(3) high speed machining mechanism of graphite
Scholars at home and abroad have studied the crack formation during chip formation in graphite ordinary cutting and high-speed machining
And its extension, chip shape and size, and the interaction between tool and workpiece material are discussed
Preliminary analysis and research. DAS (1973 & gt) believes that when graphite is turned with positive rake angle tools, the first
First, a large chip will be generated, and an arc-shaped groove will be left on the surface of the workpiece to be processed, and then it will be removed in the form of small chips; When negative rake angle tools are used for machining, due to the synchronous expansion of multiple sliding surfaces
The chips are mainly small particles [47]. Chen Changjing (1989) studies the turning process of carbon graphite materials
It is pointed out that the cutting tool does not simply peel off the surface of the graphite blank, but according to the cutting tool
Different from the properties of the blank, the cutting factors of the cutting tool and the sharpness of the cutting edge
The particles on the surface play the role of "cutting and peeling" or "crushing and peeling": the
Cutting force is irregular and intermittent high-frequency impact force; In addition, carbon particles in high-speed relative motion
There is considerable friction between the particles and the cutting edge [ill. Hu Jianwen (1991) believes that the cutting of graphite materials
The process is mainly that the surface of the processed material is cracked (crushed) by the pressing force of the cutting edge of the tool. The pressing force is actually
The upper is the friction between the blade 1:3 and the material to be processed [4]. Yan Qiusheng (1994) mentioned the cutting force when burning stone ink
The chip powder particles are in the shape of concave convex fragments. The chip shape of the new grinding tool is seriously irregular, and the surface is multi angular. The size is several
Ten to hundreds of microns, with the increase of tool wear, the average diameter of chip particles is approximately spherical, and the surface of powder is concave
The crown is reduced by 14 ". Masuda (1996) observed through high-speed photography during the high-speed turning of graphite materials,
The initial crack generated inside the graphite material propagates along the cutting direction, causing the graphite material to break up, which is large
Most chips slide along the rake face, resulting in tool crescent wear [50L. Sato (1996) will burn stone ink
Graphite chips in high-speed turning are divided into four grades: 500 "m, 250 PM, 125 ¨ m and 63 TTM,
The weight of graphite chip particles with particle size less than 250 i.tm accounts for most of the total weight of chips,
Moreover, with the increase of feed rate, the proportion of large particle chips will increase [sh. k6nig (1998)
After the high-speed milling process of graphite, it is considered that the formation process of graphite chips is very similar to that of brittle materials such as ceramics;
The graphite material is crushed at the tool tip to form fine chips, and the cracks generated by cutting will first move forward and downward toward the tool tip
The square extends and then extends to the free surface to form large pieces of broken chips, and forms a break on the processed surface of graphite
Crack pit; The contact state between chips and tool rake face can be divided into cutting contact impact zone and chip sliding along rake face
They lead to different tool wear morphologies 152]. Cutting force and wave in turning graphite electrode materials