Basic knowledge of CNC tools for metal processing
When selecting the tool angle, it is necessary to consider the influence of many factors, such as workpiece material, tool material, machining properties (rough and finish machining), which must be reasonably selected according to the specific situation. Generally speaking, the tool angle refers to the marked angle for manufacturing and measurement. During actual work, due to the different installation position of the tool and the change of cutting motion direction, the actual working angle is different from the marked angle, but the difference is usually very small.
The materials for manufacturing cutting tools must have high high temperature hardness and wear resistance, necessary bending strength, impact toughness and chemical inertia, good processability (cutting, forging and heat treatment), and are not easy to deform.
Generally, when the hardness of the material is high, the wear resistance is also high; When the bending strength is high, the impact toughness is also high. However, the higher the hardness of the material, the lower the flexural strength and impact toughness. High speed steel is still the most widely used tool material in modern times, followed by cemented carbide because of its high bending strength, impact toughness and good machinability.
Polycrystalline cubic boron nitride is suitable for cutting high hardness hardened steel and hard cast iron; Polycrystalline diamond is suitable for cutting non-ferrous metals, alloys, plastics and FRP; Carbon tool steel and alloy tool steel are now only used as tools such as files, dies and taps.
Cemented carbide indexable inserts have now been coated with titanium carbide, titanium nitride, alumina hard layer or composite hard layer by chemical vapor deposition. The developing physical vapor deposition method can be used not only for cemented carbide tools, but also for high-speed steel tools, such as drill bits, hobs, taps and milling cutters. As a barrier to chemical diffusion and heat conduction, hard coating slows down the wear speed of cutting tools, and the service life of coated blades is about 1 ~ 3 times higher than that of uncoated blades.
Due to the parts working at high temperature, high pressure and high speed and in corrosive fluid medium, more and more difficult machining materials are used, and the automation level of cutting and the requirements for machining accuracy are higher and higher. In order to adapt to this situation, the development direction of cutting tools will be to develop and apply new cutting tool materials; Further develop the vapor deposition coating technology of cutting tools, deposit higher hardness coatings on high toughness and high strength substrates, and better solve the contradiction between hardness and strength of cutting tool materials; Further develop the structure of indexable tools; Improve the manufacturing accuracy of cutting tools, reduce the difference of product quality, and optimize the use of cutting tools.
According to the cutting motion mode and the corresponding blade shape, the cutting tools can be divided into three categories. General tools, such as turning tool, planer, milling cutter (excluding formed turning tool, formed planer and formed milling cutter), boring cutter, drill bit, reamer, saw, etc; Forming cutter, the cutting edge of which has the same or nearly the same shape as the section of the workpiece to be processed, such as forming turning tool, forming planer, forming milling cutter, broach, conical reamer and various thread processing tools; It is a tool for generating bevel gear, shaper, etc. with a cutter, such as a gear hob or a gear shaper.
The structure of various cutting tools is composed of clamping part and working part. The clamping part and working part of the overall structure tool are made on the tool body; The working part (cutter tooth or blade) of the cutter with inlaid structure is inlaid on the cutter body.
The clamping part of the tool has two types: with hole and with handle. Tools with holes are sleeved on the spindle or spindle of the machine tool by means of inner holes, and transmit torsional torque with the help of axial keys or end face keys, such as cylindrical milling cutter, sleeve face milling cutter, etc.
Tools with handles usually have rectangular handles, cylindrical handles and conical handles. Turning tools and planers are generally rectangular handles; Conical handle * taper bears axial thrust and transmits torque with the help of friction; Cylindrical shank is generally suitable for small twist drills, end mills and other tools. When cutting, the torsional torque is transmitted with the help of the friction generated during clamping. The shank of many tools with shank is made of low alloy steel, while the working part is welded by high-speed steel.
The working part of the tool is the part that produces and processes chips, including the blade, the structure that breaks or rolls up the chips, the space for chip removal or storage, the channel of cutting fluid and other structural elements.
The working part of some cutting tools is the cutting part, such as turning tools, planers, boring tools and milling tools; The working part of some tools includes cutting part and calibration part, such as drill bit, reamer, inner surface broach and tap. The function of the cutting part is to cut chips with the blade, and the function of the calibration part is to polish the machined surface and guide the tool.
The structure of the working part of the tool has three types: integral type, welding type and mechanical clamping type. The overall structure is to make a cutting edge on the tool body; The welding structure is to braze the blade to the steel cutter body; There are two mechanical clamping structures, one is to clamp the blade on the tool body, and the other is to clamp the brazed tool head on the tool body. Cemented carbide cutting tools are generally made into welding structure or mechanical clamping structure; All ceramic cutting tools adopt mechanical clamping structure.