INTElligent FIXture systems advancing machining processesadmin
The INTEFIX project (FP7 Grant Agreement 609306) aims to increase the performance of the machining processes by the use of intelligent fixture systems, allowing the monitoring, control and adaptation of the process to obtain suitable results according to precision, quality and cost requirements.
Normally, the main function of fixtures is to securely hold and accurately locate the workpiece considered as an undeformable body. Nowadays, the required high precision and the need for increasing the manufacturing process‘ performance make other characteristics of the fixtures important, taking into account aspects like deformations, vibrations and distortions in the workpiece during processing. Furthermore, the machining system (machine-fixture-workpiece) cannot be considered as a stable system due to its dynamic behaviour and geometrical shape variations along the process. In that context, adaptive fixtures can be used to control and adapt the machining system’s behaviour in order to obtain adequate results in manufacturing precision, quality and cost.
As the project moves forward, some specifc developments are reported by two of the work packages (WPs).
The main goal of the WP11 is the development of a low time consuming workpiece clamping system with low requirements for the operator. This objective was achieved by the development and testing of a comprehensive solution that makes the workpiece adjustment process automatic with the help of active fixture units with centralized control and uses a machine tool touch probe automatically. This approach is more effective then manual setting and also reduces the risk of errors. In addition, the developed solution allows the workpiece’s automatic clamping in adjusted position and pre-deformation if necessary.
The developed active fixture units can offer a stroke of 50 mm with a positioning accuracy of 0.006 mm and a maximum load of 5,000 N per unit. For better stiffness during machining and machining force compensation, units are equipped with a hydraulic brake implemented directly to the guide bars.
Leveling and clamping tests of the developed solution were performed with the demonstration part on the TYC FPPC 250/6 CNC machining center with a Heidenhain iTNC530 control system. This solution decreased the idle time for workpiece clamping by more than 70%.
Moreover, technical and economic aspects were also compared on another industrial case study. It has been proven that solutions developed by INTEFIX decreases idle time, but the initial investment is higher. Nevertheless, the investment return period is 20 pieces in the case of the train side panel. In essence, the fixtures can be used as an intelligent universal clamping solution. It means that the investment return period is computed for specific parts, not only for the train side panel. The main advantage of the developed fixture system is its universality that enables us to easily use the fixture for a variety of applications.
INTEFIX‘ WP9 focuses on the development of intelligent fixtures and machining methodologies able to manufacture highly slender ribbed parts in such a way that the final part, after the machining process, achieves the required geometrical tolerances. Manufacturing these parts usually involve high material elimination (up to 90-95%) by machining processes that, together to an unsymmetrical geometrical configuration of the part, can generate significant distortion on the part after the release of the clamps used during the machining process. As so, this WP deals with the development of specific fixtures that can avoid the distortion problems reported by the enduser (KaleAero) concerning aeronautical structural parts manufactured in aluminium alloys.
The developed solution’s capabilities have been evaluated by comparing its results to the results obtained from the actual manufacturing process from the industrial enduser, yielding the following:
- Improved part accuracy from 2 mm distortion to 0.3 mm distortion thanks to the application of the distortion minimization procedure.
- Reduced machine time from 4 days to 2 days due to the avoidance of chemical clamps.