| by Mike Richman
The process of measurement gives shape to the nature of reality. According to 19th century mathematician and physicist William Thomson, Lord Kelvin, “When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind.”
With an attitude like that, it’s clear that Lord Kelvin would have enjoyed a long and successful career in the quality industry if he hadn’t frittered away his time on trivial pursuits like thermodynamics and electromagnetism. Without a doubt, the old Scottish lord would smile at the variety and sheer number of metrology instruments available to quality professionals today. Technological innovations have increased the measurable world to the molecular level. Year after year, metrology grows increasingly subtle, and metrological tools grow increasingly sensitive. But we haven’t seen anything yet.
All of this directly affects the world of quality, which relies on increasingly sophisticated measurement tools and techniques as the lifeblood of quality assurance. For manufacturing applications in particular, the ability to properly measure materials and parts leads to fewer defects and higher levels of quality and customer satisfaction.
In the future, we are likely to see significant advances in the following five key elements of metrology tools and equipment:
 Increased speed
Improved accuracy
Reduced measurement size
Better environmental control
Lower costs
For metrology equipment manufacturers and the customers who buy from them, these are the five areas where technological advances lead to measurable results. For high-end users with the resources to afford it, the next generation of CMMs, articulated arms, laser trackers and the like will yield astonishing increases in speed and accuracy, with a corresponding reduction in size and greater portability. Those working under more limited budgets will also benefit from a “trickle down” effect as most of these advances become incorporated into systems that may not have state-of-the-art speed or accuracy, but which operate at an extremely high level in most operating environments.
Several of the world’s leading metrology companies are taking active roles in pushing forward the advances that will alter the landscape for measurement in the near future. The quality industry in general, and metrology in particular, will be very different in the coming years. Following are some of the companies that will be at the forefront of that change.
Contact scanning speeds have increased to a remarkable degree in recent years. The need for very high-speed scanning--with better accuracy--will only increase in the future for manufacturers and others seeking inspection or measurement data.
“Today, we’re scanning a few hundred data points [per second], but in the future, we’ll be scanning 10,000 data points a second,” says Barry Rogers, national sales and marketing manager for Renishaw Inc. of Hoffman Estates, Illinois, speaking of contact scanning in particular. “From 5-15 mm/second scanning speeds today, we’ll go to 500-1,000 mm/second speeds tomorrow. This leap in technology is possible in Renishaw’s Universal CMM control (UCC), embedded with RenScanDC for dynamic compensation of machine structural errors induced during high-speed measurements.”
Dynamic compensation software first measures each feature on a part at slow speeds, where inaccuracies due to machine movement are negligible, and then at faster scanning speeds, where machine movement influences measurement accuracy. The UCC analyzes the differences and creates a map of the part in question. Once the map is established, all other parts with the same features can be measured at high speed with the same accuracy achieved at low speed.
“Historically, speed has been the physical limit to accurate measurement,” says Rogers. “The faster the machine moves, the more inaccuracies creep into the process, caused by structural changes in the CMM as it changes both velocity and direction in moving around a part. In the near future, you’ll see both hardware and software developments which will overcome the dynamic influence of the machine making the measurement.”
Speed is a critically important factor for manufacturers seeking to reduce their cost of quality. Time is money, and slower scanning speeds can cause unacceptable delays and backlogs for busy, high-volume shops. But increased scanning speeds are sometimes accompanied by decreased accuracy--and inaccurate scanning is certainly worse than slower scanning.
“One of the most demanded requirements by manufacturing today is the ability to scan surfaces,” says Bill Wilde, marketing manager for Mitutoyo America Corp. of Aurora, Illinois. “Speed is critical, and scanning allows manufacturers to collect many more data points than touch samples. More data translate into more information about the manufacturing process. The more information about the process, the better and more efficient the management--translating into improved productivity and profit.”
“Historically, accuracy is everything,” says Rogers of Renishaw. “If it’s not accurate, why bother measuring it?”
The importance of speed vs. accuracy has long been an issue in metrology circles. The appearance of products that combine both of these important elements are now beginning to affect the way parts and materials are measured and inspected. New tools, building on existing technologies, will lead the way.
“Precision optical measurement technologies will change the traditional coordinate measurement market,” says Jürgen Dold, Ph.D., vice president for business development at Leica Geosystems’ Metrology Division in Unterentfelden, Switzerland. “Our local positioning technology forms the basis for a new series of high-precision coordinate measuring solutions such as the Walk Around CMM T-Probe and the T-Scan, which is a hand-held scanner.”
Improvements in accuracy, tied to increases in scanning speeds, will give the companies using these devices a real breakthrough in their measurement and inspection processes. The technical specifications of some of these new solutions are impressive.
“The T-Scan requires less setup time, which in turn speeds up scanning processes by over 50 percent. The T-Scan enables rapid noncontact digitization of large objects at a rate of 7,000 points per second, with an accuracy of up to 50 mm,” says Dold.
As the technology grows more nimble and accuracies continue to increase, users of metrology solutions such as the T-Scan will find that they have the ability to better inspect their parts and materials. For extremely complex assemblies such as those found in the aerospace industry, ever-higher accuracy isn’t a luxury--it’s a competitive necessity. In the coming years, higher accuracies will become the standard.
The shrinking of high-tech gadgets is one of the hallmarks of the technical revolution. The number of transistors per integrated circuit continues to double every two years or so, which is right in line with computer researcher and Intel Corp. co-founder Gordon Moore’s astonishing prediction, made more than four decades ago. Moore’s Law is holding steady and should be valid at least until 2010. Mind-boggling as it may seem, super large-scale integrated circuits now feature up to 1 billion devices. Where will it end--and what ramifications will this trend have in the metrology industry?
 The beginning of an answer can be found in the area of micro-parts metrology. This emerging discipline is gaining in importance, as evidenced by the number of micro-machining workshops and conferences that are beginning to pop up on a regular basis. Trying to measure these extremely tiny part features, some of which are as small as 0.1 mm, is a huge challenge, especially if a technician is attempting to use a typical CMM.
One of the companies striving to find a solution to this dilemma is Carl Zeiss IMT Corp., with U.S. offices in Maple Grove, Minnesota, and Brighton, Michigan.
“To meet this challenge, we’re now developing our F25 Micro 3-D CMM,” says Kevin Legacy, engineering manager for Zeiss. “This device uses a combination of contact and noncontact measurement technology to achieve a measurement uncertainty in the 250-nanometer range.”
As parts continue to shrink and components grow increasingly dense and complex, nanometrology will assume greater importance to parts manufacturers and their customers. The measurement and inspection of these parts will continue to demand new approaches and new technologies.
Controlling environmental factors, particularly temperature, is one of the keys to accurate measurement. This challenge must be considered when developing both manufacturing and metrology instruments. As a practical matter, the effect of temperature must be managed and controlled, not only from an accuracy standpoint, but from an economical one as well. Large enclosures that help maintain temperature generally take up a great deal of space. When one considers that most plant managers are seeking to improve revenue per square foot of floor space, allocating a large amount of space to controlling temperatures is not always feasible.
“There is no perfect solution in this area,” says Legacy. “For many years, experts have preferred to keep their shop floor CMMs surrounded by a temperature-controlled enclosure that has enough room to allow parts to reach a predefined constant temperature [the generally accepted standard is 68° F]. While this approach works well, it does increase cost and complexity, and typically requires more floor space.”
Driven at least in part by economics, plants are now leaning towards a different theory of operation--that shop-floor measurement and inspection equipment will no longer be surrounded by enclosures such as climate-controlled rooms. Zeiss, for example, will continue to develop its Max line (including GageMax and CenterMax CMMs), which don’t require enclosures and are minimally affected by typical shop environments.
Another method for dealing with environmental issues is the use of computer tomography (CT) for coordinate metrology (see the article “X-ray Inspection” in the April 2005 issue of Quality Digest). CT technology is primarily used in nondestructive defect testing and analysis for industrial and medical applications. In using CT scans for inspection, a part is placed on a rotary table between an X-ray source (generator) and an X-ray receiver. As the table rotates, X-rays penetrate the part and coordinate data are captured by the receiver. These data are then passed onto an image reconstruction system that produces a mathematical model of the part. Because CT scanners generally gather data quicker than CMMs, this technology allows users to ease some of the issues related to environment and temperature.
The advantages of CT scanners are at least partially offset by some of their practical problems. “The disadvantage of a typical CT system is that it cannot produce results with the same uncertainty as a CMM,” says Legacy. “As measurement requirements move from defect analysis to dimensional inspection, the amount of operator interaction dramatically increases. We’ve been improving the strengths of CT and developing solutions for their weaknesses, and will soon be able to demonstrate the potential for CT in the world dominated today by CMMs.”
Nonenclosed CMMs and CT scanners are examples of systems that help users control costs and are minimally affected by typical shop environments. Now and in the future, systems such as these will continue to find a place in the hearts of metrologists (and CFOs) everywhere.
The pressure to respond to outsourcing has directly affected the metrology industry in surprising ways, not the least of which is economic in nature.
To reduce waste and improve speed and productivity, manufacturers are increasingly combining traditionally independent operations such as metrology with the manufacturing design process. Design engineers now must consider how work pieces will be measured, and manufacturing engineers must figure out how to best make those measurements. Streamlining saves money but can cause problems.
“To this market demand, we’re developing technology that can be integrated into the manufacturing process and performs multiple functions,” says Wilde of Mitutoyo. “Slaved or single-function products cannot meet the new requirements that U.S. manufacturers are facing. For this reason, metrology manufacturers are creating multisensing devices (such as CMMs with vision, laser and touch-probe systems) that can be used on a wide variety of prismatic surfaces and materials.”
Economics play into metrology in other important ways. Not every user of measurement and/or inspection solutions needs to purchase the biggest, most accurate and most expensive machines and gadgets. In fact, there’s a burgeoning market for smaller and less costly solutions that, while they aren’t as accurate as some of their larger brethren, give perfectly acceptable results in many settings.
Immersion Corp. of San Jose, California, has been in business for just over a decade but has already established a niche as a provider of portable test and measurement equipment. The company’s MicroScribe articulated arms digitize 3-D objects for modeling and reverse-engineering applications, particularly in the medical, automotive and manufacturing industries.
Smaller and somewhat less accurate machines such as these (Immersion’s highest-accuracy model, the MX, has an accuracy of about 0.004 in.) can be extremely useful. Smaller manufacturers needing to inspect sheet-metal parts, standings, forgings and/or pressings, for example, find the accuracies perfectly acceptable. These companies also like the affordability.
“One of the interesting things about the MicroScribe is that it’s an articulated-arm digitizing machine. It will do 100 percent of everything that the high-end machines will do,” says Bill Hoverter, Immersion’s senior director of 3-D worldwide sales. “Perhaps not in as large of an area, and not at as high of an accuracy, but from a functional standpoint using [CAD] software, all of it works in exactly the same way.”
Even better, the MicroScribe articulated arms cost just a fraction of their more accurate brethren. “Our costs are very easily a tenth of what someone could spend, especially if they don’t need [the accuracy],” says Hoverter.
For many of his clients, state-of-the-art solutions are out of reach and unnecessary. Metrology companies such as Immersion aren’t necessarily taking business away from the “big boys”--they’re simply increasing the options for manufacturers of all kinds and sizes, many of which weren’t measuring or inspecting at all before products like the MicroScribe hit the market. As the range of metrology options continue to increase in the future, we’ll see fewer manufacturers foregoing inspection due to cost.
It’s been said that the only constant is change. Nowhere does this aphorism ring truer than in the metrology industry. The constant evolution of tools and concepts forced by the demands of the marketplace lead to faster and more accurate measurement options for companies and organizations. Competition between the makers of metrology equipment adds more fuel to the fire, spurring further advances. Manufacturers benefit by being able to offer their customers better-produced materials, and consumers gain when those materials are turned into better, safer and cheaper finished products.
The key is flexibility. With ever-increasing options in terms of scanning speed, accuracy, measurement size, environmental control and cost, manufacturers and others who require measurement and inspection will be able to choose a solution that’s just right for their needs. As measurement becomes ubiquitous, quality will improve. Profitability and customer satisfaction will increase. It’s simple: Everybody wins when everybody measures.
By any measure, the future of metrology looks bright indeed.
Mike Richman is Quality Digest’s managing editor.
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