Quality Scan: Articulating Arms Can Enhance
From automobiles to consumer goods, the technologies used to manufacture products "faster, cheaper, better" must consistently add value to the process or fall by the wayside. Over 25 years ago, the articulating arm made its debut on the shop floor. Once an unusual tool with limited use, today's articulating arm is an engine of innovation for inspection and reverse-engineering applications performed at companies ranging from the largest aircraft manufacturers to the smallest job shop.
Hardware is only one aspect of articulating arm evolution. Inspection software and the quality control process have come a long way in the past decade. Early portable CMM software only provided discrete distance/position data for the metrologist. Real-time surface inspection software had its rise in the mid 1990s. This development allowed the use of a CAD model as the nominal. A user can simply touch areas of a machined, forged, or molded part with the arm's probe, and compare the measured features to the related CAD model in real-time.
What does all this innovation mean for the industrial marketplace? First, in-place measurement. By melding portable CMMs into production operations, articulating arm technology takes quality assurance to the shop floor. Second, affordability. Articulating arms are priced less than half of what they were in the 1980s. And last, regularity in inspection routines. Articulating arms continue to replace more checking fixtures in machine shops, and perform more on-machine inspections.
Integration with other metrology vehicles such as laser scanners now extends the utility of the articulating arm. Modern scanners can return more than 400,000 points per second. A technician can use a hand-held scanner to "paint" an object, and extract data for reverse-engineering applications. Or a manufacturer can fully scan and inspect a complete part during the "build" process needing only a holding fixture. Not only large companies use this equipment. In an era of increasing aftermarket design and manufacturing, small custom shops are utilizing the same technologies to replace or augment traditional hand-modeling techniques.
Now constructed of newer, lighter materials, the articulating arm integrates the latest electronics and encoders, Wi-Fi, and cable-free operation based on long-life batteries, and can be moved from job site to job site. Its long-range wireless capability enables large-scale inspection, and the arm can also transmit data to other systems.
In recent years, the fusion of large-volume inspection with portable CMMs has opened the door to seamless inspection data within a single coordinate system for parts and assemblies up to the size of a small aircraft. Current integration work continues to combine articulating arm technology with advanced measurement systems such as laser-tracking systems, multisensor systems, and photogrammetry.
The articulating arm was designed to mimic the human arm and hand. Its main contribution to improving part quality lies within its ability to reach around, underneath, and inside a part "in-place" to precisely measure areas other metrology devices cannot. This flexibility eliminates part handling, repositioning on fixtures, and multiple machine setups.
Verifying part quality with hard gages and layouts often ends in less than satisfactory results. These tools do not support part design changes readily, which is certainly a drawback in today's digital manufacturing realm. In contrast, using an arm to capture 3-D coordinates from a machined part results in high-value data—data that can be evaluated instantly and used for troubleshooting or to make design changes.
The integration of arm-scanning technologies with analysis software enables users to implement better QA practices for early detection of inconsistencies in forging, machining, and other upstream manufacturing processes. These technologies enable on-demand reverse engineering and data comparison to master CAD models to help reduce scrap rates, and in some cases, can significantly decrease setup time for inspection.
This article was first published in the December 2007 edition of Manufacturing Engineering magazine.