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22 Common Sense Tips for CNC Engraving Machine Machining
2025-11-13
CNC engraving machines excel at precision machining with small tools and are capable of milling, grinding, drilling, and high-speed tapping. They are widely used in various fields such as the 3C industry, mold industry and medical industry.
1. What are the main differences between CNC engraving and CNC milling?
Both CNC engraving and CNC milling utilize the milling principle. The main difference lies in the diameter of the cutting tools used. CNC milling typically uses cutting tools with diameters ranging from 6 to 40 millimeters, while CNC engraving uses tools with diameters ranging from 0.2 to 3 millimeters.
2. Is CNC milling only for roughing and CNC engraving only for finishing?
Before answering this question, let's first understand the concept of a machining process. Roughing involves a large amount of machining, while finishing involves a smaller amount. Therefore, some people habitually consider roughing as "heavy cutting" and finishing as "light cutting." In reality, roughing, semi-finishing, and finishing are concepts representing different stages of machining. Therefore, the accurate answer to this question is that CNC milling can perform both heavy and light cutting, while CNC engraving can only perform light cutting.
3. Can CNC engraving be used for rough machining of steel materials?
The ability to machine a material using CNC engraving depends primarily on the size of the cutting tool available. The cutting tool used in CNC engraving determines its maximum material removal capacity. If the mold shape allows for the use of a tool with a diameter exceeding 6 mm, it is strongly recommended to first perform CNC milling and then use engraving to remove any remaining material.
4. Can engraving be completed by adding a speed-increasing head to the spindle of a CNC machining center?
It can’t be completed. This product was showcased at an exhibition two years ago, but it couldn't perform engraving. The main reason is that the design of Cnc Machining Centers, considering their tool range, makes their overall structure unsuitable for engraving. The primary reason for this misconception is that they mistakenly believe a high-speed electric spindle is the sole feature of an engraving machine.
5. CNC engraving can use tools with very small diameters. Can it replace electrical discharge machining?
It can’t replace milling. Although engraving has reduced the range of milling tool diameters, allowing small molds that could previously only be machined using electrical discharge machining (EDM) to be engraved, the length-to-diameter ratio of engraving tools is generally around 5:1. When using small-diameter tools, only very shallow cavities can be machined, whereas EDM has almost no cutting force; as long as an electrode can be created, the cavity can be machined.
6. What are the main factors affecting carving and processing?
Machining is a relatively complex process, and many factors influence it. These mainly include: machine tool characteristics, cutting tools, control systems, material properties, machining processes, auxiliary fixtures and the surrounding environment.
7. What are the requirements for the control system in CNC engraving?
CNC engraving begins with milling, so the control system must have milling capabilities. For small tool machining, feed forward functionality is also necessary to reduce tool breakage frequency by slowing down the path in advance. Simultaneously, the feed rate should be increased on smoother path sections to improve engraving efficiency.
8. What properties of a material affect its processing?
The main factors affecting the carving performance of materials are material type, hardness, and toughness. Material types include metallic and non-metallic materials. Generally speaking, the higher the hardness, the worse the machinability; the higher the viscosity, the worse the machinability. The more impurities, the worse the machinability; the greater the hardness of the internal particles, the worse the machinability. A general standard is: the higher the carbon content, the worse the machinability; the higher the alloy content, the worse the machinability; the higher the non-metallic element content, the better the machinability (but the non-metallic content in general materials is strictly controlled).
9. Which materials are suitable for carving?
Suitable non-metallic materials for carving include plexiglass, resin, and wood, while unsuitable non-metallic materials include natural marble and glass. Suitable metallic materials for carving include copper, aluminum, and mild steel with a hardness less than HRC40, while unsuitable metallic materials include hardened steel.
10. What impact does the cutting tool itself have on machining, and how?
Factors affecting engraving tools include tool material, geometric parameters, and grinding technology. Engraving tools are typically made of cemented carbide, a powder alloy. The main performance indicator determining the material's properties is the average diameter of the powder. A smaller diameter results in a more wear-resistant tool and higher tool durability. Tool sharpness primarily affects cutting force. A sharper tool generates less cutting force, resulting in smoother machining and higher surface quality, but also lower tool durability. Therefore, different sharpness levels should be selected for different materials. Softer, stickier materials require a sharper tool, while harder materials require a lower sharpness to increase durability. However, the tool shouldn't be too dull, otherwise the cutting force will be too high, affecting machining. A key factor in tool grinding is the grit count of the finishing wheel. A higher grit count wheel produces a finer cutting edge, effectively improving tool durability. A higher grit count wheel also produces a smoother flank face, improving the surface quality of the cut.
11. What is the tool life formula?
Tool life primarily refers to the tool life during the machining of steel materials. The empirical formula is: (T is tool life, CT is the tool life parameter, VC is the cutting speed, f is the depth of cut per revolution, and P is the depth of cut). The cutting speed has the greatest impact on tool life. In addition, tool radial run out, tool grinding quality, tool material and coating, and coolant also affect tool durability.
12. How to protect the engraving machine during the processing?
1) Protect the tool setter from excessive oil corrosion.
2) Control flying chips carefully. Flying chips are very harmful to machine tools. If they get into the electrical control cabinet, they can cause short circuits; if they get into the guide rails, they can reduce the lifespan of the lead screw and guide rails. Therefore, seal the main parts of the machine tool during machining.
3) Do not pull on the lamp holder when moving the lighting, as this can easily damage it.
4) Do not approach the cutting area during machining to avoid eye injuries from flying chips. Do not perform any operations on the worktable while the spindle motor is rotating.
5) Do not open or close the machine tool door abruptly. During finishing, the impact and vibration during opening the door can cause tool marks on the machined surface.
6) Allow the spindle to reach the desired speed before starting machining. Otherwise, a slow spindle start may cause the motor to stall before reaching the desired speed.
7) Do not place any tools or workpieces on the machine tool's crossbeam.
8) It is strictly forbidden to place magnetic tools such as magnetic chucks and dial indicator bases on the electrical control cabinet, otherwise the display will be damaged.
13. If a new cutting tool experiences a stalling or spin-locking phenomenon during machining, making machining very difficult, what parameters need to be adjusted?
The reason for the difficult machining is that the spindle power and torque can't withstand the current cutting parameters. A reasonable approach is to redesign the cutting path, reducing the depth of cut, grooving depth, and trimming amount. If the overall machining time is less than 30 minutes, the cutting conditions can also be improved by adjusting the feed rate.
14. What is the function of cutting fluid?
When machining metal, it's important to use cooling oil. The cooling system removes cutting heat and chips, and also lubricates the machining process. Coolant carries away cutting heat, reducing the heat transferred to the cutting tools and motor, thus extending their lifespan. It also removes chips, preventing secondary cutting. Lubrication reduces cutting forces, making machining more stable. In copper machining, using an oil-based cutting fluid can improve surface finish.
15. What are the stages of tool wear?
Tool wear can be divided into three stages: initial wear, normal wear, and rapid wear. In the initial wear stage, the main cause of tool wear is the low tool temperature, which has not yet reached the optimal cutting temperature. At this stage, the wear is primarily abrasive wear, which has a significant impact on the tool and can easily lead to tool breakage. This stage is very dangerous; improper handling can directly cause tool failure. Once the tool passes the initial wear stage and the cutting temperature reaches a certain value, the main wear is diffused wear, which primarily causes localized spalling. Therefore, the wear is relatively small and slow. When the wear reaches a certain level, the tool fails and enters the rapid wear stage.
16. Why do cutting tools need to be broken in, and how should they be broken in?
As mentioned above, cutting tools are prone to chipping during the initial wear stage. To avoid this, we must break them in. This involves gradually increasing the cutting temperature to a suitable level. Experiments using the same machining parameters have shown that tool life increases more than twice after break-in. The break-in method involves reducing the feed rate by half while maintaining a suitable spindle speed, with a machining time of approximately 5-10 minutes. Use a smaller value when machining soft materials and a larger value when machining hard metals.
17. How to determine if a cutting tool is severely worn?
The methods to determine severe tool wear are:
1) Listen to the machining sound, a harsh squeal will be heard;
2) Listen to the spindle sound, the spindle will show obvious signs of stalling;
3) Feel the increased vibration during machining, the machine tool spindle will show obvious vibration;
4) Observe the machining effect, the tool marks on the machined bottom surface will be good and bad (if it is like this at the beginning, it means the depth of cut is too deep).
18. When should the blade be changed?
We should change tools when they are about two-thirds of their lifespan. For example, if a tool shows severe wear after 60 minutes, it should be changed after 40 minutes during the next machining session, and we should make it a habit to change tools regularly.
19. Can a severely worn cutting tool continue to be used for machining?
When a cutting tool is severely worn, the cutting force can increase to three times its normal value. This cutting force significantly impacts the lifespan of the spindle electrode; the lifespan of the spindle motor is inversely proportional to the cube of the force applied. For example, machining for 10 minutes with a three-fold increase in cutting force is equivalent to 10 * 33 = 270 minutes of normal spindle operation.
20. How do you determine the tool extension length during roughing?
The shorter the tool extension length, the better. However, in actual machining, if it's too short, the tool length needs frequent adjustments, which significantly impacts machining efficiency. So how should the tool extension length be controlled in actual machining? The principle is as follows: a φ3 diameter tool holder with a 5mm extension is sufficient for normal machining; a φ4 diameter tool holder with a 7mm extension is sufficient; and a φ6 diameter tool holder with a 10mm extension is sufficient. Try to extend the tool to below these values when mounting it. If the tool extension length needs to exceed these values, try to control it to the depth of cut when the tool wears out. This is somewhat difficult to master and requires practice.
21. What should you do if a tool suddenly breaks during machining?
1) Stop processing and check the current sequence number of the processing.
2) Check the broken part of the blade. If there is a broken blade, remove it.
3) Analyze the cause of tool breakage. This is the most important step. Why did the tool break? To analyze this, we need to consider the various factors affecting machining mentioned above. The cause of tool breakage is usually a sudden increase in force on the tool. This could be due to a problem with the tool path, excessive tool vibration, hard lumps in the material, or an incorrect spindle motor speed.
4) After analysis, change the tool for machining. If the path isn’t changed, machining should be performed one step ahead of the original sequence number. At this time, it is important to reduce the feed rate, firstly because the broken tool is severely hardened, and secondly because the tool needs to be broken in.
22. How to adjust machining parameters when rough machining isn’t performing well?
If tool life can't be guaranteed even at a reasonable spindle speed, when adjusting parameters, prioritize adjusting the depth of cut, followed by the feed rate, and then the lateral feed rate. (Note: There are limitations to adjusting the depth of cut. If the depth of cut is too small, there will be too many layers. Although the theoretical cutting efficiency is high, the actual machining efficiency is affected by other factors, resulting in very low machining efficiency. In this case, a smaller tool should be used for machining, which will actually lead to higher machining efficiency. Generally speaking, the minimum depth of cut shouldn't be less than 0.1mm.)