A well know auto maker was looking to automate the QC regarding the thickness of coatings on sheet metal parts. After discussing the range of the size and weight of the parts the following solution was proposed:

We offered them a simple flatbed XYZ gantry machine with approximately 20x40x6” travel.
Flatbed XYZ Cartesian Robot
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Flatbed XYZ Cartesian robot on stand, used for automating coating thickness measurements on sheet metal parts at auto assembly plant.  
They had been using an Elcometer 456 thickness gauge with manual positioning.
The Elcometer 456 was used in the measurement of the coating thickness on the sheet metal parts used in the auto assembly plant. The gauge was mounted on a spring loaded bracket to accomodate variations in fixturing and dimensions.

By mounting it on a spring loaded bracket, they were able to control the pressure applied to the surface as well as take readings along straight lines at regular intervals on the fly. The pressure is controlled by determining the “at rest” location of the gauge tip. The force from the spring is proportional to the spring compression so the overtravel on the Z that causes the spring to compress produces a proportional force on the tip.

Another way that the force could be controlled would be to use a servo pressure valve. These pressure valves can very accuratly, actively and quickly adjust the pressure supplied to a linear cylinder. The pressure applied by the cylinder is a product of the cylinder cross sectional area and the pressure set on the servo valve.

The final result was a great success with a ROI of months. The benefits included:
  • Greater number of data points collected vs manual data collection
  • Data collected more quickly vs manual data collection
  • Data collected more repeatably vs manual data collection
  • Increased confidence in process quality