When determining the coordinate axis of CNC machine tool, the Z axis is generally determined first, and then the X axis and Y axis are determined.
(1) Z axis. The axis parallel to CNC machine tool spindle (transmitting cutting power) is regarded as z-axis, and the direction of tool away from workpiece is the positive direction of z-axis. For CNC machine tools with spindle, such as horizontal lathe and vertical lifting table milling machine, the spindle axis of CNC machine tool is taken as Z axis; for CNC machine tools without spindle, such as shaper, the coordinate axis perpendicular to the clamping surface is specified as Z axis. For CNC machine tools with several spindles, such as gantry milling machine, one of the main spindles perpendicular to the worktable surface is selected as the main spindle, and the z-axis direction is determined by it.
(2) X axis. The x-axis is located in the horizontal plane, perpendicular to the Z-axis and parallel to the workpiece clamping surface. For CNC machine tools with workpiece rotation, such as lathe, the X axis is in the radial direction of the workpiece and parallel to the horizontal carriage, and the direction of the cutter leaving the workpiece rotation center is the positive direction of the X axis. For CNC machine tools with tool rotation: if z-axis is horizontal, such as horizontal milling machine, boring machine, etc., the positive direction of x-axis points to the right when viewed from the back end of the tool (spindle) to the workpiece. If the z-axis is vertical, such as vertical milling machine, drilling machine, etc., the positive direction of x-axis points to the right when looking at the column when facing the cutter (spindle). For CNC machine tools without spindle: such as planer, the main cutting direction is x axis.
(3) Y axis. The y-axis direction is determined according to the selected Z and X axes according to the Cartesian coordinate system of right-hand right angle.
(4) Steering of a, B and C. After selecting the X, y and Z axes, the positive rotation directions of a, B and C are determined according to the right hand helix rule.
(5) Additional coordinates. If the CNC machine tool is outside the basic rectangular coordinate system X, y, Z, and other axes are parallel to their coordinate system, the additional rectangular coordinate system is designated as u, V, W and P, Q, R.
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