Crankshafts have three main parts: webs, counter weights and journals. Typically, only journals go through grinding processes. When there are problems in the journal grinding process, grinding burn can appear on the journal OD, radius or/and face surfaces. All of these surfaces can be easily analyzed for possible grinding burn with the Barkhausen noise method.
Crankshaft analyzing parameters
Scanning area
The crankshaft OD sensor makes a line-shaped tangential contact with the surface to be scanned. The crankshaft radius sensor makes a point shaped contact, and the crankshaft face surface sensor makes a rectangular area of contact. Journal OD surfaces can be scanned with a single or multiple circumferential scans. On the face and radius surfaces, normally one circumferential scan is required. The effective measurement area of the sensor is nearly as wide as the sensor itself, with the highest sensitivity near its center.
Scanning speed
The recommended typical scanning speed for crankshafts is around 50 mm/s. This translates to various angular speeds depending on the diameter of the journal and the throw of the crank in the case of pins. The maximum speed depends on the material and sensor type. In order to meet the cycle time requirements, two sensors can be added in a single sensor fixture for two channel measurements. Normally one fixture is equipped with an OD sensor and sensor for radius or face measurement.
For example, one robotized system for truck sized crankshafts (journals between 69-125 mm) can measure 13 OD surfaces (7 main + 6 pin) and all radius and face surfaces in less than 8 minutes cycle time. In these measurements, all OD, radius and face surfaces are scanned. This cycle time also includes automated part clamping/unclamping and indexing.
Results
Since 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. The lines presented in the pictures below are one circumferential scan on crankshaft surface. In the first example, there is no grinding burn detected.
In the second example, heavy burns are detected:
Barkhausen noise sensors for crankshafts
There are fixtures for semi-automated systems and robotized systems. Crankshafts sensors for robotized systems are designed with automated sensor changing and automated tool posturing to allow single-sided sensors to measure on both sides of the crankshaft journal.
Crankshaft sensors for RoboScan systems are designed with a self-aligning fixture. With semi-automated systems, like the CrankScan 300, measurements require operator assistance.
Crankshaft OD sensor
- Line shaped contact.
- Sensor pick-up width is defined case by case.
- Sensor and fixture are adaptable to a range of diameters. In some cases, a geometry specific “shoe” is needed.
- Self-aligning sensor and fixture.
Crankshaft face sensor
- Rectangle shaped contact
- Sensor and fixture are adaptable to a range of diameters. In some cases, a geometry specific “shoe” is needed.
Crankshaft radius sensor
- Point shaped contact
- Sensors come with different radiuses. One sensor can cover a range of radiuses.
- Sensor and fixture are adaptable to a range of diameters. In some, cases a geometry specific “shoe” is needed.
Grinding burn detection systems for crankshafts
RoboScan M-XL are suitable for crankshaft measurements. RoboScan can be fully automated and integrated to production line.
CrankScan 200 is a semi-automated grinding burn and heat treatment defect detection system heavy-duty crankshafts. It is designed for quality control needs of medium to large sized crankshafts.
CrankScan 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 crankshafts.