Application Note: Grinding Burn Detection on Gears

The problem: Grinding burn on gear teeth

During the gear production process, tooth or root grinding can prove to be a problematic step. Improving cycle time requires changes in feed rate, coolant flow, and/or wheel dressing intervals. If these factors are not balanced correctly the gear can overheat, resulting in re-tempering of the teeth also known as grinder burn.

The testing method: Non-destructive Barkhausen noise analysis

Barkhausen noise ananlysis on gear tooth flank. — Figure 1: Gear sensor on tooth flank

Barkhausen noise analysis is a non-destructive method involving the measurement of a noise-like signal induced in a ferromagnetic material by an applied magnetic field. The Barkhausen noise signal is sensitive to changes in stress and microstructure.

In this application a gear was loaded into an automated Barkhausen Noise (BN) inspection system. Similar to an analytical gear checker, this system is programmed using the dimensions and parameters of the gear. Angular indexing is performed automatically followed by measurement of the flank surfaces utilizing the BN sensor. As the sensor traverses the lead of the gear, the BN data is recorded in data acquisition software for analysis and application of acceptance/rejection criteria.

The results

After the inspection is complete the BN results are displayed visually and any teeth which exceed the grinding burn rejection criteria are marked in red.

Barkhausen noise response provides a clear separation between acceptable teeth (green) from those affected by grinding burn (red). — Figure 2: The BN response provides a clear separation between acceptable teeth (green) from those affected by grinding burn (red).

Instruments used for this application:

GearScan 500

GearScan 500 is designed for quality control needs of small to medium sized gears. The system provides ease-of-use achieved with full automation but with the size, cost and simplicity of a manual gauge. Standard system includes EasyGear software for programmable measurement positioning. Sensors can be changed with quick coupling without any tools, by only unplugging and plugging in the sensor connector.

Rollscan 350

Barkhausen noise signal analyzer Rollscan 350 is designed for surface quality control and testing of near-surface defects such as grinding burns, heat treatment defects, as well as changes in stress and microstructure in a wide variety of ferritic steel and other ferromagnetic materials.