In order to obtain the desired cutting effect, it is necessary to know the cutting mechanism in detail. Many of these variables must be considered: (1) workpiece material and shape; (2) machine tool; (3) cutting edge associated with the center axis of the part; (4) type of blade and chip breaker; (5) cemented carbide Grades and coatings; (6) Other cutting conditions that affect tool life. This article focuses on the first three variables.

1. Workpiece Materials and Shapes To simplify the problem, the three most common workpiece shapes are discussed here. Solid, hollow, and irregular shapes requiring intermittent cutting (such as square and hexagonal materials and hollow materials with inconsistent wall thickness).

The materials are generally divided into 7 types. To simplify the problem, there are three categories.

The first category is a material that requires cutting with a sharp positive rake cutting edge. It includes superalloys, titanium alloys, aluminum, plastics and other non-ferrous metals as well as austenitic stainless steels. The sharp cutting edge prevents work hardening of these materials. For example, a sharp cutting edge allows for high cutting speeds and feed rates, and neatly cuts the silicon-aluminum alloy without leaving a bead. It is also suitable for most non-metallic materials (such as plastics, nylon and other soft, process-free materials).

The second category is a material that requires cutting with a zero rake angle or a negative rake angle cutting edge. It includes standard carbon steel, alloy steel and cast iron. A zero rake angle or a negative rake angle increases the strength of the cutting edge and allows for greater feed rates and prevents damage to the cutting edge during interrupted cutting. For most materials that produce continuous long chips, such zero or negative rake angle tools should be used, which is the most commonly used type in industrial production.

The third category includes materials that require machining with a chip breaker, and the type of chip breaker will be discussed later. These materials will produce filamentous long chips at normal cutting speeds and feed rates, such as 52100# steel and other high grade steels used in the bearing industry.

Machine tools usually require the use of chip breakers when machining. When processing soft mild steel and alloy steel at low rated feed rates, undesirably long chips are often produced, requiring the operator to frequently shut down to remove chips. This will reduce productivity and endanger the operator because these chips are very sharp. The same problem occurs when machining some types of superalloys at very low cutting speeds.

When the blade is selected to be severed, the geometry of the blade can be at the same angle as the blade for turning or even milling. Usually if a material is machined with a large positive rake turning or milling insert, the same geometric angle can be selected when cutting.

2. Machine tool

The key to an effective shut-off operation is the ability to control cutting speed and feed rate. The right combination of the two will extend tool life, maintain process dimensional stability and effectively control chipping. The machine tool used (its type and characteristics) largely determines the extent to which the user can control the cutting parameters.

Here the machine tools are divided into two categories: CNC and non-CNC machines. Automation equipment is the most common form of mass production. This may cause some important problems when using a cutting tool.

When a tool is working at the lowest feed rate, the maximum speed that the machine can use is determined. Since in the automated production, some tools are cut at several different positions at the same time, the cutting speed and feed rate can hardly be adjusted during machining. For example, when a high-speed steel twist drill or forming tool is operating in one of its positions, its optimum cutting speed will determine the cutting speed of all other tools, which is too low for most carbide tools. New automation equipment allows the operator to control the feed rate more. Some CNC-type automation devices give complete control over the entire cutting cycle.

The machine tool used will determine the grade, chip breaker and cutting edge type of the carbide insert. For traditional automation equipment, you need to choose a hard graded carbide grade. Carbide tools below the normal cutting speed will be tested on these devices.

Ultra-fine carbide grades have greatly improved the performance of cutting tools for automated equipment. They have the same strength as high speed steel and have the same good wear resistance as cemented carbide.

Another machine that can be cut off is a CNC lathe. It is usually equipped with a bar feed mechanism or the like for mass production. This machine has many advantages, the most important of which is the complete control of the cutting speed and feed rate during the cutting cycle. This makes it possible to work efficiently with carbide inserts with high cutting speeds. However, it must be noted that the cutting speed and feed rate should be within the range recommended by the manufacturer.

CNC machines are easy to program and change to suit the needs of different parts. Therefore, they are the preferred type of short stroke cut operation, and their ability to adjust cutting speed and feed rate also helps control chip and increase tool life consistency.

3. Correct installation When using carbide to cut off, it is very important to install the tool correctly. If the cutting edge and workpiece contact position are incorrect, the tool may chip or damage the workpiece and sometimes even damage the machine.

The two most common problems are that the cutting tool is not perpendicular to the workpiece or the cutting edge is mounted too high or too low relative to the center axis of the workpiece. They will have a large tool life, chip control and whether vertical and smooth cutting will occur. The effect will also result in a convex or concave surface on the finished part surface. If these problems are very serious, the tool will fail.

To ensure that the tool is perpendicular to the workpiece, the operator should follow a simple installation procedure. First carefully clean the locking area and install the cutting tool on the hex turret. Then use a meter to measure the tool deviation on a stroke with a length of 100 mm. The deviation should not exceed 1 mm. Previous 1 2 3 4 Next one method for detecting whether the tool is vertical is to check the generated chips. If the chips generated by the workpiece flow in a filament shape to one side, it may be that the tool is not installed correctly. Another phenomenon is the premature wear of the cutting blade rounding, which indicates that one side of the blade is under more pressure than the other side.

If the tool performance during machining or the quality of the part being produced changes, follow the installation steps mentioned earlier. Sometimes a slight collision of the tool can cause a deviation. Therefore, it is a good idea to check the cutting conditions of the cutting tool as soon as possible after installation. This can help identify and prevent serious tool failure.

Another major consideration in the cutting tool installation is the position of the cutting edge relative to the workpiece axis. Incorrect blade installation will cause a series of problems, the most common of which are premature and sudden failure of the tool, poor chip form, poor side roughness and vibration. These problems will be further aggravated by the difficulty in identifying the actual position of the cutting edge. These phenomena occur more frequently on older manual and automatic machines.

Most carbide inserts designed by the manufacturer must be installed slightly above the center axis of the workpiece. This position facilitates the use of a welded chip breaker and ensures that the blade is securely clamped to the tool holder.

When the blade is mounted slightly above the center, the tangential force can act on a larger blade area. This increases the strength of the tool and secures the blade in the sipe.

In addition, when the angle between the cutting edge and the workpiece is determined, the carbide cutting blade is often designed to maximize strength and robustness. If the blade is too far above the centerline, the back corner of the blade will decrease. As a result, the upper half of the knives rubs against the workpiece, so a large amount of heat is generated in the cutting zone. This, in turn, causes the blade to wear out in advance and the workpiece to harden. The most common sign of this situation is that the blade has excessive flank wear after short-term cutting.

Blades below the centerline will create more problems. When the blade is below the centerline, the back angle will increase. This allows the small tip portion to withstand the full cutting force, thereby reducing tool life and increasing the likelihood of sudden tool failure.

Another problem with blades below the centerline is the irregular deviation of the blades. As most cutting forces act on the tip, it tends to vibrate and bounce. This irregular motion will have an effect on tool life, usually in the form of chip breaking in front of the cutting edge. It will produce vibration marks and poor surface roughness on the bottom and sides of the part slot.

One of the most serious consequences of using a blade below the centerline is that the blade is pulled out. When the blade contacts the monolith, the rotation of the part actually pulls the blade out of the sipe; residual burrs in the center of the part accumulate on the cutting edge, and as the part continues to rotate, the blade is pulled out of the sipe.

If this condition is not judged in time, the tool holder will be damaged when the next part is machined and may cause damage to the machine and the machined part. This means a waste of time. Even if the blade is not pulled out of the toolholder, burrs that rotate through the top of the cutting edge can cause damage to the tool.

For these reasons, it is necessary to prevent the cutting tool from cutting deeper than the center portion of the workpiece. After the center point, the actual direction of rotation is reversed and the resulting cutting force may pull the blade out of the holder. At the same time, this rotation will rub the flank of the blade, causing the blade to wear in advance.  Previous 1 2 3 4 Next To overcome the problem of blade pull-out, many cutter manufacturers are adopting the automatic clamping concept proposed by ISCAR in the early 1970s. This method does not require screws and levers to position and clamp the blade, it relies on rotation and tool pressure to position the blade within the wedge slot. In this way, the cutting depth of the tool can be almost unlimited without the use of a pressing device, and the type of the tool holder and the blade is another factor that keeps the tool at the center high position during installation. The most common type of cutting tool is the body and blade system. It consists of a locking body mounted in the machine chuck and a replaceable double-sided blade for mounting the alloy blade with a self-locking sipe.

The T-cutting knife is a combination of two types of blades and blades, with a simple wedge lock. On the top and bottom of the blade there is a bevel that matches the blade. The blade is wedged by the blade and is held in the sipe. Under certain conditions, the blade may be further pressed into the sipe, changing the position of the cutting edge to be lower than the center. Large feed rate cutting, interrupted cutting and worn sipe may cause this phenomenon to occur.

In the F-cutting tool, the blade and the blade have a fixed positioning groove. A positioning block is welded to the blade in contact with the top surface of the support blade. Once the blade is installed in the sipe, it will remain in a fixed position.

Any combination of blade and blade should allow the chips to drain smoothly from the cutting zone. If the chips accumulate and invade the groove before the part is cut, the blade is likely to cut the chips again and will suddenly fail. If the swarf rubs the blade violently, a large amount of heat will be generated, which will also cause fatigue and accelerated failure.

All carbide cutting tool manufacturers offer a high center for their products. Therefore, the manufacturer's recommended value should be strictly observed.

The geometry of the insert and the type of tool holder have an effect on the center height. For blades with a width greater than 0.5 mm, the following formula is useful for determining the maximum center height: center height = 0.8 mm x width + 0.025 mm.

When cutting, it is important to remember that the cutting edge is mounted at the center height or slightly above the center height. Operators and installers who use high-speed steel cutting knives or similar tools often think that these tools work better when they are below the center height. However, for modern carbide inserts, working below the center height will make the cutting operation more difficult.