The industrial world is continuing its adoption of Geometric Dimensioning and Tolerancing (GD&T), the advanced tolerancing methodology. The symbolic language is intended to be both more precise while providing more latitude in allowable variations, replacing the simpler method of adding tolerances to each dimension.
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Until the middle of 2010, first-tier subcontract machinist, JJ Churchill, could produce turbine blades only if they had their fir-tree root-forms preground elsewhere, or if they were subsequently added by another subcontractor. No longer is this the case.
Burrs, sharp edges, and rough surfaces plague even the most precise metal-cutting or forming process. Deburring and finishing can often be treated as the step-child of a manufacturing process, but its importance is growing as tolerances get tighter and precision devices become the norm.
“Five years ago, our fit and finish was below average,” said Dr. Raj Kawlra, director of dimensional strategy and management of Chrysler Group (Auburn Hills, MI). “To be the future world-leaders, we knew that we had to focus on all aspects of quality … vehicles that look good, feel good, sound good, and are reliable.”
Modern manufacturing is rapidly adopting model-based definition (MBD). When employing an MBD strategy, the CAD model becomes more than the nominal to which all parts are measured and inspected against. MBD keeps the all-important digital thread intact—from design to manufacturing to inspection and quality reporting.
Micro components continue to shrink in size, demanding ever-greater precision and improved handling of parts with sub-micron-sized features. New approaches in micro machining technology include higher-precision systems from traditional micro machining developers, as well as techniques using additive manufacturing processes and semiconductor wafer-scale technology on the smallest of micro parts.
While high-end metrology devices like advanced laser scanners or precision CMMs garner a lot of attention, it is hard to imagine any industrial setting without the presence of work-a-day hand-held, contact metrology tools such as calipers or micrometers. That is what Justin Frazzini, quality manager for A.A. Jansson (Waterford, MI), retailer and calibration and repair service provider, observes in his practice.
Why use a metrology device on or near a machine tool? It isn’t just useful for making sure a tool is present or monitoring tools for wear or breakage. On-machine measurement technologies can save time and money, by speeding up processes and eliminating extra personnel, and they are a critical step in the movement towards “lights-out” manufacturing.
The challenges to manufacturing as it evolves into the 21st century are now familiar, and impact how metrology must contribute. Manufacturers face uncertain production volumes with roller-coaster demand, shorter production runs and faster product development cycles. Automation, while alluring as a way to reduce cost, needs to adjust.
Off-line programming software tools for CMMs allow manufacturers to increase measurement capacity and throughput by programming CMMs, probes, and fixtures before parts are made.