Now many industries of precision parts will use CNC machining production, but after CNC machining is completed, many products surface is still relatively rough, this time you need to carry out secondary surface finishing treatment.
First of all, surface treatment is not suitable for all CNC processing products, some products can be directly used after processing, and some need to be hand-polished, electroplating, oxidation, radium carving, screen printing, powder spraying and other special processes. Here are some things you should know about surface treatment.
1, improve product accuracy; After the product processing is completed, some products have a rough surface and leave a large residual stress, which will reduce the accuracy of the product and affect the precision of the match between the parts. In this case, the product surface treatment is required.
2, provide product wear resistance; If the parts usually use scenarios are interacting with other parts, long-term use will increase part wear, which also requires processing of the product surface to extend the service life of the parts.
3, improve the corrosion resistance of the product; Parts used for a long time in highly corrosive places require special surface treatment, requiring polishing and spraying of anti-corrosion materials. Improve corrosion resistance and service life of the product.
The above three points are the prerequisites for surface processing after CNC precision parts processing, and several surface treatment methods will be introduced below.
What is electroplating? What are the types and applications of electroplating?
01. What is electroplating?
Electroplating refers to the surface engineering technology of obtaining a solid metal film on the surface of the substrate by electrolysis in a salt solution containing the metallized group, with the metallized group as the cathode and the metallized group or other inert conductor as the anode under the action of direct current.
02. Why electroplate?
The purpose of electroplating is to improve the appearance of the material, while giving the surface of the material a variety of physical and chemical properties, such as corrosion resistance, decorative, wear resistance, brazing and electrical, magnetic, optical properties.
03. What are the types and applications of electroplating?
1, galvanized
The galvanized layer is of high purity and is an anodic coating. The zinc layer plays a mechanical and electrochemical protective role on the steel matrix.
Therefore, galvanized layer is widely used in machinery, hardware, electronics, instruments, light industry and other aspects, is one of the most widely used plating species.
2. Copper plating
The copper coating is a cathode polar coating, which can only play a mechanical protection role on the base metal. The copper plating layer is usually not used as a protective decorative coating alone, but as the bottom or middle layer of the coating to improve the adhesion between the surface coating and the base metal.
In the field of electronics, such as through hole copper plating on printed circuit boards, as well as hardware technology, crafts, furniture decoration and other fields.
3. Nickel plating
Nickel plating layer is a negative polarity protective layer, which only has a mechanical protection effect on the base metal. In addition to the direct use of some medical devices and battery shells, the nickel-plated layer is often used as the bottom or middle interval layer, which is widely used in daily hardware, light industry, home appliances, machinery and other industries.
4. Chrome plating
The chromium-plated layer is a negative polarity coating, which only plays a mechanical protection role. Decorative chrome plating, the bottom layer is generally polished or electrodeposited bright coating.
Widely used in instruments, meters, daily hardware, household appliances, aircraft, automobiles, motorcycles, bicycles and other exposed parts. Functional chrome plating includes hard chrome plating, porous chrome, black chrome, opal chrome and so on.
Hard chrome layer is mainly used for various measuring calipers, gauges, cutting tools and various types of shaft, loose hole chrome layer is mainly used for cylinder cavity piston failure; The black chrome layer is used for parts that need a dull surface and wear resistance, such as aviation instruments, optical instruments, photographic equipment, etc. Opalescent chromium is mainly used in various measuring tools.
5. Tin plating
Compared to the steel substrate, tin is a negative polar coating, while compared to the copper substrate, it is an anode coating. The tinning layer is mainly used as the protective layer of thin plate in the can industry, and most of the malleable iron skin is made of iron plate tinning. Another major use of tin coatings is in the electronics and power industries.
6, alloy plating
In a solution, two or more metal ions are co-precipitated on the cathode to form a uniform fine coating process called alloy plating.
Alloy electroplating is superior to single metal electroplating in crystal density, porosity, color, hardness, corrosion resistance, wear resistance, magnetic conductivity, wear resistance and high temperature resistance.
There are more than 240 kinds of electroplating alloys, but less than 40 kinds are actually used in production. It is generally divided into three categories: protective alloy coating, decorative alloy coating and functional alloy coating.
Widely used in aviation, aerospace, navigation, automobile, mining, military, instruments, meters, visual hardware, tableware, Musical Instruments and other industries.
In addition to the above, there are other chemical plating, composite plating, non-metal plating, gold plating, silver plating and so on.
What is polishing?
The surface of the items processed by CNC machining or 3D printing is sometimes rough, and the surface requirements of the products are high, so they need to be polished.
Polishing refers to the use of mechanical, chemical or electrochemical action to reduce the surface roughness of the workpiece in order to obtain a bright, flat surface processing method.
Polishing can not improve the dimensional accuracy or geometric accuracy of the workpiece, but for the purpose of obtaining a smooth surface or mirror gloss, and sometimes to eliminate gloss (extinction).
Several common polishing methods are described below:
01. Mechanical polishing
Mechanical polishing is by cutting, plastic deformation of the surface of the material to remove the polished convex and smooth surface polishing method, the general use of whetstone strip, wool wheel, sandpaper, etc., mainly manual operation, surface quality requirements can be used to super-fine polishing method.
Super finishing polishing is the use of special grinding tools, in the polishing liquid containing abrasive, tightly pressed on the workpiece to be machined surface, for high-speed rotation. This method is often used in optical lens molds.
02. Chemical polishing
Chemical polishing is to dissolve the microscopic protruding part of the surface of the material in the chemical medium preferentially than the concave part, so as to obtain a smooth surface.
The main advantage of this method is that it does not require complex equipment, can polish the workpiece with complex shape, and can polish many workpieces at the same time, with high efficiency.
The core problem of chemical polishing is the preparation of polishing liquid.
03. Electrolytic polishing
The basic principle of electrolytic polishing is the same as that of chemical polishing, that is, the surface is smooth by selectively dissolving small protruding parts on the surface of the material.
Compared with chemical polishing, the effect of cathode reaction can be eliminated and the effect is better.
04. Ultrasonic polishing
The workpiece is put into the abrasive suspension and placed together in the ultrasonic field, and the abrasive is ground and polished on the workpiece surface by relying on the oscillation of the ultrasonic wave.
Ultrasonic processing macroscopic force is small, will not cause workpiece deformation, but tooling production and installation is more difficult.
05. Fluid polishing
Fluid polishing relies on high-speed flowing liquid and the abrasive particles it carries to wash the surface of the workpiece to achieve the purpose of polishing.
Common methods are: abrasive jet processing, liquid jet processing, hydrodynamic grinding and so on. Hydrodynamic grinding is driven by hydraulic pressure to make the liquid medium carrying abrasive particles flow through the surface of the workpiece at high speed.
The medium is mainly made of special compounds with good flow under low pressure and mixed with abrasives, which can be silicon carbide powder.
06. Magnetic grinding polishing
Magnetic grinding and polishing is the use of magnetic abrasive under the action of magnetic field to form an abrasive brush, grinding the workpiece.
This method has the advantages of high processing efficiency, good quality, easy control of processing conditions and good working conditions.
The above are 6 common polishing processe.
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