Monitoring the fitting process in electromechanical presses increases production reliability
High precision fitting monitoring is essential for high quality in production.
Hydraulic press systems are presently dominating the assembly and fitting market. In automated production and manufacturing lines, however, electromechanical press systems are on the advance.
Besides their benefits such as the possibility of implementing high pressing forces and rigidity, hydraulic systems also involve inherent drawbacks which have to be overcome, for example, their large size, a potential pressure loss during pressing, or the necessity of using a hydraulic aggregate. Electromechanical presses, on the contrary, offer substantial benefits with respect to their size, power consumption, and ease of maintenance.
However, what is the decisive factor here is that force and position during lifting can be controlled precisely. Therefore, this technique allows inline process monitoring to be implemented easily. In view of new techniques and materials, hydraulic press systems ever more often reach their technical limits. Composite materials for sophisticated designs in automotive engineering using carbon fiber, aluminum, steel, or fiber glass require extremely precise fitting processes. Conventional techniques such as welding or screw-fitting can no longer be used for these purposes.
HBM recognized this trend at an early stage and now supports an electromechanical press system that has set standards with respect to precision and system travel speed. Compressive and especially tensile forces up to 100 kN have been implemented. A particular benefit is provided by the hollow shaft servo motor with integrated torque support through a grooved-shaft guiding mechanism enabling compact-sized press-fit spindles to be implemented. The motor is controlled by means of a servo amplifier that stores and handles the system travel profile.
The fitting module includes a linear actuator with planetary roller gear and grooved shaft guiding mechanism, booster control, SSI emulation, and compressive/tensile force sensor. The DT85 is the central component for visualization and control. It enables the paths of travel to be selected and visualized. CANopen is used for networking. The MP85DP fitting and press system module facilitates the monitoring of process parameters to ensure full traceability of production data. In addition to the force signal supplied by the strain gage force transducer, the MP85DP uses the SSI interface to read the positional signal directly from the servo converter. The MP85DP allows stand-alone analysis and documentation of the force versus displacement curves of the pressing process. Analysis is based on a tolerance band or tolerance windows using absolute or relative references.
The 32 parameter sets for fitting and monitoring are stored in a non-volatile memory in the monitoring module or servo amplifier. Several thousands of results, curves, statistical data, and additional parameter sets can be stored on the internal memory card. Users are enabled to configure process monitoring individually to meet their requirements. In addition, all cyclic and non-cyclic parameters are available via the Profibus with DBV-1 functions. Process data can also be accessed through the Profibus or the digital I/Os of the super-ordinate control system.
Electromechanical fitting modules have already been used in assembly machines for press-fitting of sleeves and bearings. Further application fields include fitting, functional testing, stamping, hot embossing, or metal forming. The modular design of the system permits individual adaptation to different applications. It can also be easily modified at a later stage to suit new operating conditions.
