Seeing the light: CMM Inspection

Auto parts manufacturer Mann+Hummel reaps the benefits of optical scanning.

Parts manufacturing thrives on innovation, and every so often new equipment is developed that revolutionizes production processes. When these changes are implemented, the enhanced efficiency reduces operating costs and increases profits. A prime example of this phenomenon has been the evolution of coordinate measurement.

Mann+Hummel USA Inc.’s operation in Portage, Mich., recently streamlined its coordinate measurement through new technology twice in 3 years. Historically, the operation relied on a coordinate measuring machine with tactile probes, which was prone to crashes and didn’t produce an adequate amount of data. Three years ago, the CMM was replaced by a Capture 3D SO4M white-light scanner. It provided more data, but it was a manual system, which required M+H to bring in outside help to run the scanning operation. That’s because manual scanning is a time-consuming process that requires parts to be moved and scanned multiple times to obtain the critical angles.

Courtesy of Mann+Hummel

Mann+Hummel uses the ATOS III Triple Scan to measure prototype parts. The resulting data is used to determine whether or not the parts meet specifications.

In January, however, M+H uncrated an ATOS III Triple Scan, which the company purchased from Capture 3D, Costa Mesa, Calif., a supplier of products for 3-D industrial measurement. The ATOS III is a high-resolution, noncontact, structured-light 3-D scanner that can be configured as a portable system or automated with a robotic arm.

The new scanner allowed M+H to take control of the measurement process. M+H Senior CMM Programmer Jeremy Comment estimates the process is now 300 percent more efficient and that the company saved about $212,000 in 6 months.

And M+H now uses the manual SO4M scanner at a different facility. With an increase in demand for automotive parts, the manual scanner was no longer viable for the Portage facility, Comment said. Many parts needed to be repositioned up to 50 times for 50 scans, depending on part size and level of detail required.

Enter the Digital Realm

M+H produces plastic injection-molded parts for the automotive industry. The parts range in size from 1 cu. in. to about 3 sq. ft. and 6 ” deep. Each part feature is digitized with structured-light triangulation.

In simplest terms, 3-D scanning measures the geometries of a physical part and brings it into the digital world. The data output is typically a “point cloud” represented in an STL (stereolithography) file format, which can be compared to a nominal CAD model or a previously recorded 3-D scan for inspection. After a part is scanned, CAD software can analyze the relationship between each point and triangulate the neighboring groups. These triangles create a polygonal mesh, which digitally represents the part’s 3-D surface profile.

This data is used throughout the design-to-manufacturing product life cycle for various applications, such as creating a CAD model, inspection analysis, reverse engineering, finite element analysis and rapid prototyping.

The ATOS III Triple Scan takes various volumetric scans, 360° of a part, to create an accurate 3-D model. Conversely, hand-held tools, CMMs, lasers and articulating arms measure in points or lines.

The ATOS III Triple Scan collects data by projecting a structured blue-light pattern onto the object. Two cameras on the sensor calculate the X, Y and Z coordinates for every pixel in the camera. The time it takes to collect data depends on the detail and size of the object, explained Marc Demarest, Detroit-based sales executive for Capture 3D, with about 10 to 30 minutes needed for objects ranging from the size of a cell phone to a car bumper.

M+H uses the scanner primarily to measure prototype parts and create specifications for molds. The resulting data is used to determine whether or not the parts meet specs. If out of spec, M+H can correct the mold prior to production.

Typically, M+H scans the parts during the initial production launch and then scans only a few, say, one in 3,000, according to Comment.

With the scanner, the company also measures the accuracy of the molds that produce the parts. Identifying problem molds and advising about corrections is a snap with optical scanning, which literally collects millions of data points.

According to Comment, the new scanner assists with morphing of nominal CAD models. After a part is scanned, the data collected is directly compared to its CAD model. The model represents 100 percent of the part, and morphing creates a displacement map to expose deviations, Comment noted. This information can then be used for mold corrections.

“It is similar to mirroring, except you are doing it three dimensionally over the entire part,” Comment said. This exposes the problem molds in production, which are corrected by third parties that specialize in that process. Outsourcing is necessary because during first-article inspection, nearly every mold needs some correction prior to production.

Once programmed, the ATOS III Triple Scan’s robotic arm maneuvers around an object to scan the critical angles. It remembers each angle and repeats the process every time.

Scan Preparation

One employee mans the automated ATOS III scanner, performing gage calibrations and prep work. The prep work includes spray painting the black parts with a flat-white primer. A black part requires a longer exposure time when scanning. This often creates hot spots on the image. The result is lost data. Painted parts are scrapped, but they scan faster and more accurately.

Prep work also includes randomly placing small targeting stickers, white dots with a black border, on the object’s surface. These targets are reference points for the scanner, which allows the computer to identify relationships between multiple positions. Therefore, the top of the part can always be distinguished from the bottom and the right side from the left.