High-speed sorting technologies, including vision-based hole and thread detection, make traditional detection methods obsolete

December 2016 - It is critical to inspect formed metal fasteners to ensure zero defects whether for safety, mission-critical performance or to optimize the manufacturing process. Conventional methods to do this exist, such as sorting mechanically for size or hand sorting with optical comparators. 

Historically, it has been difficult to inspect internal threads for tiny defects such as chips, tears, weld spatter, or for short or missing threads.

Inspecting the vertical walls of a fastener hole and its threads is difficult for the human eye, due to the hole’s small size as well as lighting and viewing conditions. This type of inspection process is not only slow, labor intensive and subject to interpretation but also prone to human error—particularly over long periods when fatigue can degrade accuracy.

“Because many of our parts, such as small fuel fittings and unions for the auto industry, are safety parts, our customers will not accept anything but 100 percent quality, so we carefully check key areas, including internal threads,” says Chuck Abbate, vice president of operations at H&L Tool, an ISO-TS 16949:2009 registered manufacturer of precision turned and cold formed fastener products. “We needed a way to make sure that all the internal features were perfect and within the print.”

However, even typical cameras and laser-based equipment have difficulty detecting required features inside of parts, and the deeper the hole or recess, the more challenging this becomes.

“One of the problems that arises when looking at internal features on a machine is the different color in the plating and different lighting,” says Abbate. “It is very important to get a machine that determines what it is looking at, that it is truly looking at the part and not at glare or a shadow.”

To help manufacturers ensure zero defects in their fasteners, a number of advanced high-speed sorting technologies are making slower, less reliable traditional methods obsolete.

In order to make certain that its couplers, tube nuts and internal female nuts were flawless, Abbate turned to a high-speed vision-based measuring machine.

These devices use a series of front and backlit cameras to calculate a part’s height, profile and inner and outer diameters. The device configured for H&L Tool also has several advanced options, including cameras to check for internal threads, an axial viewer that detects surface imperfections on multiple sides of a part at once, and eddy current capability, which enables checking for metallurgical defects along with plating or hardness variations.

With 360-degree internal thread inspection capability, these devices incorporate hole inspection optics to specifically image and measure both the bottom of a hole and its vertical walls. This captures great detail of ID threads and detects very small defects like weld spatter, torn threads, reamed threads, chips in threads, short or missing threads, as well as a single damaged thread.

Inside the part

“The GI-100DT from General Inspection has the capability to totally look inside the part,” says Abbate. “The different types of special lenses on these cameras are very good at looking at all the internal features, which we could never get before.”

A conventional V-track model inspection machine, with a 30-degree incline to drop the part, would have limited how much of the part interior is visible.

“Other machines cannot look at the sealing surfaces of a coupler, for instance, because they view it at an angle,” says Abbate. “You have to be able to see down into it.”

“With the glass-dial-style table that the parts ride around on, we can view the top and bottom of a part at the same time,” he continues. “On a double-featured piece like a union, this allows us to run it through once instead of twice.”

According to Abbate, an axial viewer also allows detection of any surface discontinuities on six sides of a part at once. With such a capability, the camera could, for instance, simultaneously inspect the top and sides of a fastener.

Abbate has found the device provides the efficient, zero defect fastener sorting required. “We have found our new system to be at least 10 times faster than hand sorting and much more effective than typical sorting machines that look only on the outside of a part,” concludes Abbate. “It is a must for those who make internally threaded fasteners or connectors.” MM

Mike Nygaard is president of General Inspection, a developer of high-speed measuring and sorting fastener inspection systems. General Inspection, Davisburg, Michigan, 248/625-0529, www.generalinspection.com.