Moldmaking Report: ABCs of machine movement — Part II
By Mark Benoit -- Tooling Tips
In the last regular Tooling Tips column (Dec., '01) I discussed some of the basics of spatial orientation in CNC machine tool movement. One of the most fundamental prerequisites for correctly setting ...
In the last regular Tooling Tips column (Dec., ’01) I discussed some of the basics of spatial orientation in CNC machine tool movement. One of the most fundamental prerequisites for correctly setting up tools and workpieces is a grasp of the concept of the Cartesian coordinate system.
The Cartesian coordinate system is based on a number of intersecting, parallel and extended axes labeled A, B, C, P, Q, R, U, V, W, X, Y and Z. In the last column I reviewed the Right Hand Rule, which is used to visualize the spatial relationship between the X, Y and Z primary axes; and the Right Hand Rotational Rule, which is used to find the positive direction of the corresponding rotation axis, A, B or C.
I will now discuss the relationship of the additional axes, U, V and W to the primary and rotation axes. The X, Y and Z axes help us define linear and rotational movement in a work envelope. Many horizontal machining centers have a quill that can be extended, as well spindle or table motion. These movements are referred to as the secondary axes of motion. When a machine has secondary motion that is parallel to the X, Y or Z-axis, it is defined by the U, V and W axes. An axis parallel to the X axis is the U axis; an axis parallel to the Y axis is the V axis and an axis parallel to the Z axis is the W axis. The U and V axes are designated on wire EDM’s, horizontal machining centers and boring mills, where the quill “W” can move in and out (see diagram).
On a wire EDM machine the upper head through which the wire is fed can move independent of the X and Y table movement allowing for taper cutting on contours. The movement of the head that controls the wire independent of the table are the U, V axis respectively. Each axis could in turn have a rotation axis P, Q and R. The U axis has a P rotational axis, V axis has a rotational Q axis and W axis has a rotational R axis (see the table below).
Understanding and applying these basic concepts of spatial orientation is a prerequisite for avoiding errors and making consistently high quality molds from CNC machines.
