Types and Characteristics of Common Cutting Tools for 1. NC Machining

CNC machining tools must adapt to the characteristics of high speed, high efficiency and high degree of automation of CNC machine tools, and should generally include universal tools, universal connection handles and a small number of special handles. The handle is connected to the tool and mounted on the power head of the machine tool, so it has been gradually standardized and serialized. There are many ways to classify NC cutting tools. According to the tool structure, it can be divided into: ① integral type; ② mosaic type, welding or machine clamp type connection, machine clamp type can be divided into non-indexable and indexable two kinds; ③ special type, such as compound type tool, shock absorption type tool, etc. According to the materials used in the manufacture of cutting tools can be divided into: ① high-speed steel tools; ② carbide tools; ③ diamond tools; ④ other material tools, such as cubic boron nitride tools, ceramic tools. From the cutting process can be divided into: ① turning tools, divided into outer circle, inner hole, thread, cutting tools, etc.; ② drilling tools, including drills, reamers, taps, etc.; ③ boring tools; ④ milling tools, etc. In order to meet the requirements of CNC machine tools for tool durability, stability, easy adjustment, replaceable, etc., in recent years, the machine clamp type indexable tool has been widely used, reaching 30% to 40% of the whole CNC tool in quantity, and the metal removal amount accounts for 80% to 90% of the total.

Compared with the tools used on ordinary machine tools, CNC tools have many different requirements, mainly with the following characteristics: ⑴ good rigidity (especially roughing tools), high precision, vibration resistance and small thermal deformation; ⑵ Good interchangeability, easy to change tools quickly; ⑶ high life, stable and reliable cutting performance; ⑷ The size of the tool is easy to adjust to reduce the adjustment time of tool change; (5) The tool should be able to reliably break chips or roll chips to facilitate the elimination of chips; (6) serialization and standardization to facilitate programming and tool management.

Selection of 2. NC Machining Tool

The selection of cutting tools is carried out in the state of human-computer interaction of numerical control programming. Should be based on the processing capacity of the machine tool, the performance of the workpiece material, processing procedures, cutting parameters and other related factors, the correct selection of tools and tool holder. The general principle of tool selection is: easy installation and adjustment, good rigidity, high durability and precision. On the premise of meeting the processing requirements, try to choose a shorter handle to improve the rigidity of the tool processing.

When selecting a tool, the size of the tool should be adapted to the surface size of the workpiece to be processed. In production, end mills are often used to process the peripheral contours of plane parts. When milling planes, carbide blade milling cutters should be selected. When machining bosses and grooves, high-speed steel end mills are selected. When machining blank surfaces or rough holes, corn milling cutters with carbide inserts can be selected. For the processing of some three-dimensional surfaces and variable-angle contour shapes, ball-end milling cutters, annular milling cutters, conical milling cutters and disc milling cutters are often used.

In the free-form surface machining, because the end of the ball head tool cutting speed is zero, therefore, in order to ensure the machining accuracy, cutting row spacing is generally achieved very close, so the ball head is often used for surface finishing. The flat head tool in the surface processing quality and cutting efficiency is better than the ball end knife, therefore, as long as the premise of ensuring not cut, whether it is the surface of the roughing or finishing, should give priority to the flat head knife. In addition, the durability and accuracy of the tool and the price of the tool is greatly related. It must be noted that in most cases, the choice of a good tool increases the tool cost, but the resulting processing quality and processing efficiency The improvement can greatly reduce the entire processing cost.

In the machining center, all kinds of tools are installed on the tool magazine, and the tool selection and tool change are carried out at any time according to the procedures. Therefore, it is necessary to use the standard tool handle, so that the standard tools used in drilling, boring, expanding, milling and other processes can be quickly and accurately installed on the machine tool spindle or tool magazine. The programmer should understand the structural dimensions of the tool holder used on the machine, the adjustment method and the adjustment range, so that the radial and axial dimensions of the tool can be determined during programming. At present, China's machining center using TSG tool system, the handle has a straight shank (three specifications) and taper shank (four specifications) two, including a total of 16 different uses of the handle.

In economical CNC machining, due to the grinding, measurement and replacement of cutting tools are mostly manual, which takes a long time to assist. Therefore, the order of cutting tools must be reasonably arranged. Generally, the following principles should be followed: ① minimize the number of tools; ② after a tool is clamped, all machining parts that it can carry out should be completed; ③ rough and finishing tools should be used separately, even if they are of the same size and specification; ④ milling before drilling; ⑤ surface finishing first, then two-dimensional contour finishing; ⑥ Where possible, the automatic tool change function of CNC machine tools should be used as much as possible, to improve production efficiency, etc.