Discussion on high speed cutting technology and op

2022-07-23
  • Detail

High speed cutting technology has become the development direction of modern mold manufacturing industry and has brought significant changes to the mold processing technology. In this paper, the influence of high-speed cutting on die roughness is studied, and the high-speed cutting process and optimization suitable for die machining are discussed

in recent years, high-speed machining technology has been more and more widely used in developed countries such as Europe and the United States. Taking mold machining as an example, a large number of high-speed cutting machines are gradually replacing electrical machining equipment to carry out efficient and precise machining of mold cavity. At present, the mold manufacturing and processing in China are mainly ordinary machining and EDM. The process is cumbersome, low efficiency and long cycle, which is becoming more and more inadequate under the trend of accelerating product upgrading in today's market. High speed cutting technology has a bright application prospect in shortening the mold manufacturing cycle and reducing the cost because of its high speed, high quality and direct processing of hardened steel

high speed cutting technology can be traced back to the high speed cutting theory put forward by Dr. carlsalomon of Germany in the 1930s. Compared with traditional cutting, high-speed cutting has higher cutting speed and machining efficiency; And the surface quality after processing is high. Hardened materials with hardness up to 50-60hrc can be directly processed to realize "cutting instead of grinding". Compared with EDM in traditional mold machining, high-speed cutting saves the process of electrode design and machining, significantly improves the machining accuracy, greatly reduces or even cancels the fitter's polishing amount and grinding matching amount, and greatly improves the machining efficiency. Statistics have proved that high-speed cutting can reduce the machining cycle by at least 40% or more for molds with general complexity. Even for some mold cavity surfaces with particularly complex shapes (such as deep grooves and narrow slots), EDM is still required, and high-speed milling can also help to obtain higher quality EDM graphite electrodes

1 research on mold surface roughness in high-speed cutting

surface roughness is a very important indicator of mold surface quality. The impact of high-speed cutting on surface roughness can be achieved through experiments. Experimental conditions: the cutting material is mold steel 3Cr2Mo, the tool material is SG4 ceramic, and the tool diameter is 100mm. The angle is 75 ° for adhesive manufacturers who want to achieve product differentiation through innovation, The axial forward angle and radial forward angle are both 0 °, single edge. The effect on surface roughness was observed by changing cutting speed, feed rate, axial and radial cutting depth

the experimental results show that the roughness decreases with the increase of cutting speed. When the speed reaches 1000mm/min, the surface roughness reaches the minimum value, and the grinding effect is completely achieved. In the process of high-speed cutting, the increase of cutting speed shortens the contact extrusion time between the tool and the workpiece, and reduces the plastic deformation of the workpiece. High cutting speed is not conducive to the formation of chip nodules, so better surface quality can be obtained. On the other hand, the high rotation speed of the spindle also makes the excitation frequency of the machine tool very high during cutting, which is far greater than the natural frequency of the process system, reducing the possibility of resonance and improving the machining accuracy and surface quality. In the experiment, when the cutting speed exceeds 1000mm/min, RA shows an upward trend, which is mainly caused by tool grinding

relative to the cutting speed, the increase of feed speed, axial cutting depth and radial cutting depth in high-speed cutting will make the surface roughness become larger. Therefore, it can be concluded from the experiment that higher cutting speed should be selected when selecting cutting parameters in actual high-speed cutting, and smaller feed speed and cutting depth are more conducive to improving surface roughness

2 mold high-speed cutting process

2.1 the cutting method is in the mailbox: ang@ when determining the mold processing process, we should consider adapting to the requirements of high-speed cutting, and try to select the forward milling. During the forward milling, the chip thickness generated by the tool just cutting into the workpiece is the maximum, and then gradually decreases. It is just the opposite in the up milling, so the friction between the tool and the workpiece is greater in the up milling, the heat generated on the blade is more than that in the down milling, and the radial force is also greatly increased, thus reducing the service life of the tool

2.2 the direct vertical downward feeding mode shall be avoided when machining the die. Oblique line feed or spiral feed is more suitable for the needs of high-speed machining of mold cavity. The oblique feed mode is to gradually increase the axial cutting depth movement to the set axial cutting depth value, the milling force is gradually increased, the impact on the tool and spindle is small, and the phenomenon of tool collapse can be significantly reduced. The screw feed starts from the top of the workpiece, and the screw cuts into the workpiece downward. Because of the continuous machining method, it is easy to ensure the machining accuracy, and there is no sudden change in speed, so it can be processed at a higher speed

2.3 tool path high speed cutting puts forward higher requirements for the setting of tool path. In high speed cutting, because the cutting speed and feed speed are very fast, if the tool path is unreasonable, it is very easy to cause sudden change of cutting load in the cutting process, which will bring impact to the machining, damage the machining quality, and damage the tool and even the equipment. This damage is much more serious than in ordinary cutting. Therefore, the corresponding tool path should be selected according to different machining objects and shapes in high-speed cutting, and high speed and efficiency should not be pursued blindly

in the process of mold cavity machining, most of the tool motion tracks are not simple straight line but curve motion. At this time, special attention should be paid to the inertia impact caused by high-speed motion. When the cutting direction changes, the change is gradual rather than sudden. For example, when cutting the corner of the mold cavity, try to use arc transition to make the steering smooth. At the same time, if you can properly reduce the feed speed, we have launched the old carton recycling plan at these sites, which has a better effect. This setting can reduce the impact on the system and avoid damage to the tool or workpiece caused by over cutting. In the traditional machining method of cavity corner, linear cutting is generally used. When approaching the corner, the movement speed slows down and the feed reversing is completed at the same time. During this period, the movement of the tool is discontinuous, and a lot of friction and heat will be generated in the intermittent process; After setting the corner as an arc to avoid large accidents, the arc interpolation movement of the NC machine tool is a continuous process, so the intermittent movement of the tool will not occur, thus reducing the contact length and time between the tool and the workpiece, and avoiding the impact of overheating on the surface quality of the die

in high-speed cutting, the tool path should be kept stable to avoid sharp speed changes. Because the sudden acceleration or deceleration will lead to the instantaneous change of cutting thickness, which will lead to the change of cutting force and make the machining become unstable, thus reducing the machining quality of the workpiece. Many modern CAM software provide the function of optimizing cutting speed, so it is necessary to select the appropriate cutting speed and acceleration/deceleration strategy according to the needs to reduce the impact of speed changes on machining

3 conclusion

using high-speed cutting in mold cavity processing can greatly improve the processing efficiency of mold manufacturing, and has a good promotion prospect for the domestic mold industry. In the practical application of high-speed cutting, different from the traditional machining, the advantages of high-speed cutting can be brought into full play only by selecting reasonable cutting parameters and combining appropriate machining processes according to the specific requirements of the die and the characteristics of high-speed cutting

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