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Managers of the huge Caterpillar Inc. factory in Aurora, Ill., have
found that the operational flexibility offered by rapid new-product
introductions, outsourcing and Just-in-Time (JIT) inventory demands a
matching level of flexibility in dimensional measurement.
In the hands of Don Barkman, supervisor for “G” operations and his team
of seven quality specialists, flexibility in dimensional measurement
takes several forms on the factory floor:
• Simple portability. This is the capability of taking measurements
anywhere in the 4,000,000-square-foot plant at just about any
time—often beginning within minutes. Portable coordinate measuring
machines (CMMs) are the key to Barkman’s department’s ability to
resolve quality concerns on the spot in an assembly line, for example,
or with a welding fixture.
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• Ability to handle a wide variety of measuring situations. This is the
key to the unparalleled ability of portable CMMs in ferreting out root
causes in trouble-shooting situations that can occur anywhere in this
sprawling fabrication and assembly facility.
• A complete spectrum of measurement techniques. At Caterpillar in
Aurora, this includes four conventional, fixed-in-place CMMs, a
portable laser tracker, a GridLOK® dimensional measuring system that
also uses a portable CMM, and 100% inspection of machined parts with
on-the-machine gauging or the use of long-proven setups, fixturing,
tooling and programming.
The portable CMMs are “easily three times more accurate than the old
linear-encoder based measuring systems. And they are at least 75%
faster in measuring, too, not counting setup time.”
“There is little overlap among the systems and no gaps between them,
providing the plant with a complete and essentially seamless set of
dimensional measuring capabilities,” Barkman said.
The Aurora plant has six portable CMMs, all of them touch-probe systems
with 12-foot arms. These are 3000i™ systems. Five are on the factory
floor and one is the tool room. The ability to measure almost anything,
in almost any orientation, comes from the arm’s infinite rotation in
three principal axes. The rigid but lightweight arms can go almost
anywhere, including more than once to a nearby subcontractor’s plant.
All six arms came equipped with PowerINSPECT™ software developed by
Delcam Inc., Windsor, Ontario, Canada. The flexibility of the
measurement methods offered by the Delcam software, and its ease of
use, are important factors in the 3000i systems’ fast set-ups and
unambiguous outputs.
The plant also has a portable laser tracker system equipped with its
own uninterruptible power supply and mounted on a motorized cart. “It
has excellent precision and can measure increments spanning up to 200
feet,” Barkman pointed out, “but it is costlier and less flexible than
the portable CMMs.” Like all lasers, whether portable or fixed in
place, it is limited to line-of-sight checking—no reaching underneath,
around, over, behind or inside.
Dimensional measurements are also met with a GridLOK system adjacent to
the plant’s CMM room. Pointing to a wheel-loader “tower” mounted on the
GridLOK’s 16- by-20-foot steel base floor plate, Barkman observed:
“This is a life saver for us because of the large parts we have to
check.” Fabricated and welded steel towers link the fronts and rears of
the articulated wheeled loaders (the majority of the machines built at
Aurora).
The GridLOK system was created on top of a steel floor mounted
measuring plate leftover when a 25-year-old Portage measuring system
was retired in 2002. A state-of-the-art system in the 1980s the Portage
system had one big drawback: It could only measure orthogonally. That
meant anything being measured “had to line up precisely and squarely
with the machine,” Barkman explained.
“Some of our subassemblies weigh thousands of pounds,” he noted. “With
the old systems, you could spend hours banging on them with a maul to
get them lined up before they could be checked. With the portable CMMs,
whether GridLOK is being used or not, the machines line up with the
parts.”
Installation of the GridLOK required only the countersinking of
pre-existing locator holes in the Portage floor plate. The holes act as
fixtures, allowing the portable CMM’s arm to be repositioned as needed
without losing registration. This lets Aurora benefit from the set-up
speed and measurement flexibility of any portable CMM while offering
convenient 360-degree access to the workpiece. Working from any of the
54 locator points in the GridLOK base plate, the arm can measure
virtually anything within a 12-foot radius. GridLOK measuring accuracy
is typically 0.006 to 0.007 inch, Barkman said.
The portable CMMs are “easily three times more accurate than the old
linear-encoder based measuring systems,” he noted. “And they are at
least 75% faster in measuring, too, not counting setup time.” |
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CIMCORE
a brand of ROMER Inc.
a Hexagon Metrology Company
51170 Grand River Ave.
Wixom, MI 48393
Toll Free Phone: 800.218.7125
Phone: 248.449.9519
Fax: 248.449.9445
sales@cimcore.com
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