“Servo technology enables the process to be controlled such that the required offset is reached with an accuracy of a few micrometers.” Frank Neugart, Product Manager for servo presses at IEF-Werner GmbH
“This series enables high-precision joining processes to be performed in an automatic and reproducible way,” explains Frank Neugart."The systems are designed flexibly and can be integrated in assembly lines as well as manual work places. The servo technology has significant advantages in this application. This technology enables the operators to set parameters such as speed. Depending on the required precision, very short cycle times can be implemented, because the driving force acts on a spindle,” says Frank Neugart. A massive and torsion-resistant C-frame made of tool steel forms the base of the press. The system eliminates deformations, bending, or setting processes that affect the force-transmitting parts during the pressing process through mechanical decoupling of the measuring system and compensates for them through the servo control. The drive train consists of a precision spindle, a servo motor, and a quill guide that enable lateral forces to be fully absorbed. With the aiPRESS, a precision guide keeps the drive train precisely on track through the entire duty stroke. “Positioning errors resulting from the deflection of a quill can be excluded,” says Frank Neugart. A configuration system allows the drive train to be adapted to the required force range. Thus, the servo drive always works under optimum operating conditions. The user can adapt process factors such as feed force, traverse speed, positioning time, and accuracy to the specific application.
“To enable both process steps to be implemented precisely, we fitted the aiPRESS with a piezoelectric force sensor that has two scalable operating ranges,” explains Frank Neugart.
“They ensure accurate measurement through parameter switching in the sensor.” IEF-Werner cooperated closely with HBM Test and Measurement (HBM) to implement this sub-range calibration.
Piezoelectric sensors are real alternatives to sensors based on strain gauges, particularly when a very large measurement range is required. Piezoelectric force transducers allow the acquisition of force ranging from few newtons to many kilonewtons. Provided that the required calibration has been made, a single sensor can be used in different force ranges.
IEF-Werner uses the CFTplus/25kN piezoelectric force transducer from HBM. The sensor has been pre-stressed and calibrated and is ready for immediate use. A gallium phosphate crystal makes up the core of the CFTplus sensor with 25 kN capacity. The material offers the advantage that it achieves twice the sensor sensitivity than the frequently used quartz. Drift and noise are low, which significantly increases the usable measurement range. The sensor is connected to the CMD 600 charge amplifier using particularly noise-free cables. CMD 600 has two programmable parameter sets, an extremely high bandwidth, as well as a very low drift – optimal prerequisites for use in demanding measurement tasks.
IEF-Werner, in cooperation with the user, developed a special pressing process that can also be used for other applications. During the joining process, the pressing punch, driven by a servo motor, initially moves quickly downward to bring the components into contact. Then the process slows down. In general, the system measures the pressing force and the position of the components to be joined. Due to its special design, the aiPRESS crimps the fine metal parts at a force of maximum 3,000 newtons, with an accuracy of less than ±15 newtons. “Usually 500 to 600 newtons at the most are used with such components,” says Frank Neugart. “This enables us to guarantee a high-quality joining process.” In the second process step, the servo press crimps the more massive parts at 6,000 newtons, with an accuracy of less than ±30 newtons.