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How many types of CNC machine tools are there? What categories are they divided into in processing?

With the improvement of my country’s machine tool manufacturing industry, CNC machine tools have been put into various parts processing and automated production lines. It is an indispensable connection equipment for major smart factories in the future. Due to the large variety of CNC machine tools, there are two major categories: metal cutting equipment and sheet metal equipment. At the same time, according to their control principles, functions and components, they are classified from different angles. Below we classify them from the functional manifestations in actual parts processing:

CNC machine tools with point control in part hole processing

Point-controlled CNC machine tools mainly include CNC drilling machines, CNC boring machines, CNC punching machines and three-coordinate measuring machines. Printed circuit board drilling machines are the simplest point-controlled CNC machine tools. Point-controlled CNC machine tools are used to process hole systems in a plane. They control two coordinate axes (one coordinate axis is a feed motion in one direction) in the processing plane to drive the relative movement of the tool and the workpiece, from one coordinate bus (one coordinate axis is a feed motion in one direction) to drive the relative movement of the tool and the workpiece, quickly move from one coordinate position (coordinate point) to the next coordinate position, and then control the third coordinate axis for cutting. This type of machine tool requires a high positioning accuracy at the seat position. In order to improve production efficiency, the machine tool uses the set maximum feed speed for positioning movement, and advances in stages or continuously decelerates when approaching the positioning point, so as to approach the end point at a low speed, thereby reducing the inertial overshoot of the moving parts and the positioning error caused by it. During the positioning movement process, the CNC machine tool does not perform cutting and has no requirements for the motion trajectory.

In cutting processing, it should be used for the most linear control CNC machine tools

Linear control CNC machine tools can control the appropriate feed speed of the tool or worktable, and perform linear movement and cutting in the direction parallel to the coordinate axis. The feed speed can be adjusted within a certain range according to the cutting conditions. Simple CNC lathes with linear control have only two coordinate axes and can be used to process step shafts. The linear control CNC milling machine has three coordinate axes and can be used for plane milling. Modern modular machine tools use CNC feed servo systems to drive the power head with multiple axle boxes to feed along the axial direction for cutting. It can also be regarded as a linear control CNC machine tool.

CNC machine tools for complex parts controlled by curves and contours

Contour control CNC machine tools are divided into CNC machine tools for plane contour processing and CNC machine tools for space contour processing. CNC machine tools for plane contour processing include CNC lathes for turning curved surface parts and CNC milling machines for milling curved surface contours. The contour shape of the processed parts. The contour of the part can be composed of straight lines, arcs or any plane curves (such as parabolas, Archimedean spirals, etc.). Regardless of what kind of line segments the contour of the spare parts is composed of, small straight lines are usually used to approximate the contour of the curve during processing. When a cylindrical milling cutter is used to mill the contour surface on a CNC milling machine, the CNC system controls the tool center to move △xi and △y1i relative to the workpiece in the unit time in the two coordinate axis directions at the same time. The synthetic displacement △Li of the tool to the workpiece is moved from point I’ on the equidistant line of the contour curve to point J’, thereby processing a small straight line IJ on the workpiece to approximate the IJ arc on the contour curve. By continuously controlling the two relative displacement components △xi and △yi, a broken line composed of multiple small straight lines can be processed to approximate the curve contour. The feed components △xi and △yi are determined by the synthetic feed speed per unit time, the mathematical formula y=f(x) of the contour curve, the tool radius R, and the offset of the tool center to the part contour (D=R+6) determined by the machining allowance δ, and are calculated in real time by the CNC system. Such operations are called interpolation operations and tool radius compensation operations.

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