CNC machining parts include: CNC milling machine machining parts and CNC lathe machining parts, which often use: electrochemical polishing (also known as electrolytic polishing)
Electrolytic polishing is abbreviated as ECP in English. This machining method was invented by P.A. Jacques of France in 1931. Soon after, it was widely used in the surface treatment of CNC machining parts such as automobile parts; motorcycle parts; robot parts; automation equipment parts; drone parts; medical CNC machining parts, etc.
Principle:
The principle of electrolytic polishing is mainly:
The metal ions detached from the metal parts form a layer of phosphate film with the phosphoric acid in the polishing liquid adsorbed on the surface of the metal parts. This mucous film is thinner at the protrusions and thicker at the concave parts. Because the current density at the protrusions is high, it dissolves quickly. As the mucous film flows, the concave and convex changes continuously, and the rough surface is gradually leveled.
The metal part is connected to the positive pole of the DC power supply as an anode. Conductive materials corroded by electrolytes are used as cathodes
An electrolytic processing method that uses the principle that the microscopic convex points on the metal surface first undergo anodic dissolution in a specific electrolyte and at an appropriate current density to perform polishing
When the power is turned on for a certain period of time (generally tens of seconds to a few minutes), the tiny convex parts on the surface of the metal parts will first dissolve and gradually become a smooth and bright surface. The characteristics of electrolytic polishing are: ① The polished surface will not produce a metamorphic layer, no additional stress, and the original stress layer can be removed or reduced; ② Hard materials, soft materials, thin-walled, complex-shaped, and small parts and products that are difficult to polish mechanically can be processed; ③ The polishing time is short, and multiple parts can be polished at the same time, with high production efficiency; ④ The surface roughness that can be achieved by electrolytic polishing is related to the original surface roughness, and can generally be improved by two levels. However, due to the shortcomings of poor versatility, short service life, and strong corrosiveness of the electrolyte, the application scope of electrolytic polishing is limited. Electrolytic polishing is mainly used for metal products and parts with small surface roughness, such as reflectors, stainless steel tableware, decorations, injection needles, springs, blades and stainless steel tubes in medical equipment. It can also be used for polishing certain molds (such as bakelite molds and glass molds) and metallographic grinding discs.
Electrolytic polishing is mainly used for the surface brightening of stainless steel workpieces. Stainless steel workpieces are divided into 200 series, 300 series, and 400 series materials. Each series of materials must use a targeted electrolytic polishing liquid. For example, stainless steel of the 200 series must use the 200 series formula, which cannot be adapted to 300 series or 400 series stainless steel. This has always been a major problem, because some manufacturers' materials are combined workpieces, with both 200 series stainless steel and 300 or 400 series stainless steel.
Electrolytic polishing production process:
①Hanging electroplated metal parts.
②Electrochemical degreasing and film removal to facilitate electrochemical polishing.
③Wash with hot water first, then with cold water. If necessary, add ultrasonic field to thoroughly clean the oil, rust, acid, etc. on the surface.
④Electrochemical polishing to make the surface of the plated part smooth and bright, and improve the bonding strength of the coating.
⑤Wash in a flowing cold water tank to clean the polishing liquid remaining on the surface to prevent the surface from being corroded.
⑥Neutralize in an alkali tank to further remove the traces of acid.
⑦Wash in a moving cold water tank to remove the alkali remaining on the surface and make it neutral.
⑧Immerse in weak acid for a few seconds to expose the metallographic structure on the surface and improve the chemical and physical bonding strength of the surface.
⑨Wash in a cold water tank to eliminate the residual acid on the surface to avoid affecting the adhesion between the electroplated layer and the substrate.
⑩Electroplating in a copper plating tank to obtain a transitional coating on the surface of the plated part.
Effect of electrolytic polishing:
Improve the precision of various measuring tools and make the surface finish of products reach a very high level, especially for parts that have been mechanically polished in advance, they can achieve a mirror-like gloss, which is essential for the production of reflective equipment such as lighting fixtures. Electropolishing of cutting tools can eliminate the deformation layer on their surface, increase the finish of the tool working surface, improve the working conditions of cutting tools, extend the service life, and avoid the defects of metallographic structure deformation, hardness reduction, and even cracks on the tool surface after mechanical grinding and polishing. After electropolishing, measuring tools such as micrometers, vernier rulers, and cylindrical gauges can meet the extremely high finish and accuracy requirements required by measuring tools. In the medical device industry, electrolytic polishing is an ideal processing method for sharpening stainless steel suture needles and surgical instruments. For some special equipment, electropolishing can produce thorium, niobium, and uranium wires with a diameter of several microns and high surface finish, which are difficult to obtain by drawing methods, and their metallic luster will not darken after being placed for a long time. Electropolishing is also widely used in the preparation of metallographic grinding discs. Production practice has shown that when the original finish of the parts is low, the finish can generally be improved by 1 to 2 levels after electropolishing; when the original finish is high, the finish can be improved by 2 to 3 levels.
Electropolishing can also remove some mechanical damage on the metal surface. Compared with mechanical polishing, the surface after electropolishing is stress-free. However, it is not suitable to directly electropolish a surface that is too rough.
This method is often used to improve the surface finish of aluminum and its alloys, carbon steel, stainless steel and other non-ferrous metals to meet the needs of certain working conditions of components (such as the need to reduce the surface friction coefficient, require precise tolerance matching, etc.) and to improve the decorative appearance of metal products.
A bright surface can be obtained by extending the polishing time, increasing the polishing temperature and current density.
Electropolishing dissolves very little metal. Judging from the surface finishing after polishing and the surface finishing after polishing, the polishing thickness is usually between 2.5 and 65 μm.
the role and advantages of electrolytic polishing:
1. Improve surface finish: Electrolytic polishing can effectively remove the oxide layer, oil and impurities on the metal surface, thereby improving the surface finish.
2. Increase surface brightness: The polished metal surface has a higher reflectivity and refractive index, thereby increasing the brightness of the surface.
3. Eliminate surface defects: Electrolytic polishing can repair scratches, dents and other defects on the metal surface, making the surface smoother.
4. Improve corrosion resistance: The polished metal surface is smoother, which is conducive to improving its corrosion resistance.
5. Improve surface quality: Electrolytic polishing can improve the overall appearance quality of metal products and increase the market competitiveness of products.
Application of electropolishing in different fields:
1. CNC machining: Electropolishing is widely used in surface treatment of various metal materials, such as steel, aluminum, copper, etc.
2. Automobile industry: Electropolishing can be used for the manufacture and maintenance of automobile parts, such as engine cylinders, crankshafts, etc.
3. Aerospace industry: Electropolishing has a wide range of applications in the aerospace field, such as aircraft engine blades, aviation instrument panels, etc.
4. Consumer electronics industry: Electropolishing can be used for the manufacture and assembly of electronic components, such as circuit boards, capacitors, etc.
5. Robot parts and drone parts: Electropolishing makes the surface of robot parts and drone parts smooth and reduces friction between parts. At the same time, it can improve the accuracy of parts and is used for custom precision parts.
6. Medical device parts and medical equipment parts industry: As mentioned earlier, electropolishing is the most ideal processing method for some special medical parts.
If you are interested in other surface treatment methods, you can click to view the following short articles: nickel plating; zinc plating; oxidation; anodizing; material surface hardening; passivation; pickling; polishing; brushing; sandblasting...
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