Quality Innovations: The Need for Speed
December 1, 2009
Whether transporting parts or people, linear motor technology provides many benefits. The technology has been used on both high-speed trains and high-speed measuring machines to provide speed and accuracy without generating unwanted heat or friction.
This technology is one aspect of the large-format multisensor video measurement systems from The L.S. Starrett Co. Metrology Division (Laguna Hills, CA) that help speed up measurement processes.
In the past several years, as the quality industry has progressed, so have the products, says Mark Arenal, general manager of the Starrett Metrology Division. Video measurement systems have continued to evolve, while adding the ability to measure with multiple sensors. “This machine was designed with that in mind,” he says.
And, of course, they also considered their customers. “Before developing a new product, the company looks at customer applications and requests, industry trends and available technology, and then aims to balance new technologies or materials with customers’ needs,” Arenal says. “The product has to be driven by the market, not the latest design capabilities or materials.”
The video measurement system has been well received by customers thus far. It provides high measuring accuracy, repeatability and throughput, with transports that are driven by balanced linear motors-rather than drives-that are close-looped to precision scales in all three axes. The motors generate almost no heat and position to a fraction of a micron.
“That’s why linear motors are in the system,” Arenal explains. “They keep any kind of heat source down in the machine and don’t transfer heat to the part.”
The systems also offer porous carbon air bearings for quiet, frictionless motion requiring no lubrication or maintenance, and resulting in repeatability greater than 3 microns. “Air bearings are common in CMMs [coordinate measuring machines], but not as common in vision machines,” Arenal says.
In addition, the moving axes of the systems are center-driven to reduce asymmetric thrust and minimize scale hysteresis. The systems also include a massive granite base and bridge, which provides mechanical and thermal stability.
“A key factor that’s important to us is to build inherent mechanical accuracy into machines,” Arenal says. Error compensation is then used to enhance performance.
Customers also can recover their investment with throughput gains. Depending on the application and the quality department, the system is designed to be used all day, every day, or just as needed.
Arenal points out that customers may have been using a CMM, optical comparator or hand tools, and the large-format video system can take the place of the other machines. While it is versatile and suited for a range of applications, including quality control labs, research, engineering or manufacturing environments, Arenal says it would not be used for large 3-D objects. For example, an engine block would be more suited to a CMM.
The system has been used for LCD applications, molded plastic parts for the automotive industry and other applications in aerospace, electronics and medical. Some customers may use it for first article qualification in biomedical applications, while others may use it for high-volume and high-speed inspection in a production cell.
Operators can download a computer-aided design (CAD) file to streamline the programming of the measurement sequence, and after the machine is programmed, they just place parts in a fixture on the machine for measurement.
The machines, introduced at the Control show in May, start at $70,000, depending on size. Models are available with vision, contact probe and laser scanning attachments. The systems offer an encoder resolution of 0.1 micron. A color optical video system provides a zoom magnification ratio of 12:1 with programmable magnifications to 2,000X via auxiliary lenses.
Multiple programmable LED sources provide the lighting. The system includes a 22-inch widescreen flat-panel LCD, and Heidenhain/Metronics Quadra-Chek QC-5000 3-D metrology software is included with the system.
For more information, contact:
The L.S. Starrett Co. Metrology Div.
26052 Merit Circle, Ste. 103, Laguna Hills, CA 92653