Advances in Metrology Science Set to Improve Manufacturing
Metrology is the science of measurement, and as the old saying goes, “to measure is to know.” This makes inspection and quality assurance part and parcel of the manufacturing process. The downside is that today’s complex supply chains and hyper-competitive business environment make production efficiencies and improving delivery times even more important since the temptation to cut corners to save time is ever-present.
Luckily, today’s manufacturers have an ever-growing number of metrology technology choices. These include:
- Fixed coordinate-measuring machines (CMMs). CMMs are well-known in manufacturing operations. They feature high-precision probes that “touch off” a part’s critical dimensions and feed the data into reports. They are very accurate but require a separate measurement function, meaning parts are made, then taken aside and measured. If mistakes are detected, time and production suffer.
- Laser scanners. High-tech laser scanners for industrial measuring are often hand-held or mounted on portable robot arms. Now measurement can be taken to the part on the production line. Laser scanners also can be customized to individual production requirements.
- X-ray computed tomography (CT) equipment. Similar in function to those used in hospitals, X-ray CT scanners are coming on strong in manufacturing applications. In newly emerging 3D-printing production processes, X-ray CT scanners can inspect parts inside and out, detecting any flaws and assuring parts meet their CAD (computer-aided design) requirements.
In addition to assuring inspection accuracy, many manufacturing operations are demanding fully automated scanning and report generation. While many choices and claims vie for attention, it pays to keep in mind some straightforward goals: simplified and more direct measuring and inspection functions that speed time to market while being able to handle a wider range of parts and surfaces.
Evaluating what metrology solution is right for a particular shop involves satisfying many, if not all of the following common-sense business concerns:
- Accuracy. What is the accuracy threshold the shop and its customers will be demanding now and in the foreseeable future? How accurate must you be?
- Measuring volume. What parts demand measuring and inspection — bone screws, car panels or something in between? Do parts need to be measured on the factory floor, in-process or delivered to a metrology department in a controlled environment?
- Automation. Does robot handling make sense? What about conveyors or other options?
- Data acquisition speed and software compatibility. The nonstop growth in computing power has made many advances in inspection possible. Is report data available in easily understood forms? Can reporting be completed offline, leaving articulated arms or CMMs dedicated to inspection tasks?
Laser trackers have been around awhile. Where laser trackers require using a probing device held against the object being measured, new technologies such as “laser radar,” by comparison, direct a focused laser beam to a point on the object being measured and recaptures a tiny portion of the reflected light to determine absolute range to the measured point. Combined with measured horizontal and vertical laser beam angles, 3D coordinates of the acquired points are determined in real time.
Being target-less and non-contact is a productivity multiplier – one person can handle setup, fewer procedures are required and the entire process becomes significantly faster. The system even runs unattended.
The major strength of laser radar is that it can scan complex geometry impossible to scan before because it was too large, too hard to reach, too complex, too delicate or too labor-intensive. The system works indoors or out, in any lighting, and on any material or finish surface with a reflectivity of even less than 1 percent.
X-Rays for Emerging Tech
Metal 3D printing is remaking the manufacturing landscape. Consulting firm IDC says global spending on 3D printers, both desktop and industrial, will reach $13.8 billion this year, up 21.2 percent over 2018. Discrete manufacturing will be the dominant industry for 3D printing, delivering more than half of all worldwide spending throughout the report’s 2018-2022 forecast.
Metal 3D-printed parts are increasingly being considered for lowering component weight without compromising on strength, critical in aerospace applications where decreased weight leads to increased efficiency. It is essential to know whether voids or inclusions are present, how large such voids are (both individually and in total) and where they occur – and also whether the dimensions of the part conform to those of the design.
In such cases, X-ray computed tomography (X-ray CT) is a powerful answer. By supplying a full 3D density map of the samples, X-ray CT gives all this information in an easy-to-read visual format.
Plus, modern X-ray CT equipment is now much faster and more suitable for production-line use. CT scanning of similar parts can be automated for loading and unloading. Scan times down to a few tenths of seconds per part are possible. Users gain:
- Better insight into the inside of 3D-printed parts
- Faster optimization of prototyping and production processes
- Quality control – much higher confidence in incoming and outgoing parts
- Reduced costs by avoiding destructive testing
It is an exciting time to be considering new metrology options. The right configuration and combination can yield groundbreaking production efficiency improvements without sacrificing an inch on quality assurance.
Some opinions expressed in this article may be those of a contributing author and not necessarily Gray.