September 2020 – Page 10 – CNC Machining & Turning, Milling, Metal parts

Four axis high speed machining center

1、 Four axis high speed machining center

High speed machining center and machining center have three axes, four axes and five axes. Three axis and four axis high-speed machining centers are used more, while five axis high-speed machining centers are rare because of the high price.

High speed machining center is a kind of high-speed machine tools. High speed machining center is mainly used for mass production of small parts and products. It is also one of the most used CNC machine tools. Under normal circumstances, the default axis of high-speed machining center is three axis. If the fourth axis needs to be added, the customer needs to make a request to the manufacturer. The processing range of four axis high speed machining center is wider than that of three axis high-speed machining center. For the same brand and the same type of high-speed machining center, four axis is definitely better than three axis, because it can process some complex workpieces.

2、 Characteristics of four axis high speed machining center

In the above, we said that the machining range of four axis high speed machining center is wider than that of three axis machining center, so what is the reason? Four axis high speed machining center has one more dividing head than three axis high speed machining center, which is the source of the fourth axis. Among the six degrees of freedom of the workpiece, the three axis high-speed machining center only uses three basic x, y, Z linear degrees of freedom, and the remaining three a, B, C rotation degrees of freedom are not used, and the four axis high-speed machining center selects one of these three degrees of freedom, and then installs the corresponding dividing head.

Speed of high speed machining center

High speed machining center is a common machining center in the market. It is widely used in the fields of automobile, machinery and hardware. Because the processing speed of high-speed machining center is fast, and the quality is stable, the production efficiency is greatly improved, which is the advantage of high-speed machining center. The biggest disadvantage of high-speed machining center is that it is not suitable for heavy cutting, but only suitable for finishing. For example, some workpieces with large cutting force are difficult to be processed by high-speed machining center.

Processing speed of high speed machining center

As is known to all, the cutting speed of high-speed machining center is 5-10 times faster than that of ordinary machining center. According to the hardness and strength of materials, the processing speed is different. Aluminum alloy is 1500-5500 M / min; copper alloy is 900-5000 M / min; titanium alloy is 100-1000 M / min; cast iron is 750-4500 M / min; steel is 600-800m / min. The feed speed range of high-speed cutting for various materials is 2-25m / min. From these data, we can know how fast the processing speed of high-speed machining center is, which is beyond the ability of general machining center.

The field of high speed machining center

High speed machining center involves many fields of processing, such as automobile, machinery, train, ship, aircraft, aerospace and mold. The parts in these fields can be processed by high-speed machining center. No matter how high the precision requirements are, it is difficult to defeat the high-speed machining center, because in addition to the advantages of high-speed machining, high-speed machining center also has the advantage of precision machining. High speed machining center is also called high precision high speed machining center.

Advantages of line rail machining center

Introduction to guide rail of machining center

The line rail machining center is quite common in the market, but we didn’t pay attention to it. The line rail machining center simply means that the guide rail uses the line rail. There are two types of guide rails used in machining centers, which are line rails and hard rails. There are few machining centers using hard rails in the market, while more machining centers use line rails. The line rail is called linear guide rail and linear guide rail. The line rail can be divided into ball guide rail and roller guide rail. In fact, there is no difference between the two kinds of line rail in essence. The ball guide rail is in point contact by moving friction, while the roller guide rail is in line contact by moving friction.

The line rail is generally composed of slide rail and slide block. The size of slide rail is customized according to the needs of the machine itself, and the sliding block has built-in circulating ball or roller.

Advantages of line rail machining center

The main advantages of the line rail machining center are fast running speed, small rolling friction resistance, no signs of slow crawling, high machining accuracy and convenient lubrication. After a long service time, the machining accuracy of the line rail machining center is not affected, and the damaged line rail can be disassembled and replaced. Line rail machining center is rolling friction, point or line contact, the contact area is small, the friction resistance is naturally small, more suitable for high-speed machining and small cutting capacity of workpiece processing.

Disc type tool magazine and hat type tool magazine of CNC machining center

The tool magazine commonly used in machining center includes hat type tool magazine and disc type tool magazine, and there is also a kind of chain type tool magazine. This kind of tool magazine is generally installed on gantry machining center and horizontal machining center, but rarely used in vertical machining center.

Characteristics of bamboo hat type tool magazine

The biggest feature of the bamboo hat type tool magazine is its high cost performance and simple structure. Its tool change speed can be completed in 8s. It is better to use it in small batch production. The maintenance and maintenance of the bamboo hat type tool magazine is simple and convenient. The disadvantages of the bamboo hat type tool library are that the tool change speed is slow, when the handle is placed in the magazine, the cone surface is open without protection, and the cone surface is easy to stick Dirt will directly affect the accuracy of tool repeated installation.

Characteristics of disc type magazine

Disk magazine can be called manipulator magazine and arm magazine. They are different in each place, but they are the same. They are all disc magazine. The tool change speed of disc type magazine is fast, complex and expensive. The tool change speed of disc magazine is less than 4 s because of its tool change action: the mechanical arm pulls the tool from the tool magazine and the main shaft at the same time, and installs it to the spindle and magazine through 180 ° rotation, thus completing the tool change process. The price of the magazine is much higher than that of the hat magazine. The magazine can load up to 40 tools. The disc type magazine is extremely strict on the weight of the tool. Once the loaded tool exceeds the bearing range of the magazine, the tool will be easily thrown out of the magazine, which is easy to cause accidents. If the length of the tool exceeds the specified size, it will collide with the tool in the process of tool change, which will cause damage to the magazine and the tool.

According to the characteristics of the above magazine, which is better? The problem is clear at a glance. The bamboo hat type magazine is cheap and easy to maintain, while the disc magazine is fast and expensive.

Spindle drive mode of machining center

CNC system is the control core of machining center, which is equivalent to human brain. The spindle of machining center is equivalent to human heart, which is the source of main processing power of machining center. To sum up, the spindle of machining center is essential, so the selection of spindle must be careful. There are four kinds of main shaft transmission structures, which have different characteristics and speed.

What is the main shaft drive structure of machining center and its speed and characteristics

There are four kinds of spindle of machining center according to the transmission structure, which are gear drive spindle, belt drive spindle, direct connection spindle and electric main power. These four kinds are common in the market. These four kinds of transmission structure spindle speed and characteristics are different, each has its own advantages. Gear drive spindle: its speed is generally 6000r / min, and its rigidity is good and it is suitable for heavy cutting occasions. Its main shaft is generally equipped with multi head machine tools; belt drive spindle: its speed is 8000 R / min, simple structure, easy production, strong buffer capacity, effective protection of spindle in case of spindle overload; direct spindle: its spindle and motor are connected through coupling Drive, large distortion, low energy consumption, its speed is more than 12000r / min, this kind of spindle is generally used in high-speed machining center; motorized spindle: the spindle and motor are integrated, the motor is the spindle, the spindle is the motor, it can be said that the spindle and motor are integrated into one, the transmission chain of this spindle is almost zero, and the spindle speed is between 18000-40000 R / min, and higher For example, maglev bearing and hydrostatic bearing are used in motorized spindle bearing of foreign advanced countries, and its speed can reach 100000r / min. this kind of spindle is generally used in high-speed machining center;

What are the common transmission structure spindles used in machining centers

There are three kinds of spindle with the above four kinds of transmission structure commonly used in machining center, which are belt drive spindle, straight spindle and motorized spindle. These three kinds of transmission structure spindle are commonly used in machining center, while gear drive spindle is rarely used in machining center, but there are also some, such as those used in multi head machining center. Belt drive spindle is generally used in small machining centers and large machining centers, while straight spindle and motorized spindle are commonly used in high-speed machining centers.

Spindle composition of vertical machining center

Introduction of spindle of machining center

The CNC system of machining center is the core component, which is mainly used to control the action of machining center. It usually controls the position, angle and speed of the three axes of the machining center. From the above, the CNC system of the machining center is equivalent to the human brain, so the spindle of the machining center is the cutting processing, and the output of the power is equivalent to the heart of the human body. The spindle determines the cutting ability, dynamic stiffness and machining accuracy of the machining center. The start, stop and rotation speed of the spindle are controlled by the CNC system. After the spindle is installed with a tool, it can participate in the cutting of the workpiece. The spindle is the most important mechanical part of the machining center, which has a great influence on the performance, stability and machining accuracy of the machining center.

Composition of spindle of machining center

The spindle of machining center is mainly composed of spindle, spindle support, spindle bearing, spindle drive and seal. According to the different transmission parts of the spindle, it can be divided into four types: gear driven spindle, belt driven spindle, direct coupling spindle and motorized spindle. The speed and application of these four types of spindles are different. The speed of gear driven spindle is generally 6000r / min, which is more suitable for heavy cutting; belt driven spindle is also known as synchronous belt drive spindle, which is mainly driven by belt teeth, and its spindle speed is generally at 8000r / min, which is more suitable for heavy cutting occasions; direct connected spindle is composed of motor The spindle is connected by a shaft coupler to drive. The speed of this kind of spindle is generally 12000-18000r / min. the direct connected spindle is not suitable for heavy cutting, but only suitable for processing workpieces with small cutting capacity, which is suitable for finishing. Motorized spindle: its spindle is integrated with the motor, the motor is the spindle, and the main shaft is the motor. The motor and the spindle are integrated into one, and its spindle is the most in the world For a fast spindle, its speed is more than 18000r / min. if the motorized spindle adopts aerostatic bearing and maglev bearing, the maximum speed can reach 100000r / min. this kind of spindle is generally used in finish machining, not suitable for heavy cutting.

Three axis and five axis machining center

Difference between five axis machining center and three axis machining center

The biggest difference between 5-axis machining center and 3-axis machining center is that on the motion axis, five axis machining center has five motion axes, namely XYZ linear motion axis and AC rotation motion axis; while three-axis machining center has only three motion axes, which are the conventional XYZ linear motion axis. This is the biggest difference in structure between five axis machining center and three axis machining center. There are also differences in the processing range. The processing range of the five axis machining center is relatively wide. The five axis machining center can process parts that are difficult or impossible to process with three axes. It can be generally understood that the processing range of the five axis machining center is wider than that of the three axis machining center. Today’s editor mainly introduces the advantages of five axis machining center.

Advantages of five axis machining center

Five axis machining center can process parts that cannot be processed or difficult to process by three axes, such as complex curved surface parts. Using five axis machining center to process complex curved surface parts can complete all processes processing at one time, while using three axis machining center to process complex curved surface parts is very difficult and complex, and it needs many clamping and adjustment to complete its complex processing procedures. Generally speaking, the three-axis machining center can not complete the processing of complex curved surface parts at one time. These complex curved surface parts mainly include turbine engine blades, marine propeller and other special complex curved surface parts. These parts can be processed by five axis machining center, and the angle, position and cutting path of the cutter can be adjusted freely, so the five axis machining center can be clamped and assembled at one time All processing procedures.

It is necessary to use ball end milling cutter to process complex curved surface parts with three-axis machining center. The cutting rate of parts processed by ball end milling cutter is low, and the angle of cutter can not be adjusted freely in the process of machining, so the smooth surface can not be machined. The use of five axis machining center to process complex curved surface parts does not need to use ball end milling cutter, and does not need to use special tools, because the five axis machining center can freely adjust the angle of the tool, so the surface of the workpiece processed is smooth, thus improving the quality of processing.

Tool change form of machining center

Machining center is a common processing equipment in the market, which is widely used by major processing enterprises. The machining center can clamp the workpiece at one time, and can complete the processing of multiple faces, so it is favored by the processing industry. Different from other machining centers, the machining center has an automatic tool change device, which is the biggest advantage of the machining center. This automatic tool change device can automatically select tools and automatically exchange and install on the spindle during processing. There are two kinds of tool changing forms, which are manipulator tool changing form and non manipulator tool changing form.

Manipulator tool change form

Manipulator tool change form is generally used in the machining center using disc magazine and chain magazine. The biggest feature of this kind of tool change form is that the tool change speed is very fast, and the whole tool change process can be completed in 4 s. And this kind of tool change form is completed by the manipulator, which is more common in the machining center.

No manipulator magazine (bamboo hat magazine)

This kind of tool change is mainly completed by the tool magazine and the spindle to complete the tool change, and the tool storage direction in the tool magazine should be consistent with the direction of the spindle, otherwise it is impossible to change the tool. During tool change, the tool magazine moves to the tool change position in the direction of the spindle, and the tool is directly taken out or put back by the spindle, and then the tool moves back to the original point. This kind of tool change form usually appears in the machining center using the hat type tool magazine. This kind of tool change form has the advantages of simple structure, convenient maintenance and high cost performance. Its disadvantage is that the tool change speed is slow, and the whole tool change process takes 8 seconds. This kind of tool change is common in machining centers.

There are two common tool change forms in machining center, which are widely used in machining center

Horizontal machining center is suitable for parts

Horizontal machining center refers to the processing in which the spindle and the table are set in parallel. Generally, it has 3-5 moving axes. Generally, the horizontal machining center is a reverse rotation table with automatic indexing. The most common horizontal machining center is three linear motion coordinate axes plus one rotary motion coordinate axis.

What types of parts are suitable for horizontal machining center

Horizontal machining center is most suitable for processing these large box type workpieces, mainly for the box type workpiece hole system processing and plane processing. The workpiece can be clamped at one time, and other surfaces except the mounting surface and the top surface can be processed. The rotary shaft is installed on the worktable and the workpiece can be rotated to process all sides of the workpiece. It can also install multiple rotation axes to make joint movement, so as to process the box parts with complex surface type.

Characteristics of horizontal machining center

Compared with the vertical machining center, the horizontal machining center has the advantages of easy chip removal and favorable clamping. Some horizontal machining centers have two worktables, one is processing and the other is loading and unloading. This design allows the horizontal machining center to process continuously, which greatly improves the processing efficiency. But the structure is complex and expensive.

Function of vertical machining center

Vertical machining center in the domestic CNC machine tool market has reached 50% utilization rate. It can be imagined that vertical machining center is widely used in various processing enterprises, and it is favored by many enterprises. Vertical machining center is developed from the basic CNC milling machine. It integrates all the features and functions of CNC milling machine, and also integrates the functions of many other CNC machine tools, such as boring machine, drilling machine, milling machine, etc.

The vertical machining center has the following main function points:

Automatic tool change function

The structure of vertical machining center and CNC milling machine are basically the same, and the processing technology is basically similar, but the biggest difference between them is that the machining center replaces the automatic tool changer and tool magazine, and the CNC milling machine does not have this function. Vertical machining center with automatic tool change device and tool magazine has automatic tool change function, which can be changed according to the tool used in processing. Generally speaking, the vertical machining center can change the tool at will to process the different working procedures of the workpiece.

One time workpiece clamping can process multiple processes

From the last function point, the vertical machining center has the function of automatic tool change. With this function, it can carry out multi process processing, such as boring, drilling, milling, tapping and tapping.

The function of expandable axle number

Because the conventional three-axis machining center can not meet the requirements of customer product processing, such as: Machining impeller, blade, shaft, propeller and other complex curved surface workpiece is unable to be processed by three axis vertical machining center, so the four axis or five axis function is expanded according to the requirements of customer products. From the above, we know that the vertical machining center has the function of expanding the number of shafts, and can expand the functions of four axis, five axis and multi axis.

A workpiece clamping can process multiple machining surfaces

It is known from the above that the vertical machining center can expand the number of shafts, so after the vertical machining center expands the number of shafts, the workpiece can be clamped to process multiple machining surfaces at one time. It avoids the precision error of clamping repeatedly, and saves the time of manual clamping workpiece.