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Linear Suspension Test (LST)

Optional module of the KLIPPEL QC SYSTEM

Linear Suspension Test

This software module and hardware accessory for the KLIPPEL QC System is dedicated to the quality control of suspension parts (spiders, cones, surrounds) and passive radiators (drones). Linear mechanical parameters like resonance frequency, effective stiffness (LST Lite) or relative mass and stiffness deviation (LST Pro) are determined dynamically from the displacement frequency response. The displacement is measured by a cost effective triangulation laser while the device under test (DUT) is stimulated pneumatically. 

Circular suspension parts are easily attached to the measurement bench without time consuming mounting effort by using a set of mounting parts (rings, cones) fitting to any size of circular geometries up to 222 mm diameter (optional). The easy-to-handle fast loading mechanism is designed to change DUTs as fast as possible while ensuring stable and robust measurement conditions. The efficient mounting and measurement times guarantee a short cycle time. Due to purely mechanical measurements the LST provides perfect production noise immunity. 

For quality control limits can be calculated based on reference units to provide pass/fail verdicts.

Requirements

Applications

Spider testing (LST Lite)

A standard application of the LST Lite module is spider testing. In this case the resonance frequency f0, the Q-factor and the effective stiffness k0 are determined.

Common circular objects can be attached to the measurement bench using a subset of the modular ring set optionally provided.

The mounting cone is selected by the inner hole diameter of the spider. The laser distance may be adjusted with the mounting screw. Measuring the effective stiffness requires entering the moving mass which is dominated by the inner mounting parts.

Once the measurement bench is adjusted and the software properties are set large amounts of spiders can be tested with a very efficient cycle time. The test objects are only attached by gravity. This ensures fast exchange.

Measurement setup for spider testing

Passive radiator testing (LST Pro)

For testing passive radiators the LST Pro is recommended. It offers monitoring both mass and stiffness deviation that may vary during production.

If the geometry of the test object is non-circular a custom platform may be mounted on the top of the LST Bench. No additional mass is attached to the radiator. Therefore the outer frame needs to be fixed (e.g. using clampers).

To monitor the parameter deviation a reference (“golden”) unit is required. This may be determined by the R&D specifications or automatic golden DUT selection based on a batch of units.

All subsequently measured radiators are related to the reference unit. If the reference moving mass is known (e.g. added mass method) the parameter deviation can be monitored in absolute values instead of percent.

In case the ambient conditions (temperature/humidity) have changed with the time the measurement and limits may be recalibrated with the golden unit. It should be kept under the same ambient conditions close to the measurement setup.

 

Measurement setup for passive radiator testing

Related Information

Other modules of the QC SYSTEM