Increment pulse coder

Rotary position measuring element, installed on the motor shaft or ball screw, sends out equal interval pulse 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 coordinate system of the machine tool is established, can the position of the worktable or cutter be indicated. It should be noted that there are two ways of signal output of incremental encoder: serial and parallel. Some CNC systems have serial interface and parallel interface.

Useful CNC machining terms 1

Absolute pulse coder

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

Useful CNC machining terms 2


In order to carry out spindle positioning or tool change, it is necessary to position the machine tool spindle in the circular direction of rotation with a certain angle as the action reference point. Generally, there are four methods: position encoder orientation, magnetic sensor orientation, external one turn signal such as proximity switch orientation, external mechanical method orientation.

Tandem control

For large worktable, when the torque of one motor is not enough to drive, two motors can be used to drive together. One of the two shafts is the driving shaft and the other is the driven shaft. The driving shaft receives the control command from CNC, and the driven shaft increases the driving torque.

Rigid tapping

The tapping operation is realized by the synchronous operation of spindle rotation and tapping feed shaft instead of floating chuck. When the spindle rotates, the feed rate of the tapping shaft is equal to the pitch of the tap, which can improve the accuracy and efficiency. Wechat of metal processing has good content and deserves attention. In order to achieve rigid tapping, the spindle must be equipped with a position encoder, which is usually 1024 pulses per revolution. The corresponding ladder diagram is required to be compiled and the relevant system parameters are set.

A,B,CTool compensation memory A,B,C

Generally, the available parameters of tool compensation memory can be set to any one of type A, type B or type C. The external performance is that type A does not distinguish between geometric compensation and wear compensation. Type B separates geometric compensation from wear compensation. Type C not only separates geometric compensation from wear compensation, but also separates tool length compensation code and radius compensation code. The length compensation code is h and the radius compensation code is d. DNC Operation

It is a working mode of automatic operation. The CNC system or computer is connected by RS-232C or RS-422 port. The processing program is stored on the hard disk or floppy disk of the computer, and is input into the CNC section by section. Each input section of the program is processed one section, which can solve the limitation of CNC memory capacity.

Advanced preview controlM

The function is to read several program segments in advance, interpolate the running track and preprocess the speed and acceleration. In this way, the following error caused by acceleration, deceleration and servo lag can be reduced, and the tool can follow the contour of the program accurately at high speed, so that the machining accuracy is improved. Pre read control includes the following functions: linear acceleration and deceleration before interpolation; automatic corner deceleration.

Polar coordinate interpolationT

Polar coordinate programming is to change the Cartesian coordinate system of two linear axes into the coordinate system in which the horizontal axis is the linear axis and the vertical axis is the rotary axis. It is usually used for turning linear groove or grinding cam on grinder.

NURBS InterpolationM

In order to ensure the accuracy, the non-uniform rational B-spline function NURBS is used to describe the sculpture surface and curve. Wechat of metal processing has good content and deserves attention. Therefore, the CNC system has designed the corresponding interpolation function, so that the expression of NURBS curve can directly instruct CNC, and avoid using the method of small straight line segment approximation to process complex contour surface or curve.

Automatic tool length measurement

The contact sensor is installed on the machine tool, and the tool length measurement program is compiled with g36 and G37, and the offset number used by the tool should be specified in the program. The program is executed in the automatic mode 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 into position control, realize the positioning of the spindle according to the rotation angle, and can be interpolated with other feed shafts to process the workpiece with complex shape.

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 during automatic operation.

Manual handle interruption

The movement distance of the moving axis can be increased by shaking the hand wheel during automatic operation. Used to correct travel or dimension.

Axis control by PMC

Feed servo axis controlled by PMC programmable machine tool controller. The control instructions are written in the program ladder diagram of PMC. Due to the inconvenience of modification, this method is usually only used for the control of feed shaft with fixed movement.


CF Axis ControlT

In the lathe system, the rotation position and angle control of the spindle is realized by the feed servo motor just like other feed axes. This axis can be processed with any other feed curve. (common in older lathe systems)


When the servo switch off, emergency stop or servo alarm occurs, the position error will appear in the CNC position error register if the worktable moves mechanically. The position tracking function is to modify the position of the machine tool monitored by CNC controller, so that the error in the position error register becomes zero. Of course, whether to perform position tracking should depend on the actual control needs.

Simple synchronous control

One is the driving shaft and the other is the driven shaft. The driving shaft receives the motion command from CNC, and the driven shaft follows the drive shaft to move synchronously. CNC monitors the moving positions of the two axes at any time, but does not compensate the errors. If the moving positions of the two axes exceed the set value of the parameters, the CNC will give an alarm and stop the movement of each axis at the same time. This function is often used in the double axis drive of large worktable.

Useful CNC machining terms 4

Three-dimension tool compensation

In multi coordinate machining, tool offset can be compensated in three coordinate directions during tool moving. It can realize the compensation of side machining with cutter and the compensation of machining with tool end face.

Tool nose radius compensation

There are arcs on the tool tips of turning tools. In order to make accurate turning, the radius of tool tip arc is compensated according to the cutting direction and the relative orientation between the tool and the workpiece.


Tool life management

When more than one tool is used, the tools are grouped according to their service life, and the use order of the tools is preset in the tool management table of CNC. When the tool used in machining reaches the life value, the next tool in the same group can be replaced automatically or manually. After the same group of tools is used up, the next group of tools will be used. Whether it is automatic or manual tool replacement, ladder diagram must be prepared.


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