Unlike manually operated gages or portable measurement devices, coordinate measuring machines (CMMs) can automate the measurement process and therefore remove quality inspection bottlenecks. The highly versatile tools can measure a wide range of parts and materials. They can use a variety of methods and quickly adapt to production changes.
For example, CMMs can perform dimensional analysis, reverse engineering, tooling certifications, and CAD comparison; handle multiple sensors including contact or noncontact, tactile, scanning, or optical; and handle complex parts more efficiently than comparable tools, experts say.
“CMMs are incredibly accurate and repeatable measurement tools,” says Ryan Toole, product manager, automated measurement systems North America, Hexagon Manufacturing Intelligence. “They quickly identify errors in the manufacturing process and can feed this information back into the manufacturing loop for continuous improvement.”
Today’s CMM Technology
David Wick, manager of product management at ZEISS Industrial Quality Solutions, describes how CMMs can be used in industries from electric vehicles to additive manufacturing, and offers advice on getting the most out of the technology.
The first CMM was developed almost 60 years ago, says Brandon Stephenson, marketing and communications manager, LK Metrology.
“Because of this long history, there is a strong understanding and trust in CMM technology, so the manufacturing industry can confidently depend on this technology for quality verification,” he says. Today, the CMM is still the foundation for quality and process verification across all major manufacturing sectors.
“The flexibility of the CMM allows manufacturers to inspect a wide range of components by utilizing the various sensor technologies to include touch trigger and scanning contact probes, noncontact laser/vision sensors, and roughness sensors,” Stephenson says. “In addition, there are a multitude of CMM software options available to support manual or automated measurements and the simple feature to complex surface scanning, and 3D modeling. The CMM is the universal dimensional inspection tool that provides a high level of flexibility to the owner.”
Gene Hancz, CMM product specialist at Mitutoyo America, says CMMs are less prone to operator error than hand gages, which improves quality. They offer single source inspection instead of multiple inspection devices, maintain a constant workflow and repeat measurement routines with precision.
Although the CMM has been around for more than half of a century, technological advancements have allowed the product to maintain its prime position as the go-to technology for manufacturing quality inspection, Stephenson says.
“Over the last 10-15 years, the introduction of new probing technology, such as infinite positioning, laser scanning, vision, surface roughness, etc., has really changed the capabilities of what can be inspected on a CMM,” he says.
While inspection software packages provide users with more functionality and support for newer industry standards, such as ASME and ISO, CMMs can have the most impact when paired with model based definition (MBD) software.
“With advances in MBD, the CAD model contains the inspection information, such as dimensions, tolerances, and the datum features necessary to create an inspection program on a CMM,” Stephenson says. “Blueprints are no longer needed.”
CMMs can also effectively utilize the tracking of metrics associated with Industry 4.0.
“This information allows the programmer to effortlessly create a program in the CMM software adhering to the design intent,” Stephenson says. “CMM metrics, such as utilization, performance, environment, etc., are captured and reported in web-based applications that when combined with the inspection results, provide customers the ability to understand every aspect of their inspection processes and provide immediate feedback to manufacturing.”
As the skills gap continues to affect manufacturing, the field has seen a drastic drop-off in skilled CMM users and programmers, Toole says. For that reason, CMMs are getting easier to operate and program.
“This is leading CMM suppliers to focus on not just building a high quality, highly accurate measurement system but one that anybody in a production setting can walk up to and be comfortable with in minutes,” Toole says.
This is a new noncontact laser sensor for coordinate measuring machines (CMMs). The scanner can measure 600,000 individual points per second with a probing form error of just 8μm, rapidly capturing a complete high-resolution digital representation of a part that is valid for both surface and detailed feature inspection. Source: Hexagon (Click on image to enlarge.)
Today’s CMM has higher accuracy performance specifications than machines produced 20-30 years ago, Stephenson says. Material and design changes have produced lighter and stiffer frames, smaller air bearing gaps, higher temperature stability and improved error mapping technology.
“Although the technology is driving improved accuracies, the CMM is still a measurement tool and overall results are dependent on the entire measurement process to include the operator, the programs, holding fixtures, and the environment (temperature and vibration),” Stephenson says. “The challenge to thoroughly understand these elements that affect end results still persists today as it had 30 years ago. The CMM programmer/operator must understand and take into consideration these areas to ensure the integrity of the measurement results.”
Coordinate measurement machines are being increasingly moved to the point of part production versus sitting in a lab across the factory floor, Toole says.
“This is being driven by a push towards autonomous production workflows to drive down cost and inefficiencies,” he says. “As this trend continues, traditional CMMs need to become more robust to be able to handle the environment on the shop floor as well as flexible enough to be quickly re-deployed as production and measurement requirements change over time.”
Noncontact measurement is also becoming more popular. As accuracy and speed increase for technology like laser line scanners, manufacturers want to take advantage of the exponentially higher data quantity they can obtain from this type of sensor vs. a traditional single point sensor, Toole says.
Three-dimensional scanners bring better insight, higher productivity and reduced costs to fixed bridge CMMs, and have become key in industries such as automotive and machine shops, Stephenson says.
“Since the introduction of scanners, customers have been eager to have these fast and accurate noncontact measuring devices attached to the traditional bridge CMMs,” he explains. “The standalone tactile probing solutions will be driven by strong price point competition.”
He also pinpoints 5-axis measurement technology as a trend to watch, as it affords extraordinary measuring throughput and versatility.
“Five-axis scanning of complex forms provides the invaluable ability to gather very large quantities of accurate inspection data at ultra-high scanning speeds,” he says. “Additionally, through a rapid inferred calibration from a single probe head position and accurate at all angles of rotation, manufacturers are typically saving several hours in the set-up routine alone. This multi-sensor 5-axis measurement system helps minimizes lead times and gives manufacturers a more comprehensive understanding about the quality of their products.”
Automation in industries such as machine shops, automotive, and heavy industry has continued to evolve and incorporate new metrology solutions to meet the increasing pace of production, experts say. As result, manufacturers enjoy 24/7 operations, real-time corrective action and the elimination of operator error. A focus on offering in-line automated metrology solutions will also boost profit margins.
