All Features
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…
Fred Mason
A metrologist wants to know that any variations in measurements are the result of variations of the parts being measured, not variations in the measuring devices or their users. Subjective interpretation of inspection or measurement devices is a complex variable that can influence the quality of…
Fred Mason
Last month, I talked about vision vs. video and brought up the possibility of confusion between inspection and measurement. Some think that inspection is qualitative and measurement is quantitative. I can’t say I’ll put the matter to rest, but I’ll present a few different…
Fred Mason
Using the eye is visual. The use of magnified imaging by eye or with a camera is a common part of manufacturing. Some of that use is for inspection. Some is for measurement. Some is online. Some is offline. There are vision-inspection systems. There are video-inspection systems. There…
Fred Mason
It’s New Year’s resolution time. Many of the things we resolve to do in the New Year are measurable—lose weight, run farther or faster, quit smoking, do more of some things and less of other things. All can be measured. But how do you measure success (or failure)? What do you measure…
Michael H. Brill Ph.D.
As part of a volunteer team that cleared a walking trail in my neighborhood, I helped to shovel a straight path through a small berm. Seeking to solve another problem at the same time, a member of the party started to use the dirt he removed to fill in a nearby puddle on the trail.…
Fred Mason
Continuing last month’s topic of temperature effects on measurements, what about temperature compensation? Some measuring systems claim increased accuracy with the usually optional temperature compensation. What’s that? What’s it supposed to do? And does it do what it claims to do?
Remember that…
Fred Mason
This is the first “Measurement Matters,” a column that will show how much measurement matters in achieving and maintaining quality, especially in manufacturing. I will cover topics such as types of measurements and measurement devices, how measurements are made, what can be done with the…
Fred Mason
The local environment can be an important factor in the quality of measurements. No matter what is being measured, the higher the resolution of the measurement (the finer the detail), the more significant the effect of environmental influences can be. The measurement you’re after is one…
Stephen C. Webb
Slow monitors that don’t pick up the exact end-point when a part is seated properly can hamper high-volume press-fitting operations. This process-control problem is especially widespread in automotive-powertrain assembly. A transmission, transfer case or differential can contain four to…
Fred Mason
Usually, when people discuss measurements they speak in absolute terms—degrees of temperature, millimeters of length, ounces of weight, candela of illumination intensity, degrees of angle, etc. For example, when I say the temperature is 56.4° F, the implicit understanding is that there’s direct…
Michael H. Brill
Referring to human relations, my father advised me always to "save the surface," which is something like "don’t burn your bridges," only more subtle. The connection between the homilies becomes literal in the paint industry: You must save the surface of an iron bridge to avoid burning…
Fred Mason
No, this isn’t about promises you made on New Year’s Eve and broke the next day. It’s about measurement resolution—the number of decimal places to which a measured value is calculated and presented. The measurement can be of any parameter—voltage, distance, weight, temperature, whatever. The…
George Rodrigues Ph.D.
The pipette is a reliable precision instrument that has been used and trusted for many years. However, as with many forms of instrumentation, a pipette performs only as well as the operator’s technique allows. Differences in technique—some more than others—can alter delivery volumes and affect data…
Fred Mason
Many people know about William Tell shooting the apple on his son’s head. What can this archery event teach us about accuracy and precision? What do these words mean? When are they equal, and when are they not? “Accuracy,” “precision” and “resolution” are sometimes misunderstood or…
