The latest developments in high-speed machine tools and their tooling technology have made it possible to achieve “cut-and-wear” in the field of mold and part manufacturing. High-speed machining of difficult-to-machine materials such as hardened die steel with super-hard tools has become more and more widely used. Since high-speed machining of molds or parts can eliminate subsequent processes such as grinding or polishing, it is an important issue for researchers to ensure the final surface quality of the workpiece while controlling the processing cost to an acceptable range. Based on the investigation, the paper analyzes the cutting performance and economy of the solid carbide coated end mill for high-speed milling of hardened die steel, and gives some application examples.

1 Introduction

High-speed cutting (HSC) is an important part of advanced manufacturing technology. Its main advantage is the high efficiency and high quality of processing. In recent years, high-speed machining technology has developed rapidly in the world's major economically developed countries (such as Germany, Britain, the United States, Italy, Japan, etc.). The high-speed cutting machine tools and auxiliary, distribution, software and hardware produced in these countries are almost every year. The speed of the steps has been updated, and the performance indicators that can be achieved so far are already eye-catching. Micron, Jobs, Haas, Fpt, Dmg and other world-renowned machine tool companies have developed the rapid replacement spindle head technology in recent years, so that the same machine can adapt to a variety of load and speed requirements (the so-called rough finishing with the same machine "once"), A large amount of non-processing time can be saved in the positioning, installation and transmission of the workpiece.

The high-speed rotation of the machine tool spindle and the corresponding increase of the feed speed and acceleration can directly shorten the machining time. On the other hand, the high-speed cutting has the advantages of particularly high excitation frequency, stable operation and small vibration, which is beneficial to improve the machining surface. Quality, ie high-speed machining, can be used as the final machining of molds and structural parts, improving machining efficiency and processing quality by “cutting or grinding” or “cutting discharge” (ie no need for time-consuming and inefficient subsequent grinding operations) , mold electrode EDM); the workpiece can also be quenched and then cut, directly cutting the material with hardness up to 65HRC to the final size.

In addition to high-speed machine tools, high-speed machining requires high-speed cutting. According to the special report of Micron, Jobs, Kenner Feishuo and other companies in the 2002 International Mould High Speed ​​Processing Technology Seminar of Guangdong Province, in recent years, German SGS, Mitsubishi (Kobelco) and Sumitomo, Swiss Sandvik, and Kenner Feishuo and other famous foreign tool companies have successively introduced their own high-speed cutting tools, not only high-speed cutting of ordinary structural steel tools, but also super-hard tools such as ceramic tools that can directly cut hard-hardened steel, especially coating tools. It plays a huge role in the semi-finishing and finishing of hardened steel.

In recent years, China's (especially South China) manufacturing industry has developed rapidly, and the manufacturing of molds, automobiles and motorcycles has developed, and the number of enterprises with high-speed cutting machine tools has increased. However, compared with the rapid development of high-speed cutting machine tools and tool technology, these companies are still relatively backward in high-speed cutting technology, testing and application software, and can not be matched with hardware, resulting in the advanced equipment imported by many manufacturers. It should have a role. On the one hand, high-speed machine tools with a spindle speed of tens of thousands of revolutions have been operating at only a few thousand revolutions. The conditions for high-speed finishing are only used for roughing and semi-finishing. Machines and tools that can cut high-hard materials are It is only used to cut ordinary materials; on the other hand, due to improper matching of workpiece materials with tools and processes, processing costs are high and even quality accidents occur from time to time. In order to promote the development of high-speed machining technology and help enterprises to rationally apply high-speed machining equipment and technology, it is necessary to conduct in-depth discussions on the technical and economic issues of high-speed machining.

2. Common hardened die steel and high speed cutting end mill

2.1 Common plastic mold steel and hot work steel

Common mold hardened steels on the market are mostly used in the manufacture of plastic molds and forging and die-casting cavity molds. The main suppliers are Sweden ASSAB, LUNG KEE, SAARSTAHIL, Japan. Companies such as Datong (DAIDO). Table 1 lists the product names and properties of some plastic mold steels and hot work steels. The traditional mold steel processing method is first milling and then hardening and grinding, while high-speed cutting can be rough milling, hardening and fine milling, and even rough finishing can be completed in one machine.

Table 1 several commonly used plastic mold steel and hot work steel

Trade name - standard - characteristics and use - surface hardness ASSAB S136; S316H - AISI 420ESR - acid and corrosion resistance, high wear resistance, small heat treatment dimensional change; suitable for PVC, PP, EP, PC, PMMA Plastic mold, high-tempering mirror plastic mold after high temperature tempering - low temperature tempering HRC50 ~ 55, high temperature tempering HRC34 ~ 38SAARSTAHL (SSE) GS2344EFS; GS2344ESR - AISI H13 - excellent red hardness, high temperature impact strength , high temperature wear resistance and thermal shock resistance, can be used for extrusion, die casting, hot forging and high temperature blanking tools - 180 ~ 300 ° C hardened to HRC52LKM2311; LKM2312 - AISI P20 - uniform hardness, processing properties Good, good core toughness, can be used as advanced pre-hardened plastic mold - HRC53~36DAIDO NAK80-AISI P21 modified ESR - small deformation, easy to grind and polish, long-term use can maintain high precision, can be used as high hardness and high mirror mold ——HRC37~41 when supplied, can be hardened to about HRC60

2.2 High-speed cutting hardened steel common end mill

This article focuses on solid carbide PVD coated end mills for high speed machining (other tools such as CBN and ceramic tools for machinable hardened steel are not the focus of this paper).

(1) Tool coating: The tool coating that can be used for high-speed cutting hardened steel mainly includes (Ti, Al)N or (Ti, C)N, and the tool base is ultrafine grained cemented carbide. (2) Main form of milling cutter: The main form of integral end mill for high-speed cutting hardened steel includes conventional 2-blade and multi-blade ball-nosed knives, long-neck ball-nosed knives, 2-blade cone-face ball knives, and 2-edge belts. Round head flat bottom knife, long neck with round head flat bottom knife, 2 blade right angle flat bottom knife and multi-blade right angle flat bottom knife.

The main suppliers of end mills for hardened steel in China are: KOBELCO, Mitsubishi, Japan, UNIMAX, HITACHI, SUMITOMO ELECTRIC, SGS, USA KENNAMITAL and coating tool manufacturers in Korea and Israel, domestic companies have also launched products for trial development.

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