In the process of machining, it is often difficult to use standard tools for machining, so the production of non-standard tools is very important for machining.
The use of non-standard tools in metal cutting is more common in milling, so this paper mainly introduces the production of non-standard tools in milling.
Since the production of standard tools is aimed at the cutting of ordinary metal or non-metal parts with a wide range of surfaces, when the workpiece is overheated and the hardness increases, or the workpiece is stainless steel, it is very easy to stick to the knife, and there are also some workpieces whose surface geometry is very complex, or when the machined surface has high roughness requirements, etc., the standard tool cannot meet the processing needs. Therefore, in the processing process, the material of the tool, the geometry of the knife edge, the geometric angle, etc. need to be designed specifically, which can be divided into two categories: special customization and non-special customization.
Non-custom-made tools mainly solve two problems, namely, dimensional issues and surface roughness issues.
1. Size issues.
You can choose a standard tool with a size similar to the required size, which can be solved by changing the grinding, but two points should also be noted: 1) The size difference should not be too large, generally not more than 2mm, because if the size difference is too large, it will cause the groove shape of the tool to change, directly affecting the chip space and geometric angle; 2) If it is an end mill with an edge hole, it can be changed on a common machine tool, and the cost is lower. If it is a keyway milling cutter without an edge hole, it cannot be carried out on a common machine tool. It needs to be changed on a special five-axis linkage machine, and the cost will be higher.
2. Surface roughness issues.
It can be achieved by changing the geometric angle of the blade. For example, increasing the degree of the front and back angles will significantly improve the surface roughness of the workpiece. However, if the rigidity of the machine tool used is not enough, the edge may be blunt but the surface roughness can be improved. This aspect is very complicated, and a conclusion can only be drawn after analyzing the machining site.
The need for a custom-made tool is mainly to solve three problems, including special shape, special strength and hardness, and special chip capacity and chip removal requirements.
1. The workpiece to be machined has special shape requirements.
Such as lengthening the tools required for processing, adding end teeth inverted R, or having special cone angle requirements, shank structure requirements, blade length size control, etc. If the shape requirements of this type of tool are not very complicated, it is actually easy to solve. The only thing to note is that the processing of non-standard tools is more difficult. Therefore, the user should not pursue high precision excessively when it can meet the processing needs. Because high precision itself means high cost and high risk, it will cause unnecessary waste to the manufacturer's capacity and its own costs.
2. The workpiece to be machined has special strength and hardness.
If the workpiece is overheated, the strength and hardness are high, the general tool material cannot be cut, or the knife is sticky, which requires special requirements for the material of the tool. The general solution is to use high-grade tool materials, such as cobalt-containing high-speed rigid tools with high hardness to cut quenched and tempered workpiece materials, and high-quality carbide material tools can be used to process high-quality hard materials, or even milling instead of grinding. Of course, there are also some special cases, such as when machining aluminum parts, there is a type of super hard tool on the market that is not necessarily suitable. Although aluminum parts are generally soft, it can be said to be an easy-to-machine product. However, the material used in super hard tools is actually an aluminum high-speed steel. This material is indeed harder than ordinary high-speed steel, but when machining aluminum parts, it will cause an affinity between aluminum elements, which will exacerbate the wear of the tool. At this time, if you want to get high efficiency, you can choose cobalt high-speed steel instead.
3. The workpiece to be machined has special chip capacity and chip removal requirements.
At this point, fewer teeth and deeper chip flutes should be selected, but this design can only be used for materials that are easier to machine, such as aluminum alloys.
In the machining design and machining process of non-standard tools, there are many issues that need to be paid attention to: the geometry of the tool is more complex, and during heat treatment, the tool is prone to bending, deformation, or local stress concentration. This should be done in the design to avoid areas prone to stress concentration, and for parts with large diameter changes, plus oblique transition or step design. If it is a slender part with a large aspect ratio, during the heat treatment process, it needs to be checked and straightened every time it is quenched and tempered to control its deformation and beating. The material of the tool is relatively brittle, especially the material of cemented carbide, which makes the tool break once it encounters large vibration or processing torque during processing. This often does not cause great damage in the processing of conventional tools, because the tool can be replaced if it is broken. However, in the processing of non-standard tools, the possibility of replacement is not high, so once the tool breaks, it will cause a series of problems, such as delivery delays, etc., which will cause great losses to the user.
The above is all for the tool itself. In fact, the manufacture of non-standard tools is by no means so simple. It is a systematic project. The experience of the manufacturer's design department and the understanding of the processing conditions of the user will affect the design and production of non-standard tools. The processing and testing methods of the manufacturer's production department will affect the accuracy and geometric angle of non-standard tools. The repeated visits, collection of data and information by the manufacturer's sales department will also affect the improvement of non-standard tools. These will play a decisive role in the success of the user's use of non-standard tools. Non-standard tools are a special kind of tools that are produced according to special requirements. Choosing an experienced manufacturer will save a lot of time and effort for the user.