CNC technology: refers to the automatic control technology that can be programmed with numbers, letters and symbols for a certain working process.
CNC system: refers to the organic integrated system of software and hardware modules that realize the functions related to numerical control technology, which is the carrier of numerical control technology.
Computer numerical control system (CNC): refers to the computer-based CNC system.
CNC machine tool: refers to the machine tool that uses CNC technology to control the machining process of the machine tool.
Point-controlled CNC machine tools: This type of CNC machine can only control the two coordinate axes in the machining plane to drive the relative movement of the tool and the workpiece, move from one coordinate position to the next coordinate position, and then control the third coordinate axis for drilling.é•—Cutting. Features: No cutting process is carried out during the whole movement process, so there is no requirement for the movement track, but the coordinate position is required to have higher positioning accuracy. Point-controlled CNC machine tools are used to machine the hole system in the plane. These machine tools mainly include CNC drilling machines, printed circuit board drilling machines, CNC boring machines, CNC punching machines, and coordinate measuring machines.
Linear Control CNC Machine: This type of CNC machine can control the tool or table to move and cut in a direction parallel to the coordinate axis at an appropriate feed rate. The feed rate can be adjusted within a certain range according to the cutting conditions. Early, simple two-axis CNC lathes can be used to machine stepped shafts. Simple three-axis CNC milling machine for flat milling. The modern combined machine tool adopts the CNC feed servo system, and the drive power head carries the multi-axle axial feed for the drill collar machining. It can also be regarded as a linear control CNC machine tool. It is worth mentioning that CNC machine tools with only linear control functions are rare.
Contour control CNC machine tools: This type of CNC machine tool has the ability to control several coordinate axes and coordinate movements at the same time, that is, multi-axis linkage, so that the tool moves relative to the workpiece according to the specified trajectory and speed of the workpiece, and performs continuous cutting processing during the movement. Features. Linkage processing is the essential feature of this type of CNC machine tool. These CNC machine tools include CNC lathes, CNC milling machines, machining centers, and other CNC machine tools for machining curved and curved shape parts. Modern CNC machine tools are basically of this type. According to the number of linkage axes, it can be subdivided into: 2-axis linkage CNC machine tool, 3-axis linkage CNC machine tool, 4-axis linkage CNC machine tool, 5-axis linkage CNC machine tool.
Open loop feed servo system: This type of servo system has no position measuring device, and the signal flow is one-way (CNC device → feed system), so the system stability is good. However, due to the lack of position feedback, the accuracy is not high relative to the closed-loop system, and its accuracy mainly depends on the performance and accuracy of the servo drive system and the mechanical transmission mechanism. Such a system generally uses a power stepping motor as a servo drive component, and has the advantages of simple structure, stable operation, convenient debugging, simple maintenance, low price, and the like, and is widely used in applications where accuracy and speed are not high and driving torque is not large. It is generally used for numerical control transformation of economical CNC machine tools and old machine tools.
Semi-closed-loop feed servo system: The position detection point of this type of servo system is taken from the drive motor (usually AC/DC servo motor) or the screw end, and the displacement of the table is indirectly detected by detecting the rotation angle of the motor and the screw. It is not directly detecting the actual position of the workbench. Since the semi-closed loop does not include or only includes a small number of mechanical transmission links, stable control performance can be obtained. The stability of the system is not as good as that of the open loop system, but better than the closed loop. In addition, since the error of each component in the position loop can be corrected to some extent, the pitch error of the screw outside the position loop and the motion error caused by the gear gap are difficult to eliminate. Therefore, its accuracy is better than open loop, and worse than closed loop. However, such errors can be compensated and satisfactory accuracy can still be obtained. The semi-closed loop CNC system has a simple structure, convenient debugging and high precision, so it has been widely used in modern CNC machine tools.
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