Measuring Machining Imperfections and Runout in Automobile Wheel Spindles - MTI Instruments - #1

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MTI Instruments, Inc. 325 Washington Avenue Extension Albany, NY 12205 PH: +1-518-218-2550 OR USA TOLL FREE: 1-800-342-2203 FX: +1-518-218-2506 sales@mtiinstruments.com www.mtiinstruments.com APPLICATION NOTE Measuring Machining Imperfections and Runout in Automobile Wheel Spindles Introduction A cylindrical grinding process fi nishes most wheel spindle surfaces. It is essential that this grinding process leave a surface fi nish that is smooth and free of defects with minimal runout. Any defects or “chatter” marks left on the surface can lead to premature bearing failure, unwanted noise and nuisance vibrations. The Problem No grinder produces a perfect surface. Grinder wheel runout, improperly dressed wheels and fi xture vibrations can cause chatter on the spindle surface fi nish. Chatter is a series of microscopic, repetitive imperfections, or waves, in the surface of the material being machined. A large, Tier 1 Supplier to the automotive industry approached MTII looking for a method to measure and classify these imperfections as a 100% quality control check. They required a production environment sensor that had small spatial resolution, high frequency response and large standoff distance for easy loading and unloading of parts. Additionally, the measurement accuracy had to be less than 4 micro-inches (0.1 microns) with a resolution of 1 microinch (0.025 microns), or better, in order to properly quantify the defects. System noise had to be kept to a minimum in order to prevent unnecessary parts rejection and scrap. The Solution MTII worked closely with the manufacturer and arrived at a unique capacitance sensor design to fulfi ll the project requirements. The probe design incorporated a rectangular sensing element with an area of 0.020” x 0.10” (0.5 mm x 2.5 mm) and a measurement range of 0.25-mm. Several different tip designs were provided utilizing either a radiussed or chamfered face in order to accommodate a number of different wheel spindle confi gurations. The probes were used in conjunction with the Accumeasure 9000, an ultra high-resolution capacitance amplifi er. Built in digital displays quickly alerted the operator in real time of the test results. connector provides “real-time” output waveform data. This waveform can be analyzed to determine frequency, amplitude and consistency of the horn output, which is helpful in analyzing new horn designs as well as detecting horn defects. MTII appnote: spindles.pdf - Page 1 of 2