All Features
William Tandler
What’s a datum reference frame?
As discussed in workshop No. 5, datum reference frames (DRF) are coordinate systems, and preferably—at least to start with—Cartesian coordinate systems.
As we know, coordinate systems serve to orient and locate objects, and in the world of GD&T in particular…
FARO
At rare moments, an idea comes along that makes people rethink how jobs are done from that point on. The engineers at Falk PLI Engineering & Surveying have hit on such an idea for one of the most basic concepts of all: measuring.
The larger-than-life nature of steelmaking would seem to belie…
With the ever-growing demands of energy, the demands on high value-added vessels, such as container vessels, liquefied natural gas (LNG) carriers, and crude oil carriers, have skyrocketed in recent years. As of 2006, shipbuilding orders received by South Korean shipbuilders accounted for 42…
Rina Molari-Korgel
Welcome to the second issue of CMSC World—the place to catch up on the latest happenings in portable 3-D metrology and imaging. This is the official newsletter of the Coordinate Metrology Society, and once again we are gearing up for our Coordinate Metrology Systems Conference—“the” conference…
How much is a kilogram?
It turns out that nobody can say for sure, at least not in a way that won’t change ever so slightly over time. The official kilogram—a cylinder cast 118 years ago from platinum and iridium and known as the international prototype kilogram or “Le Gran K”—has been losing…
Fred Mason
In dimensional measurement it isn’t unusual to measure feature locations relative to reference edges. How one measures an edge depends on how we define it. So what exactly is an edge? Basic edges Back when people thought the world was flat, they feared that explorers who ventured out to sea might…
William Tandler
As we know, GD&T is a symbolic language with which to specify permissible limits of imperfection in manufactured parts, namely limits that maximize the parts’ operability, assemblability, and affordability. It’s complex only to the extent that the real world of imperfect geometry is complex. If…
William Tandler
Back in the 1940, when Stanley Parker, Mr. GD&T, decided it was time to create a set of tolerancing tools that realistically dealt with reality, two objectives were near the top of his list.
The first was to find a way to encode the fact that as bores get larger they may become ever more offset…
Anne Willimann
The Airbus A380 is the most modern, spacious, and capable civilian aircraft ever. The project was launched in December 2000, christened “The Flagship of the 21st Century,” and developed in close cooperation with air carriers, airports, and air traffic authorities.
The A380 incorporates the most…
Fred Mason
Happy New Year! One resolution many people have made is to cut costs. One way to do that is to manufacture in China. Just transfer your current manufacturing processes, use China’s lower-cost labor, and increase profits. It’s not that easy. If you rush into it you may find costs actually go…
William Tandler
Our original plan for workshop No. 3 was to discuss what are generally referred to as material condition modifiers, namely the encircled letters “M,” “L,” and “S” which sometimes follow tolerance values and sometimes follow datum-feature labels in feature-control frames. The idea was to explain…
Fred Mason
During this annual holiday shopping melee, economists project the implications of our spending for the country’s overall economic health in the coming year. That can be like claiming a warm December day proves global warming. What does this have to do with measurement? Quite a bit, actually,…
Rina Molari-Korgel
The CMSC is proud to sponsor this inaugural issue of CMSC World, an electronic information guide for users of industrial, high-precision, 3-D measurement technology. This quarterly e-newsletter will deliver the latest metrology industry news, best practices, new techniques, product and personnel…
Neven Jeremi
Dirk Noffke, a metrology technician at DaimlerChrysler Bremen, inspects the dimensional accuracy of the left fender on a Mercedes SLK body-in-white. The comparison between the actual and CAD data is displayed in real time on an application PC running the PolyWorks…
Belinda Jones
The 23rd Coordinate Metrology Systems Conference convened at the Grand Sierra Resort in Reno, Nevada, July 16-20, 2007. The CMSC Society hosts this gathering each year. The organization is comprised of 3-D measurement technology professionals, service providers, and original equipment…
William Tandler
Continuing with our analysis of the Greatest Design Tool ever, our objective in this article is to take a detailed look at the structure and contents of feature control frames to demonstrate that they represent “encoded” information which may only be “decoded,” not “interpreted.” With their…
Fred Mason
You manufacture a part that must be within design tolerances to work properly, so you need to measure it. It costs to: Buy the measuring device Provide a space and/or utilities for it Develop fixtures or part-holding accessories Make sure people are trained to do the measurements Develop…
William Tandler
What is GD&T, anyway? The Greatest Design Tool ever, or a whole bunch of Gol-Derned Trouble? Actually, geometric dimensioning and tolerancing is both, and worth every penny.
Only with the help of GD&T can we test and guarantee the functionality of parts and assemblies on the design…
Fred Mason
Many measurements assume that a measuring device performs in the same way throughout its measuring range. In other words, a 1 mm distance measured near the center of a machine will measure 1 mm at its periphery. But will it? This column discusses some of the factors that can cause nonlinear…
Fred Mason
All this talk about work in past columns—and the end of summer looming—makes me think about golf. You may not discuss golf and measurement in the same breath, but there are a lot of critical measurements involved in golf. There are also a lot of variables in angle, force, and direction to be…
Fred Mason
In last month’s column, I talked about the accuracy funnel, which shows that in a measurement system where the sensor or the part is moved in one or more axes, the greater the distance, the larger the potential inaccuracies in the measured distance. In the case of an imaging system as used in a…
Fred Mason
In last month’s column, I talked about the format of accuracy specifications for video measuring machines. The following is a typical format for a single axis accuracy specification: Ex = ±[k + (multiplier * L)/1000] μm And this is an example of an actual specification (linear accuracy in the X-…
Fred Mason
Accuracy, repeatability, performance—knowing how to interpret specifications for measuring devices and systems is important. This month I’ll talk about accuracy specifications for video measuring machines, which I described last month. The concepts apply to other measuring devices as well…
Fred Mason
The past few columns about inspection and measurement have led to discussion of different systems for measuring based on images. One type of measurement done via image analysis is dimensional, or coordinate, measurement. The systems are called video, or vision measuring, systems. Here…
Richard Curtis Ph.D.
The speed, convenience and cost benefits of microliter volume, air displacement pipettes drive the frequent use of these precision instruments. However, pipettes, like all mechanical instruments, are subject to failure, and this—along with the technique of operators—can have a significant effect…
