Function of High Speed Hard Milling of Molds

High speed hard milling of dies and moulds is widely used because it can obtain better surface quality, significantly shorter processing time, shorter production process and lower processing cost.

High Speed Hard Milling of Molds

When high-speed hard milling is applied in mold manufacturing, the following principles should be observed:

1. The overhang of the tool should be as short as possible, and the tool handle of the tool should have a sufficient clamping length in the hot installed and cold shrinkable tool holder.

2. The forward milling method should be adopted in order to improve the service life of the tool (at least 20%) and obtain better machining surface quality.

3. The circular run out error of end mills should be as small as possible.

4. Wet machining should be abandoned and cooled compressed air should be used for chip blowing and tool cooling as much as possible.

5. The appropriate cutting speed and feed speed should be selected according to the material, hardness and processing conditions of the mold.

6. During rough milling, most of the material allowance should be cut off as much as possible, that is, a machining allowance of about 0.05 mm should be reserved for fine milling, and the semi fine milling process should be avoided to shorten the production process.

Why Choose Compressed Air For Chip Blowing And Tool Cooling?

During high-speed hard milling, high temperature will be generated on the cutting edge. If coolant is used for cooling and lubrication, sharp temperature sudden change load will be generated on the tool, resulting in micro cracks in the structure of cemented carbide tool body. In this way, the tool will fail prematurely. Therefore, it is not suitable to use coolant for cooling and lubrication during high-speed hard milling, and dry hard machining should be used. However, considering that the cutting temperature during hard milling increases with the increase of workpiece hardness and cutting speed, micro lubrication can also be considered in high-speed hard milling when the workpiece hardness is not very high. When the workpiece hardness is very high, this micro lubrication will also cause a strong thermal shock load on cemented carbide tools. Therefore, for this kind of high-speed hard milling, compressed cold air should be used to blow away the chips to avoid thermal shock load, and the tool life can generally be increased by 20 ~ 30%. In addition, especially for six edge end mills, the use of compressed air blowing can also avoid the entanglement of chips during processing.

When compressed cold air is used to blow chips, the pressure of compressed air shall at least reach 0.6MPa. For example, a die with a hardness of 61hrc uses compressed air with a pressure of 0.6MPa and cooled to -30 ℃ during high-speed hard milling. Such compressed cold air is not only conducive to blowing away chips, but also can improve the durability of the tool by 30% under the most favorable circumstances.

It should be mentioned here that the compressed cold air used here is to accelerate the compressed air to the speed of sound through a special vortex tube device. During the acceleration process, it is separated into cold and hot parts, which are led out respectively. The resulting cold air of -30 ℃ is then blown through the plastic hose equipped with nozzle and aligned with the milling cutter blade.

Function of High Speed Hard Milling of Molds | CNCLATHING

High Speed Hard Milling of Molds

Why Choose Compressed Air For Chip Blowing And Tool Cooling?

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