Consideration on the selection of cutting tool mat

Consideration of tool material selection for mold processing

selecting the most favorable processing material for processing mold and template is as important as the design of the tool itself, because the material involves the machinability, hardness and desired surface finish of the tool. New materials in molds and templates, new coatings for material hardening, the use of pre hardening materials and mixed materials, etc. make manufacturing engineers feel uncertain about the choice of the best cutting tools

new cemented carbide ball cutters, especially those used in milling, have improved their ability to quickly and effectively lay mold grooves, cut molds, hook edges, and perform profiling cutting and finishing. The development of multifunctional milling cutters that can use a wide range of different blade geometries now allows all types of milling to be completed by one blade - which allows greater flexibility and reduced costs

some new shaped milling system designs even allow users to change the tool handles of different length regulators to provide versatility. Coupled with the new "shrink fit" fixture technology, which uses the performance advantages of induction heating, fixture and shrink installation cutting tools, the concentricity and rigidity of deep groove tools have been greatly improved. These improvements provide mold manufacturers with a better range of metal cutting options than previously available. There are many options here. For example, carbide blade manufacturers have more than 20 different carbide blade substrates, which can be coated with titanium nitride (TIN), titanium carbonitride (TiCN), titanium carbide (TIC), aluminum oxide (Al2O3), zirconium carbonitride (zrcn), and titanium aluminum nitrides (TiAIN) or aluminum titanium nitrides, which are mainly exported to developed countries. These coatings can be applied separately, or mixed by physical coating process (PVD) or chemical coating process (CVD) or multi-layer CVD process that allows the application of 70% ultra-thin layer

the coating does greatly improve the wear resistance, increase the tool life, and make higher speed and feeding possible. PVD and CVD coatings are different due to different process temperatures. PVD process is a low-temperature process, which provides finer fracture resistance coating particle structure with low friction coefficient. Therefore, the blade with PVD coating has more sharp edge anisotropy and fracture failure than traditional materials

now, several ceramic materials are added to this selection list. At this time, you will find how difficult it is to choose the right one. Therefore, first of all, consider where and why blade failure occurred and some basic requirements for processing different mold materials, which can be used as a reference for the selection of specific blade types

failure analysis

the main failure of the cutting tool blade used in mold manufacturing is thermal fracture, followed by corrosion around the crack, accumulation of rolled piece material (similar to the material welded on the edge of the tool blade), and finally edge fragmentation. Rolled piece materials such as H11, H13, D2 and A2 tool steels are prone to thermal fracture and tool edge fragmentation

the use of coolant and high feed rates during machining enhances thermal fracture. Traditional CVD coated carbide tools are usually limited to dealing with thermal fracture resistance. Traditional CVD coatings such as tic, TiCN and tin can provide limited thermal insulation performance, but they have high stability, oxidation resistance and chemical resistance. Al2O3 or al2o3/zro2 synthetic oxide coatings can provide enhanced chemical wear resistance and thermal insulation protection. The disadvantage of these types of coatings is their limited fracture toughness characteristics. Generally, the tensile stress is higher in high temperature (~ 1000 ℃) CVD coatings

when used in combination with oxide coatings, medium temperature (~ 850 ℃) multilayer mtcvd coatings such as TiCN or zrcn have less tensile stress and are more suitable for comprehensive fracture toughness, abrasion resistance, chemical wear resistance and thermal fracture resistance

in the past five years, the use of PVD coatings based on TiAIN composites has many advantages. The high oxidation resistance, high chemical stability, high thermal hardness and enhanced thermal insulation of these types of PVD coatings promote their use in the field of high-speed (1, 500sfm) machining. There is no doubt that the use of PVD TiAIN coating improves the productivity of machining

mold materials

because milling method is the main part of mold machining, it is best to focus on the currently commonly used mold materials. In addition, in terms of carbide grade and coating, the products of most carbide blade manufacturers are similar, so they are essentially universal

aluminum

for some parts of the plastic molding industry, aluminum is the preferred mold material. Its metal cutting rate can be 8 ~ 10 times faster than that of machine steel. In recent years, aluminum manufacturers have developed better high-strength materials with hardness characteristics ranging from 158 to 168 Brinell. It is difficult to machine a very smooth surface on aluminum, so it becomes more important to complete the polishing operation in the process stage

generally, milling aluminum requires that the carbide level of rough machining is C2 and that of finish machining is C3. These are the milling levels of medium grain for general purpose, where medium grain has excellent wear resistance in rough and finish machining applications requiring sharp edges. The cutting distance of each tooth is 004-. SFM can be obtained between 014. In addition, cermet grade is ideal for wrought aluminum materials that require good edge toughness and lubricity. SFM can be obtained by using these ceramic blades. For end mills and plane milling cutters, the cutting amount per tooth is generally 006-. 014. The blade is designed with a good positive knife face angle to ensure that the debris leaves the blade as soon as possible

in most cases, the only requirement is the uncoated carbide level. Aluminum is easy to cut, and the extra cost of using any coating is usually difficult to prove cost-effective

however, in high-speed machining, you can choose to use PCD blades hard welded with polycrystalline diamond, because it has excellent surface finish, which can be produced when the speed is increased

beryllium copper

in terms of thermal conductivity characteristics, copper based alloy molds can bring many benefits to mold manufacturers. They also have hardness levels from 10 to 40rc, almost twice that of aluminum. However, the carbide grade C2 applicable to machined aluminum is also applicable here. The recommended cutting amount and speed for rough and finish machining are slightly less. It is more realistic between SFM, and the cutting amount of each tooth is 003-. 008in. On the other hand, it is recommended that the positive front angle of the blade design be at least 7 degrees

P20 tool and die steel

P20 is a commonly used die steel, which is usually chromium, nickel and molybdenum alloys. It is generally quenched and tempered with a uniform hardness of about 32rc. A very smooth surface finish can be obtained by using P20 steel. However, depending on the machining variables and the desired surface finish, the blade level and coating type that can be used can be expanded. A coated blade or cermet may be the best solution because it can obtain a higher cutting amount. For rough machining, C5 and C6 carbide grades are recommended, and C6 and C7 grades are recommended for finish machining. The impact toughness of the carbide substrate is required to be good - a substrate with both the lubricity of tin coated CVD and the wear resistance of multi-layer CVD with tin/ticn/al2o3/tin coating. Tic/ticn cermet can also be used because it has good edge toughness. Rough machining can obtain machining speed between sfms, and finish machining can obtain machining speed between sfms

with different coatings, the cutting amount of each tooth can be within 005-. 008in. The use of uncoated carbide materials can also be successful. These materials have good edge toughness and impact strength. However, it is really unrealistic to require a lower machining speed today

it should be pointed out that harder tool steels - such as those over 45rc - are still in use today in order to produce a better surface finish and eliminate all polishing operations. Try to use the cutting tool blades that process P20 steel and test the cutting amount and speed. It will be a good start

stainless steel series

these include all 400 series stainless steel. Generally, the hardness range of these stainless steels is also the ideal material for manufacturing automobile dashboard, which is between RC. The heavy carbide substrate required here is better. CVD coating tic/ticn/tin or tin/ticn/al2o3/tin blade works well. In addition, PVD coating tin is as effective as Ti TiCN coating cermet. As usual, they all come for speed. Using CVD coating can run faster. Of course, ceramic and metal are the fastest - characterized by rough machining from 360 to 650sfm and fine machining from 400 to 850sfm. Each tooth is in 004～. Between 012in, the cutting amount of each tooth is quite stable

superalloy

in order to prolong the service life of the mold, the mold manufacturers continue to conduct tests on harder nickel based and cobalt based model materials. The machinability of these materials has always been a disadvantage. They are very hard. Sometimes the hardness tester is a precision instrument, and the hardness reaches 57rc. Generally, new AlTiN coatings with high aluminum content are very effective because of their higher hardness and oxidation stability. The coating adopts a unique sputtering ion process, which can cast a thick and uniform coating. The coating acts as an insulation layer, which transfers the generated heat to the debris rather than the blade. The rough machining speed is between 80 ~ 115sfm, and the finishing speed is 90sfm. The cutting distance of each tooth is 004～. 012in. Diamond coating is still in the development stage, but it will eventually become an option, which will make the machining of these superalloy materials more effective

conclusion

in the process of mold manufacturers continuing to use different mold materials to optimize the molding process, the machinability of these materials and the economy of metal cutting process are also changing. Cutting tool blade manufacturers will continue to develop new materials, coatings and processes to improve the wear resistance and tool life of these cutting tools. New micro carbide grade in PVD TiAIN coating（