With the development of high-tech, the manufacturing process of graphite materials has been continuously improved. Graphite high-speed milling machines have emerged in the market. Graphite materials that can meet different processing needs are emerging in an endless stream, and the graphite discharge performance of CNC EDM machines has also been comprehensively improved.
Graphite has high temperature strength, low thermal expansion coefficient, good machinability, and good thermal and electrical conductivity. It is currently widely used in graphite products such as graphite electrodes, graphite molds, graphite crucibles, 3D hot bending molds (mainly mobile phone glass hot bending molds), etc. In Europe, where manufacturing technology is leading, more than 90% of the electrode materials of mold companies have adopted graphite.
How to Choose the Right Graphite Milling Tool
Tool material. Tool material is an important factor in determining tool cutting performance, and has a great impact on processing efficiency, processing quality, processing cost and tool durability. The harder the tool material, the better its wear resistance, but the higher the hardness, the lower the impact toughness, and the more brittle the material. Hardness and toughness are contradictory, which is a problem that tool materials should solve. For graphite tools, ordinary TiAlN coatings can appropriately select materials with relatively better toughness, that is, slightly higher cobalt content. For diamond-coated graphite tools, materials with relatively higher hardness, that is, slightly lower cobalt content, can be appropriately selected. For polycrystalline diamond PCD tools, coarse-grained grades with better wear resistance can be selected.
Tool geometry. Choosing appropriate geometry for graphite-specific tools helps reduce tool vibration, and in turn, graphite workpieces are not easy to break.
Tool coating. Diamond coated end mills have the advantages of high hardness, good wear resistance and low friction factor. At this stage, diamond coating is the best choice for graphite processing tools, and it can best reflect the superior performance of graphite tools.
The purpose of tool passivation is to solve the defects of the microscopic notches on the tool edge after sharpening. Reduce or eliminate the edge value to achieve the purpose of smoothness, flatness, sharpness, firmness and durability.
Machining conditions of the tool. Choosing appropriate processing conditions has a considerable impact on the life of the tool.
Based on the above points, the material, geometric angle, coating, edge reinforcement and machining conditions of the tool play different roles in the service life of the tool, and they are indispensable and complementary. A good graphite tool should have a smooth graphite powder chip groove, a long service life, deep engraving, and can save processing costs.
Factors to Note When Determining the Geometric Angle of Graphite Milling Cutter
Front Angle of Graphite Machining Tool
When using negative rake angle to machine graphite, the tool edge strength is better and the impact and friction resistance is good. As the absolute value of the negative rake angle decreases, the wear area of the back tool face does not change much. But it shows a decreasing trend overall. When using positive rake angle for machining, as the rake angle increases, the tool edge strength is weakened. Instead, it leads to increased wear of the back tool face. When machining with negative rake angle, the cutting resistance is large, which increases the cutting vibration. When machining with large positive rake angle, the tool wear is serious and the cutting vibration is also large.
Back Angle of Graphite Machining Tool
If the back angle increases, the tool edge strength decreases and the wear area of the back tool face gradually increases. When the tool back angle is too large, the cutting vibration is enhanced.
Helix Angle of Graphite Machining Tool
When the helix angle is small, the blade length of the same cutting edge that cuts into the graphite workpiece at the same time is longer, the cutting resistance is larger, and the cutting impact force borne by the tool is large. Therefore, the tool wear, milling force and cutting vibration are relatively large. When the helix angle is large, the direction of the milling force deviates greatly from the workpiece surface, and the cutting impact caused by the graphite material breaking is aggravated. Therefore, tool wear, milling force and cutting vibration are also increased.
Therefore, the influence of tool angle change on tool wear, milling force and cutting vibration is a combination of rake angle, back angle and helix angle, so more attention should be paid when selecting.
Structural Forms of Graphite Machining Tools
Different graphite specific tools need to be selected according to different machining procedures and machining requirements.
The tool structures of graphite milling tools include rod-shaped milling cutters and milling inserts. Types include: PCD end mills, PCD ball nose end mills, PCD single edge end mills, PCD double edge end mills, PCD slot mills, PCD chamfer mills, diamond PCD face mills, PCD milling inserts and CVD diamond coated end mills, etc.
The tool structures of graphite turning tools are divided into composite PCD inserts and welded turning tools, including: PCD inserts, PCD welded turning tools, PCD slotting tools, PCD external turning tools, PCD slotting tools, etc.
The forms of graphite hole processing tools include: PCD drill bits, PCD internal turning tools, PCD boring tools, PCD milling-specific milling cutters, CVD diamond-coated drills, etc.
Extension: PCD Tools and CVD Diamond Coated Tools
Polycrystalline diamond PCD tools and CVD diamond coated tools are ideal tool choices for processing graphite materials. CVD diamond coated tools have the advantages of high hardness and good wear resistance. However, the cost of diamond coated tools has remained high, and as the manufacturing technology of PCD tools becomes more and more mature, the cost and price have also decreased. Therefore, the application of PCD tools in the field of processing graphite materials is becoming more and more extensive.
In general, for graphite tools for micro-diameter and small hole processing, it is recommended to choose CVD diamond coated tools, such as graphite drills and graphite end mills with small micro-diameters below 3mm. The effect of using CVD diamond coated graphite tools is better. For graphite tools with larger diameters, it is more cost-effective to choose polycrystalline diamond PCD graphite tools. PCD tools can be made into various structural forms, such as PCD turning tools, PCD drills, PCD end mills, PCD ball head milling cutters, PCD milling inserts, PCD slot cutters, PCD boring cutters, etc.
