22 Common Senses that High Precision CNC Engraving Must Know

Application of high precision CNC engraving service

High precision CNC engraving is good at small tool finishing, with the ability of milling, grinding, drilling, and high-speed tapping, and is widely used in the 3C industry, mold industry, medical industry, and other fields. This article collects frequently asked questions about CNC engraving.

1. What is the main difference between high precision CNC engraving and CNC milling?

Both high precision CNC engraving and CNC milling use the milling principle. The main difference is in the diameter of the tool 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. Is CNC milling only for rough machining and high precision CNC engraving for finishing?

Before answering this question, let's first understand the concept of process. The amount of machining in the roughing process is large, and the amount of finishing machining is small. Some people habitually regard roughing as "heavy cutting" and finishing as "light cutting." Roughing, semi-finishing, and finishing are process concepts that represent different processing stages. Therefore, the accurate answer to this question is that CNC milling can do heavy or light cutting, while CNC engraving can only do the light cutting.

3. Can high precision CNC engraving be used for rough machining of steel materials?

To judge whether CNC engraving can process a certain material depends on how big a tool 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 of more than 6 mm, CNC milling is strongly recommended, followed by engraving to remove the remaining material.

4. Can the engraving process be completed by adding a speed-increasing head to the spindle of the CNC machining center?

Can not finish it. This product appeared at the exhibition 2 years ago, but it could not complete the engraving process. The main reason is that the design of the CNC machining center considers its tool range, and the overall structure is unsuitable for engraving processing. The main reason for this misconception is that they mistook the high-speed motorized spindle as the only feature of the engraving machine.

5. high precision CNC engraving can use small diameter tools. Can it replace EDM?

It cannot be replaced. Although engraving has reduced the range of tool diameters for CNC machining milling, small molds that were previously only possible with EDM can now be achieved with engraving. However, the length/diameter ratio of engraving tools is generally around 5:1. When using a small diameter tool, only a very shallow cavity can be machined, and 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 the engraving process?

Machining is a relatively complex process. Many factors affect it, mainly the following: machine tool characteristics, tools, control systems, material characteristics, processing technology, auxiliary fixtures, and the surrounding environment.

7. What are the requirements for the control system of high precision CNC engraving?

CNC engraving processing is milling processing first, so the control system must have the control ability of milling processing. For small tool processing, the feedforward function must be provided simultaneously, the path speed is reduced in advance, and the frequency of tool breakage of small tools is reduced. At the same time, increasing the cutting speed in the relatively smooth path section is necessary, thereby improving the engraving processing efficiency.

8. What properties of the material affect processing?

The main factors affecting materials' engraving performance are material type, hardness, and toughness. Material categories include metallic and non-metallic materials. The higher the hardness, the worse the processability, and the higher 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 non-metallic element content, and the better the workability (but the non-metal content in the available material is strictly controlled. of).

9. Which materials are suitable for engraving?

Non-metallic materials suitable for engraving include plexiglass, resin, wood, etc.; non-metallic materials unsuitable for engraving include natural marble, glass, etc. Metal materials suitable for engraving include copper, aluminum, and mild steel with hardness less than HRC40, and metal materials unsuitable for engraving include quenched steel.

10. What effect does the tool have on machining, and how?

The tool factors that affect the engraving process include tool material, geometric parameters, and grinding technology. The tool material used in engraving processing is cemented carbide, a powder alloy. The main performance index that determines the material's performance is the powder's average diameter. The smaller the diameter, the more wear-resistant the tool, and the higher the durability of the tool. For more CNC programming knowledge, pay attention to the WeChat public account (NC programming teaching) to receive the tutorial. The sharpness of the tool mainly affects the cutting force. The sharper the tool, the lower the cutting force, the smoother the machining, and the higher the surface quality, the lower the tool's durability. Therefore, different sharpness should be selected when processing different materials. When processing soft and sticky materials, the tool needs to be sharper. When the hardness of the processing material is large, the sharpness should be reduced to improve the tool's durability. But not too blunt. Otherwise, the cutting force will be too large, affecting the processing. A key factor in tool grinding is the mesh size of the finishing wheel. Grinding wheels with high mesh can grind finer cutting edges, effectively improving the tool's durability. Grinding wheels with high mesh can grind a smoother flank and improve the surface quality of cutting.

11. What is the tool life formula?

The 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 line speed, f is the amount of cutting tool per revolution per red, and P is the cutting depth). Among them, the cutting line speed is the biggest influence on tool life. In addition, tool runout, grinding quality, material and coating, and coolant affect tool durability.

12. How to protect the engraving machine equipment during the processing?

1) Protect the tool setter from excessive soil erosion.

2) Pay attention to the control of flying chips. Flying chips are very harmful to the machine tool. Flying 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 should seal the main part well.

3) When moving the lamp, do not pull the lamp head. It is easy to break the lamp head.

4) During processing, do not observe near the cutting area to avoid flying chips from hurting the eyes. Do not perform any operations on the work surface when the spindle motor is rotating.

5) When opening and closing the door of the machine tool, do not open and close it violently. During finishing, the impact and vibration during the opening process will cause the machined surface to have knife lines.

6) Give the spindle speed, and then start processing. Otherwise, because the spindle starts to rotate slowly, it will start processing without reaching the desired speed, causing the motor to suffocate.

7) It is forbidden to place any tools or workpieces on the beam of the machine tool.

8) It is strictly forbidden to place magnetic tools such as magnetic suction cups and dial indicator holders on the electric control cabinet. Otherwise, the display will be damaged.

13. During the machining process of the new tool, the turning phenomenon occurs, and the machining is very laborious. What parameters need to be adjusted at this time?

The laborious processing is because the spindle's power and torque cannot withstand the current cutting amount. The reasonable approach is to re-make the path and reduce the depth of the knife, the depth of the slot, and the amount of trimming. If the overall processing time is less than 30 minutes, the cutting state can also be improved by adjusting the cutting speed.

14. What is the function of cutting fluid?

Metal processing pays attention to adding cooling oil. The cooling system's function is to remove the cutting heat and flying chips and lubricate the machining. Coolant removes the cutting heat, reduces heat transfer to the tool and motor, and increases service life. Take the flying chips away to avoid the phenomenon of secondary cutting. Lubrication can reduce cutting forces and make machining more stable. In copper processing, selecting oily cutting fluid can improve the surface quality.

15. What are the stages of tool wear?

The tool's wear 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's temperature is low and does not reach the optimal cutting temperature. At this time, the tool's wear is mainly abrasive wear, which has a greater impact on the tool. More CNC programming knowledge Pay attention to the WeChat public account (CNC programming teaching) to receive the tutorial, which can easily lead to tool breakage. This stage is very dangerous, and if not handled properly, it may lead to tool breakage and failure. When the tool passes the initial wear period, the cutting temperature reaches a certain value, which is the main wear is diffusion wear, and its role is mainly to cause local spalling. Therefore, the wear is relatively small and relatively slow. When the wear reaches a certain level, the tool fails and enters a period of rapid wear.

16. Why should the tool be run, and how?

We mentioned above that the tool easily breaks in the initial wear stage. To avoid the phenomenon of chipping, we must run the tool. The cutting temperature of the tool is gradually increased to a reasonable temperature. Validated experimentally, comparisons were made using the same machining parameters. 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 to 10 minutes. Take a small value when machining soft materials and a larger value when machining hard metals.

17. How to judge severe tool wear?

The method for judging severe tool wear is:

1) Listening to the processing sound, there is a harsh cry;

2) Listening to the sound of the main shaft, the main shaft has an obvious stagnation phenomenon;

3) It feels that the vibration increases during processing and the machine tool spindle has obvious vibration;

4) Looking at the processing effect, the processed knife pattern on the bottom surface is sometimes good or bad (if it is like this at the beginning, it means that the depth of the knife is too deep).

18. When should the tool be changed?

We should change the tool around 2/3 of the tool life limit. For example, the tool is severely worn in 60 minutes. In the next machining, you should start changing the tool at 40 minutes and develop the habit of changing the tool regularly.

19. Can a severely worn tool continue machining?

After severe tool wear, the cutting force can be increased to 3 times 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, machining for 10 minutes is equivalent to using the spindle for 10*33=270 minutes under normal conditions.

20. How to determine how long the tool sticks out during roughing?

The shorter the extension of the tool, the better. However, in actual processing, if it is too short, the length of the tool should be adjusted frequently, which will greatly affect the processing efficiency. So how do we control the protruding length of the tool in actual processing? The principle is this: a 3-diameter shank can be processed normally with a 5mm extension. The φ4 diameter shank extends 7mm and can be processed normally. The φ6 diameter shank extends 10mm and can be processed normally. Try to get below these values ​​when you apply the knife. If the length of the upper knife is greater than the above value, try to control the depth of processing when the tool is worn. This is a bit difficult to grasp and requires more exercise.

21. How to deal with the suddenly broken tool during processing?

1) Stop processing and check the current serial number of processing.

2) Check the broken tool to see if there is a broken tool body; if so, take it out.

3) Analyze the reasons for the broken tool. This is the most important; why is the tool broken? If we want to analyze, we need to analyze the various factors that affect the processing mentioned above. But the reason for the broken knife is that the force on the knife suddenly increased. Either the path is wrong, the tool shakes too much, the material has a hard block, or the spindle motor rotates incorrectly.

4) After analysis, replace the tool for processing. If the path is not replaced, the original serial number should be processed by a serial number in advance. At this time, paying attention to reducing the feed speed is necessary. One is that the broken tool is hardened seriously, and the other is that the tool must be run in.

22. How to adjust the processing parameters when the roughing condition is not good?

If the tool life is still not guaranteed at a reasonable spindle speed, when adjusting the parameters, adjust the depth of the knife first, then adjust the feed speed, and then adjust the lateral feed. (Note: There is also a limit to adjusting the cutting depth. If the cutting depth is too small, there will be too many layers, and the theoretical cutting efficiency is high. Still, the actual processing efficiency is affected by other factors, resulting in too low processing efficiency. At this time, a smaller tool should be used for processing, but the processing efficiency is higher. Generally speaking, the minimum depth of the knife cannot be less than 0.1mm.

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