(Aurora, IL) One engine-component supplier has been anything but passive in responding to a sluggish market and new quality system requirements. To upgrade a manufacturing line for more flexibility during lean times, DACO Inc. (N. Aurora, IL) recently re-engineered a machining cell to integrate an old coordinate measuring machine (CMM) with part-handling robots and six machining centers, automating the entire production and inspection process for multiple part numbers.

The 70-year-old family-owned and -run business has about 90 employees and essentially two customers, one of which is a major diesel engine manufacturer. DACO’s product line is fairly specialized; in fact, it’s the large OEM’s sole U.S. supplier of engine flywheels. The company’s longstanding customer relationships are based on contracts that run much longer than a few months. Despite recent slow-downs in orders, this gives the company a bit of confidence, says vice president Bruce Lindgren, "so we can invest in things like robotics and CMMs and rearrange our plant to give a total commitment."

The need for flexibility in the shop is clear. The company’s cast-iron flywheels range from 16 inches in diameter and 40 lb. in weight to about 42 inches and 2000 lb. Moreover, the volumes for these parts can vary radically: "We make one a year or we make 50,000 a year," says Lindgren. As a value-added service, the company not only ships the flywheels just-in-time but also packs them in the right build sequence for assembly—sometimes knowing only a day ahead of time what’s needed. When customer orders shrank to only about half the volume of the previous year, DACO decided to re-engineer a dedicated machining line to handle parts of various sizes, weights, and complexity. "That’s the challenge right now: to redirect that equipment to lower volume and build more flexibility into the cell and less dedication."

The first step towards complete cellular integration was a big one: the company installed three Fanuc robots for automatically loading and unloading six Okuma lathes and horizontal machining centers via twelve pallets. Each machining center can handle a single flywheel part number, providing production flexibility, and each robot knows exactly which part it’s handling, providing reliability and nearly doubling productivity.

This re-engineering project paralleled the company’s progress towards another objective: QS-9000 certification. Although it’s not a typical automotive supplier, DACO had no choice but to answer the certification requirement in its purchasing agreement. Despite the challenge of QS, the company has viewed it as an investment for moving into the broader marketplace. Certification has brought team-building skills and more cooperation into the shop, which made it worthwhile, according to engineering manager Steve Lindgren. "We invested in this quality system so that we could change our life, and now we are living that new healthier life and we don’t want to lose that."

QS-9000 requires consistent part inspection and tool qualification procedures, though not necessarily an automated inspection system, he explains. "Our quality system doesn’t say that you need a robotically loaded CMM in-line, but it does say that you have to audit every fixture and pallet a couple of times each day."

However, after the initial cell automation project, inspection of the flywheels’ threaded holes and dimensions remained a mundane manual process, tying up one or more operators, says Steve Lindgren. The company realized that automating the inspection would improve the quality of the inspection while freeing up operators to do other value-added work. "We spent a lot of time taking labor out of a part, but it’s strange because inspection is labor too, and so why not take the labor out from the inspection standpoint?"

Fortunately, finding a CMM to integrate with the automated cells wasn’t a problem. The company had just brought in a CMM to measure larger part sizes, replacing an older machine. "As we bought the bigger CMM, we looked at the smaller CMM and said: ‘What are we going to do with this? If we parked it down at the other end of the line, we could really take some more labor and handling out of this part, so why don’t we see if we can integrate it?’" explains Lindgren. Given the prohibitive cost of a new heavy-duty CMM, the company decided to upgrade this used, lighter-duty machine.

For integration, both software and hardware upgrades were needed for the CMM, so DACO turned to Mitutoyo America Corporation (MAC) for solutions. "We gravitated toward MAC’s Geomeasure 6000 software, which offers a higher-level language," Lindgren says. This advanced version of Geomeasure provides the programmability for inspecting a variety of part numbers, and "we could use it to interface with the outside world of robots."

The software was the only direct investment in the CMM the company had to make; the more intimidating part was its integration with the cell’s control system. It was a challenge to get the robots and CMM to "talk" with each other to allow the system to handle parts appropriately without human involvement. "If you’re going replace the human, you have to also account for all of the useful things that the human does," explains Lindgren. "The human does a lot of visual checking and inspecting and so forth; the other thing a human does is to use some common sense."

Thus, the upgrade had to provide the mindset and reasoning of a human inspector. For example, "if we check ten holes, we’re going to find some that are out of tolerance, just from the nature of cast iron and tapped holes," he says. Therefore, the software had to be programmed to make the proper judgements about what percentages of good holes are necessary for acceptable parts. "So we can throw out the ones that are ‘bad,’ and if the majority is ‘good’ we can make the assumption that the batch is good." But there was a question of whether this kind of reasoning would work for the automated line. "When we took this on, I knew it could be done, [but] I just didn’t know that it hadn’t ever been done," Lindgren adds.

It’s true that even Mitutoyo hadn’t performed exactly this kind of robot-CMM integration when MAC systems analyst Jay Elepano arrived at DACO. Elepano’s job was to install MAC’s Universal Inspection Interface (UII) to allow the CMM’s software and the manufacturing cell’s PLC to communicate. The link allows a robot to pull a part off the line, send it to the CMM, and then send a signal to the PLC (through the UII) instructing the Geomeasure software to run one of up to 2400 inspection programs. After the inspection is complete, the software signals the UII and PLC of the inspection results, and the PLC directs the robot to handle the part accordingly. "They wanted to periodically pull a part off of each of those six lathes, and if the part is good, they could continue to run that lathe," explains Elepano. If the part is bad, automatically a second part from the same machine tool is checked; if that’s still out of spec, the system flags that machine tool for service.

Elepano says the robots always confirm what part number they’ve pulled for the CMM, instructing the Geomeasure software to run the specific measurement program for that part. The selection of parts for inspection is random, except that the frequency of inspection can be controlled, allowing the CMM to serve as a qualification tool for specific machine tools.

Thus, besides eliminating human inspection duties, CMM integration also reduces scrap by catching machine tool problems 24 hours a day—problems that might not have been caught with manual inspection, explains Steve Lindgren. "We had a case, for instance, where a single flute on a drill, not the tip of the drill, but a single trailing flute chipped, and it started making oversized minor diameters through the threaded hole." Because the hole on the part looked OK with visual inspection, the problem didn’t become apparent until a screw was inserted on the customer’s assembly line. Now, with the more rigorous and reliable integrated CMM, the off-diameter hole would raise an immediate inspection flag, he adds.

Lindgren reports that automating the CMM with the six machining centers has reduced that department’s burden rate by about 25%. The system also allows operators more time to develop other types of projects and new ways of inspecting parts and cutting scrap. For example, they’ve noticed excessive CMM idle time, so they’ve determined how to increase the number of inspections, up from the current minimum 4.8% audit rate (48 pieces/day). Now, the shop’s computer-savvy operators are learning to optimize the CMM to give the robots even more specific instructions for inspecting particular part numbers.

MAC’s Elepano emphasizes the cost-effectiveness of what DACO has accomplished. Above the cost of the Geomeasure retrofit, a full integration project at DACO’s level would cost under $10,000, or under $100,000 for both a new CMM with Geomeasure and full line integration. Fortunately, the economics are getting better as the technology progresses; he adds that 20 years ago the full project would’ve cost around $200,000.

He also thinks other shops can take advantage of the benefits of integrated CMMs. "This concept of letting inspection be done without human intervention—letting the machine decide whether that part is good or bad and sending this information to the next machine—that’s the concept we really want to show here."