Effective Techniques for Burr Removal in Manufacturing
Burrs are a common issue in metal processing. Regardless of the precision equipment used, burrs will form on the final product. They are excess metal remnants created on the edges of the processed material due to plastic deformation, especially in materials with good ductility or toughness.
The main types of burrs include flash burrs, sharp burrs, and splashes. These protruding metal residues do not meet the product design requirements. Currently, there is no effective way to completely eliminate this issue in the production process. Therefore, engineers must focus on removing burrs in the later stages to ensure the product meets design requirements. Various methods and equipment are available for removing burrs from different products.
In general, the methods of removing burrs can be divided into four categories:
1. Coarse grade (hard contact)
This category includes cutting, grinding, filing, and scraping.
2. Ordinary grade (soft contact)
This category includes belt grinding, lapping, elastic grinding, wheel grinding, and polishing.
3. Precision grade (flexible contact)
This category includes flushing, electrochemical processing, electrolytic grinding, and rolling.
4. Ultra-precision grade (precision contact)
This category includes various deburring methods, such as abrasive flow deburring, magnetic grinding deburring, electrolytic deburring, thermal deburring, and dense radium with strong ultrasonic deburring. These methods can achieve high part processing accuracy.
When selecting a deburring method, it’s important to take into account various factors, including the material properties of the parts, their structural shape, size, and precision, and to pay special attention to changes in surface roughness, dimensional tolerance, deformation, and residual stress.
Electrolytic deburring is a chemical method used to remove burrs from metal parts after machining, grinding, or stamping. It can also round or chamfer the sharp edges of the parts. In English, this method is referred to as ECD, which stands for Electrolytic Capacitive Discharge. During the process, a tool cathode (usually made of brass) is placed close to the burred part of the workpiece with a gap of usually 0.3-1 mm between them. The conductive part of the tool cathode is aligned with the edge of the burr, and the other surfaces are covered with an insulating layer to concentrate the electrolytic action on the burr.
The tool cathode is connected to the negative pole of a DC power supply, while the workpiece is connected to the positive pole. A low-pressure electrolyte (usually a sodium nitrate or sodium chlorate aqueous solution) with a pressure of 0.1-0.3MPa flows between the workpiece and the cathode. When the DC power supply is turned on, the burrs are removed by anode dissolution and carried away by the electrolyte.
After deburring, the workpiece should be cleaned and rust-proofed because the electrolyte is corrosive to a certain extent. Electrolytic deburring is suitable for removing burrs from hidden cross holes or complex-shaped parts and is known for its high production efficiency, usually taking only a few seconds to tens of seconds to complete the process. This method is commonly used for deburring gears, splines, connecting rods, valve bodies, crankshaft oil passage openings, and for rounding sharp corners. However, a drawback of this method is that the area around the burr is also affected by electrolysis, causing the surface to lose its original gloss and potentially affecting the dimensional accuracy.
In addition to electrolytic deburring, there are several other special deburring methods：
1. Abrasive grain flow to deburr
Abrasive flow processing technology is a new method for fine finishing and deburring that was developed abroad in the late 1970s. It is especially effective for removing burrs in the final stages of production. However, it is not suitable for processing small, long holes, or metal molds that have closed bottoms.
2. Magnetic grinding to deburr
Magnetic grinding for deburring originated in the former Soviet Union, Bulgaria, and other Eastern European countries in the 1960s. In the mid-1980s, in-depth research on its mechanism and application was conducted by Niche.
During magnetic grinding, the workpiece is put into the magnetic field formed by two magnetic poles. The magnetic abrasive is placed in the gap between the workpiece and the magnetic pole, and the abrasive is neatly arranged along the direction of the magnetic field line under the action of the magnetic field force to form a soft and rigid magnetic grinding brush. When the workpiece rotates the shaft in the magnetic field for axial vibration, the workpiece and the abrasive material move relatively, and the abrasive brush grinds the surface of the workpiece.
The magnetic grinding method can efficiently and quickly grind and deburr parts, and is suitable for parts of various materials, multiple sizes, and various structures. It is a finishing method with low investment, high efficiency, wide use, and good quality.
Currently, the industry has been able to grind and deburr the inner and outer surfaces of the rotator, flat parts, gear teeth, complex profiles, etc., remove the oxide scale on the wire rod, and clean the printed circuit board.
3. Thermal deburring
Thermal deburring (TED) is a process that uses hydrogen, oxygen, or a mixture of natural gas and oxygen to burn off burrs at high temperatures. The method involves introducing oxygen and natural gas or oxygen alone into a closed container and igniting it through a spark plug, causing the mixture to explode and release a large amount of heat energy that removes the burrs. However, after the workpiece is burned by the explosion, the oxidized powder will adhere to the surface of the CNC products and must be cleaned or pickled.
4. Miradium powerful ultrasonic deburring
Milarum’s strong ultrasonic deburring technology has become a popular method in recent years. It boasts a cleaning efficiency that is 10 to 20 times higher than that of ordinary ultrasonic cleaners. The tank is designed with evenly and densely distributed cavities, allowing the ultrasonic process to be completed in 5 to 15 minutes without the need for cleaning agents.
Here are the ten most common ways to deburr:
1) Manual deburring
This method is commonly used by general enterprises, employing files, sandpaper, and grinding heads as auxiliary tools. Manual files and pneumatic tools are available.
The labor cost is high, and the efficiency could be improved, particularly when removing complex cross holes. The technical requirements for workers are not very demanding, making it suitable for products with small burrs and simple structures.
2) Die deburring
The production die is utilized for deburring with the punch press. It incurs a specific production fee for the die (including rough die and fine stamping die) and may also necessitate the creation of a shaping die. This method is best suited for products with uncomplicated parting surfaces, and it offers better efficiency and deburring effects compared to manual work.
3) Grinding to deburr
This type of deburring includes methods such as vibration and sandblasting drums, and it is commonly used by businesses. However, it may not remove all imperfections completely, requiring manual finishing or the use of other methods to achieve a cleaner result. This method is best suited for small turning components produced in large quantities.
4) Freeze deburring
Cooling is used to rapidly embrittle the burrs, and then the projectile is ejected to remove the burrs. The equipment costs around two to three hundred thousand dollars and is suitable for products with small burr wall thicknesses and small sizes.
5) Hot blast deburring
Thermal energy deburring, also known as explosion deburring, involves directing pressurized gas into a furnace and causing it to explode, with the resulting energy used to dissolve and remove burrs.
This method is costly, technologically complex, and inefficient and may lead to side effects such as rust and deformation. It is primarily utilized in the production of high-precision parts, particularly in industries like automotive and aerospace.
6) Engraving machine deburring
The equipment is reasonably priced (tens of thousands) and is suitable for products with a simple spatial structure and a straightforward and regular deburring position.
7) Chemical deburring
Based on the principle of electrochemical reaction, the deburring operation is carried out automatically and selectively on metal parts.
This process is ideal for removing internal burrs that are hard to eliminate, as well as small burrs (less than seven wires in thickness) from products such as pump bodies and valve bodies.
8) Electrolytic deburring
Electrolytic machining is a method that uses electrolysis to remove burrs from metal parts. The electrolyte used in this process is corrosive, and it causes electrolysis in the vicinity of the burr, which can result in the loss of the part’s original luster and even affect its dimensional accuracy.
Electrolytic deburring is well-suited for removing burrs in hidden parts of cross holes or in casting parts with complex shapes. It offers high production efficiency, with deburring times generally ranging from a few seconds to tens of seconds. This method is suitable for deburring gears, connecting rods, valve bodies, crankshaft oil circuit orifices, and for rounding sharp corners.
9) High-pressure water jet deburring
When water is used as the medium, its immediate force is utilized to eliminate burrs and flashes after processing. This method also helps achieve the goal of cleaning.
The equipment is costly and is primarily utilized in the automotive industry and the hydraulic control systems of construction machinery.
10) Ultrasonic deburring
Ultrasonic waves create instant high pressure to eliminate burrs. Mainly used for microscopic burrs; if they require observation with a microscope, ultrasound can be used for removal.
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