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Do You Know The Secret Language Of CNC System?

Jun 03, 2019

Listen to ALLES CNC engineers say that in the industry of CNC machine tool actual operation, there are also secret Spy-like secret language. The use of these secret language determines how the whole CNC system can change its operation. Now let ALLES CNC unveil this mystery.

numerical control machining

Increment pulse coder

Rotary position measuring element is mounted on motor shaft or ball screw, and equal interval pulse is sent out to indicate displacement when rotating. Because there is no memory element, it can not accurately represent the position of the machine tool. Only when the machine tool returns to zero and the zero point of the machine tool coordinate system is established can the position of the worktable or tool be indicated. It should be noted that the signal output of incremental encoder has two ways: serial and parallel. Individual CNC systems correspond to this with serial interface and parallel interface.

Absolute pulse coder

Rotary position measuring element has the same purpose as incremental encoder and memory element, which can reflect the actual position of machine tool in real time. The position after shutdown will not be lost, and the machine can be put into operation immediately without returning to zero. As with incremental encoder, attention should be paid to the serial and parallel output of pulse signal.


In order to perform spindle positioning or tool changing, the spindle of machine tool must be positioned at a certain turning angle in the circumferential direction of rotation as the reference point of action. Generally, there are four methods: position encoder orientation, magnetic sensor orientation, external turn signal orientation (such as proximity switch), external mechanical orientation.

Tandem control

For large workbench, when the torque of one motor is insufficient to drive, two motors can be used to drive the workbench. One of the two axles is the active axle and the other is the driven axle. The driving shaft receives CNC control instructions, and the driven shaft increases driving torque.

Rigid tapping

Tapping operation does not use floating chuck, but is realized by synchronous operation of spindle rotation and tapping feed shaft. When the spindle rotates, the feed of the tapping shaft is equal to the pitch of the tap, which can improve the accuracy and efficiency. Metal processing Wechat, the content is good, worthy of attention. To achieve rigid tapping, the spindle must be equipped with a position coder (usually 1024 pulses per turn), and the corresponding ladder diagram is required to set the relevant system parameters.

Tool compensation memory A, B, C

Tool compensation memory can be set to either type A, B or C in general. The external performance is that type A does not distinguish between geometric shape compensation and wear compensation. Type B separates geometric shape compensation from wear compensation. Type C not only separates geometric shape compensation from wear compensation, but also separates tool length compensation code from radius compensation code. The length compensation code is H and the radius compensation code is D.

DNC Operation

It is a way of working automatically. CNC system or computer is connected by RS-232C or RS-422 port. Processing program is stored on the hard disk or floppy disk of the computer, and is input to CNC in a segment. Each input program is processed in a segment. This can solve the limitation of CNC memory capacity.

Advanced preview control (M)

The function is to read several program segments in advance, interpolate the trajectory and preprocess the speed and acceleration. In this way, the following error caused by acceleration and deceleration and servo lag can be reduced, and the tool can follow the contour of the parts accurately at high speed, so as to improve the processing accuracy. Pre-reading control includes the following functions: linear acceleration and deceleration before interpolation; automatic corner deceleration and other functions.

Polar coordinate interpolation (T)

Polar coordinate programming is to change the Cartesian coordinate system of two straight axes into the coordinate system of the horizontal axes into the straight axes and the vertical axes into the rotating axes, and use this coordinate system to compile the processing program of the non-circular contour. Usually used for turning straight grooves or grinding cams on grinders.

NURBS Interpolation (M)

Most industrial dies such as automobiles and airplanes are designed by CAD. In order to ensure accuracy, NURBS is used to describe sculpture surfaces and curves. Metal processing Wechat, the content is good, worthy of attention. Therefore, the interpolation function of CNC system is designed, so that the expression of NURBS curve can directly instruct CNC, avoiding the use of small linear segment approximation method to process complex contour surface or curve.

Automatic tool length measurement

Install contact sensors on the machine, and work out the measuring program of tool length (using G36, G37) as the processing procedure. In the program, the offset number of tool should be specified. The program is executed automatically to make the tool contact with the sensor, so as to measure the length difference between the tool and the reference tool, and automatically fill the value into the offset number specified by the program.

Cs Contour control

CS contour control is to change the spindle control of lathe into position control to realize the spindle positioning according to rotation angle, and can interpolate with other feed shafts to process complex workpieces.

Manual absolute ON/OFF

It is used to determine whether the coordinate value manually moved after feed pause is added to the current position value of automatic operation.

Manual handle interruption

When the handwheel is shaken during automatic operation, the moving distance of the motion axis can be increased. For revision of stroke or dimension.

Axis control by PMC

Feed servo axis controlled by PMC (Programmable Machine Tool Controller). The control instructions are programmed in the PMC program (ladder diagram). Because of the inconvenience of modification, this method is usually only used for the feed shaft control with fixed movement.

Cf Axis Control (T series)

In lathe system, the control of spindle rotation position (angle) is realized by feed servo motor just like other feeding axles. The axis is interpolated with other feeding axes to process arbitrary curves. (common in older lathe systems).

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