Shoe Sorter Backlash Detector (APPS)
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Shoe sorter failure is dangerous and costly
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Maintenance: perform overhaul every three years
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Solution: created pin bounce monitoring system
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Results: $250 per unit monitoring system for individual pins, eliminating the need for massive overhauls to replacing brakes as they begin to fail
Shoe Sorter Project Scope
Shoe sorters use a three slat system with one primary and two followers. The primary has a passive brake and pin on it which allows the trio to reset to home. When a machine fails it is due to the brakes wearing out allowing the pin to bounce out of home and crash into the machine's drive causing catastrophically disassemble.
The current way to try to prevent machine failure is to overhaul the machine every 3 years. This is a gut and replace process. By monitoring individual slat groups, the brakes can be replaced individually rather than performing a massive overhaul procedure.
To Create this device, I developed an armicher using 3d printing and nylon rods since one of the requirements of this project was that if it broke off into the machine it would not damage it. The armnicher holds a prox sensor for identifying the zero of the machine which was a copy of the one already on the machine and two laser and two light sensing diodes as receivers to capture when the pin passes.
From there it is a simple ratio to calculate the distance a pin is from home based on the law of similar triangles. This allows for an E-stop condition to be coded when a pin bounces a set distance from home. With the Raspberry Pi, the system has an accuracy of .25 inches based on the Pi’s read rate and the speed of the machine.
For production, the plan is to use plexiglass C-channels instead of the armicher and nylon rod. The cost is about $250 per unit.
