Since the 1990s, the global economy has recovered and has shown a trend of accelerating growth. The production and sales of the global plastics industry have also shown a steady growth trend. It is predicted that the global demand for plastics will reach 200 million tons in 2007 and 380 million tons in 2020. As one of the basic materials for modern social and economic development, plastic has been widely applied to various fields of the national economy, and steel, wood and cement have become the four pillars of the material field. Therefore, research and development of plastic molding technology has great engineering significance. Plastic mold is one of the important equipments in plastic molding processing. It plays an important role in the manufacturing process of plastic products, directly affecting the quality and performance of plastic products. With the development of plastic molds in the direction of small, precise, diversified and large, complex and precise, the manufacturing process is increasingly complex, the production cycle is long, and the production cost is high. In particular, most precision molds are imported from abroad, and the price is extremely high, and there are few standard accessories. If it is an early failure, it will cause significant economic losses to the company. There is therefore a great need for a convenient way to replenish metal to the mold to restore the mold surface.
In practice, there are several ways to choose from. The earlier method used was the soldering process. The weld adhesion is very good, but the weld layer contains a large amount of oxide, and welding inevitably causes stress in the metal, resulting in thermal deformation or crack formation. The newer process is spark or plasma, which is quick and easy and can form 2 5.4 mm thick metal, alloy, metal oxide or carbide layers on the surface of the part. However, such process equipment is expensive, and the adhesion of the deposited layer generally requires subsequent machining, and the deposited layer usually contains more pores. In recent years, a new type of metal deposition process has emerged, which is commonly used in the processing area of ​​about 1 m2, and the thickness of the deposited layer is about l" to lmm. It is mainly used in applications where high-quality metals need to be deposited. This method is called electrochemical plating. Process.
1 The basic principle and characteristics of electrochemical plating 1.1 The basic principle of electrochemical plating This process is simple to operate, just like arc welding, the cathode wire is clamped on the mold or machine. The anode lead is connected to a cotton or polyester coated anode and the power supply assembly is adjusted to a suitable voltage value. The anode pad is immersed in a small amount of electrolyte and moves back and forth over the surface of the mold until a uniform desired metal deposition layer is formed. In order to monitor the thickness of the metal layer, the power pack should also contain an energy meter whose reading is proportional to the thickness of the metal coating.
1.2 Electrochemical Plating General Process Electrochemical plating The general process consists of three parts: pre-plating pretreatment, plating and electroplating, and each part contains several processes. During the operation, the plating parts should be rinsed off immediately after each process.
(1) Pre-plating pretreatment 1 Surface refurbishment: The surface of the parts to be plated must be smooth, usually sanded with sandpaper and metallographic sandpaper.
2 Surface cleaning: chemical and mechanical methods are used to clean the oil stains and rust spots on the surface of the plated parts.
3 electric net treatment: electric net treatment is electrolytic degreasing. The same degreasing solution is used for any base metal in brush plating, except that the voltage and degreasing time required for different base metals are different. The surface after electric cleaning has no oil traces, and it is well immersed in water and does not hang water drops.
4 activation treatment: used to remove the oxide film that may be formed after the degreasing of the plated part and subject the surface of the plated part to a slight etching to present the crystal structure of the metal, ensuring that the metal ions can be reduced on the surface of the fresh substrate and firmly bonded to the substrate. A plating layer of good strength is formed.
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