Gains in Gaging

Thursday, December 26th, 2024

The path of gaging progress has led to many good things for manufacturers. To name just a few: Manufacturers can measure parts more accurately than ever before, collect and leverage measurement data to improve part quality, and automate traditionally manual measuring processes to boost efficiency and repeatability. They can even replace humans with robots capable of handling part-checking tasks around the clock and in a variety of inspection scenarios.

Manufacturers also benefit from physical changes to their measuring tools. An example of this is the titanium nitride-coated thread gages now offered by Emuge-Franken USA of West Boylston, Mass. The TiN coating increases the hardness and wear resistance of the gages, extending their life and reducing the frequency of replacement and calibration, says Emuge-Franken sales support specialist Robert Adamiak. Not only that, but the coating also reduces friction, which improves accuracy to help ensure consistent measurements and precise thread sizing, Adamiak says.

With the rise of electric vehicles (EVs), demands for greater gaging accuracy are coming from the automotive industry, says Stuart Graham, business development specialist for automation and metrology at Heidenhain Corp., Schaumburg, Illinois. Although EVs have far fewer mechanical parts than conventional gas-powered vehicles, “the parts that you do need to check have much [tighter] tolerances than what you saw previously in that space,” Graham says.

He adds that Heidenhain’s current gage technology is capable of handling the demands of that key market, offering measurement accuracies of 1 µm or better. In fact, the company’s top performer in that area, the CT 6001 series incremental length gage, features accuracy down to 30 nm, Graham says. “They don’t need 30 nm for conventional parts in the automotive industry yet,” he says. (At present, the CT 6001 is primarily used to check gage blocks). But, he adds, “our lineup is prepared for the push for tighter and tighter” tolerances.

An Electronic Surge

The biggest recent advances in gaging can be seen in the electronic tools used to do the job, according to Mike Ingman, director of research and development at The L.S. Starrett Co. in Athol, Mass.

One such tool is Starrett’s new W4900 digital electric indicator. Featuring touchscreen technology instead of buttons, the W4900 is designed to be intuitive and easy to use. By tapping a large, capacitive touchscreen, users can select option menus for a variety of settings, including limits, presets, language (seven options), resolutions, and digital and dial configurations.

“With older versions of our indicators or calipers, there was a combination of buttons you had to go through or a bunch of gaging you had to play around with to get everything exactly where you wanted,” Ingman says. By contrast, he says, the touchscreen on the W4900 “is similar to what you see on your phone. You can scroll through [options] and set up your tool all with touch.”

This change is especially popular with younger workers, who sometimes have trouble reading a mechanical caliper or micrometer, Ingman says. “Most of the younger people I’ve handed this new tool to are able to start using it really without any help,” he explains. “They’re born with a phone in their hands; this is just like that to them. Upon first use, they can tap around on the touchscreen, and in five minutes they’re pretty much up and running.”

Another W4900 feature is a customizable backlighting function that enables both digital and analog readouts to be viewed in the same indicator. “If you like the digital readout with big numbers, you have that,” Ingman says. “And if you want a dial—and some older people don’t want to let go of dial-type indicators—it has that as well.”

The W4900 also provides wireless output for statistical process control using systems such as Starrett’s DataSure 4.0. “All of our electronic tools are capable of sending [measurement data] to any SPC program, instead of having people write it down and then type it into an Excel sheet and hoping nobody makes a mistake,” Ingman adds.

Other features of the new indicator include accuracy of ± 0.00012″ (0.003 mm) and IP67 protection for internal electronic components in harsh manufacturing environments.

Monitoring and Measuring

Today, gaging devices such as the W4900 can be complemented by equipment that monitors measurement-impacting variables such as temperature and vibration. For example, “we can look at ambient temperature of the room the gage sits in,” says Scott Lukomski, EV business director at Marposs Corp., Auburn Hills, Mich. “And we can also look at the part temperature. Many times, that’s different because the part is coming out of some sort of heat treat [process] or a washer that washes the part with hot fluids.”

In such situations, Marposs measurement systems can employ temperature compensation. “We know the expansion rate of steel,” Lukomski says. “So if a shaft is coming out [of production] and it’s 20° C hotter than it should be, we can provide a numerical offset” for the measurement.

Marposs also supplies closed-loop feedback systems that send gage readings to upstream equipment that can make changes to the manufacturing process if part measurements are approaching limits set by the customer. The idea is to catch potential problems “when you’re trending toward bad parts and make corrections before they become bad,” Lukomski says, adding that “we try to make [the process] as autonomous as possible so that no operator intervention is required.”

A variation of this process can be employed by companies making lithium-ion battery cells for EVs. According to Lukomski, an autonomous Marposs system can monitor and adjust the amount of slurry deposited on a copper or aluminum substrate. As measurement data comes in, he explains, “the closed-loop system is feeding back, saying, ‘apply a little more’ or ‘apply a little less.’”

Computer-Aided Gaging

Today, many modern manufacturing facilities put gages in computerized systems to improve both process control and measurement repeatability.

“You’ve heard of computer-aided design and computer-aided manufacturing, but there’s also what’s called computer-aided inspection or computer-aided gaging,” says David Olson, director of sales and marketing at Anaheim, Calif.-based Verisurf Software Inc., which sells inspection and measurement software, as well as coordinate measuring machines.

The idea, Olson explains, is to pre-program or create highly repeatable inspection plans prior to the measurement process. These plans can include some manual steps, or “you can jump all the way to a fully automated process using a programmable coordinate measuring machine,” Olson says.

Among other things, he notes, computer-aided inspection systems can record measurements automatically, digitally display the measurements in real time on quality dashboards, and save measurement data in quality databases. In semi-automated versions, the technician plays a role but gets computer assistance to reduce measurement uncertainty.

For example, Olson points out that users of Verisurf’s Master3DGage CMM are shown on a display exactly where to measure a part. And when the probe is placed in the right location, the system automatically triggers the measurement.

Computer-aided inspection also incorporates the Industry 4.0 concept of the digital twin, which is used to simulate a process before the real thing begins. “Simulation is as important in computer-aided inspection as it is in traditional CAM,” Olson says. “And the goal is similar: to avoid problems.”

In the case of a CMM, Olson notes, simulating an automated inspection process with a digital twin can help users ensure that there is enough room for measurements to be taken and that moving CMM components won’t collide with fixturing.

Rise of Robotics

Taking automated gaging a step further, more manufacturers are adding cobots and industrial robots to the process, according to Heidenhain’s Graham. As an example, he points to a hypothetical cell that uses air gages to measure the diameters of shafts being manufactured for the automotive market. In this cell, a robot can pick up a shaft, place it onto an air gage for a measurement to be taken, and then rotate the part for a second measurement. The robot arm is connected to a measuring system that analyzes the data in real time to determine whether the part is good or bad, then signals the robot arm to place the shaft in the good or bad pile.

Such measurement automation was rare a decade ago, “but now it’s really picked up and is a lot more prevalent,” Graham says, adding that it allows manufacturers to run processes 24/7 without the need for operators, who are relieved of monotonous inspection tasks.

Graham also points out that robots are getting better at this kind of work. In earlier systems of this kind, “you would have had to basically hard code end-to-end everything you wanted the robot to do and [put in] some safeguards for yourself to make sure that it did exactly what you want it to do,” he says. “But now there’s more capability built into the robots.”

For instance, they can work with cameras and sensors so that differences between parts can be identified by the control system. So instead of robot-equipped measurement being restricted to high-volume, low-mix applications, “I think things are trending toward a scenario where you can have the mix and have a robot deal with a wide variety of situations,” Graham says.

In a more flexible gaging process described by Graham, instead of just picking up a part and then blindly putting it on a gage, there could be an intermediate step where the robot holds the part in front of a camera to be identified, then reorients it and places it on the gage.

“Or maybe there’s even [a second] gage system set up on that machine, and the robot puts it on that other fixture instead,” Graham says. “So you can take simple ideas like this and build them up into larger and larger customized applications.”