The milling cutter is generally a multi-edged tool. Due to the large number of teeth participating in the cutting at the same time, the long cutting edge, and the higher cutting speed, the productivity is high. The application of different milling cutters can process planes, grooves, steps, etc., and can also process gears, threads, spline shaft tooth profiles and various forming surfaces.

 

The structure of the milling cutter

 

Take indexable milling cutter as an example:

 

1) Main geometric angle

The milling cutter has an entering angle and two rake angles, one is called the axial rake angle and the other is called the radial rake angle.

 

The radial rake angle γf and the axial rake angle γp. The radial rake angle γf mainly affects the cutting power; the axial rake angle γp affects the formation of chips and the direction of the axial force. When γp is positive, the chips will fly away from the machining surface.

 

 

 

 

Rake angle (contact surface of rake face)

Negative rake angle: used for steel, steel alloy, stainless steel, cast iron.

Positive rake angle: used for viscous materials and some high-temperature alloys.

The front corner is placed in the middle: used for threading, grooving, profiling turning and forming cutters.

 

 

 

Use a negative rake angle as much as possible.

 

2) Milling cutter geometry

 

The first is: positive angle-positive angle

 

 

 

 

 

 

Cutting is brisk, chip removal is smooth but the cutting edge strength is poor. Suitable for processing soft materials and stainless steel, heat-resistant steel, ordinary steel and cast iron. This form should be preferred when low-power machine tools, insufficient rigidity of the process system, and built-up edge generation.

 

Advantage:

+ Smooth cutting

+ Smooth chip evacuation

+ Good surface roughness

 

Disadvantages:

-Cutting edge strength.

-Not conducive to cut-in contact.

-The workpiece leaves the machine table.

 

Followed by: negative angle-negative angle

 

 

 

 

 

 

 

 

Strong impact resistance, using negative blades, suitable for rough milling of cast steel, cast iron and high hardness and high strength steel.

However, milling power consumption is high and requires excellent process system rigidity.

 

Advantage:

+ Cutting edge strength

+ Productivity

+ Push the workpiece to the machine table

 

Disadvantages:

-Greater cutting force

-Chip blocking

 

Finally: positive angle-negative angle

 

 

 

 

 

 

 

The cutting edge has strong impact resistance and the cutting edge is sharper. Suitable for processing steel, cast steel and cast iron. The effect is also better when milling with a large margin

 

Advantage:

+ Smooth chip evacuation

+ Favorable cutting force

+ Wide range of applications

 

3) Milling cutter pitch

 

 

 

 

 

 

1) Close tooth: high-speed feed, large milling force, small chip space.

2) Standard tooth: conventional feed speed, milling force and chip space.

3) Sparse teeth: low-speed feed, small milling force, large chip space.

 

If the milling cutter is not equipped with a special wiper blade, the surface roughness depends on whether the feed per revolution exceeds the blade wiper plane width.

 

Example: slot milling & contour milling

 

 

 

 

 

 

Number of teeth:

•Sparse teeth or standard teeth for slot milling (safety)

• Close-tooth for contour milling (productivity)

Types and uses of milling cutters

 

The types of milling cutters can be divided into sharp tooth milling cutters and relief tooth milling cutters according to the tooth structure. According to the relative position of the tooth and the axis of the milling cutter, it can be divided into cylindrical milling cutter, angle milling cutter, face milling cutter, forming milling cutter, etc. According to the tooth shape, it can be divided into straight tooth milling cutter, helical tooth milling cutter, angular tooth milling cutter and curved tooth milling cutter. According to the tool structure, it can be divided into integral milling cutter, combined milling cutter, group or complete set of milling cutter, insert milling cutter, machine clamp welding milling cutter, indexable milling cutter, etc. But it is usually divided into the form of cutting tool tooth back processing.

 

 

 

 

 

 

 

Point cutters can be divided into the following categories:

 

(1) Face milling cutters There are integral face milling cutters, toothed face milling cutters, machine clamp indexable face milling cutters, etc., which are used for rough, semi-precision and finishing of various planes and step surfaces.

 

(2) End mills are used for milling step surfaces, side surfaces, grooves, holes of various shapes on the workpiece, and inner and outer curved surfaces. If the end mills are easily distinguished, they can be divided into two categories: left-handed and right-handed. Many people still have no concept of left-handed and right-handed.

 

 

 

 

 

 

 

Right-hand milling cutter

First, determine whether the tool is left-handed or right-handed according to the following methods. Facing a milling cutter placed vertically, if the flute rises from the bottom left to the top right, this is right-handed; if the flute rises from the bottom right to the top left, it is left-handed. Right-hand rotation can also be ruled by the right hand. The four curved fingers are the rotation direction, and the lifted thumb is the right-hand rotation direction. Spiral flutes play the role of chip holding, and also constitute the front corner and front part of the milling cutter.

 

 

 

 

 

Left-hand milling cutter

Left-handed milling cutters are generally selected for high-precision machining needs. Left-handed milling cutters are generally used for mobile phone button processing, membrane switch panels, liquid crystal panels, acrylic lenses and other finishing processes. However, there are some demanding ones, especially the production and processing of some mobile phone buttons or electrical panels. The precision and finish are also very demanding. It is necessary to choose the lower row and turn left, so as to avoid the whitening of the knife edge and processing. Phenomenon such as the cut edge of the piece

 

 

 

 

 

 

(3) Keyway milling cutter is used for milling keyway and so on.

 

(4) Slot milling cutters and saw blade milling cutters are used for milling various grooves, sides, step surfaces and sawing.

 

(5) Special slot milling cutters are used for milling various special groove shapes, such as shaped slot milling cutters, half-moon keyway milling cutters, dovetail milling cutters, etc.

 

(6) Angle milling cutters are used for milling straight grooves, spiral grooves and so on.

 

(7) Mould milling cutter is used for milling convex and concave forming surfaces of various moulds.

 

(8) Group milling cutter Combine several milling cutters into a group of milling cutters, which are used for milling complex forming surfaces, surfaces of different parts of large parts, and wide planes.

 

Relief tooth milling cutters: some milling cutters that require regrinding the front face to maintain the original section shape, and their back face uses relief tooth form, including disc slot milling cutters, convex semicircular, concave semicircular milling cutters, double-angle milling cutters, and forming milling cutters Knife etc.

Down milling and up milling

 

 

There are two ways relative to the feed direction of the workpiece and the direction of rotation of the milling cutter:

 

 

 

 

The first is down milling. The rotation direction of the milling cutter is the same as the cutting feed direction. When the cutting starts, the milling cutter bites the workpiece and cuts off the final chips.

 

 

The second type is up-milling. The rotation direction of the milling cutter and the cutting feed direction are opposite. The milling cutter must slide on the workpiece for a period of time before starting to cut, starting with the cutting thickness as zero, and reaching the cutting thickness at the end of the cutting maximum.

 

 

 

 

 

 

In the face milling cutter, some end milling or face milling, the cutting force has different directions. When face milling, the milling cutter is just on the outside of the workpiece, and special attention should be paid to the direction of the cutting force. During down milling, the cutting force presses the work piece against the worktable, and during up milling, the cutting force pushes the work piece away from the worktable.

 

Because the cutting effect of down milling is the best, down milling is usually the first choice. Only when the machine has thread clearance problems or problems that cannot be solved by down milling, then up milling is considered. Under ideal conditions, the diameter of the milling cutter should be larger than the width of the workpiece, and the axis of the milling cutter should always be slightly away from the centerline of the workpiece. When the tool is placed directly at the cutting center, it is very easy to produce burrs.

 

When the cutting edge enters and exits the cutting, the direction of the radial cutting force will constantly change, the spindle of the machine tool may vibrate and be damaged, the blade may chip and the machined surface will be very rough, the milling cutter is slightly off center, and the direction of the cutting force will no longer fluctuate -The milling cutter will receive a preload. We can compare center milling to driving in the center of a road.

 

Every time the milling cutter blade enters the cutting, the cutting edge must bear an impact load, and the load depends on the cross section of the chip, the workpiece material and the cutting type. When cutting in and out, whether the cutting edge and the workpiece can be properly engaged is an important direction.

 

When the milling cutter axis is completely outside the width of the workpiece, the impact force during cutting is borne by the outermost tip of the blade, which means that the initial impact load is borne by the most sensitive part of the tool. The end of the milling cutter also leaves the workpiece with the tip of the tool, that is to say, from the beginning of the cutting to the departure of the blade, the cutting force has been acting on the tip of the outermost tool until the impact is unloaded.

 

When the center line of the milling cutter is exactly on the edge line of the workpiece, when the chip thickness reaches the maximum, the blade is released from the cutting, and the impact load reaches the maximum when cutting in and out. When the milling cutter axis is within the width of the workpiece, the initial impact load during cutting is borne by the part farther from the most sensitive tip along the cutting edge, and the blade exits the cutting smoothly when the tool is retracted.

 

For each insert, the way the cutting edge leaves the workpiece when it is about to exit the cutting is important. The remaining material when approaching the retract may reduce the blade gap somewhat. When the chips leave the workpiece, an instantaneous tensile force will be generated along the rake face of the blade and burrs are often produced on the workpiece. This tensile force endangers the safety of the cutting edge in dangerous situations.