CNC engraving machines are good at finishing small tools and have the capabilities of milling, grinding, drilling and high-speed tapping. They are widely used in many fields such as 3C industry, mold industry, and medical industry. This article collects common questions about CNC engraving processing.
1. What are the main differences between CNC engraving and CNC milling?
Both CNC engraving and CNC milling use the principle of milling. The main difference is in the diameter of the tools used. The commonly used tool diameter range for CNC milling is 6-40 mm, while the tool diameter for CNC engraving is 0.2-3 mm.
2. Can CNC milling only do rough machining, while CNC engraving can only do fine machining?
Before answering this question, we first understand the concept of process. The roughing process requires a large amount of processing, while the finishing process requires a small amount of processing. Therefore, some people habitually regard roughing 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 correct answer to this question is that CNC milling can do heavy cutting or light cutting, while CNC engraving can only do light cutting.
3. Can CNC engraving be used for rough machining of steel materials?
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 shape of the mold allows the use of tools with a diameter exceeding 6 mm, it is strongly recommended to CNC mill first and then use engraving to remove the remaining material.
4. Can engraving be completed by adding a speed-increasing head to the spindle of a CNC machining center?
Can’t be done. This product appeared at the exhibition 2 years ago, but it could not complete the engraving process. The main reason is that the CNC machining center is designed with its own tool range in mind, and the overall structure is not suitable for engraving processing. The main reason for this misconception is that they mistakenly regard the high-speed electric spindle as the only feature of the engraving machine.
5. CNC engraving can use tools with very small diameters. Can it replace EDM?
Not replaceable. Although engraving has narrowed the tool diameter range for milling, small molds that could only be machined with EDM before can now be realized with engraving. However, the length/diameter ratio of engraving tools is generally around 5:1. When using small-diameter tools, only very shallow cavities can be machined, while the EDM process has almost no cutting force. As long as the electrode can be produced, the cavity can be machined.
6. What are the main factors that affect engraving processing?
Mechanical processing 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.
7. What are the requirements for the control system of CNC engraving processing?
CNC engraving processing is first of all milling processing, so the control system must have the ability to control milling processing. For small tool processing, a feedforward function must be provided to slow down the path in advance and reduce the breakage frequency of small tools. At the same time, the cutting speed should be increased on smoother path sections to improve the efficiency of engraving processing.
8. What characteristics of materials affect processing?
The main factors that affect the engraving performance of materials are material type, hardness, and toughness. Material categories include 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, and the greater the hardness of the particles inside the material, the worse the processability. A general standard is: the higher the carbon content, the worse the processability; the higher the alloy content, the worse the processability; the higher the content of non-metallic elements, the better the processability (but the non-metallic content in general materials is strictly controlled of).
9. What materials are suitable for engraving?
Non-metallic materials suitable for engraving include organic glass, resin, wood, etc. Non-metallic materials not suitable for engraving include natural marble, glass, etc. 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, etc.
10. What impact does the tool itself have on processing, and how?
Tool factors that affect engraving processing include tool materials, geometric parameters, and grinding technology. The tool material used in engraving processing is cemented carbide material, which is a powder alloy. The main performance indicator that determines the performance of the material is the average diameter of the powder. The smaller the diameter, the more wear-resistant the tool is and the higher its durability. 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 tool needs to be sharper. When the hardness of the processed material is relatively high, the sharpness must be reduced to improve the durability of the tool. But it cannot be too blunt, otherwise the cutting force will be too large and affect the processing. The key factor in tool grinding is the mesh size of the finishing grinding wheel. A grinding wheel with a high mesh number can grind a finer cutting edge, which can effectively improve the durability of the tool. A grinding wheel with a high mesh number can grind a smoother flank surface and improve the surface quality of the cutting.
11. What is the formula for tool life?
Tool life is mainly the tool life during 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 cutting amount per revolution, and P is the cutting depth). Among them, the biggest influence on tool life is the cutting linear speed. In addition, the radial runout of the tool, the grinding quality of the tool, the tool material and coating, and the coolant will also affect the durability of the tool.
12. How to protect engraving machine tools during the processing process?
1) Protect the tool setter and prevent it from being corroded by oil too much.
2) Pay attention to the control of flying chips. Flying chips are very harmful to machine tools. Flying chips into the electric control cabinet will cause a short circuit. Flying into the guide rail will reduce the life of the screw and guide rail. Therefore, during processing, the machine tool must be The main part is sealed well.
3) When moving the lighting lamp, do not pull the lamp holder, as this may easily damage the lamp holder.
4) During the processing, do not get close to the cutting area for observation to avoid flying chips from hurting your eyes. When the spindle motor is rotating, no operations are allowed on the work surface.
5) When opening and closing the machine door, do not open and close it violently. During finishing, the impact and vibration during the door opening process will cause knife marks on the machined surface.
6) Set the spindle speed before starting processing. Otherwise, due to the slow start-up of the spindle, processing will start without reaching the desired speed, causing the motor to suffocate.
7) It is prohibited to place any tools or workpieces on the crossbeam of the machine tool.
8) It is strictly prohibited to place magnetic tools such as magnetic chucks and dial indicator holders on the electrical control cabinet, otherwise the display will be damaged.
13. The new tool is holding back during machining, and the machining is very laborious. 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 bear the current cutting amount. The reasonable approach is to re-make the path and reduce the cutting depth, grooving depth and trimming amount. If the overall processing time is less than 30 minutes, the cutting condition can also be improved by adjusting the feed speed.
14. What is the function of cutting fluid?
Be careful to add cooling oil when working with metal. The function of the cooling system is to take away cutting heat and flying chips, and to lubricate the machining process. The coolant takes the cutting heat away, reducing the heat transferred to the tool and motor and extending their service life. Take away flying chips to avoid secondary cutting. Lubrication can reduce cutting forces and make processing more stable. In copper processing, the use of oily cutting fluid can improve the surface quality.
15. What are the stages of tool wear?
The wear of cutting tools is divided into three stages: initial wear, normal wear, and sharp wear. In the initial wear stage, the main cause of tool wear is that the tool temperature is low and has not reached the optimal cutting temperature. At this time, the tool wear is mainly abrasive wear. Such wear has a greater impact on the tool and can easily lead to tool collapse. knife. This stage is a very dangerous stage. If not handled properly, it may directly lead to tool collapse and failure. When the tool passes through the initial wear period and the cutting temperature of the tool reaches a certain value, the main wear is diffusion wear, which mainly causes 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.
16. Why do tools need to be run-in and how to run-in?
We mentioned above that the tool is prone to chipping during the initial wear stage. In order to avoid tool chipping, we must run in the tool. Gradually increase the cutting temperature of the tool to a reasonable temperature. After experimental verification, the comparison was carried out using the same processing parameters. It can be seen that after running-in, the tool life has increased by more than 2 times.
The running-in method is to reduce the feed speed by half while maintaining a reasonable spindle speed. The processing time is about 5 to 10 minutes. Use a small value when processing soft materials and a large value when processing hard metals.
17. How to judge whether the tool is seriously worn?
The method to judge severe tool wear is:
1) Listen to the processing sound, and there will be a harsh cry;
2) Listening to the sound of the spindle, there is obvious rotation phenomenon of the spindle;
3) I feel that the vibration increases during processing, and the machine tool spindle vibrates obviously;
4) Looking at the processing effect, the knife pattern on the processed bottom surface is sometimes good or bad (if this is the case at the beginning, it means that the cutting depth is too deep).
18. When should the tool be changed?
We should change the tool at about 2/3 of the tool life limit. For example, if the tool is severely worn at 60 minutes, the next time the tool is processed, the tool should be changed at 40 minutes, and a habit of regular tool change should be developed.
19. Can severely worn tools continue to be processed?
After the tool is severely worn, the cutting force can increase to 3 times normal. The cutting force has a great influence on the service life of the spindle electrode. The relationship between the life of the spindle motor and the force is inversely proportional to the third power. For example, when the cutting force is increased by 3 times, processing for 10 minutes is equivalent to using the spindle for 10*33=270 minutes under normal conditions.
20. How to determine the protrusion length of the tool during rough machining?
The shorter the tool extension, the better. However, in actual processing, if the length of the tool is too short, the length of the tool must be adjusted frequently, which will greatly affect the processing efficiency. So how to control the extension length of the tool in actual processing? The principle is this: a φ3 diameter tool bar can be processed normally if it extends 5mm. The φ4 diameter tool shank extends 7mm and can be processed normally. The φ6 diameter tool bar can be processed normally if it extends 10mm. When cutting, try to get below these values. If the length of the upper knife is greater than the above value, try to control it to the depth of processing when the tool is worn. This is a bit difficult to grasp and requires more practice.
21. How to deal with a sudden tool breakage during processing?
1) Stop processing and check the current serial number of processing.
2) Check the broken knife point to see if there is a broken knife body, and if so, take it out.
3) Analyze the reason for the broken tool. This is the most important thing. Why did the tool break? If we want to analyze it, we must analyze it from the various factors that affect processing mentioned above. But the reason for the broken knife is that the force on the knife suddenly increases. Either there is a path problem, or the tool shakes too much, or there are hard lumps in the material, or the spindle motor speed is incorrect.
4) After analysis, replace the tool for processing. If the path is not changed, the original serial number must be processed one serial number earlier. At this time, attention must be paid to lowering the feed speed. First, because the broken tool is severely hardened, and second, the tool needs to be run-in.
22. How to adjust the processing parameters when roughing conditions are not good?
If the tool life cannot be guaranteed at a reasonable spindle speed, when adjusting parameters, adjust the tool engagement depth first, then adjust the feed speed, and then adjust the lateral feed amount. (Note: There is also a limit to adjusting the cutting depth. If the cutting depth is too small, there will be too many layers. Although the theoretical cutting efficiency is high, the actual processing efficiency is affected by other factors, resulting in the processing efficiency being too low. At this time, you should change to a smaller tool for processing, but the processing efficiency will be higher. Generally speaking, the minimum cutting depth should not be less than 0.1mm.
