What is burr？
Speaking of burr, first of all, let’s understand what burr are?
Burr refers to the extremely fine micro metal particles formed on the machined surface of the workpiece.
They are residues or very fine micro metal particles formed in metal casting, grinding, cutting, milling and other similar cutting processes.
Classification of burr
The generation of burr varies with different processing methods. According to different processing methods, burr can be roughly divided into:
1. Casting burr:
The size of the burr of the excess material produced at the joint of the mold or the root of the gate is generally expressed in millimeters.
2. Forging burr:
At the joint of the metal mold, it is caused by plastic deformation of the forging material.
Electric welding and gas welding burr:
Electric welding burr refers to the burr that the filler at the weld protrudes from the surface of the part;
Gas welding burr is the slag overflowing from the cut when the gas is cut.
3. Stamping burr:
During stamping, there is a gap between the punch on the die and the lower die, or between the cutters at the notch, and burr are generated due to die wear.
The shape of the stamping burr varies according to the material of the plate, the thickness of the plate, the gap between the upper and lower dies, and the shape of the stamped parts.
4. Cutting burr:
Turning, milling, planing, grinding, drilling, reaming and other processing methods can also produce burr.
Burr produced by various machining methods have different shapes with different tools and process parameters.
5. Plastic forming burr:
Like casting burr, burr generated at the joint of plastic mold.
How to deburr?
Because of the gap at the joint between the mold and the die, burrs are generated.
At present, the perfect combination between the mold and the die cannot be achieved, so it is difficult to completely avoid the generation of burrs.
However, with the development of metal materials in the direction of high hardness, high strength and high toughness, there are more and more complex and various integral components in mechanical products, and the difficulty of deburring is also increasing.
With the development of science and technology and the continuous improvement of our product performance, the requirements for product quality are becoming more and more strict, and it is increasingly important to remove burrs from workpieces.
The appearance of burr not only affects the appearance of products, but also greatly reduces the quality standard of metal workpieces, and affects the assembly, service performance and life of products.
Therefore, we should try our best to select good cutting tools to prevent burr during machining, such as high-quality milling cutters with good finish, which can effectively avoid burr.
In order to remove burrs, in addition to selecting good tools to avoid, it is usually necessary to carry out secondary operation of deburring.
Three deburring and edge finishing of precision parts may account for 30% of the cost of finished parts.
In addition, the secondary finishing operation is difficult to be automated, so burring has really become a very difficult problem.
The traditional manual deburring operation can hardly meet the requirements of the above development for deburring, and various mechanized and automatic deburring new technologies and processes emerge as the times require.
Next, I will introduce the following deburring methods:
1. Die deburring
The burr is removed by making a die and cooperating with a punch press.
Blanking die deburring requires a certain amount of rough die and fine blanking die production costs, and it may also need to make a shaping die, and the module may need to be replaced for a long time.
It is suitable for products with simple parting surface, and the efficiency and effect of deburring are better than that of manual method.
2. Grinding deburring
Grinding deburring is a method of deburring through vibration, sandblasting, roller and other methods, which is also widely used by enterprises.
The problem of grinding deburring is that sometimes the removal is not very clean, which may require subsequent manual treatment or deburring in cooperation with other methods.
This method is suitable for small products with large quantities.
3. High temperature deburring
High temperature deburring, also known as thermal deburring and thermal explosion deburring, is a method of introducing some natural gas into an equipment furnace, and then making the gas explode instantaneously through the action of some media and conditions, and using the energy generated by the explosion to dissolve and deburr.
The equipment required for this method is expensive, usually more than one million yuan, and the requirements for operating technology are also high.
The deburring efficiency is low, and side effects such as rust and deformation will also be caused.
Thermal explosion deburring is mainly used in some high-precision parts, such as automotive and aerospace parts.
4. Freeze deburring
This is a method that uses a sudden temperature drop to quickly embrittle the burr, and then sprays bullets to remove the burr.
Frozen deburring is suitable for products with small burr wall thickness and small workpieces.
The price of the whole set of equipment is not low, about two to three hundred thousand yuan.
5. Chemical deburring
Chemical deburring is a process of automatically and selectively deburring metal parts based on the principle of electrochemical reaction.
It is suitable for those internal burrs that are difficult to remove, especially for removing fine burrs on pump body, valve body and other products.
6. Engraving machine deburring
Using the engraving machine to remove burrs on the workpiece, the price of this set of equipment is not very expensive, usually only tens of thousands of yuan, which is suitable for removing burrs with simple spatial structure and simple and regular positions.
7. Electrolytic deburring
A method of removing burrs from metal parts by electrolysis.
The tool cathode (usually brass) is fixed near the burred part of the workpiece with a certain gap between them.
During machining, the tool cathode is connected to the negative pole of DC power supply, and the workpiece is connected to the positive pole of DC power supply.
Let the low-pressure electrolyte flow between the workpiece and the cathode.
After the DC power supply is connected, the burr will be dissolved by the anode and removed, and taken away by the electrolyte.
It is used to remove the burr of hidden parts, cross holes or complex shaped parts, with high efficiency.
Generally, it takes only a few seconds to several tens of seconds.
It is suitable for deburring gears, connecting rods, valve bodies and crankshaft oil passage orifices, as well as sharp corner rounding.
The vicinity of the burr of the part is also affected by electrolysis, and the original luster of the surface will be lost, and even the dimensional accuracy will be affected.
However, electrolyte has corrosive effect, and after deburring, it needs cleaning and rust prevention.
8. Ultrasonic deburring
The propagation of ultrasonic wave can also generate instantaneous high pressure, which can be used to remove burrs on parts.
This method has high accuracy and is mainly used to remove some micro burrs that can only be observed through a microscope.
9. High pressure water jet deburring
The instantaneous impact of water is used to remove burrs and flash generated after machining, and at the same time, the purpose of cleaning can be achieved.
And it is divided into two types: workpiece moving type and nozzle moving type.
Workpiece moving type
Low cost, suitable for deburring and cleaning of simple valve body.
Its disadvantage is that the matching degree between nozzle and valve body is not ideal, and the deburring effect of cross holes and oblique holes in the valve body is not good.
The distance between the nozzle and the burr generating part of the valve body can be effectively adjusted through CNC control, which effectively corresponds to the burr of the cross hole, oblique hole and blind hole inside the valve body.
However, due to the high cost of this equipment.
Good removal effect and fast speed.
Simple equipment is not ideal, and ideal equipment is not cheap.
10. Deburring of mechatronic device
Mechatronic devices comprehensively use the latest research results of machinery and precision machinery, microelectronics and computers, automatic control and drive, sensors and information processing, artificial intelligence and other disciplines.
Typical parts include aluminum hub, frequency converter housing, synchronizer housing, synchronizer gear hub, bearing cover, cylinder block, valve body, valve cover, output shaft, engine gear, etc.
Medium cost, good effect, high accuracy and high efficiency.
In the developing stage, it has not reached the level of popularity, and needs very accurate data support.
11. Magnetic deburring
Using the unique magnetic field distribution, it produces a strong and stable magnetic induction effect, so that the magnetic steel needle and the workpiece can be fully ground in all directions and multi angles, so as to achieve the effect of fast deburring.
It has special effects on complex shapes, multi hole crevices, internal and external threads, etc.
For products with magnetism, it is easy to destroy the magnetism of the product itself. Please use with caution.
12. Manual deburring
Manual deburring is also used by most small manufacturers at present.
Most of them are small burrs, and the burr removal rate is not high, as long as there is no burr.
The tools used for manual deburring used to be files, scrapers, sandpapers, etc., but now they are mainly edge trimmers.
Flexible manual operation, deburring of different parts of the workpiece can be carried out by replacing different tools.
The labor cost is expensive, the efficiency is low, and it is not easy to remove some cross holes and complex workpieces.
13. Deburring with hand tools
This kind is not much different from manual deburring, except that it uses different things.
Manual deburring, using cold tools for deburring.
Here are some tools.
For example, tools such as grinding machine and electric drill can also deburr and chamfer with milling cutter, drill bit, grinding head and other materials.
Deburring of most workpieces can be completed with different tools.
Advantages: high flexibility, can adapt to the grinding of most workpiece environments.
Disadvantages: slow speed, easy to cause a certain loss to the workpiece.
14. Process deburring
How to avoid burr in process design?
Here are six measures to avoid burrs in process design:
1) Adopt reasonable processing methods:
In the process of metal cutting, the burr size and shape produced by various processing methods are different.
In the process design, the processing method with small burr generation should be selected as far as possible.
For example, when machining planes, the effect of down milling is better than that of down milling.
2) Arrange the processing sequence reasonably:
When arranging the processing sequence of parts, try to arrange the process with large burr in the front, and arrange the process with small burr in the back, and use the processing of the next process to remove the burr generated in the previous process.
For example, for the machining of shaft parts with keyways, it is reasonable to change the general machining sequence of turning before milling to milling before turning.
3) Reasonable choice of direction:
According to the corner effect of burr, during metal cutting, the outlet should be located at the part with large corner angle to reduce burr generation.
At the same time, it should also be noted that the cutting edge should be located at the position where burring is easy to remove, so as to reduce the cost of burring.
4) Reasonable selection of cutting parameters:
In the cutting process of parts, if the machining method of producing large chips is adopted, the burr generated will be large.
Because when large chips are produced, the cutting resistance increases, the cutting heat increases, the tool wear increases, the durability decreases, and the plastic deformation of the workpiece material also increases, which makes the burr generated larger.
Therefore, in the processing of parts, it is generally to reduce the burr generation by reducing the cutting depth and the cutting amount, especially in the precision processing of parts.
5) Arrange heat treatment process reasonably:
The heat treatment process is reasonably arranged at different stages of the processing process to change the physical and mechanical properties such as the hardness and elongation of the workpiece material, which can reduce the burr generated during the processing of parts.
For example, in the production of parts in batches, if the forming grinding wheel is used to grind the snap ring groove of shaft parts at one time after heat treatment, more burrs will be generated than the process of reheating treatment after turning.
6) Processing with accessories:
In the process of part cutting, various accessories can be used at the cutting edge of the part, such as auxiliary support, mandrel or low melting point alloy filler.
It is used to improve the rigidity of the cutting edge of the machined part, reduce the cutting deformation, and reduce the generation of burrs at the cutting edge.
In the process of processing, burr is inevitable, so it is best to solve the burr problem from the process to avoid excessive manual intervention.