Monthly Archive September 23, 2020

The machining center is developed from the basic CNC milling machine. It integrates all the functions and characteristics of the CNC milling machine. Its structure is the same, and the processing technology is also similar. Not only that, the machining center also centralizes the processing functions and processing procedures of various machine tools, which can complete the processing of multiple processes such as milling, boring, drilling, tapping and tapping at one time. OK, the machining center is finished. Let’s take a look at how the machining center is classified and how to classify it.

As far as we know, there are six ways to classify machining centers. The first is to classify according to the relative position of the spindle and the worktable according to the structure; the second is to classify according to the number of control axes; the third is to classify according to the machining process; the fourth is to classify according to the number of worktables; the fifth is to classify according to the tool change mode of the machining center’s tool magazine; the sixth is to classify according to the tool change mode of the machining center According to the machining accuracy of machining center, the five classification methods of machining center.

Classification according to the relative position of spindle and table

According to the relative position of spindle and table, machining center can be divided into four types: vertical machining center, horizontal machining center, gantry machining center and composite machining center.

Classification according to the number of control axes

According to the number of control axes, machining can be divided into three axis machining centers, four axis machining centers, five axis machining centers, six axis machining centers, and other multi axis machining centers.

Classification according to processing procedure

Machining centers can be divided into two categories according to the processing procedures, namely boring and milling and turning milling.

Classification according to the number of worktables

According to the number of worktables, machining centers can be divided into three types: single worktable machining center, double worktable machining center and multiple worktable machining centers.

According to the tool change mode of tool magazine

Machining center can be divided into manipulator tool changing center and non manipulator tool changing machining center according to the tool changing mode of tool magazine.

Classification according to machining accuracy

According to the machining accuracy of machining center, it can be divided into three types: ordinary precision machining center, high precision machining center and precision machining. General precision machining center: the resolution is 1 μ m, the maximum feed speed is 15 ~ 25m / min, and the positioning accuracy is about lo μ M. High precision machining center: the resolution is 0.1 μ m, the maximum feed rate is 15 ~ 100M / min, and the positioning accuracy is about 2 μ M. The precision machining center is more than ± 5 μ m between 2 and lo μ M.

Structure types of high speed machining center

There are two types of high-speed machining center, which are vertical high-speed machining center and horizontal high-speed machining center. Vertical high-speed machining center and vertical machining are basically the same in structure type and processing technology. The only difference is their processing speed. Vertical machining center is not as fast as vertical high-speed machining center, so it has the name of high-speed processing. The structure of horizontal high-speed machining center and horizontal machining center are basically the same, and their processing technology is also type. The only difference is that the processing speed of horizontal high-speed machining center is faster than that of horizontal machining center, so it has the name of high-speed.

Characteristics of vertical high speed machining center

Vertical high-speed machining center refers to the high-speed machining center whose spindle and worktable are set vertically. The common vertical high-speed machining center has three linear coordinate axes, and the fourth axis and the fifth axis can be added to the conventional three-axis vertical high-speed machining center. It only needs to install the CNC rotary table on the workbench or spindle. The vertical high-speed machining center has the characteristics of high cost performance, small floor area, simple structure, convenient installation and measurement of workpiece.

Characteristics of horizontal high speed machining center

Horizontal high-speed machining center is a kind of high-speed machining center whose spindle and worktable are parallel. The common horizontal high-speed machining center in the market has three linear motion coordinate axes and one table rotation axis. This kind of machining center mainly processes box type workpiece. The biggest feature of the horizontal high-speed machining center is that it can process other surfaces except the mounting surface and the top surface by clamping the workpiece at one time. In short, it can process the four peripheral surfaces of the box type workpiece, which is the biggest feature of the horizontal machining center. Its horizontal high-speed machining center has some disadvantages, such as high price, complex structure and large area, which is the worst place of the horizontal high-speed machining center.

Schematic diagram of horizontal high speed machining center

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Recently, Xiaobian received a consultation call, mainly to understand the composition and structure of the machining center. Today, I’d like to introduce the main components of the machining center?

Components of machining center

The machining center is mainly composed of basic components, spindle components, CNC system, automatic tool changer system, tool magazine and auxiliary devices. These are the main shaft parts of the machining center. Each of these components has its own characteristics and functions. The following is a detailed explanation by the editor.

Basic components of machining center

The basic part is the most basic structure of machining center. It is composed of bed, column and work. No matter what type of machining center, these three parts are indispensable. The machining center requires that the rigidity of the basic parts is very high. The basic parts should not only bear the static load of the machining center, but also bear the dynamic load produced by the machining center when it is working.

Spindle parts of machining center

The spindle is one of the most important parts of the machining center. Without it, the machining center will be like scrap iron. Therefore, the spindle is equivalent to the human heart, and without the heart, there will be no life, which is so simple. Spindle is the output part of cutting power, which is composed of spindle box, spindle motor, spindle and bearing. The rotation speed, start, stop and turn of the spindle are controlled by the CNC system. The turning accuracy and positioning accuracy of the spindle can affect the machining accuracy of the machining center, so the steering accuracy and positioning accuracy of the spindle can not be ignored.

CNC system of machining center

CNC system is also one of the most important parts of machining center. The main function of CNC system is to control all actions of machining center, such as angle, position, feed speed and spindle speed. If the spindle is the human heart, then the CNC system is the human brain, which controls all the movements of the machining center.

Tool changing system and tool magazine of machining center

Tool change system and tool magazine are the systems and components that other CNC machine tools do not have. Their main function is to change tool automatically. The tool change system and tool library can be used to realize the function of automatic tool change when machining workpieces. Therefore, the machining center can complete the processing of multiple processes by clamping the workpiece at one time.

Auxiliary device of machining center

There are many auxiliary devices in the machining center, mainly including lubrication, cooling, chip removal, protection, hydraulic, pneumatic and system auxiliary devices. These devices mainly play an auxiliary role in the machining center when processing the workpiece. Although these auxiliary devices can not participate in machining, they play a great role in machining efficiency, reliability and machining accuracy

High speed machining center refers to the machining speed higher than high-speed machining center. In general, the spindle speed of high-speed machining center is more than 18000r / min, and the three-axis rapid movement is more than 24m / min. we all call it ultra-high-speed machining center. Domestic ultra-high speed machining center is not as good as foreign ultra-high-speed machining center, whether in cutting speed, machining accuracy and stability, domestic ultra-high-speed machining center is inferior to foreign ultra-high-speed machining center. At present, the spindle speed of domestic ultra-high speed machining center is about 20000 R / min, while that of foreign Swiss Mirand company has been 42000r / min and 60000r / min; therefore, the spindle speed of domestic ultra-high speed machining center is not as good as that of foreign ultra-high-speed machining center. The following is to introduce the cutting advantages of ultra-high speed machining center.

V8 high speed machining center

High efficiency of high speed machining center

The cutting speed and feeding speed are 5-10 times higher than that of conventional machining center, and the ultra-high speed machining center and the conventional machining center process the same workpiece. The conventional machining center takes three minutes to complete the processing, while the ultra-high speed machining center needs one minute to complete the processing, using only one third of the time of the conventional machining center.

The cutting force of high speed machining center is small

Compared with the conventional machining center, the cutting force is reduced by 30%, the material removal rate of single power can be increased by 40%, and the service life of the tool is increased by 70%.

The high-speed machining center has a small probability of thermal deformation

Because 95% of the heat produced by ultra-high speed machining center is not transferred to the workpiece and tool in time, but is directly and quickly taken away by the chip. Therefore, the temperature of the workpiece and the tool is not very high, and it will not cause the workpiece with thermal deformation.

The machining precision of high speed machining center is high

Because the vibration of the ultra-high speed machining center in the high-speed machining process is small, and the shock resistance of the machine body is good, not only the accuracy is improved, but also the service life of the machine tool is improved. Because the chip is far away from the workpiece rapidly, 95% of the heat produced in the high-speed machining process is taken away by the chip, so that the residual thermal stress on the surface of the workpiece is small, and the probability of the tool and workpiece deformation in the heat is reduced, which ensures the machining accuracy and better surface quality.

Because of the high vibration frequency of the ultra-high speed machining center when cutting the workpiece with high-speed rotating cutter, and beyond the natural frequency range of the machine tool, workpiece and tool system, the vibration of the process system will not be caused.

High speed machining center has good economic efficiency

Because the ultra-high speed machining center can complete all the processing procedures of the workpiece in a short time, shorten the processing time; and the processing energy consumption of the ultra-high speed machining center is low; it can process the workpiece with poor rigidity, such as thin-walled parts; its machining parts have high machining accuracy; in the process of high-speed machining center, the tool and workpiece are in point contact, so the tool is improved It not only saves the auxiliary time of tool change, but also saves the cost of tool edge grinding

What are the transmission structures? Then, what kind of transmission structure is selected for the vertical machining center? Is the spindle suitable for heavy cutting?

Gear drive spindle

What are the main shaft of transmission structure of machining center

There are four types of main shaft drive structure in machining center, which are gear drive spindle, belt drive spindle, direct drive spindle and motorized spindle. These four types of transmission structure spindle have their own advantages and are suitable for different cutting field. In the market, the vertical machining center generally adopts the belt drive spindle, which is one of the mainstream spindle structures configured on the vertical machining center; the gear driven spindle is rarely used in the machining center at present, because the overload and slipping of the gear drive spindle will directly cause the wear and tear of the spindle, and the maintenance is very difficult and the maintenance price is expensive, so it is very difficult Few machining centers use gear driven spindles; direct coupled spindles and motorized spindles are generally used in high-speed machining centers. The speed of direct coupled spindles and motorized spindles is very fast, generally more than 12000r / min. for example, belt driven spindle and gear driven spindle are several or more times faster.

Belt drive spindle

What kind of transmission structure should the vertical machining center choose? The spindle is suitable for heavy cutting

In general, the main shaft of transmission structure suitable for heavy cutting occasions includes belt drive spindle and gear drive spindle. These two transmission structure spindles are suitable for heavy cutting occasions, especially belt drive spindle. The belt drive spindle can effectively protect the spindle in case of overload and sliding wear, and the most used spindle in vertical machining center is belt drive Spindle, belt drive spindle is also widely used in machining center. However, the use of gear drive spindle in vertical machining center is less, the reason has just been said, here will not repeat.

The structure of vertical machining center refers to the machining center whose spindle and worktable are set vertically. The vertical machining center integrates the characteristics and functions of a variety of CNC machine tools. The vertical machining center is developed from the basic CNC milling machine. At the same time, it also integrates the characteristics and functions of the CNC milling machine. Its structure is basically the same, and the processing technology is somewhat similar. The difference between the vertical machining center and the CNC milling machine is that the machining center has automatic tool change device and tool library, while the CNC milling machine has no such function. Vertical machining center can finish milling, boring, drilling, tapping and tapping at one time, and vertical machining center can at least realize three axis and two linkage, general vertical machining center can realize three axis and three linkage, some can control five axis and six axis, the more control axis, the more processing range. Let me introduce the advantages and disadvantages of vertical machining center.

Advantages of vertical machining center

1. Because the structure of vertical machining center is simple and easy to understand, it is very easy to clamp the workpiece. The same fixture can be used, such as flat jaw pliers, pressure plate, dividing head, rotary table and other fixtures to clamp the workpiece. The clamping positioning and repeated positioning of the workpiece are very convenient.
2. The structure of the vertical machining center is conducive to cooling. Since the coolant is sprayed from the top to the bottom, it can be directly sprayed to the high-temperature workpiece and cutting tool.
3. The structure of the vertical machining center is relatively simple, so its field of vision is very wide. It can observe the running track of the tool, and it is convenient to debug, observe and modify the parameters. It is also convenient to measure the workpiece. If any problem is found, it will be stopped immediately for processing and modification.
4. The vertical machining center is easy to remove chip when machining plane workpiece, and the generated chip is washed away by the ejected coolant, which avoids the scraps scratching the surface of the workpiece during cutting.
5. Compared with the horizontal machining center, the vertical machining center has simpler structure, smaller floor area and lower price.

Mingwan vmc650 vertical machining center

Disadvantages of vertical machining center

1. Because the spindle and the worktable of the vertical machining center are set in parallel state, the height of the workpiece processed is limited. Not only that, but also the fixture and cutter have certain size restrictions, and the manipulator should occupy a lot of space when changing tools.
2. From the above shortcomings, the possibility of vertical machining center box type workpiece is small, and the processing range of box type workpiece is relatively small. This is one of the biggest disadvantages of vertical machining center.

Can vertical high speed machining center be equipped with five axes

A: Yes, the structure of vertical high-speed machining center is basically the same as that of conventional high-speed machining center, but there are some differences in processing efficiency, surface quality and processing accuracy. Other structures are basically the same. Therefore, vertical high-speed machining center can also be equipped with five axes, which I can also call five axis high-speed machining center. Can be configured with a, C rotation axis or B, C rotation axis, its rotation axis can be installed on the work and spindle according to the needs of processing products or molds. Some five axis high machining center a, C rotation axis is installed on the worktable, some a, C rotation axis is installed on the spindle, and so on, there are many installation methods, which are mainly determined according to the processed products or molds.

Which brand of five axis vertical high speed processing center is good

There are many brands of five axis vertical high-speed machining centers, which can be roughly divided into domestic and foreign five axis high-speed machining centers. There are many brands of domestic five axis high-speed machining centers, but they are not competitive in the international CNC machine tool market. Domestic five axis high-speed machining centers are generally competitive in the domestic low-end CNC machine tool market, and the domestic high-end CNC machine tool market It has been monopolized by foreign 5-axis high-speed machining center. In the high-end market of domestic CNC machine tools, domestic CNC machine tools are not competitive at all. Therefore, which brand of five axis high-speed machining center is better than the five axis high-speed machining center of foreign brands. For example, German alzmetall, demage and Swiss mikro brands are all at the international first-line level. But these five axis high-speed machining centers of international famous brands are very expensive, which are not affordable for small enterprises.

Linear motor used in machining center is not a new thing in foreign countries, but it is new in China. First of all, let me introduce the linear motor. At present, most of the CNC machine tools use servo motor and rolling screw to drive the linear coordinate axis. The appearance of linear motor has changed completely. Linear motor can directly replace servo motor and rolling screw to drive linear coordinate axis. The linear motor drives the coordinate axis for linear motion, which does not need to change the rotary motion into linear motion like the servo motor and rolling screw. The linear motor directly saves these tedious conversion steps.

Servo motor and linear motor of rolling screw

Characteristics of linear axis driven by linear motor

Linear motor driving linear coordinate axis is characterized by high speed, high efficiency and excellent rigidity, but there are still some problems with linear motor, such as high price, high heat output, poor transmission stability and so on. At present, CNC machine tools still use servo motor and rolling screw to drive linear coordinate axis, and servo motor and rolling screw drive linear coordinate together Axis is still the mainstream of the market.

Which machining centers use linear motors

Although there are many problems in using linear motor to drive linear coordinate axis, there are still some machining centers. For example, high-speed machining center boldly adopts linear motor to drive linear coordinate axis, and high-speed machining center adopts linear motor to drive linear coordinate axis, which is relatively common in foreign countries and less in China, because domestic linear motor technology is not very mature, so it is generally used The manufacturers dare not boldly adopt this kind of practice. However, foreign manufacturers of machining centers are different. In pursuit of processing efficiency, they boldly adopt linear motor to drive linear coordinate axis. For example, dmc75v linear high-speed machining center of German demage company adopts linear motor to drive linear coordinate axis, and its axial acceleration reaches 2G and fast stroke speed reaches 90m / min. thus, the speed of linear motor driving linear coordinate axis in high-speed machining center is 2-3 times higher than that of conventional high-speed machining center using servo motor and rolling.

To sum up, only high-speed machining center can drive linear axis by linear motor. At this stage, using linear motor to drive linear coordinate axis is not the mainstream. I believe that in the future, due to the gradual maturity of linear motor technology and the downward trend of price, the linear motor will directly replace the servo motor and rolling screw to drive the linear seat