Basic knowledge and characteristics of CNC milling machine

Characteristics of CNC Milling Machines

vmc850 (5)The CNC milling machine is developed on the basis of the general milling machine. The processing technology of the two is basically the same, and the structure is somewhat similar, but the CNC milling machine is an automatic processing machine controlled by the program, so its structure is also very different from the ordinary milling machine. CNC milling machine is generally composed of CNC system, main drive system, feed servo system, cooling and lubrication system, etc.:

1: The spindle box includes the spindle box and the spindle transmission system, which is used to clamp the tool and drive the tool to rotate. The spindle speed range and output torque have a direct impact on processing.

2: The feed servo system is composed of a feed motor and a feed actuator. The relative motion between the tool and the workpiece is realized according to the feed speed set by the program, including linear feed motion and rotational motion.

3: The center of the motion control of the CNC milling machine of the control system, executes the CNC machining program to control the machine tool for processing

4: Auxiliary devices such as hydraulic, pneumatic, lubrication, cooling systems and chip removal, protection and other devices.

5: The basic parts of machine tools usually refer to bases, columns, beams, etc., which are the foundation and frame of the entire machine tool.

 

The working principle of CNC milling machine

1: According to the technical requirements of the shape, size, accuracy and surface roughness of the part, the processing technology is formulated and the processing parameters are selected. Input the programmed machining program to the controller through manual programming or automatic programming with CAM software. After the controller processes the machining program, it sends commands to the servo device. The servo device sends control signals to the servo motor. The spindle motor rotates the tool, and the servo motors in X, Y and Z directions control the relative movement of the tool and the workpiece according to a certain trajectory, so as to realize the cutting of the workpiece.

CNC milling machine is mainly composed of bed, milling head, vertical table, horizontal saddle, lifting table, electrical control system, etc. It can complete basic milling, boring, drilling, tapping and automatic work cycles, and can process various complex cams, templates and mold parts. The bed of the CNC milling machine is fixed on the base for installation and various parts of the machine tool. The console has a color LCD display, machine operation buttons and various switches and indicators. The vertical worktable and the horizontal slide are installed on the lifting platform, and the X, Y, Z coordinate feeding is completed by the driving of the longitudinal feed servo motor, the lateral feed servo motor and the vertical lift feed servo motor. The electrical cabinet is installed behind the bed column, which houses the electrical control part.

2: Performance indicators of CNC milling machine

3: The point control function can realize the processing that requires high mutual position accuracy.

4: The continuous contour control function can realize the interpolation function of straight line and circular arc and the processing of non-circular curve.

5: The tool radius compensation function can be programmed according to the dimension of the part drawing, without considering the actual radius size of the tool used, thereby reducing the complex numerical calculation during programming.

6: The tool length compensation function can automatically compensate the length of the tool to meet the requirements for the adjustment of the length and size of the tool during processing.

7: Scale and mirror processing function, the scale function can change the coordinate value of the processing program according to the specified scale to execute. Mirror processing is also known as axisymmetric processing. If the shape of a part is symmetrical about the coordinate axis, only one or two quadrants need to be programmed, and the contours of the remaining quadrants can be achieved by mirror processing.

8: The rotation function can execute the programmed processing program by rotating it at any angle in the processing plane.

9: Subprogram calling function, some parts need to repeatedly process the same contour shape at different positions, take the machining program of a contour shape as a subprogram and call it repeatedly at the required position to complete the machining of the part.

10: The macro program function can use a general instruction to represent a series of instructions to achieve a certain function, and can operate on variables, making the program more flexible and convenient.

 

 

Coordinate system of CNC milling machine

1: The relative movement of the milling machine is stipulated. On the machine tool, the workpiece is always considered to be stationary, while the tool is moving. In this way, the programmer can determine the machining process of the machine tool according to the part drawing without considering the specific movement of the workpiece and the tool on the machine tool.

2: The provisions of the machine tool coordinate system, the relationship between the X, Y, Z coordinate axes in the standard machine tool coordinate system is determined by the right-hand Cartesian Cartesian coordinate system. On the CNC machine tool, the action of the machine tool is controlled by the CNC device. In order to determine the forming movement and auxiliary movement on the CNC machine tool, the displacement and movement direction of the machine tool must be determined first, which needs to be realized through the coordinate system. This coordinate system is called the machine coordinate system.

3: Z coordinate, the movement direction of the Z coordinate is determined by the spindle that transmits the cutting power, that is, the coordinate axis parallel to the spindle axis is the Z coordinate, and the positive direction of the Z coordinate is the direction in which the tool leaves the workpiece.

4: X coordinate, the X coordinate is parallel to the clamping plane of the workpiece, generally in the horizontal plane. If the workpiece rotates, the direction in which the tool leaves the workpiece is the positive direction of the X coordinate.

If the tool does a rotary motion, there are two cases:

1) When the Z coordinate is horizontal, when the observer looks at the workpiece along the tool spindle, the +X movement direction points to the right.

2) When the Z coordinate is vertical, when the observer faces the tool spindle and looks at the column, the +X movement direction points to the right.

5: Y coordinate, after determining the positive directions of X and Z coordinates, you can use the direction according to X and Z coordinates to determine the direction of Y coordinate according to the right-hand rectangular coordinate system.

 

 

Characteristics and composition of CNC milling machine

1: CNC vertical milling machine, vertical CNC milling machine, the main part is mainly composed of base, column, saddle, worktable, spindle box and other components, of which the five main parts are made of high-strength and high-quality castings and resin sand molding, the organization is stable , to ensure that the whole machine has good rigidity and precision retention. The three-axis guide rail pair adopts a combination of high-frequency quenching and plastic-coated guide rails to ensure the running accuracy of the machine tool and reduce frictional resistance and loss. The three-axis transmission system is composed of precision ball screws and servo system motors, and is equipped with automatic lubrication devices.

The three axes of the machine tool are made of stainless steel guide rail telescopic cover, which has good protection performance. The whole machine is fully closed. The doors and windows are larger, and the appearance is neat and beautiful. The operation control box is placed in the right front of the machine tool and can be rotated for easy operation. It can perform various milling, boring, rigid tapping and other processing, and is cost-effective. It is an ideal equipment for high-quality, high-precision and high-efficiency in the machinery manufacturing industry.

2: Horizontal CNC milling machine, the same as general horizontal milling machine, its spindle axis is parallel to the horizontal plane. In order to expand the processing range and expand functions, horizontal CNC milling machines usually use CNC turntables or universal CNC turntables to achieve 4 and 5 coordinate processing. In this way, not only the continuous rotating contour on the side of the workpiece can be machined, but also the “four-sided machining” can be realized by changing the station through the turntable in one installation.

3: Vertical and horizontal CNC milling machines. At present, such CNC milling machines are rare. Since the spindle direction of this type of milling machine can be changed, it can achieve both vertical processing and horizontal processing on one machine tool. , and has the functions of the above two types of machine tools at the same time, its use range is wider, the functions are more complete, the room for selecting processing objects is larger, and it brings a lot of convenience to users. Especially when the production batch is small and there are many varieties, and two methods of vertical and horizontal processing are required, the user only needs to buy one such machine tool.

4: CNC milling machines are classified by structure:

①The table lift type CNC milling machine, this type of CNC milling machine adopts the way that the table moves and lifts, and the spindle does not move. Small CNC milling machines generally use this method

②Spindle head lift CNC milling machine, this type of CNC milling machine uses the longitudinal and lateral movement of the table, and the spindle moves up and down along the vertical slide; the spindle head lift CNC milling machine has many advantages in terms of accuracy retention, bearing weight, system composition, etc. , has become the mainstream of CNC milling machines.

③ Gantry type CNC milling machine, the spindle of this type of CNC milling machine can move on the horizontal and vertical slides of the gantry frame, while the gantry frame moves longitudinally along the bed. Large-scale CNC milling machines often use a gantry mobile type to consider the problems of expanding the stroke, reducing the footprint and rigidity.


Post time: Jul-09-2022