Hard milling technology of the hottest cutting too

Hard milling technology of cutting tools and molds

hard milling technology of cutting tools and molds Abstract: how to ensure the reliable operation of bearings, oil-free bearings drive the revolution in the mold industry, electrical troubleshooting of printing machines, three prospects for China's cutting technology, mathematical processing of graphics, pumps, valves and other water supply equipment and main accessories, basic knowledge of Higher Vocational numerical control major teaching reform practice, lathe coordinate axis and direction introduction, processing technology analysis and research of V-shaped thrust rod spinning Simple cleaning and oiling method of woven seal bearings fault diagnosis of FANUC system fault diagnosis of floor lathe precision parameters poor indexing of turntable fault maintenance of open CNC system in ultra precision machining application of automobile body welding fixture design the new generation Coriolis mass flowmeter CNC machine tool launched by Siemens process instrumentation department is transformed with intelligent functions to optimize milling processing. The new high-speed five axis linkage processing technology and equipment project has passed the national inspection Design of CNC engraving and milling machine numerical control system [label: tag] generally, people call hard cutting for processing steel materials with hardness exceeding 56hrc or strength RM> 2000 n/mm2. In most cases, after pre-processing, the mold or forging die must be carburized or quenched. After pre machining, a certain finishing allowance must be reserved. Especially when machining workpiece with spherical or toroidal shape, hard milling is more important. Hard milling can cut the hardness to 70hrc

generally, people call hard cutting for processing steel materials with hardness exceeding 56hrc or strength RM> 2000 n/mm2. In most cases, after the pre-processing of the mold or forging die, it is necessary to continue to improve the reasonable or higher requirements to the equipment through carburization or quenching. After pre machining, a certain finishing allowance must be reserved. Especially when machining workpiece with spherical or toroidal shape, hard milling is more important. Hard milling can cut materials with hardness up to 70hrc, and the required surface roughness can only be achieved by hand polishing. This is a very expensive processing procedure. In order to shorten the time required for manual polishing, it is necessary to use a knife edge with a certain geometric shape during milling. For example, in HSC processing, make the machined surface close to the roughness of the polished surface: the maximum surface quality is RZ1

hard metal milling cutters commonly used in the market are not suitable for cutting within this range. To solve the problem of milling hard materials, some prerequisites must be met. For example, one solution is to use horn DS milling cutters made of special cemented carbide matrix materials with unique geometric shapes and corresponding coatings. This means that the tool must have the following three important elements, and special attention must be paid to the balance between these elements in the manufacturing process of the tool

cemented carbide

cemented carbide materials are mainly made of tungsten carbide and cobalt by powder metallurgy, and the wear resistance of its matrix increases with the increase of hardness. When milling workpieces with surface hardness exceeding 56hrc, only cemented carbide tools with cobalt content less than 10% and particle diameter less than 0.7 m can be used

conventional ISO K-M or P cemented carbide tools are not suitable for cutting materials with higher strength. Cemented carbide with the finest and ultra-fine particle size has higher piston lift because of its hardness, ultimate strength and toughness, which is obviously more suitable than conventional cemented carbide

geometry

among the used carbide milling cutters, only a few can be used for hard milling. From the perspective of machining, many factors of milling cutter play a decisive role in hard milling. The factors that belong to the geometry of milling cutter are: the accuracy and precision of machining in the range of microns, and the horn DS milling cutter shank must reach the accuracy grade of H5. In particular, the transition between the arc part of the cutting edge of the tool and the auxiliary cutting edge should be smooth without turning points, so as to achieve the maximum cutting stability

cutting hard workpiece materials is very different from cutting traditional soft materials, so it is necessary to design appropriate rake angle, rake angle and wedge angle for hard milling tools

DS spherical, toroidal and micro milling cutters used in hard cutting can only be designed into a double-edged structure. The two main cutting edges of the spherical milling cutter must smooth the signal output by the load sensor without transition. According to the workpiece material and hardness, the maximum transverse feed of hard cutting milling cutter is ap=0.2mm. At this time, only two edges of the four edge milling cutter are cutting. Coating

a hard coating with a thickness of about 3mm can prevent direct wear of cemented carbide. Facts have proved that TiAlN coating has good application effect when the maximum temperature is 800 ~ 1000 ℃. Compared with uncoated cemented carbide tools, increasing hard coating can improve the surface hardness of tools and significantly reduce the friction coefficient. The importance of coating is as important as other elements in the three elements of cemented carbide, geometry and coating. Because it is in direct contact with the workpiece material being cut, it must meet its special requirements

knife handle

in order to achieve the best use, keep clean (it is best to clean after each experiment); Effect. In order to obtain satisfactory machining effect of horn DS milling cutter, appropriate tool handle must be selected. The radial runout of every 1mm will reduce the durability of the milling cutter and weaken its performance

the slotted tool handle or universal spring chuck is not suitable for hard milling because of its large radial runout. The best effect can be obtained by using hydraulic expansion liner or contraction liner. This is the reason why horn tools are used in tool and mold manufacturing, and horn tools are designed into straight cylindrical structure according to DIN 6535 ha standard without exception. The additional clamping surface will destroy the accuracy of the tool and affect its performance

cutting

generally, it is possible to cut workpieces with a hardness of more than 56hrc by using HSC processing. The limiting condition 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. Generally, the melting point of the workpiece material is higher than the maximum temperature allowed by the coating, so care must be taken. The best aphorism here is to keep the tool cool. This means that on the one hand, the contact area with the workpiece must be as small as possible, on the other hand, the cutting process must be completed at a certain speed, so that the cutting edge has no time to heat up beyond the allowable temperature of the coating

it is particularly important to detect the rotating speed correctly. Therefore, it must be based on the actual effective tool diameter. When the transverse feed rate ap=0.1mm, the actual effective diameter of the ball end milling cutter with a diameter of 6mm is 1.54mm. In order to make the cutting speed reach 200m/min, the rotating speed must reach 41000 R/min

the chips produced during processing and the heat brought by the chips must be eliminated as soon as possible. The best way is to blow compressed air directly to the cutting edge through the spindle. According to different workpiece materials, compressed air can carry a small amount of lubricating oil. The workpiece with material of 1.2343 and hardness of 56hrc can be processed with a small amount of lubricating oil to obtain better surface quality, because the chips will not adhere to the cutting edge. For hard cutting, emulsion must not be used. Just a drop of water may cause a sudden change in temperature and decompose the tool into a single component. Micro cracks in cemented carbide caused by sudden temperature changes will lead to the cracking of cutting edges. In the case of HSC processing, depending on the tool diameter and speed, these fragments may have the energy equivalent to bullets fired from light weapons

application

HSC milling, which was first developed for graphite cutting, not only means high speed and large feed, but also its application range continues to expand under the joint action of many factors

discussing the requirements for machine tools is beyond the scope of this article. The power of hard milling depends largely on the machine tool used. In a word, the concept of hard cutting is inseparable from high-speed machining