What is burr ？
Regarding burrs, let's start by defining what burrs are.
Burrs are tiny particles of metal that form on the machined surface of a part. These fine particles are created as a result of metal casting, grinding, cutting, milling and other similar processes.
Burr Classification
Burr formation varies depending on the manufacturing process used. Based on these processes, burrs can generally be classified into:
1. Casting Burr:
Typically, the size of flash, which is the excess material produced at the mold joint or gate root, is measured in millimeters.
2. Forging Burr:
At the metal mold joint, burrs are caused by the plastic deformation of the forged material.
Electric welding and gas welding burrs:
Electric welding burr refers to excess filler material protruding from the surface of the part.
Gas welding burrs are the slag that overflows from the cut during the gas cutting process.
3. Stamping burr:
During stamping, there is a gap between the die punch and the lower die, or between the cutters in the slot, which results in the generation of burrs due to die wear.
The shape of the stamping burr varies depending on factors such as the plate material, the plate thickness, the space between the upper and lower dies, and the shape of the stamped parts.
4. Burr Cutting:
Turning, milling, planing, grinding, drilling, reaming and other processing methods can also create burrs.
The burrs produced by these different machining methods have different shapes, which are influenced by the type of tool used and the process parameters.
5. Plastic forming burr:
Such as casting burrs, burrs generated at the plastic mold joint.
How to deburr?
The generation of burrs occurs due to the gap in the joint between the mold and the die.
Currently, it is challenging to completely eliminate burrs due to imperfect alignment between the mold and die.
However, with advances in metal materials that are becoming harder, stronger and more durable, there are an increasing number of complex integral components in mechanical products, making deburring increasingly difficult.
As technology advances and product performance improves, the demand for higher quality products grows, making removing burrs from parts increasingly important.
The presence of burrs not only impairs the appearance of products, but also significantly reduces the quality standard of metal parts and affects their assembly, performance and useful life.
To mitigate the occurrence of burrs, it is essential to choose high-quality cutting tools that minimize their appearance, such as cutters with a smooth finish.
Even with the proper tools, burr removal may still require a secondary deburring operation.
This secondary deburring process can account for up to 30% of the cost of finished parts and is difficult to automate, making burrs a persistent problem.
Manual deburring techniques are insufficient to meet the demands of modern deburring requirements, leading to the development of new technologies and automated deburring processes.
Next, I will discuss the following deburring methods:
1. Deburring
The deburring process is carried out using a die in conjunction with a punching machine.
Deburring the cutting die incurs production costs for both the rough cutting die and the fine cutting die and may require the creation of a shaping die. Additionally, tools may need to be replaced frequently.
This method is suitable for products with a simple cutting surface and is more efficient and effective than manual deburring.
2. Deburring grinding
Grinding deburring is a widely used method for deburring, which involves techniques such as vibration, sandblasting and roller.
However, the problem with rough deburring is that it does not always result in a completely smooth surface, which may require additional manual intervention or the use of additional deburring methods.
This method is ideal for small products produced in large quantities.
3. High temperature deburring
High temperature deburring, also known as thermal deburring and thermal explosion deburring, is a process that involves introducing natural gas into an equipment furnace and causing it to explode instantly through specific media and conditions. This explosion generates energy that is used to dissolve and remove burrs.
This method requires expensive equipment, typically costing more than one million yuan, and operates with high technological requirements.
However, the deburring efficiency of this method is low and may result in side effects such as rust and deformation.
Thermal explosion deburring is mainly used on high-precision parts in industries such as automotive and aerospace.
4. Freeze deburring
Frozen flashing is a process that involves a rapid drop in temperature to make the flash brittle quickly, followed by projectile spraying to remove it.
This method is ideal for products with thin walls of burrs and small parts.
However, the cost of the complete set of equipment is not cheap, typically ranging from two to three hundred thousand yuan.
5. Chemical deburring
Chemical deburring is an automated process that selectively removes burrs from metal parts using the principle of electrochemical reaction. It is particularly useful for removing difficult-to-remove internal burrs, such as fine burrs on pump bodies, valve bodies and other similar products.
6. Deburring of engraving machine
The cost of this set of equipment for removing burrs on workpieces using an engraving machine is normally only tens of thousands of yuan, making it an affordable option for burr removal with simple spatial structures and regular positions.
7. Electrolytic deburring
A technique for removing burrs from metal components using electrolysis:
The cathode tool, typically made of brass, is positioned close to the deburred section of the metal part with a specific distance between them.
During machining, the cathode tool is connected to the negative terminal of a DC power source, while the metal workpiece is connected to the positive terminal.
The low-pressure electrolyte can then flow between the metal part and the cathode.
Once the DC power supply is activated, the burr will be dissolved by the anode and removed, carried away by the electrolyte.
Benefits:
It is used to remove burrs from hidden parts, cross holes or complex shaped components with high efficiency.
Typically, the process only takes a few seconds to a few tens of seconds.
It is ideal for deburring gears, connecting rods, valve bodies, crankshaft oil passage holes, as well as rounding sharp corners.
Disadvantages:
The area around the component's burr is also impacted by electrolysis, causing the original surface shine to be lost and potentially affecting its dimensional accuracy.
In addition, the electrolyte has a corrosive effect, so it is necessary to clean and prevent rust after deburring.
8. Ultrasonic deburring
The transmission of ultrasonic waves can also produce momentary high pressure, which can be used to eliminate burrs on components. This method has high precision and is mainly used to eliminate small burrs that can only be seen under a microscope.
9. High pressure water jet deburring
The instantaneous impact of water is used to eliminate burrs and burrs produced during machining, in addition to fulfilling the purpose of cleaning.
It is categorized into two categories: parts movement type and nozzle movement type.
Type of part movement
This tool is economical and suitable for deburring and cleaning simple valve bodies. However, it has the disadvantage that the compatibility between the nozzle and the valve body is not optimal and may not provide effective deburring for transverse and oblique holes in the valve body.
Movable nozzle
The distance between the nozzle and the burr-generating part of the valve body can be adjusted effectively through CNC control, which corresponds to the burrs in the transverse, oblique and blind holes inside the valve body. However, this equipment is prohibitively expensive.
Benefits:
Good removal effect and fast speed.
Disadvantages:
The basic equipment is not enough and the premium equipment is not affordable.
10. Mechatronic device deburring
Mechatronic devices incorporate the latest advances from diverse disciplines, such as precision machinery and machinery, microelectronics, computers, automatic control and drive systems, sensors, information processing, and artificial intelligence.
Some common components of mechatronic devices include an aluminum hub, a frequency converter housing, a synchronizer housing, a synchronizer gear hub, a bearing cover, a cylinder block, a valve body, a valve cover, an output shaft and a motor gear.
Benefits:
- Cost benefit
- Effective performance
- High precision and efficiency
Disadvantages:
- Limited popularity as it is still in the development phase
- Requires highly accurate data support.
11. Magnetic deburring
The unique magnetic field distribution produces a strong and stable magnetic induction effect, enabling complete grinding of the magnetic steel needle and workpiece in all directions and at various angles for efficient deburring.
Benefits:
This method is effective for complex shapes, slots in parts with multiple holes, internal and external threads, etc.
Disadvantages:
It can negatively impact the magnetism of products with magnetic properties, so care must be taken when using it.
12. Manual deburring
Manual deburring is currently used by many small manufacturers.
Most burrs are small and the removal rate is not particularly high as long as there are no burrs present.
Tools used for hand deburring included files, scrapers and sandpaper, but now edge trimmers are predominantly used.
Benefits:
- Flexibility in manual operation, different tools can be replaced to deburr different parts of the part.
Disadvantages:
- Labor costs are high, efficiency is low, and it can be challenging to remove cross holes and complex parts.
13. Deburring with hand tools
This type of deburring is not significantly different from manual deburring except for the use of different tools.
Manual deburring involves the use of cold tools. Some examples of these tools include a grinder and an electric drill, which can deburr and chamfer using cutters, drills, grinding heads, and other materials.
Different tools can be used to complete deburring of most parts.
Advantages: Provides high flexibility and can adapt to grinding most workpiece environments.
Disadvantages: The speed is slow and may cause some damage to the workpiece.
14. Deburring process
How to avoid burrs in process design?
Here are six steps to avoid burrs in the design process:
(1) Adopt appropriate processing methods:
In metal cutting, the size and shape of burrs produced by various processing methods vary. In the design process, it is best to choose a method that generates the smallest burrs possible. For example, when machining flat surfaces, up milling is more effective than down milling.
(2) Reasonably organize the processing sequence:
When organizing the processing sequence of parts, try to put the process that generates the largest burrs first and the process that generates the smallest burrs last, using the next process to remove the burrs generated in the previous process. For example, when machining shaft parts with keyways, it is more reasonable to change the typical machining sequence from turning before milling to milling before turning.
(3) Choose direction wisely:
Based on the corner effect of burrs, during metal cutting, the outlet should be located on the workpiece with large corner angle to reduce the formation of burrs. At the same time, it is important to note that the cutting edge should be located in a place where it is easy to remove burrs, so as to reduce the removal cost.
(4) Appropriately select cutting parameters:
In the process of cutting parts, using a method that produces large chips will result in large burrs. This is because the production of large chips increases cutting resistance, cutting heat, tool wear and decreases durability, as well as increasing plastic deformation of the workpiece material, which results in larger burrs. Therefore, when processing parts, it is generally better to reduce burr formation by reducing the depth and amount of cutting, especially in precision processing.
(5) Reasonably organize the heat treatment process:
The heat treatment process should be organized into different stages of the processing process to change the physical and mechanical properties such as hardness and elongation of the workpiece material, which can reduce the burrs generated during processing. For example, in batch production of parts, using a forming grinding wheel to grind the snap ring groove of shaft parts in one go after heat treatment generates more burrs than the reheat treatment process after turning .
(6) Use accessories in processing:
In the process of cutting parts, various accessories can be used on the cutting edge of the part, such as auxiliary support, mandrel or low melting point alloy filler. They are used to improve the rigidity of the cutting edge of the machined part, reduce cutting deformation, and reduce the formation of burr on the cutting edge. Although burrs are inevitable in the processing process, it is better to solve the problem of process burrs to avoid excessive manual intervention.
