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Common knowledge of CNC milling machine

Posted by: CCHEN JIANG 2020-10-15 Leave a comment

CNC milling machine engraving machine is good at fine machining of small tools. CNC milling machine has the ability of milling, grinding, drilling and high-speed tapping. It is widely used in 3C occupations, mold occupations, medical occupations and other fields. This article collects common questions about CNC carving.

1. What is the main difference between CNC engraving and milling machine, CNC milling machine and CNC milling?

Both CNC engraving and CNC milling china use the principle of milling. The main difference is the diameter of the tool used. The commonly used tool diameter for CNC milling is 6-40 mm, while the tool diameter for CNC engraving is 0.2-3 mm.

2. Does CNC milling machine\milling can only do rough machining, and CNC engraving can only do fine machining?

Before answering this question, let’s first understand the concept of process. The rough machining process requires a large amount of machining, but the finishing machining amount is small, so some people tend to regard rough machining as “heavy cutting” and finishing as “light cutting”. In practice, rough machining, semi-finish machining, and finishing are the process concepts, which represent different machining stages. Therefore, the accurate answer to this question is that CNC milling can do heavy cutting and light cutting, while CNC engraving can only do light cutting.

3. Can CNC milling machines be used for rough machining of steel materials?

To judge whether CNC carving can process a certain kind of material, first of all depends on how big a tool can be used. The tool used in CNC carving 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 method of carving to remove the remaining data.

4. Can adding a speed-increasing head to the spindle of the CNC machining center complete the carving process?

Can’t end. This product was presented at the exhibition 2 years ago, but it couldn’t be finished. The primary reason is that the planning of the CNC machining center takes into account the scale of its own tools, add WeChat: Yuki7557 to send a copy of the macro program tutorial, the whole structure is not suitable for carving. The primary reason for this wrong idea was that they mistakenly regarded the high-speed electric spindle as the only feature of the carving machine.

5. CNC engraving can use tools with a small diameter. Can it replace EDM?

Not a substitute. Although sculpting has reduced the size of the tool diameter for milling, small molds that could only be processed by EDM can now be realized by sculpting. However, the length/diameter ratio of carving tools is generally around 5:1. When using small-diameter tools, only very shallow cavities can be processed, while the EDM process has almost no cutting force. As long as the electrode can be manufactured, the cavity can be processed.

6. What are the main factors that affect carving?

Machining is a relatively complex process, and there are many factors that affect it. First of all, there are the following points: machine tool characteristics, cutting tools, control systems, data characteristics, machining technology, auxiliary fixtures and surrounding environment.

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

CNC carving machining is first of all milling, so the control system must have the ability to control milling. For the machining of small tools, it is necessary to provide a feedforward function to reduce the speed of the small tools in advance to reduce the breaking frequency of small tools. At the same time, it is necessary to increase the cutting speed in the smoother path section to increase the carving machining power.

8. Which characteristics of the data will affect machining?

The primary factors that affect the function of data carving are data type, hardness, and resistance. The data category includes metal data and non-metal data. In general, the greater the hardness, the worse the processability, the greater the viscosity, the worse the processability. The more impurities, the worse the processability, the greater the hardness of the internal particles of the material, and the worse the processability. A general specification 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 information is strictly controlled of).

9. Which materials are suitable for carving and machining?

Suitable non-metallic materials for carving include organic glass, resin, wood, etc., and non-metallic materials that are not suitable for carving include natural marble and glass. Suitable metal materials for carving include copper, aluminum, and mild steel with a hardness less than HRC40. Metal materials that are not suitable for carving include quenched steel.

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

The tool elements that affect carving machining include tool information, geometry parameters, and grinding skills. The tool material used in carving is a cemented carbide material, which is a powder alloy. The primary functional index that determines the function of the material is the uniform diameter of the powder. The smaller the diameter, the more wear-resistant the tool, and the higher the durability of the tool. More CNC programming common sense pays attention to the WeChat public account (CNC programming education) to receive tutorials. The sharpness of the tool primarily affects the cutting force. The sharper the tool, the smaller the cutting force, the smoother the machining, the higher the surface quality, but the lower the tool durability. Add WeChat: Yuki7557 will send a copy of the macro program tutorial, so you should choose different sharpness when machining different materials. When machining relatively soft and sticky materials, the cutting tools are required to be sharper. When the machining materials are harder, the sharpness should be reduced to improve the durability of the cutting tools. But it should not be too blunt, otherwise the cutting force will be too large, which will affect the machining. The key element of tool grinding is the mesh number of the 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.

11. What is the tool life formula?

The tool life is mainly the tool life in the machining of steel materials. The experience 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 knife depth). The cutting linear speed is the biggest influence on the tool life. In addition, tool radial runout, tool grinding quality, tool materials and coatings, and coolant will also affect tool durability.

12. During the machining process, how to maintain the carving machine equipment?

1) Maintain the tool setting instrument and don’t let it be corroded by oil too much.
2) Pay attention to the control of flying debris. Flying debris is 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 lead screw and the guide rail. Therefore, you must The main part of the machine is well sealed.
3) When moving the lamp, do not pull the lamp cap, it is very easy to pull the lamp cap.
4) During the machining process, do not approach the cutting area for investigation, so as not to injure your eyes with flying chips. When the spindle motor is rotating, stop any operation on the work surface.
5) When opening and closing the door of the machine tool, do not open and close the machine violently. During the finishing process, the shock and oscillation during the door opening process will cause the machined surface to have knife marks.
6) The spindle speed must be given, and then start machining, otherwise the spindle will start to rotate slowly, which will cause the machining to start without reaching the desired speed, which will cause the motor to suffocate.
7) Stop placing anything or workpieces on the beam of the machine tool.
8) It is forbidden to place magnetic objects such as magnetic suction cups and dial indicator holders on the electric control cabinet, otherwise the display will be damaged.

13. There is a phenomenon of stubborn rotation during the machining of the new tool, 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 cutting amount at the time. A reasonable approach is to remake the path to reduce the depth of cutting, groove depth, and trimming. If the overall machining time is less than 30 minutes, the cutting condition can also be improved by adjusting the feed speed.

14. What is the effect of cutting fluid for CNC milling machine?

Pay attention to cooling oil for metal machining. The effect of the cooling system is to take away the cutting heat and flying chips and have a smooth effect on machining. The coolant removes the cutting heat, reduces the heat transferred to the cutting tool and the motor, and improves their service life. Take away flying chips to prevent secondary cutting. The smoothing effect can reduce the cutting force and make the machining more stable. In copper machining, the selection of oil-based cutting fluid can improve the surface quality.

15. CNC milling china machine What are the stages of tool wear?

Tool wear is divided into three stages: initial wear, normal wear, and sharp wear. In the initial stage of wear, the primary cause of tool wear is that the temperature of the tool is low, and the optimal cutting temperature has not been reached. At this time, the wear of the tool is primarily abrasive wear. Such wear has a greater impact on the tool, and more CNC programming knowledge Pay attention to the WeChat public account (CNC programming education) to receive the tutorial, it is very simple to cause the tool to collapse. This stage is a very dangerous stage. Poor handling may directly lead to tool collapse and failure. When the tool passes the initial wear period, the cutting temperature of the tool reaches a certain value. This is the primary wear is scattered wear, and its effect is primarily to cause partial shedding. Therefore, 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 CNC milling machine tools need to be run-in and how to run-in?

We mentioned above that the tool is very simple to collapse in the initial wear stage. In order to prevent the phenomenon of collapse, it is necessary to run-in the tool. The cutting temperature of the tool is gradually increased to a reasonable temperature. It is verified by experiment and compared with 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 speed by half while insisting on using a reasonable spindle speed, and the machining time is about 5-10 minutes. Take a small value when machining soft materials, and take a large value when machining hard metals.

17. How does a CNC milling machine distinguish severe tool wear?

  • The method for the CNC milling machine to distinguish severe wear of the tool is:
    1) Listen to the processed sound, showing a sharp call;
    2) Listening to the sound of the main shaft, the main shaft shows a remarkable holdback phenomenon;
    3) It feels that the sensation in machining has increased, and the machine tool spindle has shown a significant sensation;
    4) Looking at the machining effect, the knives on the processed bottom surface are sometimes good and sometimes bad (if the cutting depth is too deep in the initial stage).

Many of the super-manufactured metal handicrafts handed down in our country have been lost!

18. When should the CNC milling machine change tools?

We should change the tool at about 2/3 of the tool life limit. For example, the tool is severely worn in 60 minutes, and the next time the tool is processed, the tool should be changed in 40 minutes, and the habit of changing the tool on time should be cultivated.

19. Can the tools of severely worn CNC milling machines continue to be processed?

After the tool is severely worn, the cutting force can be increased to three times the normal. The cutting force has a great influence on the service life of the spindle electrode. The life of the spindle motor and the force are inversely related to the third power. For example, a CNC milling machine can process for 10 minutes when the cutting force is increased by 3 times, which is equivalent to using the spindle for 10*33=270 minutes under normal conditions.

20. How to determine the protruding length of the tool during rough machining of the CNC milling machine?

The shorter the extension of the tool, the better. However, in practice machining, if it is too short, the length of the tool must be adjusted frequently, which will affect the machining power too much. So how should the protruding length of the tool be controlled in practice? The principle is as follows: a φ3 diameter cutter bar can be processed normally if it extends 5mm. The φ4 diameter tool bar can be processed normally if it extends 7mm. The φ6 diameter tool bar can be processed normally if it extends 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 training.

21. What should I do if the tool suddenly breaks during machining on a CNC milling china machine?

  • 1) Stop machining and check the current sequence number of machining.
    2) Check if there is a broken knife body at the broken knife, if there is, take it out.
    3) Analyze the reason for the broken tool. This is the most important. Why is the tool broken? If we want to analyze, we must analyze the various factors that affect the machining mentioned above. But the reason for the broken tool is that the force on the tool suddenly increases. Or there is a problem with the path, or the tool chattering too much, or the data is hard, or the spindle motor speed is incorrect.
    4) After analysis, replace the tool for machining. If there is no alternative way, the original serial number should be processed by one serial number in advance. At this time, it is necessary to pay attention to lower the feed rate. One is because the hardening of the broken tool is severe, and the other is the tool running-in.

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