Thomas develops and produces electromagnetic and fluid actuator systems for the automotive and mobile-hydraulics industry as well as for medical products. The force-stroke characteristic curve and the force-current characteristic curve are key characteristic values for quality control. To determine these characteristic values, the company opted for a materials testing machine from ZwickRoell.
The testing system (zwickiLine, Fmax 2.5 kN) integrates two different current regulators with which the magnets can be alternately controlled in different manners. Thanks to its tilt mechanism, the entire machine can be tilted on its side up to 90° so that the magnets can be tested at their installed position.
Using testXpert III testing software and a test program for solenoid testing, tests for determining the force-stroke characteristic curve (F/s) and the force-current characteristic curve (F/I) can be performed. The force-stroke characteristic curve is checked when using proportional or switching magnets. It represents a function test on electromagnetic actuators and is usually the final test. The basic function properties of the actuators can be ascertained from the characteristic curve. The force-stroke characteristic and provides information as to whether the actuator is applying the required force inside its operating range at a fixed current level. Friction resulting from the quality of the mechanical parts enables hysteresis.
The force-current characteristic curve is predominantly tested for proportional magnets and provides information as to whether the actuator is applying the required force inside a current range at a defined armature position. The ideal characteristic curve has a linear relationship between force and current around the operating point.