The length unit size used by CNC lathes can be divided into metric system and English system, which are set by special instruction codes. For example, FANUC-0TC system uses G20 to indicate the use of English unit size, and G20 indicates the use of metric unit size. After the system is powered on, the machine tool is automatically in the metric size state.
2. Diameter programming and radius programming
(1) diameter programming: When diameter programming is adopted, the coordinate value of X axis in NC program is the diameter value on the part drawing.
(2) Radius programming: Radius programming is adopted, and the coordinate value of the X axis in the numerical control program is the radius value on the part drawing. Considering the convenience of use, diameter programming is generally adopted. The default programming mode of CNC system is diameter programming.
A) diameter programming
B) radius programming
Figure 1 Classification of NC Turning Programming
a) A:(30.0，80.0)，B:(40.0，60.0)
b) A:( 15.0，80.0)，B:(20.0，60.0)
3. The front tool rest and the rear tool rest of the lathe
CNC lathes have two tool rest layouts: as shown in Figure 2.
Fig. 2 Lathe front tool rest and rear tool rest
(1) Front tool rest. The front tool rest is located in front of the Z axis. Like the layout of the traditional horizontal lathe tool rest, the tool rest guide rail is a horizontal guide rail and uses a four-station electric tool rest.
(2) Rear tool rest. The rear tool rest is located behind the Z axis, and the position of the tool rest guide rail is inclined to the front plane. This structure is easy to observe the cutting process of the tool, easy to discharge chips, and has a large space at the back, so more tool holders can be designed. Generally speaking, the multifunctional CNC lathe is designed as the rear tool rest.
4. Tool tip radius compensation
For the convenience of programming, the tool tip is regarded as a sharp point in NC turning programming, and the tool path in NC programming is the path of an imaginary sharp point. (as shown in figure 3)
Figure 3 imaginary tip and tip radius
The tool tip radius compensation is introduced into the CNC system: after the NC program is written, the known tool tip radius value is input into the tool compensation table. When the program runs, the CNC system will automatically compensate the actual tool path according to the corresponding tool tip radius value.
Indexable blades are generally used in NC machining, and the radius of the tip fillet of each blade is certain. By selecting the blade model, the radius of the corresponding blade tip fillet can be determined.
Description of tool tip arc radius compensation:
Instruction format G4 1(G42, G43)G0 1(G00)X(U)_Z(W)
Command function G4 1 is the radius left compensation of the tool tip arc;
G42 is the right compensation of the tip arc radius;
G40 is to cancel the tool tip arc radius compensation.
The instruction points out that the left side of the tool compensates the arc radius of the tip on the left side of the workpiece when viewed in the direction of tool movement; On the right side of the workpiece, the tool compensates the radius of the tool tip arc. Only through the linear motion of the tool can the radius compensation of the tool tip arc be established and cancelled.
5. Initial state of NC machine tool
Initial state: refers to the state of the CNC machine tool after power-on, also known as the default state in the CNC system. Generally, the initial state of CNC machine tools is set to absolute coordinate programming, using metric length unit size, canceling tool compensation, and stopping spindle and cutting fluid pump. But numerical control programming is the most important. At present, there are technical talents in China. What really matters is not much. But this society. Very useful. Then there is the programming club. Main CAD. Because CAD is drawing pictures. After being accurate. You are good at NC programming.