“The arm with PowerINSPECT is a wonderful system for any organization like ours that is tasked with constantly improving its work...”  

Prior to getting the first arm in 2000, all in-house inspection was handled with “hand” measuring devices such as tapes, height gauges, calipers and micrometers. The first machine was sent to Pierce’s parent company, Oshkosh Truck Corp. in nearby Oshkosh, Wisconsin, after the second 3000i purchase to accommodate the CMM workload at Pierce.

“The most obvious impact of the arms and PowerINSPECT is the ability for us to set up welding fixtures in-house with verifiable proof of the accuracy of the stops in a timely fashion,” Nennig explained. “Now we are able to work with our design engineers to develop and build fixtures before production starts and this is a big boost in getting production started quickly.

Challenge: Getting Good Dimensions Quickly

The most sophisticated work undertaken with the portable CMM has been obtaining a surface model of the windshield to insert into the solid model for design of the cab windshield openings. Each of these glass pieces measures roughly 44 by 32 inches and is curved in all three axes. Glass is held in place by hand-stamped aluminum “trim” parts and getting these parts dimensionally precise has long been a production bottleneck.

Nennig digitized the windshields’ glass panels with the point cloud* guided planes** functions within the PowerINSPECT software. “Every time I crossed the predetermined ‘guided plane’ with the probe of the CMM, it gave me a series of points in an exact row, all lying on that plane.” That took a mere two hours, he said.

“The first one, when we were still new to computerized measuring techniques, and without guided planes, took two days,” he added. “Without the CMM it would have been virtually impossible to create a sophisticated set of fittings for each of the windshield panels.”

The cabs’ A pillars were a similar CMM challenge. Structurally speaking, the A pillar is critical. “It is the origination point for all the cab dimensions,” Nennig said, “so if the A pillar is off, everything will be.”

“It was taking us three to four hours to form each of these pillars—tap, adjust and check, saw, hammer, weld and grind,” said Ryan Lang, a Pierce manufacturing engineer assigned to Cab Fabrication. Pierce engineers felt they needed to take an hour out of that for each pillar. And because the A pillar itself is curved in two axes—in part to hold the outside edge of the windshield glass—its tooling is among the most complex. The cabs’ other pillars—B, C and D —are vertical and the glass they hold is flat.

“We take extra care to positively support the A pillars’ tooling, to ensure that all three planes of motion are locked down,” Nennig added. “The stops for the A pillar welding fixtures are meticulously set and reset, checked and double checked before the fixture leaves the tool room for production.”

“With a correct geometric model from PowerINSPECT we can produce a new A pillar and the die to form it in one step, all at the same time,” Nennig said. “Also getting extra measurement attention are the cab pivot and lockdown stops, wheel wells and step heights, and engine tunnel widths and heights. As with the A pillars, many other dimensions depend on these.”

“For me, as the incoming inspector, a first-article casting inspection consumes a good portion of my day,” said Andy Smazinski, a Pierce receiving inspector. “It takes me an hour or two to program in the geometry, set up the planes and tolerances, and so forth,” he added. “That is really good time because I am still learning,” he added. “Even after working with the CMM for a very short time, I was able to program fairly complicated part inspection files.” With the arm’s easy mobility and magnetic clamps, physical setup takes him 15 to 20 minutes. “Most inspections have 30 to 40 dimensions to verify with a minimum of 10 to 15,” he pointed out.

Solution: No More Road Trips For Inspections

“The beauty of using the portable CMM is that if just one stop in a fixture was moved,” said Lang, “we can identify it quickly and see exactly how much and in what direction it moved. Since each fixture has dozens of stops, previously finding one that was out-of-position might have taken us a week. That’s the same time as it takes to build a new fixture. There are huge time savings in troubleshooting on the shop floor.”

Nennig confirmed Lang’s point by explaining the complexity of Pierce’s big fixtures. “The main, final assembly fixture is 12 feet long and probably weighs a ton. Depending on the cab model, size and type being built, it has 120 to 150 individual stops. At best, we can ‘set’ 30 stops a day and 25 is the norm. To accommodate the cab variants, some stops have two and even three settings to accommodate differing sizes of components from the six cab models.”

Even simple fixtures are big. The “base” or cab floor frame measures 60x102x132 inches or 5x8.5x11 feet, roughly half the size of a typical bedroom. On to this frame, Pierce bolts approximately 40 stops that together have about a hundred “stopping surfaces.” Each must be dimensionally located and spatially oriented in three dimensions.

“These stops range in size from 3x3x2 inches to 4x6x15 inches “and some are even larger in a particular direction,” Nennig said. “Not only do we have to build and check these fixtures,” he added, “but we also have to recalibrate them on a rotating basis. We also have to reverify the cab weldment setups every year. So, clearly, the portable CMM helps us keep production moving.”

“Typically, we create our own part-specific files directly in PowerINSPECT rather than using downloaded CAD and IGES files,” he continued. “The CAD tools in software make this so easy to do. Most of the time I have the CMM laptop computer on my desk beside my CAD system monitor. I type data from the CAD screen directly into the program I am writing. This works extremely well.”

On the other hand, “mainly for part inspections,” he said, “we will use solid models from our CATIA software and import it directly into PowerINSPECT. This is very useful for rapid part checking. This lets us—at last—upload accurate tooling files to the CAD system. When we verify a stop’s location or verify that it has not moved, we use PowerINSPECT’s spheres of alignment tools.”***

“When we bought the first arm, we considered the competition, too,” Nennig said, “but we liked the PowerINSPECT software better than the other packages. “It is a much more powerful organizational tool for handling geometry and groups of measurements. We need to gather measurements in large groups, all at once, when we troubleshoot or do first-article inspections,” he explained. “Then we break the groups apart to retrieve the specific data and look for root causes and process-improvement opportunities. We could not do that with any other system.

“PowerINSPECT was the big selling point, the shining star of the 3000i system,” Nennig said. “The arm was a better product, too, the 3000i was more attractively priced, and we liked the level of service we got from Dean Solberg,” the distributor from Exact Metrology, Algonquin, Illinois. “When you get right down to it, we did not like the other systems at all.”

The Pierce engineers run their PowerINSPECT software on Dell Computer Corp. Latitude PP01L models. These have 1.6 gigahertz Intel Corp. Pentium III CPUs with 128 megabytes of RAM and 20-gigabyte disk drives. The operating system is Microsoft Corp.’s Windows XP Professional. At the time of the interview, Pierce was upgrading PowerINSPECT to Version 3.00 from Vers. 2.200 (Service Pack 3).

Benefit: Better Dimensional Control, Better Production

The biggest gains in inspection at Pierce stem from a fundamental change: The inspection systems—the arms with PowerINSPECT—now travel to the parts and fixtures rather than the parts traveling to contract CMM shops. No longer do those “road trips” determine when work will start on new parts.

The arms give the quality control team a huge advantage by increasing their effectiveness. “The 3000i allows us to control the quality and, to some extent, the speed of the build process.” Nennig pointed out. “We always have to be certain that the fixtures are correct and that they were built that way.

“The 3000i's capability for infinite rotation is a definite time and frustration saver,” Nennig said. “Our cab welding fixtures are big and many of the points have to be taken from inside them. Without infinite rotation we would be backtracking a large percentage of the time.” If a user is forced to back out of a welding fixture to unwind the joints of an arm, registration can be lost. In that case, the inspection has to be started all over again.”

Also of great value to Pierce is the arm's accuracy. “Our CMMs need to fill many roles,” Nennig continued. “They need to check machined parts to five- or seven-thousandths of an inch as well as be durable enough to use for setting up larger welding fixtures where tolerances are a little more forgiving.”

“The machine is rarely if ever wrong,” said Lang, a long-time user. “Once in a while a number will ‘appear’ to be way ‘off.’ Upon further investigation we find that it was our fault. “The system makes the whole dimensional measuring process foolproof.”

The CMM also minimizes the human factors that are responsible for so many measuring errors. Even better from a day-to-day use standpoint, if a dimension is off in some manner it will quickly be obvious. You know that there has been an operator error and you can see it,” Lang continued. “We correct our error and keep on measuring.”

“The 3000i also gives us better control over the content of the work instructions that go to production,” Nennig pointed out. And since Pierce is ISO 9001: 2000 certified, this is an important benefit. “There is more data in the work instructions, it is presented better, and it is more current. We are now providing foolproof dimensional data to engineering and purchasing,” he added. That’s a great reassurance for them as they make decisions.”

“The 3000i with PowerINSPECT is a wonderful system for any organization like ours that is tasked with constantly improving its work,” said Smazinski. “Everyone at Pierce is involved with quality, right to the president. It is great to have a machine that measures down to a thousandth of an inch.”

Since he joined quality control in December 2003, “I have seen an 80 to 90 percent improvement in what’s being measured,” he continued. “And in how accurately that’s being done, and in the processes that have been established to make sure it’s done correctly.”

As a result, Pierce’s inspection department —14 people—is now “getting the respect we deserve for the quality and completeness of our measurements and logging of data in the spreadsheets,” he concluded.