Next Steps - Texas State Universityd2522555-0b7d...A poka-yoke (otherwise known as fool-proofing) is...
Transcript of Next Steps - Texas State Universityd2522555-0b7d...A poka-yoke (otherwise known as fool-proofing) is...
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John Slupsky, Scott Peabody, Tim Kunze
Texas State University, San Marcos TX, 78666
Introduction
Place a quarter on a flat surface. Now, as best as you can,
place a dime concentrically overtop. It can be guaranteed,
to some degree of accuracy, that the two coins are not
perfectly concentric. This infuriating statement hinges on
the inaccuracy of visual alignment. So, how can
concentricity be achieved?
A poka-yoke (otherwise known as fool-proofing) is a
mechanical aid that can reliably take the guess-work
out of (coin) alignment.
The question is, how to design such a thing?
Caterpillar asked this very question, when faced with a
similar alignment problem on its production line. A pressing
operation relied on visual alignment, and was producing
out-of-spec assemblies. These assemblies were either
offset, or had an uneven/wrongly sized resulting gap.
Such assemblies were scrapped. A (poka-yoke) fixture
was desired to fix the problem.
Planning & Report
Find Best Design
GenerationSelectionBrainstormSketchCADH. of Quality
Build
DraftingCADPrototypeMaterials3D PrintMachine
Test
ProblemsSolutionsImprovement
Results
Mechanical stops
• Held in place by the fixture
• Prevent over-pressing
Alignment pins
• Nest inside mechanical stop
• Protrude through adapter plate
• Provide guidance for the mount
Plastic thread protectors
• Thread into the mount
• Protect mount threads
Pressing operation setup before modification
Conclusion
Although using a mechanical method is
slower and requires more operator
activity than a visual method, it is a sure-
fire way to achieve accurate alignment.
By controlling operation alignment and
final gap size via poka-yoke, we were
able to save Caterpillar money by
lowering the scrap rate at this particular
station.
Over-pressing
Mount guidance
Thread damage
Assembly purpose
Next StepsA new press-head was designed to
combine the prior operation with this one;
pressing dowel pins into the sides of the
adapter plate.
CAD drawings and manufacturing
procedures for this design will be
recommended. Cost is currently the main
prohibiting factor from manufacturing.Uneven gaps can be fixed with mechanical stops
Acknowledgements
Naveen Laxmaiahgari – Sponsor
Sagar Navle – 3D printing
Dr. Austin Talley – Advice / feedback
Roller Plunger Switch
• Bolted to the fixture
• Prevents over-pressing
• Prevents damage