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CNC engraving machine is good at fine machining of small tools, with the ability of milling, grinding, drilling and high-speed tapping. It is widely used in 3C industry, mold industry, medical industry and other fields. This article collects common questions about CNC engraving.
Both CNC engraving and CNC milling use the principle of milling. The main difference lies in the diameter of the tool used. Among them, the commonly used tool diameter for cnc manufac turings is 6-40 mm, while the tool diameter for CNC engraving is 0.2-3 mm.
Before answering this question, let us first understand the concept of the process. The rough machining process requires a large amount of machining, but the finishing machining amount is small, so some people habitually regard rough machining as “heavy cutting” and finishing as “light cutting”. In fact, rough machining, semi-finishing, and finishing are process concepts, which represent different processing stages. Therefore, the accurate answer to this question is that CNC milling can be used for heavy cutting or light cutting, while CNC engraving can only be used for light cutting.
To judge whether CNC engraving can process a certain material, it mainly depends on the size of the tool that can be used. The tool used in CNC engraving determines its maximum cutting capacity. If the mold shape allows the use of tools with a diameter of more than 6 mm, it is strongly recommended to use CNC milling first, and then use the engraving method to remove the remaining material.
Can not finish it. This kind of product appeared at the exhibition 2 years ago, but it was unable to complete the engraving process. The main reason is that the design of the CNC machining center takes into account its own range of tools, and the overall structure is not suitable for engraving processing. The main reason for this wrong idea is that they mistakenly regarded the high-speed electric spindle as the only feature of the engraving machine.
Cannot be replaced. Although engraving has narrowed the range of tool diameters for milling, small molds that could only be processed by EDM can now be processed by engraving. However, the length/diameter ratio of the engraving tool is generally around 5:1. When using small-diameter tools, only very shallow cavities can be machined, and there is almost no cutting force in the EDM process. As long as the electrode can be manufactured, the cavity can be machined.
Machining is a relatively complex process, and there are many factors that affect it, mainly including the following points: machine tool characteristics, cutting tools, control systems, material characteristics, processing technology, auxiliary fixtures and surrounding environment.
CNC engraving processing is milling processing first, so the control system must have the ability to control milling processing. For the processing of small tools, the feedforward function must be provided at the same time to reduce the speed of the path in advance to reduce the breaking frequency of small tools. At the same time, it is necessary to increase the cutting speed in a relatively smooth path section to improve the efficiency of engraving processing.
The main factors affecting the engraving performance of the material are the material type, hardness and toughness. The material category includes metallic materials and non-metallic materials. In general, the greater the hardness, the worse the processability, and the greater the viscosity, the worse the processability. The more impurities, the worse the processability, the greater the hardness of the particles inside the material, and the worse the processability. A general standard is: the higher the carbon content, the worse the workability, the higher the alloy content, the worse the workability, the higher the content of non-metal elements, the better the workability (but the non-metal content in general materials is strictly controlled of).
Non-metallic materials suitable for engraving include organic glass, resin, wood, etc., and non-metallic materials that are not suitable for engraving include natural marble and glass. Metal materials suitable for engraving include copper, aluminum, and mild steel with a hardness less than HRC40. Metal materials not suitable for engraving include quenched steel.
The tool factors that affect the engraving process include the tool material, geometric parameters, and grinding technology. The tool material used in the engraving process is cemented carbide material, which is a powder alloy. The main performance index that determines the material performance is the average diameter of the powder. The smaller the diameter, the more wear-resistant the tool, and the higher the durability of the tool. For more china turning knowledge, pay attention to the WeChat public account (CNC programming teaching) to receive the tutorial. The sharpness of the tool mainly affects the cutting force. The sharper the tool, the smaller the cutting force, the smoother the processing, and the higher the surface quality, but the lower the durability of the tool. Therefore, different sharpness should be selected when processing different materials. When processing relatively soft and sticky materials, the cutting tool needs to be sharper. When the processing material is harder, the sharpness should be reduced to improve the durability of the cutting tool. But it should not be too blunt, otherwise the cutting force will be too large, which will affect the processing. The key factor in the grinding of the tool is the mesh number of the fine grinding wheel. A high-mesh grinding wheel can grind a more delicate cutting edge, which can effectively improve the durability of the tool. A high-mesh grinding wheel can grind a smoother flank surface and improve the cutting surface quality.
Tool life is mainly the tool life in the processing of steel materials. The empirical formula is: (T is the tool life, CT is the life parameter, VC is the cutting linear speed, f is the amount of knife per revolution, and P is the depth of the knife). Among them, the cutting linear speed is the biggest influence on tool life. In addition, tool radial runout, tool grinding quality, tool material and coating, and coolant will also affect tool durability.
What parameters need to be adjusted at this time?
The reason why the machining is very laborious is that the power and torque of the spindle cannot withstand the current cutting amount. A reasonable approach is to remake the path to reduce the depth of the tool, the depth of the groove, and the amount of trimming. If the overall processing time is less than 30 minutes, you can also adjust the cutting speed to improve the cutting state.
Pay attention to cooling oil for metal processing. The role of the cooling system is to take away the cutting heat and flying chips, and play a role in lubricating the processing. The coolant will remove the cutting heat, reduce the heat transferred to the tool and the motor, and increase their service life. Take away flying chips to avoid secondary cutting. Lubrication can reduce the cutting force and make the processing more stable. In the copper processing, the selection of oil-based cutting fluid can improve the surface quality.
Tool wear is divided into three stages: initial wear, normal wear, and sharp wear. In the initial stage of wear, the main cause of tool wear is that the temperature of the tool is low, and the optimal cutting temperature is not reached. At this time, the wear of the tool is mainly abrasive wear. Such wear has a greater impact on the tool. More knowledge of CNC programming Pay attention to the WeChat public account (edm machining teaching) to receive the tutorial, it is easy to cause the tool to collapse. This stage is a very dangerous stage. If it is not handled well, it may directly cause the tool to collapse and fail. When the tool passes the initial wear period, the cutting temperature of the tool reaches a certain value. This is the main wear is diffusion wear, and its function is mainly to cause local spalling. Therefore, the wear is smaller and slower. When the wear reaches a certain level, the tool fails and enters a period of rapid wear.
We mentioned above that the tool is easy to collapse in the initial wear stage. In order to avoid the phenomenon of tool collapse, we must run-in the tool. The cutting temperature of the tool is gradually increased to a reasonable temperature. It is verified by experiments that the same processing parameters are used for comparison. It can be seen that after running-in, the tool life has increased by more than 2 times.
The method of running-in is to reduce the feed rate by half while maintaining a reasonable spindle speed, and the processing time is about 5-10 minutes. Take a small value when processing soft materials, and take a large value when processing hard metals.
The method of judging severe tool wear is:
We should change the tool at about 2/3 of the tool life limit. For example, the tool is severely worn in 60 minutes, the next time you process, you should start the tool change in 40 minutes, and develop the habit of changing the tool regularly.
After the tool is severely worn, the cutting force can be increased to 3 times the normal. The cutting force has a great influence on the service life of the spindle electrode. The service life of the spindle motor and the force are inversely proportional to the third power. For example, when the cutting force is increased by 3 times, processing for 10 minutes is equivalent to the spindle using 10*33=270 minutes under normal conditions.
The protruding length of the tool is as short as possible. However, in actual processing, if it is too short, the length of the tool must be adjusted frequently, which will affect the processing efficiency too much. So how should the protruding length of the tool be controlled in actual processing? The principle is as follows: a φ3 diameter cutter bar can be processed normally if it protrudes 5mm. The φ4 diameter tool bar can be processed normally if it protrudes 7mm. The φ6 diameter tool bar can be processed normally if it protrudes 10mm. Try to go below these values when loading the knife. If the length of the upper knife is greater than the above value, try to control the depth of the machining when the tool is worn. This is a bit difficult to grasp and requires more exercise.