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Linear Suspension Test (LST)

Optional Module of the KLIPPEL QC System

  • Check suspension parts before assembly
  • Measure stiffness and resonance (fr, Q)
  • Moving mass of passive radiators
  • Dynamic method in small signal domain according to IEC 62459
  • Model-based parameter fitting
  • Hard- & software turn-key solution
  • Easy mounting and fast measurement
  • Interface between supplier and manufacturer
  • Measure devices up to 18'' with SPM Bench

The Linear Suspension Test module and hardware accessory is dedicated to the quality control of suspension parts (spiders, cones, domes, surrounds) and passive radiators (drones). Linear mechanical parameters like resonance frequency  and stiffness as well as mass variation (passive radiators) are determined dynamically from the displacement response. The device under test is stimulated pneumatically while displacement is measured with a cost effective triangulation laser. High  test speed and simple clamping allow short test cycle times to go for 100% testing.

Requirements

Applications

Spider Test (LST Lite)

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

Round spiders can be attached to the measurement bench using a subset of the modular ring set (optional). The cone for inner clamping is selected by the neck diameter of the spider. For this application, sound pressure measurement is optional but recommended for best accuracy (resonator parameter fitting). In order to measure the spider stiffness, the approximate moving mass (dominated by the inner mounting parts) must be entered.

Once the measurement bench is adjusted and the software properties are set, large batches of spiders can be tested with a very short cycle time. The test objects are only attached by gravity to minimize mounting time. For soft suspension parts, an additional upper clamping ring may be used.

Spider mounted on LST Bench

18'' Cone Test (LST Lite)

For testing large size objects with a diameter of more than 222 mm, it is required to use the SPM test bench and custom clamping rings.

The 18’’ cone in this example is attached to the test bench using a custom wooden ring which fits the rim diameter. The ring is attached to the SPM test bench using the provided standard clamps. No upper ring is required. For inner clamping, a suitable cone has been selected from the standard plastic cone set.

Testing large size objects requires a two-signal measurement method. The laser is used for displacement measurement while a microphone (not visible in the picture) is picking up the stimulating sound pressure inside of the SPM Bench. The resulting transfer function allows accurate measurement of the resonator parameters.

Cone mounted on SPM Bench

Passive Radiator Test (LST Pro)

For testing passive radiators, the LST Pro is recommended because both mass and stiffness deviation may vary in production. In addition to LST Lite results, there are two more measures. Mass deviation and stiffness deviation are based on a physical model and defined relative to a defined reference unit (“Golden Unit”).  This unit may be selected according to R&D specifications or automatic golden unit selection based on a batch of reference units.

All subsequently measured devices are related to the reference unit. If the reference moving mass is known (e.g. from R&D or added mass method), the parameter deviation can be monitored in absolute values or percent.

If the passive radiator is not round, a custom platform may be mounted on top of the LST Bench. The outer frame must be fixed for reproducible conditions (e.g. using clampers).

In case the ambient conditions (temperature/humidity) have changed over time, the limits may be calibrated using the golden unit. It should be kept under the same ambient conditions close to the test station.

Passive radiator mounted on LST Bench

Related Information

Other modules of the QC SYSTEM

Patents

Germany: 102007005070
USA: 8,078,433
China: ZL200810092055.4
Japan: 5364271

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