The difference between machining center, engraving and milling machine and engraving machine

CNC engraving and milling machine It is a kind of CNC machine tool, which is a CNC machine tool corresponding to the traditional engraving machine. It is a CNC milling machine that uses small tools, high power and high speed spindle motors.

The advantage of the engraving machine is in the engraving. If the hardness of the processing material is relatively large, it will not work. The appearance of the engraving and milling machine can be said to fill the gap between the engraving machine and the machining center. The engraving and milling machine can be engraved or milled. It is an efficient and high-precision CNC machine tool.

Machining molds are generally based on machining center milling, but the machining center has its shortcomings, especially when machining small molds with small tools, which can be overwhelming and costly.

At the beginning of the country, there was only the concept of CNC engraving machine. The term "CNCengraving and milling machine" was very early in the country, and it was strictly speaking that the engraving was part of milling, whether it was to buy an engraving machine or to purchase a CNC milling machining center. It is a question that you often have to ask yourself. In addition, there are currently high-speed cutting machine tools (HSCMACHINE).

1. The difference between use and machining center and engraving machine

Machining Center: A highly automated multi-function CNC machine with a tool magazine and automatic tool changer. The first machining center appeared in the United States in 1958. It can realize the centralized machining of various processes such as milling, drilling, boring, reaming and tapping after the workpiece is clamped once. The function emphasizes “milling”.

Engraving machine: Its high spindle speed is suitable for the processing of small tools, the torque is relatively small, focusing on the "engraving" function, such as wood (specially processed wood called wood carving machine), two-color board, acrylic board and other low-hardness sheet, no Great for large workpieces with strong cutting. At present, most of the products on the market with the name of the engraving machine are mainly for processing handicrafts, and the cost is low. Due to the low precision, it is not suitable for mold development; however, there are exceptions such as wafer engraving machine.

CNC engraving and milling machine: as the name suggests. It can be carved or milled. On the basis of the engraving machine, the power of the spindle and the servo motor is increased, and the strength of the bed is maintained. At the same time, the high speed of the spindle is maintained, and more importantly, the precision is high. The engraving and milling machine is also developing at a high speed. It is generally called a high-speed machine. It has stronger cutting ability and high processing precision. It can also directly process materials with hardness above HRC60 and molding at one time.

2, the difference in appearance volume

The machining center is the largest, the large 1690 model is 4m*3m, and the small 850 is 2.5m*2.5m. The engraving and milling machine is the second, and the larger 750 is 2.2m*2m. The smallest.

3. The difference in overall mechanical structure

The machining center generally adopts cantilever type, the engraving and milling machine and the engraving machine generally use the gantry structure, and the gantry type is divided into the moving beam type and the fixed beam type. At present, the engraving and milling machine is mostly fixed beam type.

4. Differences in indicator data

Maximum spindle speed (r/min): machining center 8000; engraving and milling machine is the most common 24000, high speed machine is at least 30,000; engraving machine is generally the same as engraving and milling machine, engraving machine for high-light processing can reach 80,000, but that is used It is not a general electric spindle but an air-floating spindle.

Spindle power: The processing center is the largest, from several kilowatts to tens of kilowatts; the engraving and milling machine is second, usually within ten kilowatts; the engraving machine is the smallest.

Cutting capacity: The largest machining center, especially suitable for heavy cutting and thickening; the engraving and milling machine is second, suitable for finishing; the engraving machine is the smallest.

Speed: Because the engraving and engraving machine are relatively light, their moving speed and feed speed are faster than the machining center, especially the high speed machine with linear motor moves up to 120m/min.

Accuracy: The accuracy of the three is similar.

5, the difference in processing size

The work area can respond better to this. The smallest workbench area (unit mm, the same below) of the domestic machining center is 830*500 (850 machines); the largest workbench area of ​​the engraving and milling machine is 700*620 (750 machines), and the smallest is 450*450 (400 Machine); engraving machine generally does not exceed 450 * 450, the common is 45 * 270 (250 machine).

6, the difference from the application object

Machining center is used to complete the processing equipment of large milling workpieces, large molds, hardness comparison materials, also suitable for the opening of ordinary molds; engraving and milling machine is used to complete small milling, small mold finishing, suitable Processing of copper, graphite, etc.; low-end engraving machine is biased towards wood, two-color board, acrylic sheet and other low-hardness sheet processing, high-end suitable for wafers, metal casings and other polishing and polishing.

It is generally believed that the machining center and the engraving and milling machine can be used as both products and molds, and the engraving machine can only be used as a product.

7, the difference between the process and the machining center and engraving machine:

CNC milling and machining center is used to complete the processing equipment of workpieces with large milling volume; CNC engraving and milling machine is used to complete small milling, or soft metal processing equipment; high-speed cutting machine is used to complete medium milling, and milling After the grinding amount is reduced to the lowest processing equipment.

8. Distinguish the advantages and disadvantages from the mechanical point of view:

The machine tool is divided into two parts, the moving part and the non-moving part: the working table, the skateboard, the cross flower table, etc. are moving parts, the bed base, the column and the like are non-moving parts.

CNC milling machining center:

The rigidity of the non-moving part is very good. The rigidity of the moving part is very good.

Advantages: Heavy cutting can be performed; Disadvantages: Because the moving parts are equally large, the flexibility of the machine is sacrificed, and there is no power for small parts and rapid feed.

CNC engraving and milling machine

The non-moving part of the rigidity requires a good moving part of the rigidity to be flexible, as light as possible, while maintaining a certain degree of rigidity.

Advantages: It can carry out relatively small processing and has high processing precision. For high-speed machining of soft metals; Disadvantages: Heavy cutting is not possible due to poor rigidity.

There are also high-speed cutting machine tools that are commonly used nowadays. The rigidity of the non-moving part is very good, the rigidity of the moving part is better, and it is as light as possible.

Advantages: It can carry out small and medium-sized cutting (for example, a flat-bottom knives of φ10, and a depth of 0.75 for 45 steel (300) is good); Disadvantages: It can be used efficiently and at low cost under proper use, so that the amount of grinding is extremely small. Improper use will immediately make the scrap of the tool pile up.

How to do the above requirements from the mechanical, light, rigid and contradictory, the key lies in the mechanical structure.

The bed body adopts a mesh structure with high and low ribs, and some directly adopt the hexagonal mesh structure of the honeycomb. The ultra-wide column and beam, we know that the gantry structure is excellent in symmetry and excellent. Rigidity has always been the preferred structure for high-speed cutting equipment manufacturers; the difference between the moving parts and CNC milling is that the distance between the rails and the rails is widened to overcome the problem of bad torque. In terms of materials, the Mehana cast iron is generally used, that is, the cast iron is cast. When the molten iron is poured, a certain proportion of silicon (Si) is added to change the internal structure of the iron, making it more resistant to stamping and significantly improving the rigidity. The rigidity of the machine tool is mainly used to overcome the strong impact of the moving part on the non-moving part when moving at high speed, so the guide rail and the screw rod are required to be thicker, and the rigidity of the connecting part is strengthened.

9, from the perspective of numerical control

CNC milling machining center requires high speed for CNC system, spindle speed is about 0~8000RPM; engraving and milling machine requires high-speed CNC system, spindle speed is about 3000~30000RPM; high-speed cutting machine requires high-speed CNC system and excellent servo motor characteristics. The spindle speed is about 1500~30000RPM.

10, analysis on the programming software

From a software point of view, CNC milling machining centers, high-speed cutting machine engraving and milling machines can use standard CAD / CAM software such as: MasterCam Cimatron PE UG.

Milling machines usually think that the Cimatron tool path is better. The new version of the software fully examines the uniformity of the cutting amount of the tool at every moment, especially the speed and smoothness of the knife entering the moment of going out, and the following algorithm at the inflection point. The problem (followingError) makes the results and design graphics more closely. The CAD part has just been used in a large number of intuitive 3D solid modeling such as Solidworks and then transferred to CAM software through IGS.

But don't worry, the development speed of CAD/CAM is far faster than the development speed of CNC machine tools. The engraving process is controlled by a relatively small angle due to the particularity of the tool. It is better to use TYPE3.

11, the difference between the main axis

For CNC milling and machining centers, because of the low speed and high torque required, the reduction ratio of the spindle gearbox is required to increase the torque. The low speed and poor precision are inevitable, so it is unlikely that a small radius tool will be used.

For the engraving and milling machine, the spindle must work at 20,000 to 30,000 RPM, and the rotation accuracy is generally about 2 μ. Otherwise, the broken knife phenomenon is very serious, so the electric spindle must be used, that is, the motor and the main shaft are integrated. For high-speed cutting equipment, the built-in electric spindle is required, and at a low speed, a certain torque is required to have a water-cooling machine to keep the spindle operating temperature constant. The spindle power should be above 7.5~8KW, and the speed should exceed 25000RPM.

Supplement: Views of high-speed cutting equipment

The essence of high-speed cutting is to walk the length of the tool in a short time. High-speed cutting is determined by the current spindle of the machine tool itself and the limitations of the tool used. It is not always good. The current foreign practice is that the first device does not use high-speed cutting, while the second or third device can be considered. This kind of equipment.

Successful practices such as: one copy milling completes most of the cutting amount (heavy cutting) and the remaining machining allowance of 2~3mm, and the remaining cutting amount is quickly completed on the high-speed machine tool, which has many advantages:

1) Heavy cutting machine tools, processing costs are very low

2) The processing volume is large, the precision requirement is not high, and it is easy to reach

3) The tool is cheap

4) After the high-speed cutting, the cutting amount of the first knife is uniform because the object is close to forming.

5) Forming fast and accurate

6) Avoid too much grinding, with precise dimensions

7) Although the tool is expensive, the time is short, the cutting amount is not large, and the performance price ratio is very good.

8) A lot of nuances, such as small angle guides, etc., meticulous processing is done once without using sparks to help,

9) Excellent surface finish (mirror effect)

From this point of view, the coordination of the equipment is the way to win, because its remaining amount is 2~3 mm, so the two calibrated G54 baffles on the XY on the workbench complete the problem of workpiece clamping, and for cutting The small amount of the workpiece is directly completed on the high speed machine.