Automatic Brush Plating Technology And Equipment For Connecting Rod Of Diesel Engine

In the last few decades, resource and environment problems have become more and more serious along with the rapid development of economy in the whole world. More and more researchers show great interests in remanufacturing which could save the natural resource and protect the environment. In the latest decades, Chinese government releases a serial of policies to advocate the development of remanufacturing industry and remanufacturing industry experiences a great development in China. However, remanufacturing in china just starts few years before, and there are still amounts of technique problems to be solved. Taking the remanufacturing of the big end of connecting rod and the inner hole of crankshaft for examples, brush plating technology is widely used in enterprises. However, the properties of coatings prepared by manual brush plating are not uniform, and the efficiency is pretty low. Furthermore, long time exposure to plating electrolyte could be harmful to the health of manual brush plating operator. Therefore the research of automatic brush plating technology has great significance.Firstly, this paper analyses the process of nano-composite brush plating through single factor experiment, and studies the effects of electrolyte pH on Zeta potential of nano-particle and mechanical properties of composite coating and the effect of Zeta potential on co-deposition of metallic ions and nano-particles. Then a new explanation of co-deposition of metallic ions and nano-particles is given from the perspective of electric property of nano-particles. Experimental results show that changing of electrolyte pH would not change the typical "cauliflower" morphology, but it could change the size of "cauliflower". Electrolyte pH could change the co-deposition through changing the electric property of nano-particle.Then, an automatic nano-composite brush plating machine used for remanufacturing of connecting rod and crankshaft was designed and manufactured according to the technique process of manual brush plating. An electrolyte gathering and separating device was specially designed to solve the technique difficulty which is how to provide 6 kinds of electrolytes and recycle them separately during plating process. This machine could control trajectory and speed precisely and remanufacture more than one workpiece at the same time which could boost productivity, reduce labor intensity and provide technique support to engine remanufacturing industry.Lastly, single factor experiment and orthogonal experiment were designed. Coatings were prepared by the self-designed automatic brush plating machine according to experiment design. Metallographic microscope, scanning electron microscope (SEM), tribometer, white light interferometer and residual stress analyzer were used to measure coating properties. Range analysis and ANOVA (analysis of variance) were conducted to determine the effects of process parameters (voltage, speed and distance) and nano-particle concentration on morphologies, wear and friction property, residual stress and bonding strength etc. Optimal parameters for desirable wear resistance and residual stress were determined separately. The result of verification test proved the validity of the optimal parameters which could provide technique support to practical production.The automation transformation of remanufacturing technology is an important developing direction. The research about automatic brush plating machine lays solid foundation to the popularization of brush plating technology industrialization. The study of automatic machine parameters could provide theoretical support and technique guarantee to practical production in remanufacturing enterprises.The work is sponsored by School-enterprise cooperation project between Shandong University and Weichai Power Co. LTD-Automatic nano-composite brush plating technology and equipment. (31360005551213).