How to choice Vertical machining center

Vertical machining center refers to the machining center with the spindle axis and the workbench set vertically. It is mainly used to process complex parts such as plates, discs, molds and small shells.

The vertical machining center can complete milling, boring, drilling, tapping and thread cutting processes. The vertical machining center is at least three extraction and two linkage, which can generally achieve three axes and three linkage. Some can be controlled with five or six axes. The vertical machining center has a limited column height, so the machining range of box type workpieces should be reduced, which is a disadvantage of the vertical machining center. But the vertical machining center is convenient for clamping and positioning; The moving track of the cutting tool is easy to observe, the debugging program is convenient to check and measure, and problems can be found in time for shutdown or modification; The cooling conditions are easy to establish, and the cutting fluid can directly reach the tool and the machined surface; The three coordinate axes are consistent with the Cartesian coordinate system, which is intuitive and consistent with the visual angle of the drawing. The chips are easy to be removed and dropped to avoid scratching the machined surface. Compared with the corresponding horizontal machining center, it has simple structure, small floor area and low price.

Advantages:

High quality casting — the lathe bed is made of cast iron, with strong vibration absorption capacity, which is conducive to machining accuracy.

Bed structure – box type bed design is adopted, and a large number of strong bars are added to strengthen the rigidity of the bed.

Spindle box structure – The spindle box adopts lightweight design idea, and the precision of machined surface shape is improved.

Workbench structure – A large number of stiffeners are added to the design of the workbench to ensure the positioning accuracy of the workbench and the ultra-high flatness.

Applicable industries: It is mainly used to process plates, plates, shells, molds and other parts with high precision, multiple processes and complex shapes. It can continuously complete milling, drilling, expanding, reaming, boring, tapping and precise processing of two-dimensional three-dimensional surfaces and inclined surfaces in one clamping process; The fourth axis can be selected to process the revolving parts. It is applicable to the processing of mechanical parts in various industries such as aerospace, automobile, railway, IT, mold, etc.

Before you buy a vertical machining center, you should also ask yourself two most important questions: What do you want to buy this machine tool for? How much will it cost? Next, we choose the appropriate machining center according to the bed material, guide rail, spindle and tool magazine. The quality of the machine tool is determined not only by the excellent components, but also by strict assembly and reasonable collocation.

1.Bed material

In order to meet the requirements of CNC machine tools for high speed, high precision, high productivity, high reliability and high automation, compared with ordinary machine tools, CNC machine tools should have higher static and dynamic stiffness and better vibration resistance. CNC machine tool bed mainly puts forward higher requirements in the following aspects: accuracy and precision retention, enough static and dynamic stiffness, good thermal stability, smooth chip removal, safe lifting, and conducive to processing and assembly. Common bed materials include:

1) Cast iron

The lathe bed is made of cast iron, and its vibration absorption capacity is several times that of the steel lathe bed, which can effectively absorb the vibration in the machining process of the lathe, and is conducive to ensuring the machining accuracy of the lathe: – Inoculated cast iron with strength and toughness better than traditional cast iron is used, and each part of the casting has better organizational consistency, giving the lathe bed stronger tensile strength and excellent vibration absorption capacity- Compared with the traditional cast iron, the polymer concrete bed has better vibration absorption, low thermal expansion coefficient and low thermal conductivity, which can resist the change of external environment temperature, better ensure the assembly accuracy of the bed, and its good corrosion resistance can resist the bad working environment and extend the service life of the machine tool.

2) Inoculated cast iron

Inoculated cast iron is a kind of high-quality gray cast iron. Inoculant is added to molten iron before pouring. Through inoculation, the cast iron has finer and uniformly distributed graphite, and its mechanical properties are better than ordinary gray cast iron – the strength and toughness of the inoculated cast iron are better than ordinary gray cast iron, and the inoculation treatment makes the structure of castings with different wall thicknesses more uniform, and the properties are basically consistent, Therefore, inoculant cast iron is often used to manufacture castings with high requirements for mechanical properties and large changes in section size.

3) Polymer concrete

Polymer concrete has higher vibration absorption than cast iron, especially for large amplitude vibration. Mineral casting has very strong vibration absorption capacity. When mineral castings are used as the bed of the machine tool, the vibration generated in the processing process has a low impact on the geometric shape of the machine tool, thus ensuring the processing accuracy- Compared with cast iron, this material is not sensitive to temperature changes, and its thermal conductivity is much lower than that of metal. It is easier to control the geometric error caused by thermal deformation of the machine tool in a small range, which is suitable for high-precision machining. In addition, mineral castings have strong corrosion resistance to cutting fluid, coolant and other liquids. It can ensure the structural strength of the machine tool and prolong its service life.

2.Guide rails

Although the forms of the guide rail system are various, the working properties are the same. The working parts of the machine tool move on the designated guide rail system, such as the train traveling along the rail in the designated direction. It mainly embodies the following two basic functions: 1. It guides the movement of the bearing body, and provides a smooth moving surface for the bearing body. Guides are divided into two categories

1) Linear guide (ball+roller)

The full name of line rail is linear guide rail, which generally refers to rolling guide rail. There are two common structures: ball guide rail and roller guide rail. The difference is that the ball guide rail is a point contact type, and the roller guide rail is a line contact type. Their principles are the same. They are also driven by rolling on the guide rail. And the cutting force borne by the rail is relatively small.

2) Rigid guideway

Hard rail refers to a kind of hard rail, which is a casting piece that integrates the guide rail and the lathe bed, and then the guide rail is processed on the basis of the casting. That is to say, the guide rail is formed by casting the shape of the guide rail on the lathe body, and then processed after quenching and grinding. After high-frequency or ultra audio frequency quenching, the hardness of the guide rail of the hard rail machining center is generally above HRC50 ℃, which makes it have excellent wear resistance. The material arrangement is generally not lower than HT250, and the Brinell hardness of the machine body is between HB180-HB240.

3) Differences between the two

The advantage of the line rail is that the line rail machining center uses rolling friction, with relatively small friction resistance, no creeping phenomenon, and fast running speed. Therefore, it is mostly used in high-speed machining and rapid tool cutting. The disadvantage is that because of the small contact surface, the accuracy of the line rail machining center will decline after a long period of use. It can only be achieved by replacing the guide rail, and it is suitable for heavy loads, Its rigidity is also lower than that of hard track. The main configuration model is high-speed machine; Drilling and tapping machine; Small and medium-sized vertical machining center.

The advantage of the hard rail is that the sliding contact surface of the hard rail is large, which makes the machine tool strong in rigidity, stability and shock absorption. This can better provide processing efficiency and ensure high accuracy. The hard rail machining center is more suitable for heavy cutting. At the same time, when the hard rail surface is worn (when the accuracy decreases), its surface can be re machined, and its flatness can be adjusted. Its disadvantage is that when the hard rail machining center is machining the workpiece, because the rail uses sliding friction, this friction mode will bring greater friction, so when machining the workpiece, greater cutting force is required, which is not conducive to rapid cutting, and the noise is large. The main model is heavy cutting machine; Large gantry; Horizontal and vertical machining centers.

3.Spindles

Spindle, which refers to the spindle of the machine tool in particular, is the part on the machine tool that drives the workpiece or tool to rotate to execute the cutting operation of the machine tool.

In terms of mechanical structure, spindles are divided into mechanical spindles and built-in spindles (motorized spindles).

There are many different transmission modes between mechanical spindle and spindle motor, such as direct connection, synchronous belt, belt and gear, each with its own characteristics.

1) Direct connection, coupling connection, 1:1 transmission ratio, characterized by high coaxiality requirements and great difficulty; Long installation distance is required.

2) Synchronous toothed belt, 1:1 transmission ratio. Compared with direct connection, it is only necessary to ensure the parallelism of motor axis and spindle axis

3) Belt connection (with different pulley radius, the transmission ratio is basically not adjustable), 1: n transmission ratio. Unless the pulley is changed, the transmission ratio is basically unchanged; V-belt slipping is inevitable

4) Gear connection (gear shifting device, variable transmission ratio, speed regulation), 1: n transmission ratio, compact structure, stable transmission ratio, constant transmission ratio; Adjustable speed, widely used

4 tool magazine

There are many types of tool magazine, the most common is manipulator tool magazine. The automatic tool changing device of the machining center is composed of a tool magazine for storing tools and a tool changing mechanism. Tool change methods are mainly divided into two categories: random tool change and fixed tool change. Different types have different characteristics, such as large capacity of chain tool magazine; The manipulator has high stability and low tool holder cost.

1) Turret type tool magazine

The turret type tool magazine is called the fixed address tool changer magazine, that is, each tool position has a number, generally from 1 to 12, 18, 24, etc., that is, the tool number address.

The feature is that after the operator installs a tool into a tool position, no matter how many times the tool is replaced, it is always in place, and the control action mode is PMC program. It is characterized by low manufacturing cost. The main components are the tool magazine body and the index plate, and the air cylinder is mainly used for the forward and backward, up and down movements. Easy assembly and adjustment, simple maintenance; It takes a long time to change the tool changer at the fixed address, and it takes more than 8 seconds for domestic machine tools. The total number of tools in the disc type tool magazine is limited and should not be too many.

2) Manipulator tool magazine

Tool change of manipulator tool magazine is a tool change at random address. There is no number on each cutter sleeve. The biggest difference between the manipulator tool magazine and the bamboo hat type tool magazine is that it has a mechanical arm, so it is more convenient to change tools. The memory data supports the tool preselection function in advance, so it is faster and more reliable. It is characterized by high manufacturing cost. The tool magazine is combined by a chain of tool sleeves, and the movement of the manipulator is controlled by the cam mechanism, so the processing of parts is more complex. The gear oil for lubrication and cooling of the cam case shall be replaced regularly. The tool change time is generally 4 seconds. The number of tools is generally more than that of turret tool magazine, including 18, 20, 30, 40, 60, etc.

A suitable machine tool is the best.

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