How to detect grinding burn on gears with Barkhausen noise analysis

Gears are one of the most common parts that can be analyzed with Barkhausen noise.

Gears scanned with Barkhausen noise sensors

Manufacturing a gear requires multiple operation processes, in which teeth grinding is a crucial step. For more than 30 years Barkhausen noise analysis has been successfully used for detecting grinding burn on gears. In this article we share information on how gears can be analyzed with Barkhausen noise method and what types of products are available.

Gear analyzing parameters

Scanning area

Barkhausen noise analysis scanning
Examples of different sensor routes.

A Barkhausen noise sensor has a point or line shaped contact to the surface to be scanned. There are many ways to scan the surface. With different kinds of scanning routines, a gear tooth can be completely analyzed or the analyzing area can be directed to the surfaces where burns commonly appear. As the Barkhausen noise analysis is a very sensitive method, the sensors detect the burns even when the scanning line does not directly run through the heaviest burns.

Scanning speed

A recommended maximum scanning speed for gears is 50 mm/s. The scanning speed is one of the parameters that influence data quality. The maximum speed depends on the material and the type of the sensor. With too high scanning speed the smallest changes in microstructure might get undetected.

Results

Since the Barkhausen noise analysis is a comparative method, users need to determine acceptable levels for their products with the master sample procedure. The master sample procedure can be validated for example with X-ray diffraction measurements or nital etching. The Barkhausen noise results can be presented numerically or graphically.

When there is no grinding burn detected, the results look like the example below. Each line presented in the picture is one scanning line on the gear surface.

ViewScan results when no burn.

In the second example heavy burns are detected:

Heavy burns on ViewScan graphs.

Barkhausen noise sensors for gears

Examples of gear sensors for flanks and roots of straight and helical gears.
Examples of gear sensors (GearScan 500) for flanks and roots of straight and helical gears.

The contact between the sensor and the surface to be measured has a major effect on the results. There are different kinds of sensors for different gear surfaces. Gear flanks can be measured with a straight sided sensor and root requires a sensor with rounded head. In some cases, depending on gear geometry, the same sensor can be used for all the surfaces. There are options for different sized sensors for different sized gear teeth. There are no limitations on how big gears can be measured. For small gears, up to module 2, Stresstech has standard sensors.

Barkhausen noise sensor scanning positions on gear flank and root.
Measurement contacts with root and flan sensors.

In a standard gear sensor, there is one measuring channel. Gear sensors can be one sided or double sided. Double sided sensors are recommended to minimize travel time between teeth. Sensors for bevel and hypoid gears are one or two sided. When the sensor is two-sided, one side of the sensor is designed for convex surfaces and the other for concave surfaces.

Example of bevel gear sensor.
Example of bevel gear sensor.

In some cases, a Plus option for the sensor is needed for hypoid gears. Barkhausen noise sensor Plus option enables measuring of smaller and more complex surfaces.

Automated grinding burn detection systems for gears

Gears can be examined with a handheld sensor and an analyzer or measurement can be automated with robotized system like RoboScan S or multiple axis system like GearScan 500.

GearScan 500 (left) and RoboScan S (right).
GearScan 500 (left) and RoboScan S (right).

RoboScan S

RoboScan S Vertical is designed for quality control needs of small to medium sized circular symmetrical parts like gears and passenger car shafts.
Creating a measurement program with RoboScan S can be done by teaching a robot point by point or using the special software, called EasyGear, where gear parameters and measurement parameters are handled in the software. RoboScan system is suitable for various gears from simple straight gears to hypoids.

Scanning programs are created point by point with RoboScan S.
Scanning programs are created point by point with RoboScan S.

GearScan 500

GearScan 500 is an automated grinding burn and heat treatment defect detection system. It is designed for quality control needs of small to medium sized gears. GearScan 500 is always equipped with the EasyGear software. GearScan 500 is suitable for straight and helical gears.

EasyGear

Examples of EasyGear parameters.
Examples of EasyGear parameters.

EasyGear is a ViewScan software extension to visualize and create measurement paths for different types of gears for a GearScan 500 Barkhausen noise inspection system or a RoboScan system. The software adapts easily to various types of spur and helical gears and measurement paths can be created on gear flanks and root area. EasyGear visualizes geometrical parameters to 3D model to ease perceiving gear measurement.

Real life examples for detecting grinding burn on gears with Barkausen noise analysis