Quick QC

July 1, 2003
Laser inspection system gets CNC machines running sooner

Most customers of Oaks Precision Fabricating Inc. (Houston, TX) require that a certain percentage of their parts are inspected for quality control and that those inspections are documented, making accurate, efficient inspection a priority for the 16-year old, 30,000-square-foot job shop.

That's why Oaks turned to the LaserQC from Virtek Laser Systems Inc. (Waterloo, Ontario) to inspect the parts it makes for customers, who range from OEMs in the computer and medical industries to oilfield equipment manufacturers. The LaserQC is a computer-controlled, laser-driven flat part inspection system designed to reduce times for quality control inspections. Oaks was involved in the beta phase of the product's development four years ago and has used it successfully on the shop floor for first part inspection ever since. Management discovered early on that the system could deliver the results it needed.

The LaserQC enables an inspector to complete a scan on a 2-ft x 4-ft part in one to two minutes.
Click here to enlarge image

The laser system scans flat parts, measuring their dimensions and comparing them to the original CAD files (LaserQC is compatible with DXF, DWG or IGES formats). Inspectors using the system can quickly and easily measure specific part features, such as hole diameters, distances from hole to hole, or the distance from a hole to the edge of the part.

"One timesaver is the system's virtual caliper function. For example, if you click on the edge of one feature, and then on another, the distance between these two points instantly appears on the screen. Without it, the inspector ends up sitting there with a pair of calipers and a calculator subtracting half of the hole and trying to measure to the edge of the part to make sure that they're in spec," says Richard Kaase, Oaks vice president. "You're probably eliminating 30 seconds per measurement, which translates into several minutes per part."

Small increments add up quickly with such inspection requirements. Oaks inspects 10 percent of the completed parts before shipping. As production quantities increase, so do the inspection quantities. The company's highest volume production runs come from the computer sector of its customer base, where jobs can run as high as 10,000 parts per run.

Before turning to the LaserQC, Oaks was using a coordinate measuring machine (CMM) for inspection. In order to inspect a hole, the inspector first had to touch the CMM to the edge of the part, then to four places within the hole itself. "You're probably looking at a 90 percent reduction in your inspection time with LaserQC," Kaase adds.

With that kind of reduction in first part inspection time a shop might expect its inspectors to have some time on their hands. Kaase certainly did. However, instead of leaving the inspectors with more time, the machine allowed them to inspect more parts.

"Because our punch operators have less downtime on first part inspections, our inspectors are busier because we're finishing more parts and getting them to inspection quicker. It's had a different effect altogether than we anticipated," Kaase says. "It puts more on the inspectors' plates every day, and also speeds up the QC process, so I'm getting more parts out the door. It has a positive effect all the way around."

In fact, the positive effect is strong enough for the shop's customers to notice. Since the LaserQC was introduced in the first part inspection process it has alleviated a bottleneck, allowing the shop to dramatically improve its on-time part delivery without compromising quality or adding to its workforce of 32 employees.

Operating efficiency improvements from technological advances are par for the course at Oaks. The shop is highly automated, running one staffed shift on its CNC equipment, as well as overnight lights-out production on two of its turret punch presses.

Oaks equipment includes another flat part inspection machine, five press brakes, one six-foot shear, an eight-foot shear, an Amada Vipros King turret punch press with an autoloader, two Amada Pega 357 turret punch presses, one of which is equipped with an autoloader, and an Amada 1224 Pulsar laser system used for cutting applications.

The 2kW CO2 laser cutter handles material up to five feet wide and 12 feet long, and it will cut up to 3/16 in. aluminum, 1/4 in. stainless, and 1/2 in. steel plate. However, Kaase says the standard materials that are more likely to run through the shop on a daily basis are between 1/16 in. and 1/8 in. thick.

At Oaks, the first part on every job is inspected before the full production run begins, whether it's a new order or a repeat job that has been through the shop many times before. For first article inspection, the machine operators take the part to the LaserQC (which is in a central location on the shop floor), scan the part and perform a .dxf file comparison to verify the part's features and its dimensions. According to Kaase, the operators finish their inspection duties much more quickly than they used to, which means they can get back to their machine tools and continue making parts sooner.

"The machine completes the scan on a 2-ft × 4-ft part in one to two minutes. That means we start seeing our machines running sooner. When the operators punch that first part and go to scan it, that's downtime because they're waiting for the part to scan and get back to their machines. It was taking 10–15 minutes per job," he explains. "Now, with the LaserQC right between the CNC equipment, it's one minute to the inspection machine, they scan the part in two minutes or less, take another minute to get back to the punch, and they're running. It has cut two-thirds off the scan time."

Depending on the job, the 10-minute per part savings for first article inspection gives shop operators enough time to produce as many as 50 parts. While those totals may seem small, they add up quickly, just like the savings in finished part inspection. Kaase reports that his operators perform 20 first article inspections every day. During a week of typical operation at Oaks, that translates into time savings of as much as 16.5 hours, or increased production of up to 5,000 parts per week.

Seconds after scanning the part, Kaase says, the LaserQC draws an image of the part on the computer screen, using different colors to indicate degrees of variation from the dimensions specified in the original .dxf file. Next, the inspection system prints reports that include as-built dimensions, simplifying the inspection documentation requirements for company personnel. "The LaserQC's scanning speed, reporting versatility, instant display of out-of-tolerance features and quick and easy dimensioning are the factors that have led us to rely on it for our flat part inspection requirements," he says.

The inspection system has become a sales tool for Oaks, impressing visiting customers who are increasingly quality conscious, according to Kaase, who says visiting prospects tour the shop on a weekly basis. "I think it opened doors with a few new customers. You show them the new technology sitting on your floor and they're pretty much in awe over it. Especially once you show them how it scans," he says. "People are shopping quality and quick turns right now. That's what they're looking for. It definitely stands out when you've got this machine and you're spending money trying to make sure their parts are right. It opens their eyes."

Richard Herzfeld is with TechComm Associates, Milwaukee, WI. He can be reached by e-mail at [email protected].

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