German spring manufacturer, Technische Federn GmbH Otto Joos, manufactures technical springs for several industries that demand both a high-quality product and no out-of-specification items. The springs are designed and manufactured to withstand highly dynamic forces in injection pumps for automobile and truck engines as well as drive assemblies for locomotives and ships, where one billion load cycles without failure is demanded as spring failure can have severe consequences.
Since springs must have the correct length to ensure a defined restoring force, the length of every spring is measured prior to delivery using a new sorting system based on the Kistler force-displacement monitoring system, maXYmos BL. The maXYmos BL monitors and evaluates XY curves in which two measurands (force and displacement in this case) are required to exhibit a certain relationship with respect to one another. Using two switching thresholds and the UNI-BOX evaluation object, the maXYmos BL records the three possible states of the springs under test; spring too short, spring in tolerance and spring too long and reports the result to the sorting chute via a PLC. This 100 per cent testing enables Otto Joos to guarantee that every spring delivered conforms to the customer's specification.
In addition to 100 per cent pre-delivery testing, the compression springs must undergo a grinding process to ensure optimal bearing surface and exact spring length. The maXYmos BL also monitors this process based on the force threshold of approximately 0.5N; the monitor outputs the spring length at this point via its table of process values. The force of 0.5N defines the initial contact between the force sensor and the spring: the associated increase in force at this position precisely indicating the length of the spring under test.
For Otto Joos, the maXYmos BL has made the 100 per cent quality assurance demanded by the automotive industry possible without increasing production costs.
For more information about the maXYmos BL force-displacement monitoring system, please go to www.kistler.com.