CNC Equipment Basics (Part 3)
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Published Time:
2025-01-14
Classification by Control Movement Trajectory
1. Point-to-point control CNC machine tools
Point-to-point control CNC machine tools are characterized by the fact that the machine moving parts can only achieve precise positioning from one position to another, without any processing during movement and positioning. The machine CNC system only controls the coordinate value of the end point of the stroke, not the movement trajectory between points, so there is no connection between the movements of several coordinate axes. Several coordinates can move to the target point at the same time, or each coordinate can move separately in sequence.
These CNC machine tools mainly include CNC coordinate boring machines, CNC drilling machines, CNC punching machines, CNC spot welders, etc. The CNC device of point-to-point control CNC machine tools is called a point-to-point CNC device.
2. Straight-line control CNC machine tools
Straight-line control CNC machine tools can control the tool or worktable to move linearly and perform cutting processing along the direction parallel to the coordinate axis at an appropriate feed rate. The feed rate can vary within a certain range according to the cutting conditions.
Simple CNC lathes with straight-line control only have two coordinate axes and can process stepped shafts. CNC milling machines with straight-line control have three coordinate axes and can be used for planar milling. Modern combined machine tools use CNC feed servo systems to drive the power head with multi-axis box axial feed for drilling and boring. It can also be considered a type of straight-line control CNC machine tool.
CNC boring and milling machines, machining centers, etc., the feed movement speed in each coordinate direction can be adjusted within a certain range, and have the functions of point-to-point and straight-line control processing. This type of machine tool should be called a point-to-point/straight-line control CNC machine tool.
3. Contour control CNC machine tools
Contour control CNC machine tools can continuously and correlatively control the displacement and speed of two or more movements, so that the synthesized planar or spatial movement trajectory can meet the requirements of the part contour. It can not only control the starting and ending coordinates of the machine moving parts, but also control the speed and displacement of each point of the entire processing contour, processing the workpiece into the required contour shape.
Commonly used CNC lathes, CNC milling machines, and CNC grinding machines are typical contour control CNC machine tools. CNC flame cutting machines, EDM machine tools, and CNC plotters also use contour control systems. The structure of the contour control system is more complex than the point-to-point/straight-line control system. During processing, interpolation calculation needs to be continuously performed, and then the corresponding speed and displacement control is performed.
Now, the control functions of computer numerical control devices are all implemented by software, and adding contour control functions will not increase the cost. Therefore, except for a few special-purpose control systems, modern computer numerical control devices all have contour control functions.
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