The Crack Detection of Ladder Powder Metallurgy Parts Based on the Analysis of Load Current

Because of all kinds of factors affecting the process of powder metallurgy (PM) parts' manufacturing, as well as technology itself some defects are easily brought out including crack. Defect detection is an important measure to ensure the quality of PM parts. The common defect of circular ladder PM parts is ladder corner crack, generally using the method of manual moment of force to carry on the detection one by one, this kind of method needs large workload, often low efficiency and easy misses. This paper introduces a crack detection system for ladder PM parts, which is controlled by a single-chip, one conveyor belt and the U-guide groove perpendicular to the other constitute the transmission system for parts, together with crowding mechanism constituting ladder PM parts' crack detection system. We can achieve the direction of four similar 90-degree difference of the crack parts detection, the transmission of parts, the separation of qualified and non-eligible parts by this system. During the parts detection, the conveyor belt transmitted PM parts to the detection point along the path which was constituted by two relatively open U-guide grooves. We used two opposite push rods which were driven by motors from each of four directions of the parts upper half to push with a certain degree of force. If some cracks exist in the root, the parts would be broken from ladder corner. Then we used the change of the motor's load current signal to judge whether parts are qualified or not and calculate their qualified rate. The process of detection was all controlled by a single-chip, and we could detect more than one part at the same time.