xiehe model

It is usually said that the processing hardness exceeds 56HRC, or the strength exceeds Rm> 2000N/mm2. Steel materials are used for hard processing. In most cases, the mold or forging die is carburized or quenched after premachining. After pre-machining, a certain finishing allowance must be reserved. Hard milling is particularly important when machining spherical or annular workpieces.

Hard milling can cut materials up to 70 HRC hardness, and the required surface roughness can usually only be achieved by hand polishing, which is a very expensive processing step. To reduce the time required for manual polishing, cutting edges with defined geometry must be used during the milling process. For example, in HSC processing, the surface roughness is close to that of the polished surface: a maximum surface quality of Rz1. Common hard metal milling cutters on the market are not suitable for cutting in this range. To solve the problem of milling hard materials, some prerequisites must be met.

​For example, use milling cutters made from a special carbide base material with a unique geometry and corresponding coating. This means that the tool must have these three important elements. Special attention must be paid to the balance between these elements during the construction of the tool.

Workpieces with a hardness exceeding 56HRC can usually be cut by HSC machining. In this regard, the limitation is the combined effect of cutting speed and temperature. For HSC, the melting point of the workpiece material must be tested at a suitable cutting speed. Often the melting point of the workpiece material is higher than the maximum allowable temperature of the coating, so care must be taken. The best motto here is "Keep your tools cool." This means that on the one hand the contact area with the workpiece must be as small as possible, and on the other hand the cutting must be carried out at a speed such that the heat reached by the cutting edge does not exceed the temperature allowed by the coating.

Correct detection speed is particularly important. This must be based on the actual effective tool diameter. When the transverse feed ap=0.1mm, the actual effective diameter of a ball end mill with a diameter of 6mm is 1.54mm. In order to achieve a cutting speed of 200m/min, the speed must be 41000r/min.

The chips generated during the machining process and the heat carried by the chips must be removed as soon as possible. The best method is to blow compressed air through the spindle directly onto the cutting edge. Compressed air can carry small amounts of lubricant, depending on the workpiece material. Because chips don't stick to the cutting edge, using a small amount of lubricant produces a better surface quality. For hard cutting, emulsions should never be used. Just a drop of water can cause a sudden temperature change and break the tool into its individual components. Microcracks in cemented carbide caused by sudden temperature changes can lead to cutting edge cracking. In the case of HSC machining, depending on the tool diameter and speed, these fragments can have the energy equivalent to a bullet fired from a small arms weapon.

HSC milling, first developed for graphite cutting, not only means high speed and large feed, but also has a wide range of applications under the combined effect of multiple factors.

The power of hard milling depends largely on the machine tool used. In summary, the concept of hard cutting is related to high-speed machining.