In the case of CNC programming, G90 is used, and G91 is used.

The G90 instruction stipulates that the coordinates are input in the form of absolute values during programming, that is, the coordinate values X, Y, and Z at the end of the moving instruction are calculated based on the coordinate origin of the workpiece coordinate system (program zero point).

The G91 instruction stipulates that the coordinates are entered in the form of incremental values during programming, that is, the coordinate values x, y, and z at the end point of the moving instruction are calculated based on the starting point, and then the positive or negative is judged according to the direction of the end point relative to the starting point, and the positive is taken in the same direction as the coordinate axis, and the negative is taken in the opposite direction.

G90 is the absolute value of the programming, it is based on the origin of the workpiece coordinates as a reference point (that is, the program number is calculated according to the coordinate origin), G91 is the incremental mode, it is the previous program number as the reference point, that is, the current position of the tool point.

If you know the relationship between the position of the end point of your program segment and the position of the origin, then use g90, if the coordinate value of this point relative to the origin is difficult to calculate, then you can try g91, I usually use g90 to calculate the coordinate point, just use CAD to calculate.

At the time of computer programming.

Geometrically shaped objects are usually g90

There are many times when G91 is used for regular-shaped objects.

For example, when we process parts such as guide plates, limits, etc., we usually use G91, as long as we are used to it, these two programming methods can be used at will.

There are no dead rules.

The differences between the G90 and G91 directives are:

1. The programming mode is different: G90 is absolute incremental programming, and G91 is relative incremental programming.

2. Different coordinate input methods: G90 and G91 correspond to absolute position data input and incremental position data input respectively. where g90 represents the coordinate size of the target point in the coordinate system, and g91 represents the amount of displacement to be run.

The G90 G91 is suitable for all sitting-rock shafts.

3. The reference zero point is different: when G90 is programmed into the program, all the coordinate values of the subsequent programming are based on the programmed zero point. When G91 is programmed, all subsequent coordinate values are used as a starting point to calculate the programmed value of the motion.

In the next coordinate system, the previous point is always programmed as the starting point.

G90 and G91 are the two G**s used in CNC milling, which represent the working mode of absolute and incremental coordinates, respectively. The difference between them is below:

1.G90 (Absolute: When using the G-command, the machine interprets all the commands, such as moving to a specific position or line interpolation, as absolute.

This means that the coordinate values in the program are determined for the origin or reference point of the work-sitting system. The moves are positioned according to the absolute coordinates of the roam, regardless of whether there are other previous movement commands.

2.G91 (Incremental Mode): When using the G91 command, the machine will interpret all movement commands as incremental sitting.

This means that the coordinate value of the program represents the displacement relative to the position after the last time. Each move is based on the last position offset, not on absolute coordinates. When using g, you need to explicitly specify the relative displacement from the previous operation.

To sum up, G90 is the absolute coordinate programming book, and G91 is the range mode. In G90 mode, each seat is the absolute position relative to the origin of the workpiece coordinate system, while in the 91 mode, each seat is relative to the previous operation, according to the specific machining summation programming habits, you can choose the appropriate mode to write the CNC milling machine program.

In CNC lathes, G99 refers to: Feed rate per revolution. It represents that in the settings of CNC model machining, the feed rate is programmed to control the cutting speed of the tool to the workpiece, that is, the speed at which the tool rotates with the spindle at high speed and cuts forward according to the preset toolpath.

In the CNC model machining settings, the feed rate is programmed to control the cutting speed of the tool on the workpiece, that is, the cutting speed when the tool rotates at high speed, and cuts forward according to the pre-set tool path.

There is no fixed value for spindle speed and feed rate, which is usually set by empirical value, and is mainly selected according to the tool and workpiece material. Increasing the feed rate can improve production efficiency.

During machining, the feed rate can also be adjusted manually via the adjustment switch on the machine control panel. The control panel of CNC machine tools is usually equipped with a spindle speed adjustment switch, which can adjust the spindle speed as a whole during the machining process. However, the maximum feed rate is limited by the stiffness of the equipment and the performance of the feed system.

The G92 instruction is used to turn the multi-head thread thread cutting cycle G92 is a simple thread cycle, the instruction can cut the cone thread and the cylindrical thread, and the cycle route is basically the same as the single shape fixed cycle mentioned above, but the feed behind F can be changed to the pitch value, and the instruction format is: **Format: G92 X(U) Z(W) R F J K L;

J and K are tail regressions, and L is the number of multi-threaded heads

1. When JK is omitted, the parameter value determines the tail length of the tail.

2. When J is omitted, the direction of the long axis is retracted according to K, and the direction of the short axis is determined by the parameters.

3. When k is omitted, j is equal to k.

4. When j is equal to 0 or both are equal to 0, there is no tailing.

5. When J is not equal to 0 or K is equal to 0, press J to equal K to detail.

6. When j is equal to 0 and k is not equal to 0, there is no tailing.

CNC lathe is one of the most widely used CNC machine tools. It is mainly used for the cutting of the inner and outer cylindrical surfaces of shaft parts or disc parts, the inner and outer conical surfaces of arbitrary taper angles, the internal and external curved surfaces of complex rotation, cylindrical and conical threads, and can be grooving, drilling, reaming, reaming and boring.

CNC machine tools are automatically processed on the processed parts according to the pre-programmed processing program. We compile the processing process route, process parameters, movement trajectory, displacement, cutting parameters and auxiliary functions of the parts into a processing program sheet in accordance with the instructions and program formats specified by the CNC machine tool, and then record the content of the program sheet on the control medium, and then input it into the CNC device of the CNC machine tool, so as to command the machine tool to process the parts.

G94 in CNC programming—single fixed shape cyclic machining end face and inclined end face cutting cycle instruction G94 instruction format:

g94 x（u）＿z（w）＿ f＿；

Note: where x, z—absolute value programming, is the end point of the cutting in the workpiece coordinate system of the coordinates; When the increment is programmed, it is the incremental coordinate value of the end of the cut relative to the beginning of the cycle, which is represented by you and w, and f—is the feed rate.

Advantages and disadvantages of CNC programming.

1. Advantages. It is mainly used for point processing (such as drilling, reaming) or the processing of parts with simple geometry (such as plane, square groove), with a small amount of calculation, a limited number of program sections, and intuitive and easy to realize programming.

2. Disadvantages. For parts with spatial free-form surfaces and complex cavities, the calculation of tool trajectory data is quite cumbersome, laborious, error-prone, difficult to proofread, and some even impossible to complete.

Absolute value programming g91 Increment value programming g92 thread cutting cycle g94 feed per minute g95 feed per revolution g96

Constant line speed control G97 constant line speed cancels.

In CNC programming, G97 is constant angular speed control, and almost all CNC machine tools are in the state of G97 when they are turned on.

In the G97 state, the unit of the S command is: revolutions in minutes. As long as there is no new S command, the speed of the spindle of the CNC machine tool remains the speed specified in the previous S command.

The opposite of G97 is G96, which is a constant linear velocity control (keeping the linear velocity constant, the angular velocity tends to always change).

CNC programming is one of the main contents of the preparation stage of CNC machining, which usually includes analyzing the part drawings and determining the machining process; Calculate the trajectories of the tool and obtain the tool position data; Write CNC machining programs; fabrication of control media; Proofreading procedures and first article trial cutting. There are two methods: manual programming and automatic programming. In short, it is the whole process from the part drawing to getting the CNC machining program.