New Progress in Electroplating Technology of High Fine Density New External Bite Wheel Materials

The significant advantages of the sand drop method are thin sand layer, good plating solution flowability, and small influence of sand layer on liquid phase mass transfer and conductivity process. Therefore, a higher current density can be used, resulting in higher production efficiency. But when using the sand drop method to make external meshing gear honing cutters, each sand drop can only cover a few teeth. In order to evenly coat all the teeth of the substrate with abrasive particles, it is necessary to reasonably divide the substrate and step by step electroplating with sand. Due to the simultaneous electroplating of the sanded and non sanded gear teeth, the rear sanded gear teeth obtained a thicker bottom nickel. According to different electroplating process parameters, the difference in bottom nickel thickness between two adjacent sanding wheel teeth is generally between 10m and 25m, which seriously affects the contour of the abrasive particles in the adjacent sanding coating on the substrate tooth surface, causing the resulting tool to lose accuracy. After diamond shaping and grinding wheel shaping, the tool accuracy can meet the requirements, but the service life of the honing tool will be significantly reduced after shaping. Therefore, it is necessary to control the contour of the abrasive particles as much as possible to avoid tool shaping.

The reasons for the quality problem of the gear honing tool coating are relatively complex, and analysis shows that the main causes are pinholes and hydrogen embrittlement caused by cathodic hydrogen evolution. The hydrogen evolution situation is closely related to the selection of plating solution formula and electroplating process parameters. The optimal plating solution formula and electroplating process parameters can be found through orthogonal experiments.

The quality of the thickened plating and electroformed coating after sand unloading plays a decisive role in the lifespan of the honing tool. In order to ensure the mechanical properties of the nickel plating layer, it is recommended to use the electroplating process parameters of the sanding process during thickening plating and electroforming. After all CBN abrasive particles are covered with nickel, in order to shorten the electroforming time, the current density can be increased. The thickness of electroforming is determined based on the tooth thickness of the honing cutter, generally ranging from 2mm to 5mm. The electroforming metal is determined based on the casting metal. If 45 steel is used for casting the core, bismuth can be selected as the electroforming metal. During casting, bismuth is melted to reduce the impact of high temperature on CBN. At the same time, the internal stress generated by the increase in volume of bismuth when it transitions from liquid to solid and the shrinkage of nickel and iron cooling volume is utilized to press the CBN abrasive particles out of the nickel layer and stick it to the surface of the negative mold, while promoting the separation of the nickel coating from the negative mold, This will facilitate demolding; If low-temperature alloys such as bronze core casting are used, nickel can be used for electroforming metal. Due to the different linear expansion coefficients of steel, nickel, and bronze at the same temperature, this difference will facilitate demolding after cooling.

The machining is based on the outer circle of the female mold, processing the inner hole and two end faces of the steel core. The machining of internal holes should be carried out on a high-precision internal grinding machine. Firstly, align the tool with an end face runout of within 1.5m and an outer circle deviation of within 1.5m. Grind the inner hole of the steel core based on the outer circle of the female mold, leaving a grinding allowance of 0.01mm. When grinding, it is necessary to ensure the coaxiality between the inner hole of the steel core and the outer circle of the female mold to ensure the accuracy of the cutting tool. End face machining can be carried out on an external cylindrical grinder, ensuring the perpendicularity between the end face and the hole during machining. After machining, demolding, inspection and repair processes can be carried out to obtain the finished product.

Analysis of Inner Plating Casting Process: The sand embedding method used in the sanding process of the inner plating casting process solves the impact of high and uniform abrasive particles on tool accuracy in the sand drop method, and avoids the influence of edge effects in electroplating on tool accuracy. In addition, after the abrasive particles are immersed in the coating, the tool life is increased by 2-3 times compared to the external plating method, and the machining accuracy level of the finished tool can reach G