Inspec Insights

Tiny Measurements on Big Big Parts

Do you have a part that you need to inspect but is too big to move, or too big to fit into your coordinate measurement machine? Perhaps it’s an in-process, part that needs to remain on the machine tool?

Well, don’t fear there is a solution to overcome your obstacles…laser trackers; fast, accurate, in-house test, measurement and inspection tools for large-volume products.

Laser tracking is a technology that has been around for about 30 years, but it is now more accurate, capable, and robust than ever before. These line-of-sight devices are extremely appealing because of their portability, repeatability, and accuracy.

The Technology
Laser tracker technology is based on the combination of two techniques: a distance meter to measure absolute distance and angular encoders to measure the tracker's two mechanical axes--the azimuth axis and the elevation (or zenith) axis.

Laser trackers emit a low-power, eye-safe laser beam (Class 1) to a retro reflective target that is either held or mounted on the object to be measured. The laser light reflects off the target and re-enters the tracker, as it re-enters the tracker a distance meter analyzes the light and measures the distance from the tracker to the target. As the retro-reflector is moved, the laser tracker records the distance, azimuth and elevation.

The tracker can be directed to take data points at regular intervals such as every few thousandths of an inch. It can measure points continuously, so data can be gathered on critical parameters like thermal growth. Powerful software stores these values and compares the data to uploaded CAD files. 

Laser Trackers vs. Other Measurement Tools
Laser trackers can capture large volumes of 3-D coordinate data quickly and in real-time. They can be moved easily and can be installed in a variety of configurations to get the best angle. Unlike rooted to-the-floor CMMs that have a limited work envelope, are best in environmentally stable conditions, and must have the parts transported to them; laser trackers can be brought to the part, are robust enough to withstand many environmentally challenging conditions, and can track enormous parts.

But, you ask, how about my portable arm CMM?  It can move to the part and be used to inspect hidden areas. Yes, while portable CMMs are fantastic quality devices with more flexibility than stationary CMMs or handheld gages, where they cannot compare to laser trackers is in the size of the parts to be measured and accuracy. 

Portable articulating arms are accurate to approximately 0.0002 in. (new models being accurate up to 0.0007 in.) that is, in nice, clean environments, but not all shop floors are nice, clean environments.

Laser trackers on the other hand are accurate up to 0.0006 in. (0.015mm).  Another strength of the 16-inch, 28 pound, IP52 rated laser tracker its ability to be used in a wide range of conditions as it is resistant to shock, vibration, temperature cycling, and humidity. It also continuously monitors temperature, air pressure, and humidity and compensates accordingly to ensure accuracy.

So, for accurate, consistent, and repeatable measurement data of very large parts that won't work on your CMM, laser tracker technology can be the answer.

Inspec now offers laser tracker services in addition to add to its other inspection and metrology solutions. 

Learn more about laser tracking in this video or contact Inspec to see how they can help you solve your measurement obstacles.

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