Burrs are everywhere in the metal processing process. No matter how advanced precision equipment you use, it will be born together with the product. It is mainly a kind of excess iron filings generated at the processing edge of the material to be processed due to the plastic deformation of the material. Especially materials with good ductility or toughness are particularly prone to burrs. The main types of burrs include flash burrs, sharp corner burrs, spatter and other protruding excess metal residues that do not meet product design requirements.
Regarding this problem, there is no effective method to eliminate it in the production process so far. Therefore, in order to ensure the design requirements of the product, engineers can only work hard on the removal of burrs in the back process. So far, there are many different methods and equipment for removing burrs for different products.
Generally speaking, burr removal methods can be divided into four categories:
1. Coarse level (hard contact)
Belonging to this category are cutting, grinding, filing and scraper processing.
2. Normal level (soft touch)
Belonging to this category are belt grinding, grinding, elastic wheel grinding and polishing.
3. Precision grade (flexible contact)
Belonging to this category are flushing processing, electrochemical processing, electrolytic grinding and rolling processing.
4. Ultra-precision level (precision contact)
Belonging to this category are abrasive flow deburring, magnetic grinding deburring, electrolytic deburring, thermal deburring and dense radium powerful ultrasonic deburring, etc. This type of deburring method can obtain sufficient part processing accuracy.
When we choose a deburring method, we must consider many factors, such as the material characteristics of the part, structural shape, size and precision. In particular, we must pay attention to changes in surface roughness, dimensional tolerances, deformation, and residual stress.
The so-called electrolytic deburring is a chemical deburring method. It can remove burrs after machining, grinding and stamping, and round or chamfer the sharp edges of metal parts.
An electrolytic processing method that uses electrolysis to remove burrs from metal parts, referred to as ECD in English. Fix the tool cathode (usually made of brass) near the burr part of the workpiece, with a certain gap (usually 0.3~1 mm) between them. The conductive part of the tool cathode is aligned with the burr edge, and the other surfaces are covered with an insulating layer to concentrate the electrolysis on the burr part.
During processing, the cathode of the tool is connected to the negative pole of the DC power supply, and the workpiece is connected to the positive pole of the DC power supply. A low-pressure electrolyte (usually sodium nitrate or sodium chlorate aqueous solution) with a pressure of 0.1 to 0.3 MPa flows between the workpiece and the cathode. When the DC power supply is turned on, the burrs are removed by dissolving the anode and are taken away by the electrolyte.
The electrolyte is corrosive to a certain extent, and the workpiece should be cleaned and rust-proofed after deburring. Electrolytic deburring is suitable for removing burrs from cross holes in hidden parts or parts with complex shapes. It has high production efficiency and the deburring time generally only takes a few seconds to tens of seconds.
This method is commonly used for deburring gears, splines, connecting rods, valve bodies and crankshaft oil passage openings, as well as sharp corner rounding, etc. The disadvantage is that the vicinity of the burrs of the parts is also affected by electrolysis, and the surface will lose its original luster and even affect the dimensional accuracy.
Of course, in addition to electrolytic burr removal, there are also the following special burr removal methods:
1. Abrasive flow deburring
Abrasive flow machining (AFM) is a new finishing and deburring process developed abroad in the late 70s. It is particularly suitable for removing burrs on parts just entering the finishing stage, but is unsuitable for small, long holes, metal dies with blind bottoms, and similar features.
2. Magnetic grinding and deburring
This method originated in the 60s in the former Soviet Union, Bulgaria, and other Eastern European countries. In the mid-80s, Nippon Sharyo conducted in-depth research into its mechanisms and applications.
In magnetic abrasive finishing, the workpiece is placed in a magnetic field formed by two magnetic poles, and magnetic abrasive particles are introduced into the gap between the workpiece and the poles. Under magnetic force, the abrasive aligns neatly along the magnetic field lines, forming a soft magnetic abrasive brush with a degree of stiffness. As the workpiece rotates and vibrates axially in the magnetic field, relative motion between the workpiece and abrasive allows the brush to finish the workpiece surface. Magnetic abrasive finishing can grind and deburr parts quickly and efficiently. It is suitable for parts of various materials, sizes and structures, providing a finishing method with low investment, high efficiency, broad applicability and good quality.
At present, foreign countries can grind and deburr the inner and outer surfaces of rotating bodies, flat parts, gear teeth, complex surfaces, etc., remove oxide scale on wires, and clean printed circuit boards, etc.
3. Thermal deburring
Thermal deburring (TED) uses the high temperature generated after the deflagration of the mixture of hydrogen and oxygen gas or oxygen and natural gas to burn off the burrs. It is to pass oxygen and oxygen or natural gas and oxygen into a closed container, and ignite it through a spark plug, so that the mixture explodes in an instant and releases a large amount of heat energy to remove burrs. However, after the workpiece undergoes explosive combustion, its oxidized powder will adhere to the surface of the workpiece and must be cleaned or pickled.
4. Mi radium powerful ultrasonic deburring
MiLa powerful ultrasonic deburring technology is a deburring method that has become popular in recent years. The attached cleaning efficiency is 10~20 times that of ordinary ultrasonic cleaning machines. The holes are evenly distributed in the water tank, so that ultrasonic waves can be completed simultaneously within 5~15 minutes without the use of cleaning agents.
We have compiled 10 the most common deburring methods for everyone:
1) Manual deburring
This is also a method commonly used by general enterprises, using files, sandpaper, grinding heads, etc. as auxiliary tools. The files have manual filing and pneumatic shifting.
Brief comment: The labor cost is expensive, the efficiency is not very high, and it is difficult to remove complex cross holes. The technical requirements for workers are not very high, and it is suitable for products with small burrs and simple product structures.
2) Die deburring
Use a die and a punch to remove burrs.
Brief comment: A certain punching die (rough die + fine punching die) production fee is required, and a shaping die may also be required. It is suitable for products with relatively simple parting surfaces, and the efficiency and deburring effect are better than manual work.
3) Grinding and deburring
This type of deburring includes vibration, sandblasting, roller and other methods, which are currently used by many companies.
Brief comment: There is a problem that the removal is not very clean, and it may be necessary to manually deal with the remaining burrs or use other methods to remove burrs. Suitable for small products with larger batches.
4) Frozen deburring
Use cooling to quickly embrittle the burrs, and then spray projectiles to remove the burrs.
Brief assessment: The equipment costs approximately 200,000–300,000 yuan and is suitable for small products with thin burrs.
5) Thermal blast deburring
It is also called thermal deburring and explosion deburring. By passing some flammable gas into an equipment furnace, and then through the action of some media and conditions, the gas explodes instantly, and the energy generated by the explosion is used to dissolve and remove burrs.
Brief assessment: The equipment is expensive, costing over one million yuan, requires skilled operation, has low efficiency, and can cause side effects such as rust and deformation. It is mainly used for high-precision components, including automotive and aerospace parts.
6) Engraving machine deburring
Brief assessment: The equipment is relatively inexpensive, costing tens of thousands of yuan. It is suitable for parts with simple spatial geometry and straightforward, regularly arranged deburring locations.
7) Chemical deburring
Using the principle of electrochemical reaction, parts made of metal materials can be automatically and selectively deburred.
Brief comment: It is suitable for internal burrs that are difficult to remove, and is suitable for small burrs on pump bodies, valve bodies and other products (thickness less than 7 wire).
8) Electrolytic deburring
An electrolytic machining method that uses electrolysis to remove burrs from metal parts.
Brief comment: The electrolyte is corrosive to a certain extent, and the parts near the burrs are also affected by electrolysis. The surface will lose its original luster and even affect the dimensional accuracy. The workpiece should be cleaned and rust-proofed after deburring. Electrolytic deburring is suitable for removing burrs from cross holes in hidden parts or parts with complex shapes. It has high production efficiency and the deburring time generally only takes a few seconds to tens of seconds. It is suitable for deburring gears, connecting rods, valve bodies and crankshaft oil passage openings, as well as sharp corner rounding, etc.
9) High-pressure water jet deburring
Using water as a medium, its instantaneous impact force can be used to remove burrs and flash generated after processing, and at the same time achieve the purpose of cleaning.
Brief comment: The equipment is expensive and is mainly used in the heart of automobiles and the hydraulic control system of construction machinery.
10) Ultrasonic deburring
Ultrasonic waves generate instantaneous high pressure to remove burrs.
Brief comment: Mainly for some microscopic burrs. Generally, if the burrs need to be observed with a microscope, you can try to use ultrasonic method to remove them.
(Source: Frontier CNC Technology)