1.1 Overview of CNC Milling/Machining Centres

1.1 Overview of CNC Milling Machines/Machining Centres 1.1.1 Classification of CNC Machines

Machine tools that are controlled by numerical control technology are called CNC machine tools. Classified according to their processing purposes, CNC machine tools are mainly of the following types.

1. CNC milling machine

CNC machine tools used to complete milling or boring operations are called CNC milling machines.

1) Vertical CNC milling machine

CNC milling machine, vertical CNC milling machine in the number has always occupied the majority, and its application range is the most extensive. In terms of the number of coordinates controlled by the machine's CNC system, three-coordinate CNC vertical milling machine still occupies the majority. Usually capable of three-coordinate linkage, but there are also some machines that are only capable of linkage of any two of the three coordinates (often called two-and-a-half-axis machining). In addition, there are also four- and five-axis CNC vertical milling machines with a spindle capable of CNC pendulum motion around one or both of the X, Y, and Z axes. Figure 1-1 shows a vertical CNC milling machine.

Figure 1-1 Type Vertical CNC Milling Machine

2) Horizontal CNC milling machine

Horizontal CNC milling machine spindle axis is parallel to the horizontal plane, by adding CNC turntable or universal CNC turntable to achieve four, five coordinates processing, in order to expand the scope of processing and expand functionality, with this way, not only can be processed out of the side of the workpiece on the continuous rotary contour, but also at a time of installation, by the carousel to change the position, and thus carry out the “four-sided processing”, type horizontal CNC milling machine shown in Figure 1-2, type horizontal CNC milling machine. Four-sided machining", type horizontal CNC milling machine shown in Figure 1-2.

Figure 1-2 Horizontal CNC Milling Machine

3) Gantry CNC milling machine

Gantry CNC milling machine spindle, can be in the gantry transverse skateboard movement, at the same time this spindle can also be in the gantry vertical skateboard movement, and the gantry will be along the bed for longitudinal movement. For large CNC milling machines, the gantry mobile type is often used because of the need to consider a series of technical problems such as increased travel, reduced footprint and rigidity. Figure 1-3 shows the ×80 type gantry CNC milling machine, and Figure 1-4 shows the six-axis gantry CNC milling machine produced by the German company Edel.

Figure 1-3 ×80 type gantry CNC milling machine

Figure 1-4 Six-axis gantry CNC milling machine

2. CNC machining centres

CNC machine tools equipped with tool magazines, excluding those with rotary tool holders, and automatic tool changers (ATC) are called CNC machining centres. What people usually call CNC machining centres are CNC milling machines with tool magazines and automatic tool changers.

Machining centres belong to highly mechatronic products, workpiece clamping, the CNC system can control the machine tool, according to different processes, automatic selection of tools, but also automatically replace the tool, while automatic tool setting, but also automatically change the spindle speed, feed, etc., can be completed in a continuous process of drilling process, can be completed in the boring process, can be completed in the milling process, can be completed in the reaming process, can be completed in the tapping process and a variety of processes, so it greatly reduces the Workpiece clamping time, reduce the measurement time, reduce the machine tool adjustment and other auxiliary process time, for the processing of complex shapes of parts, for the higher precision requirements of the parts, for the variety of parts with frequent replacement has a good economic effect.

1) Horizontal machining centre

Horizontal machining centres are machining centres in which the spindle axis is set parallel to the table, and their main scope of application covers the machining of box-type parts. Horizontal CNC machining centres of this type are shown in Figures 1-5.

Figure 1-5 Horizontal CNC Machining Centres

2) Vertical machining centre

Machining centres with the spindle axis set perpendicular to the table are called vertical machining centres, and are mainly used for machining complex parts such as plates, discs, moulds and small housings, such as the VC600 vertical CNC machining centre shown in Figs. 1 - 6.

Figure 1-6 VC600 Vertical CNC Machining Centre

3) Gantry machining centre

A gantry machining centre with a spindle that can move on the transverse and vertical slides of the gantry, and whose gantry moves longitudinally along the bed, is mainly used for machining large parts, and is presented in the position in Figures 1-7 as the VMC 3023 gantry machining centre.

Figure 1-7 VMC 3023 Gantry Machining Centre

3. CNC lathe

CNC lathe with ordinary lathe, are used to process the rotating surface of the parts, it can usually automatically complete the external cylindrical surface processing, can complete the conical surface processing, can complete the spherical surface processing, can also complete the thread processing, but also be able to process some complex rotating surfaces, such as hyperbolic surfaces, parabolic surfaces, etc., CNC lathe and ordinary lathe workpiece mounting is basically the same way, and in order to improve the machining efficiency, CNC lathe most of the use of hydraulic Chuck, pneumatic chuck, electric chuck.

CNC lathe can be divided into two categories: horizontal and vertical, horizontal lathe exists horizontal guideway and tilt guideway, the higher grade CNC horizontal lathe will generally use the tilt guideway, in general, the turning process as the main mode and auxiliary to the milling process of the CNC turning centre is categorized as a CNC lathe category, such as Figure 1-8 shows the type of horizontal CNC lathe guideway, such as Figure 1-9 Figure 1-8 shows a horizontal CNC lathe with a horizontal guideway, and Figure 1-9 shows a horizontal CNC lathe with an inclined guideway of the CK50 type.

Figure 1-8 Model CNC Lathe

Figure 1-9 Horizontal CNC lathe with inclined guideway, type CK50

4. CNC drilling machines

For CNC drilling machine, its main role is to complete the drilling, tapping and other functions, occasionally, can also achieve simple milling function. CNC drilling machine belongs to a kind of CNC machine tool using point control system, that is to say, to control the position of the tool from one point to another point, however, not to control the tool movement trajectory. Figure 1-10 shows a type of CNC drilling machine.

Figure 1-10 Model CNC Drilling Machine

5. CNC grinding machines

CNC grinding machine, is the kind of CNC control to achieve the grinding process of machine tools, according to the function of division, the existence of cylindrical grinding machine, internal grinding machine, surface grinding machine, guideway grinding machine, profiling grinding machine, centreless grinding machine and so on many kinds. As shown in Figure 1-11, this type of CNC cylindrical grinder is a precision cylindrical grinder used for processing multi-jugular shaft parts, this machine tool uses a two-axis linkage CNC system, the feed of the grinding wheel holder and the movement of the table are driven by AC servo motors with the help of ball screws, and through the two-axis linkage to dress the grinding wheels as well as automatic compensation for the workpiece dimensional accuracy of the online automatic measurement to ensure precision, which can achieve semi-precision and high precision grinding. The workpiece dimensional accuracy is automatically measured on-line to ensure precision and to realise semi-automatic cycle grinding.

Figure 1-11 Model CNC Cylindrical Grinding Machine

6. CNC electric discharge moulding machines

CNC EDM machines for machining, commonly known as electric pulse machines, are speciality machines. With the help of two electrodes with different polarities, they produce an electrical erosion in an insulating liquid, which removes material for machining, offering special advantages for the machining of moulds with complicated shapes and for the machining of difficult materials. An EDM machine is shown in Figure 1-12.

Figure 1-12 CNC EDM forming machines

7. CNC wire-cutting machines

CNC wire-cutting machine, presented as shown in Figure 1-13, it works on the same principle as the EDM machine, however, its electrodes are electrode wires, such as molybdenum and copper wires, and then there is the workpiece.

Figure 1-13 DK-500 CNC wire-cutting machine tool

8. Other CNC machine tools

CNC machine tools in addition to those common types mentioned above, there are CNC planer, CNC punch press, CNC laser processing machine tools, CNC ultrasonic processing machine tools and many other forms.