Research Of The Multi Parameters Measurement Of Crankshaft In Automobile Engine Based On Shadow Casting

The automotive engine crankshaft is the key part which translates the piston’s reciprocating motion into it self’s rotating motion, and it bears lasting alternative stresses when the engine is running, where fatigue failure is easy to occur. So the crankshaft’s manufacturing quality is very important for the performance and reliability of the automotive engine. The configuration of crankshaft is complex and the machining time available is short, so it is hard to ensure the precision of the parameters, such as the diameters of main and pin, the roundness of main and pin, the runout of main and pin, the straightness of main and pin, the parallelism of main and pin, the surface texture, the location of the oil hole, the oil hill’s height of thrust face, the eccentric of the pin, the groove of main and pin, etc. Thus the parameters’ measuring process should be arranged reasonably between stations. However, the parameters needed to be measured are too many. So the high-efficient, integrated checking method for the crankshaft’s parameters is very significant to ensure the crankshaft’s quality.The shadow casting checking scheme is carried out for the crankshaft’s parameters, based on the robotic visualization. Through the optical system consist of telecentric lens and back-light parallel illumination, the characteristic image of the position which is needed to be checked are captured. One image or more images are processed. And based on the results of the image processing, the calculation methods for the parameters are carried out, such as the diameters, roundness, runout, etc. The error resources and precision are analyzed for these calculation methods. In real situation, burs, oil, and contaminants always exist near the journal’s groove of the crankshaft. In order to deal with this disturbing problem, the high precision corner detection algorithm is carried out and it is used to locate precisely the corner point at the joint position of the journal and the groove. Thus Multi-parameters measurement’s bases’ stability and reliability are improved.A lot of multi-parameters extending experiments are carried out, based on the developed special checking machine with shadow casting principle for the crankshaft groove. The multi-parameter checking methods are validated by the experiments, and a lot of data is obtained. Meanwhile, the accuracy, the repeat precision and the checking efficiency for each parameter’s checking are evaluated. Some parameters’ checking functions are applied on the special checking machine, and it shows good results in an engine manufacturing plant in real use.