Carved CNC Machining: 22 Common Senses That CNC Carved Machining Must Know

 

 

 

CNC engraving machine is good at small tool finishing, with the ability of milling, grinding, drilling and high-speed tapping, and is widely used in 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 CNC engraving and CNC milling?

 

Both 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 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, so some people habitually regard roughing as "heavy cutting" and finishing as "light cutting". In fact, roughing, semi-finishing, and finishing are process concepts, which represent different machining stages. Therefore, the accurate 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 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 6mm, 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 own tool range, and the overall structure is not suitable for engraving machining. The main reason for this misconception is that they mistaken the high-speed motorized spindle as the only feature of the engraving machine.

 

 

5. CNC engraving can use small diameter tools, can it replace EDM?

 

cannot be replaced. Although engraving has reduced the range of tool diameters for 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, and there are many factors affecting it, mainly the following points: machine tool characteristics, tools, control systems, material characteristics, machining technology, auxiliary fixtures and surrounding environment.

 

 

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

 

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

 

 

8. What properties of the material affect machining?

 

The main factors that affect the engraving performance of materials are material type, hardness and toughness. Material categories include metallic and non-metallic materials. In general, 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, 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, the better the workability (but the non-metal content in the general material is strictly controlled. of).

 

 

9. Which materials are suitable for engraving?

 

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

 

 

10. What effect does the tool itself 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 machining is cemented carbide material, which is a powder alloy. The main performance index that determines the performance of the material 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 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, but the lower the durability of the tool. Therefore, different sharpness should be selected when machining different materials. When machining soft and sticky materials, the tool needs to be sharper. When the hardness of the machining material is large, the sharpness should be reduced to improve the durability of the tool. But not too blunt, otherwise the cutting force will be too large, affecting the machining. A key factor in tool grinding is the mesh size of the finishing wheel. Grinding wheels with high mesh can grind finer cutting edges, which can effectively improve the durability of the tool. 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 machining 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, tool grinding quality, tool material and coating, and coolant also affect tool durability.

 

 

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

 

1) Protect the tool setter from excessive oil 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, and flying into the guide rail will reduce the life of the screw and guide rail. Therefore, during machining, the machine tool should be The main part is sealed well.

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

4) During machining, do not observe near the cutting area, so as 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 machining. Otherwise, because the spindle starts to rotate slowly, it will start machining 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 reason for the laborious machining is that the power and torque of the spindle 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 machining 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 machining pay attention to add cooling oil. The function of the cooling system is to take away the cutting heat and flying chips and lubricate the machining. Coolant removes the cutting heat, reducing heat transfer to the tool and motor, increasing their 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 machining, the selection of oily cutting fluid can improve the surface quality.

 

 

15. What are the stages of tool wear?

 

The wear of the tool 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 temperature of the tool is low and does not reach the optimal cutting temperature. At this time, the wear of the tool is mainly abrasive wear, which has a greater impact on the tool. More CNC programming knowledge Pay attention to the WeChat public account (NC programming teaching) to receive the tutorial, which can easily lead to tool breakage. This stage is a very dangerous stage, and if not handled properly, it may directly lead to tool breakage and failure. When the tool has passed the initial wear period, the cutting temperature of the tool 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-in and how?

 

We mentioned above that the tool is easy to break in the initial wear stage. In order 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 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 machining time is about 5 to 10 minutes. Take a small value when machining soft materials, and take 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 machining sound, there is a harsh cry;

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

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

4) Looking at the machining 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 CNC 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 machining, if it is too short, the length of the tool should be adjusted frequently, which will greatly affect the machining efficiency. So how to control the protruding length of the tool in actual machining? 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 machining when the tool is worn. This is a bit difficult to grasp and requires more exercise.

 

 

21. How to deal with the sudden broken tool during machining?

 

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

2) Check the broken tool to see if there is a broken tool body, and 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 machining mentioned above. But the reason for the broken knife is that the force on the knife suddenly increased. Either the path is wrong, or the tool shakes too much, or the material has a hard block, or the spindle motor rotates incorrectly.

4) After analysis, replace the tool for machining. If the path is not replaced, the original serial number should be processed by a serial number in advance. At this time, it is necessary to pay attention to reducing the feed speed. One is because the broken tool is hardened seriously, and the other is to carry out the tool running-in.

 

 

22. When the roughing condition is not good, how to adjust the machining parameters?

 

If the tool life cannot be 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 although the theoretical cutting efficiency is high, the actual machining efficiency is affected by other factors, resulting in too low machining efficiency. At this time, a smaller tool should be used for machining, but the machining efficiency is higher. Generally speaking, the minimum depth of the knife cannot be less than 0.1mm.