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 commonly used to detect grinding burn on gears. In this article we share information of how gears can be analyzed with Barkhausen noise method and what kind of products are available.
Gear analyzing parameters
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.
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 a material and sensor type. With too high scanning speed the smallest changes in microstructure might get undetected.
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.
In the second example heavy burns are detected:
Barkhausen noise sensors for gears
The contact between sensor and 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, same sensor can be used for all 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.
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 moving 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 for convex surfaces and the other for concave surfaces.
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.
RoboScan S Vertical is designed for the 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.
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 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 robot 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
- Grinding Quality Inspection at Wind Turbine Gearbox Expert Moventas
- Application note: Non-destructive Testing on Gear Teeth
- Application Note: A Correlation Between Barkhausen Noise and X-Ray Diffraction
- Application Note: Barkhausen Noise on a Failed Gear
- Application Note: Grinding Burn Detection on Gears
- Barkhausen Noise as an Alternative to Nital Etch for the Detection of Grind Temper on Gears