The Influence of the Bottom Hole of Cold Extruding Internal Thread on Thread Quality

Abstract

The diameter of the threaded bottom hole determines whether the extrusion can proceed smoothly and the fullness of the tooth shape after extrusion. The tooth height rate is an important indicator of the strength of the threaded connection. In order to establish the relationship between the diameter of the bottom hole and the tooth height of the extruded internal thread, this paper takes the aluminum alloy M8×1.25 mm internal thread as an example, and uses a method of combining numerical simulation and process test. Obtained the changing law of internal thread profile and tooth height rate of extruded workpieces with different bottom hole diameters. Using MATLAB to fit the numerical simulation results, the relationship between the tooth height of the internal thread and the diameter of the prefabricated bottom hole of the workpiece was obtained. The reliability of the numerical simulation results and the feasibility of the fitting formula are verified through experiments. The results show that the diameter of the prefabricated bottom hole of the workpiece is controlled within 7.33~7.39 mm when the M8×1.25 mm internal thread is processed by the cold extrusion process. The high rate of the internal thread after extrusion meets the requirements of thread connection strength, and the internal thread has high forming quality and good surface quality.

Quality prediction of internal thread cold extrusion based on genetic algorithm optimized BP neural network

“…Both have a great influence on the service life of extrusion taps and the quality of thread forming. 3,4 When processing different types of threads, the process parameters are different, and the extrusion torque and the resulting extrusion temperature are also different. In order to ensure the extrusion quality and the smooth implementation of the extrusion process, it is important to predict the relationship between process parameters and extrusion quality in advance.…”