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3D Laser Gaging Ensures Flawless Engine Fasteners

Jim Lorincz
By Jim Lorincz Contributing Editor, SME Media
Axial viewing reveals a defect in a fastener using
General Inspection’s laser gaging and axial viewing.

In an automobile engine, seven types of screws out of approximately 70 are considered critical to achieving the engine’s specified design performance, despite high vibration and heat. The seven include bolts for the cylinder head, crankshaft, con rod, flywheel, and main bearing cap, as well as for the camshaft cap, camshaft sprocket and VCT.

Having developed specialized engine expertise over three generations, the Italian fastener company Brugola OEB Industriale S.p.A. has focused on manufacturing these critical bolts, which are essential to engine assembly. They must combine perfectly with vital engine components to ensure the performance and dynamic structural integrity of the engine despite high vibration and heat.

When Brugola recently opened its first factory in the US, the company sought to expand into the US market as well as to enhance the precision of its critical engine bolts by pushing the limits of flawless manufacturing.

While the company retains automotive customers such as BMW, Bugatti, and Aston Martin in Europe, its third-generation president, Jody Brugola, recognized the importance of implementing state-of-the-art 3D laser gaging and axial vision inspection equipment to ensure ultra-precise fastener dimensional accuracy and eliminate all defects. So before the company opened its Plymouth, MI plant, one of its key investments in guaranteeing the quality of its critical engine bolts was to select an advanced, sophisticated gaging system.

“Once our president saw 3D laser gaging, he knew it would be a critical part of our quality control process to achieve zero defects,” said Antonino Occhionero, plant manager at Brugola’s Plymouth, MI plant. “Our philosophy has always been to assure that all fastener dimensions are 100% accurate. He recognized laser gaging as a superior method to ensure such quality.”

To meet the rigorous demands required for flawless dimensional precision, Brugola turned to a leading gaging equipment manufacturer, General Inspection LLC (Davisburg, MI), a manufacturer of high-speed measuring and sorting fastener inspection systems to develop a number of novel inspection features.

GI-360T laser inspection system includes a tilt-and-lift feature that ensures the laser head is perpendicular to the part, correcting for the cosine error of headed parts.

In order to make certain that all of its fasteners were flawless, Brugola selected a high-speed 360° laser gaging device. The machine uses eight sensors and real-time part velocity calculation to essentially create a 3D profile of each part, along with measurement of a wide range of user-defined features to determine if each part meets exact dimensional requirements.

“Measuring 360° around each part is critical,” said Chris Alexander, a product manager at General Inspection. “Defects can be located anywhere so inspection needs to take place over 360°. You have to measure all the way around or you are missing defects. The device measures 360° around each part to detect any small thread damage that may only be on a small portion of the shaft.”

The GI-360 measures a number of critical fastener features such as head and shaft diameter, lengths, straightness, concentricity, thread angle and diameter, including major, minor and pitch diameter. It also detects any damaged threads, along with cracks on the bolt head and flange.

“When you have a hexagonal bolt, you have critical dimensions from a flat to the opposite flat on each of the six sides,” said Alexander. “It is also crucial to measure across corner dimensions as well.”

“Brugola Italy and Brugola USA worked with General Inspection to advance the capabilities of the laser gaging inspection equipment,” said Occhionero. “The equipment is looking at lots of things at one time. We look at all the dimensions you can think of on the screw, all the dimensions required by the customer for a critical fastener.”

When the fastener inspection system manufacturer worked to improve the accuracy of dimensional measurements, the result was a redesigned version of the device, the GI-360T, which includes a tilt-and-lift feature for the laser head. This ensures the lasers are perpendicular to the part and corrects for the cosine error of headed parts, providing improved measurement readings for diameter (0.005 mm) and length (0.01 mm), total error.

With Brugola’s dedication to zero-defect manufacturing of its critical engine fasteners, the company sought to further enhance the fastener inspection system. As an option on its high-speed fastener inspection system, Brugola selected an axial viewer lens system for 360° head crack detection.

In support of the Brugola’s goals, General Inspection improved crack detection in order to detect cracks, scratches, or missing features on the side flange of bolts. This specialty lens “sees” around the head of the part.

General Inspection’s laser gaging and axial viewing GI-360T can see five sides and 360° of Brugola’s fasteners.

“A standard lens can’t see a crack on the side of a bolt flange, so we developed a special lens that visually flattens out the flange to detect any cracks,” said Alexander. “With a standard lens and camera, you can only see one side of a game die when viewed from above. With the specialized lens, you can see five sides of the die.”

Along with the wider viewing angle lens, the fastener inspection system manufacturer developed sophisticated image analysis software that minimizes surface and lighting variations. A strobe LED ring light also improves illumination of each part head for a better image.

“A standard light only generates so many lumens, so we used a strobe controller to overdrive the light for more light output,” said Alexander. “As each part triggers the sensor, the flash goes off at the moment the image is taken for better feature illumination.”

“We can sleep well at night because we know the 3D laser gaging, axial vision, and eddy current inspection equipment are helping to ensure flawless fastener manufacturing,” said Occhionero, who said, “the Brugola brand is becoming more recognizable internationally due in part to its exhaustive pursuit of quality and its eye for detail.”

For more information from General Inspection, go to, or phone 248-625-0529.

Edited by Senior Editor Jim Lorincz.

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