Burr in metal processing is a problem that everyone will encounter, such as drilling, turning, milling, plate cutting, etc. One of the hazards of burr is easy to cut. In order to remove burr, it is usually necessary to carry out a secondary operation called deburring. The 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 automate, so burr has become a very difficult problem.
Everyone has headaches, and the burr is all here
Burr in feed direction (inlet and outlet Burr) side and cutting direction during machining
How to solve burr?
1 chemical deburring
Chemical deburring is processed by chemical energy. Chemical ions will be attached to the surface of parts to form a film with high resistance and small conductivity, which can protect the workpiece from corrosion. Because the burr is higher than the surface, the burr can be removed by chemical action. This deburring method is widely used in the fields of pneumatic, hydraulic, engineering machinery and so on.
2 deburring at high temperature
First, put the parts that need deburring into the tight sealing chamber, then feed them into the hydrogen oxygen mixture with certain pressure. Ignition will cause the mixture to explode, release heat, and burn off the burr of the parts without damaging the parts.
3 deburring by rolling
Put the parts and abrasives into the closed drum. During the process of the drum rotation, the dynamic torque sensor and the parts and abrasives together produce grinding to remove the burr. Abrasive can be quartz sand, wood chips, alumina, ceramics and metal rings, etc.
4 manual deburring
This method is also the most time-consuming and laborious method compared with the traditional one. It is mainly polished by means of steel file, sandpaper, grinding head and other tools. The most common use in production is trimming knife.
5 process deburring
Edge rounding can be defined as all actions to remove the edges of metal parts. However, it is usually associated with the radius that creates the edge of the part.
Edge rounding is not simply to remove sharpness or deburring, but to break the edge of metal parts to improve their surface coating and protect them from corrosion.
Spin down: suitable for laser cutting, stamping or machining parts of the edge.
Manual grinder: suitable for metal processing items requiring grinding and edge rounding or deburring.
Burr in milling parts with special problems
In milling parts, deburring is more complex and cost is higher, because milling different sizes of different positions will form multiple burrs. It is very important to select the correct process parameters to minimize the burr size.
01 main factors affecting the formation of end milling burr
① Milling parameters, milling temperature and cutting environment will have some influence on burr formation. Some of the main factors such as feed speed and milling depth are reflected by the theory of plane cutting angle and EOS theory of tool tip exit sequence.
② The better the plasticity of the workpiece material, the easier it is to form I-type burr. In the process of end milling brittle materials, if the feed or plane cutting angle is large, it is conducive to the formation of type III burr (defect).
③ When the angle between the end surface of the workpiece and the machined plane is greater than the right angle, the burr can be restrained because of the increase of the support stiffness of the end face.
④ The use of milling fluid is conducive to the prolongation of tool life, reducing tool wear, lubricating milling process, and reducing burr size.
⑤ Tool wear has a great influence on the formation of burr. When the tool is worn to a certain extent, the arc of the tool tip increases, not only the burr size in the exit direction of the tool increases, but also the cutting direction of the tool will also generate the burr.
⑥ Other factors such as tool material have certain influence on burr formation. Under the same cutting conditions, diamond tools are more favorable to restrain burr formation than other tools.
How to deal with the burr produced during the process of tool withdrawal?
To suppress the burr produced during the process of cutting, it is an effective method to eliminate the burr space. For example, before cutting back, measures such as chamfering can be taken to reduce space.
Using appropriate cutting conditions to suppress burr
To reduce the cutting residual, the most suitable cutting tools and cutting conditions must be selected. The cutting tools with large front angle and sharp cutting edge are selected. Improve cutting speed and cutting characteristics. Especially in finishing cutting, the minimum depth and feed quantity must be used.
The size of the burr is determined by the space size of the tool and the workpiece. Let's look at the following diagram.
In fact, burr can not be avoided in the process of processing, so it is better to solve the burr problem from the process and avoid excessive manual intervention. The use of chamfered end milling cutter can reduce the burr space, effectively remove burr, and is also a very suitable method to remove burr.