Boldly Re-engineered CMMs Take Throughput Seriously
Exploring trends and developments in today’s inspection equipment technology.
In the realm of coordinate measuring machines (CMMs), system accuracy is no longer the bottom line. Today’s manufacturers require faster measurement speeds in addition to highly accurate machines. Improving productivity is a top priority and manufacturing engineers are focused on finding new and effective ways to eliminate production bottlenecks. In the metrology marketplace, there are exciting alternatives to conventional measurement solutions that are helping manufacturers stay competitive. New faster, sophisticated CMMs are being applied to problematic applications bogging down production, such as parts with complex geometries that require much longer inspection times.
Traditionally, a manufacturer chooses an inspection system based on the part(s) that need to be measured. Other critical factors influencing the selection process are the size of the workpiece, the type of geometry being applied, the tolerances or accuracy levels required, and operation throughput. In the end, there always seemed to be a compromise. For example, the most accurate way to measure a part may not be the quickest, so often, the choice is a system with less accuracy in the quest for greater speed. Customer demand for greater versatility in inspection systems has pushed metrology OEMs toward new approaches and technology innovations.
High Speed Scanning Sensors
One market trend is the use of optical high speed scanning sensors with CMMs. Typically, tactile or surface sensors are used for quality assurance measurement because the operator can physically touch the surface of a component while obtaining data that is highly accurate. Today, CMM manufacturers are integrating high precision noncontact sensors based on frequency-modulated interferometry into their CMM offering.
This advancement provides the same accuracy and reliability of tactile scanning sensors, but presents major benefits: higher scanning speed, increased measurement range, and the optic advantage of noncontact measurements. Additionally, optical measurements can be taken in single point mode or scanning mode with 3- or 4-axis scanning, providing more flexibility than tactile scanning. Systems being introduced to the market also significantly reduce programming time, extending the run time of the machines and effectively increasing productivity.
Ongoing industry progress can be found in the evolution of shop-hardened CMMs for high stress environments. Across the production facility, vibrations can affect the reliability of shop floor CMMs. Vibrations can be generated by operating machine tools on the production floor, but also produced by the speed of the CMM. The higher the speed, the results become less reliable. In the past, manufacturers compensated for this condition by adding vibration dampening systems. While this improved the reliability of the measurement results, it decreased the speed to efficiently run the CMM.
Metrology OEMs have devised different ways to resolve this challenge. One method is to upgrade the hardware and firmware of the system, which decouples the frame from the driving system, thus absorbing vibrations when machine speed increases. This combination of hardware and firmware upgrades significantly reduces the amount of vibration created by the machine, enabling optimum throughput during scanning measurements, without compromising accuracy.
Multi-sensor Technology Emerges
Another trend reflected in today’s industrial landscape is the emergence of multi-sensor technology. These systems combine the accuracy and reliability of a tactile probe, with the enhanced performance and speed of a noncontact sensor. This combination allows for greater flexibility with minimum effort from the user. The sensors are separated by assigning them to different CNC integrated vertical axes. This approach allows the user to reach features located deep within the workpiece, as well as part features requiring a defined insertion angle or very long styli that use a motorized indexable probe head.
Automation and Metrology
Automation remains high on the wish list for many advanced manufacturing facilities still on the hunt for greater productivity. Automation with integrated metrology solutions can deliver a total concept of a cellular manufacturing environment—raw material is delivered to a cell and travels through different operations on a variety of machines until it is a finished part. The part-in-progress is checked by a CMM after every operation, then travels on to the next machine. Each component is consistently verified throughout the production process. The final inspection occurs on the CMM within the cell and the component is validated.
Automated work cells can be used to manufacture different runs of parts, and can be coupled with a high precision, shop floor CMM with a work envelope large enough to check multiple parts at the same time.
Shop floor CMMs are designed for demanding environments like manufacturing cells, which are surrounded by constant production activities. In a cell’s footprint, the rugged CMM runs inspection routines next to a robot, a CNC mill, and other machinery. For optimum measurement results, the measurement system incorporates built-in vibration resistance, advanced thermal compensation, and protected guideways.
Most importantly, a measurement system must provide a robotic interface that seamlessly integrates into an automated system. A robotic scenario for an automated cell would look like this: a rolling cart is loaded with raw materials and delivered to the cell. For a pre-load part, a robot can be equipped with a camera to check the orientation of the part, rotate it to the right angle, and feed it into a CNC machine. After the machining process, a robot unloads the part from the CNC, washes and dries it in a separate unit, and places it on the shop floor CMM for inspection. After measurement, the robot retrieves the part and places it on the cart where it was originally picked up.
Multiple parts can be run simultaneously in an automated work cell. If a bad part is detected during cellular production, the CMM will halt the cell. Advanced software and tailored programs can be used to chart part-by-part, dimension-by-dimension, coming off the CMM. An automated cell can be monitored 24/7 and uses real-time data to communicate constantly with the operations staff so they always know if a cell is running properly. Moreover, the automated cell ensures repeatability in manufacturing operations and better part quality, removing human intervention that could impact measurement results and product quality.
Looking to the Future
With the emergence of Industry 4.0, manufacturers at all levels are utilizing data in new ways. In the past, users would acquire large amounts of data, with little thought of what to do next. Today, the focus on capturing big data has shifted toward translating this resource into actionable insights that will help improve manufacturing processes and products. On the cusp of this paradigm shift will be the development of predictive analysis playing a major role in software and systems delivering valuable data to the manufacturing industry. CMM manufacturers are now creating a data-driven manufacturing environment that obtains process intelligence, root cause analysis, and predictive capabilities from their measurement investments.
As tolerances become tighter and product demand reaches lofty heights, it is imperative that inspection systems provide practical solutions to meet these market demands. With the introduction of richer measurement data, engineers require even more detailed reports of the products produced—and solutions that assist in making smart business decisions on the fly. In the quest for speed and confidence in part quality, CMM equipment manufacturers are pushing the envelope to deliver next-generation, high performance machines to help customers achieve maximum throughput, new levels of overall manufacturing efficiency, and further gains in productivity.