Blade tool knowledge

A ball-end milling cutter is used for the surface machining of the flange root of the blade of the axial-flow turbine. The cutting speed of the center part of the ball head of the tool tends to zero, and the cutting condition is bad, which is prone to chip jamming and cutting edge chipping. The localization of ball-end milling cutters is relatively difficult, and Hitachi tools are now used.

Ball end milling cutter

φ80 and φ63 spiral end mills are required for blade entry and exit, water edge and welding groove. The price of foreign cutting tools is about 17,000 to 27,000 yuan per piece, while the price of domestic spiral end mills is about 1/4 to 1/8 of that. We cooperated with Taiyuan Wangpai Tool Factory to develop a spiral end mill suitable for processing stainless steel blades. The tool is a flat-mounted blade screw clamping structure. Deepen the chip flute and increase the helix angle, which is beneficial to chip removal and light cutting; the end of the milling cutter is the most involved part of the cutting, and it is also the most easily damaged. The structure of the interchangeable head greatly extends the life of the cutter body; improvement The interchangeable head design increases the chip holding space and the auxiliary clearance angle at the bottom edge, avoiding the common phenomenon of chipping due to clogging of chips; the end edge is changed from 2 to 4 cutting, which greatly improves the most vulnerable part of this part. Condition: The use of square blades for the peripheral edge has increased from 2 to 4 times of indexing, which improves the utilization of blades.

Spiral End Mills

The blade curved surface processing area is large, the machining allowance of the forging surface is 0～70mm, and the program empty running condition occurs during rough milling. The gantry milling machine purchased from German Wadrich Kobao company is equipped with the most powerful CNC milling head in the world, which provides a prerequisite for achieving large depth of cut and large feed. Cooperated with Harbin Institute of Technology and Miangong Tool Factory to develop a special face milling cutter with a double-layer blade diameter cutter tooth structure, which promises a cutting depth of 20mm.

Special face milling cutter

Selecting unequal tooth pitch distribution has a good effect on reducing cutting vibration.

Milling cutter tooth pitch distribution

Selecting a small value for the clearance angle can increase the strength of the cutter teeth, but the blade material has a large toughness. In order to reduce the friction between the flank face and the machined surface, the clearance angle should be larger, and the clearance angle αu003d7°～9° . The clearance angle of the face milling cutter is formed by the clearance angle of the cutter body and the clearance angle of the insert. The clearance angle series of the insert ranges from 0° to 25°. Considering the strength of the insert and the limitation of the installation angle, the clearance angle α of the insert is selected. u003d11°.

The entering angle of face milling cutter is 45°～90°. Different entering angles affect the cutting force direction and actual cutting depth. In addition, the entering angle of the face milling cutter is different, and the wiper blade ground is different. In the production, the operator does not understand or pay attention to the difference of the blade wiper edge with different entering angles, so it can be said that it is in a mixed state. The 75° entering angle is preferred, and it is extended to the whole factory when processing other parts, reducing the loss caused by the unfair use of the blade.

Face milling cutters can be divided into double negative rake angle, double positive rake angle and positive and negative rake angle according to the rake angle. During the Seventh Five-Year Plan period, the domestic heavy-duty machining industry and tool manufacturers began to research heavy-duty cutting tools, and developed double-negative rake face milling cutters with negative axial and radial rake angles. Actually, it is proved that power plant equipment manufacturing is different from heavy machining of heavy machinery manufacturers' castings and forgings. It is a misunderstanding to use heavy cutting face milling cutters when machining large welded components and parts. Double negative rake angle face milling cutters are prone to cutting vibration, which makes the surface roughness poor and the tool is easy to break. Choose positive values u200bu200bfor the axial and radial rake angles, increase the rake angle, reduce the cutting force, reduce vibration, and meet the requirements of high precision and high-speed cutting. After testing, it is preferable that the radial rake angle γfu003d0°～2°, and the axial rake angle γpu003d9°～12°.

The choice of milling cutter geometry angle

Blade clamping methods include front and rear pressure block, wedge adjustable, eccentric, lever, screw compression and elastic clamping. The basic requirements are easy clamping, firm clamping, high positioning accuracy, simple structure and easy chip removal. The blade face milling cutter adopts the pressing block clamping method, which not only has a larger chip pocket, but also has low requirements on the accuracy of the blade, and has a strong versatility.

Blade clamping method

The structure of the face milling cutter can be divided into flat mounting and vertical mounting according to the installation method of the blade. The plain packaging method was adopted earlier by the German Walter Company (WALTER), while the vertical packaging method was introduced by the German Ingersoll Company (INGERSOLL). The flat mounting method has the characteristics of large blade installation rake angle and large chip pockets, and the vertical mounting method has the characteristics of blade compression and impact resistance, and is suitable for heavy cutting. After cooperating with Harbin Institute of Technology, Harbin Working Quantity Tool Factory, Miangong Tool Factory, we have developed a structural face milling cutter for stainless steel blade processing flat-mounted blades.