Grinding lobes and bearing journals is the final machining operation that completes a camshaft. In some cases, also face surfaces of the lobes are ground. When ever the surface is ground, there is possibility for hardness and microstructure changes caused by grinding burn. Grinding quality of the camshaft can be easily detected with a Barkhausen noise analysis.
Camshaft cracking detection with Barkhausen noise analysis
In some cases, Barkhausen noise analysis can detect cracks created during the heat treatment process, sometimes called quench cracks. Barkhausen noise analysis detects stress concentrations around the crack and the conditions which create the crack. Crack detection applications are material and geometry dependent and thus require case-by-case consideration.
Camshaft analyzing parameters
Scanning area
A camshaft sensor has a line shaped contact to the surface to be scanned. Camshafts lobes and journals can be scanned with a single or multiple lines. On the face surface normally one scanning line is required with special face surface sensor. The effective measurement area of the sensor is nearly as wide as the sensor itself with the highest sensitivity near the center.
Scanning speed
The recommended typical scanning speed for camshafts is around 50 mm/s. The maximum speed depends on the material and sensor type.
In order to meet the cycle time requirements of production multiple lobes can be measured simultaneously. For example, a robotized system for passenger car sized camshafts with two sensors can measure 10 lobes in less than 50 seconds. Part loading and unloading can be fully automated.
Results
Since the Barkhausen noise analysis is a comparative method, users need to determine acceptable measurement values 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. The line presented in the picture is one scanning line on the camshaft surface.
In the second example heavy burns are detected:
Barkhausen noise sensors for camshafts
The contact between sensor and surface to be measured has a major effect on the results. When measuring camshaft lobes, the contact angle of the sensors changes during the camshaft rotation. Camshaft sensors are designed so that the angle changes have a minimum effect on the sensor data. There are camshaft sensors with different widths for different sized lobes.
Camshaft journals can be measured with camshaft sensor or OD sensor. OD face sensor is required for face surfaces.
Grinding burn detection systems for camshafts
CamScan 50
Manual grinding burn and heat treatment defect detection system for low-volume applications. CamScan 50 is designed for quality control needs of small to medium sized circular symmetrical parts like passenger car shafts.
CamScan 100
CamScan 100 is a semi-automated grinding burn and heat treatment defect detection system for low-volume applications. It is designed for quality control needs of small to medium sized circular symmetrical parts like passenger car shafts.
CamScan 200
CamScan 200 is a semi-automated grinding burn and heat treatment defect detection system for heavy-duty shafts. It is designed for quality control needs of heavy-duty circular symmetrical parts like truck shafts.
CamScan 300
CamScan 300 is a semi-automated grinding burn and heat treatment defect detection system. It is designed for quality control needs of small to medium sized circular symmetrical parts like passenger car shafts.
CamScan 500C
CamScan 500C is an automated grinding burn and heat treatment defect detection system. CamScan 500C is designed for quality control needs of small to medium sized circular symmetrical parts like passenger car shafts.
RoboScan S-XL
All RoboScans are suitable for camshaft measurement. RoboScan can be fully automated and integrated to production line.