy currents which are able to adapt to the dynamics of different large and flexible work pieces. A big improvement of more than 630% has been measured in the cutting test performed by the consortium. The concept of the adaptive dampers is in patenting process.
• A new component has been created to introduce the stability charts into the production lines in an automatic way: This device measures the critical dynamics of the tool, generating the stability charts and providing automatically the best process parameters to guarantee optimal machining and chatter free cutting conditions. The system has been able to increase the material removal rate more than three times and the surface roughness has decreased 55%.
• To reinforce the self-sufficiency, portability and plug-and-produce features the project focuses on energy harvester devices and wireless communication bridges. The energy harvesting functionality has allowed locating numerous monitoring sensors in positions extremely close to the points where the action takes place during a machining operation: the interior of the head and the clamps of the fixture. The wireless bridge is used to transmit the information monitored by these sensors to the control units of each of the components, but also to link the new plug-and-produce devices to the machine's control. A wireless monitored high speed spindle has been developed during the project.