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ACU-RITE 3500i 27
2.1 Fundamentals of Positioning
Reference system
A reference system is required to define positions in a plane or in
space. The position data are always referenced to a predetermined
point and are described through coordinates.
The Cartesian coordinate system (a rectangular coordinate system) is
based on the three coordinate axes X, Y and Z. The axes are mutually
perpendicular and intersect at one point called the datum. A
coordinate identifies the distance from the datum in one of these
directions. A position in a plane is thus described through two
coordinates, and a position in space through three coordinates.
Coordinates that are referenced to the datum are referred to as
absolute coordinates. Relative coordinates are referenced to any other
known position (reference point) you define within the coordinate
system. Relative coordinate values are also referred to as incremental
coordinate values.
Reference system on milling machines
When using a milling machine, you orient tool movements to the
Cartesian coordinate system. The illustration at right shows how the
Cartesian coordinate system describes the machine axes. The figure
illustrates the right-hand rule for remembering the three axis
directions: the middle finger points in the positive direction of the tool
axis from the work piece toward the tool (the Z axis), the thumb points
in the positive X direction, and the index finger in the positive Y
direction.
The CNC 3500i can control 3 or 4 axes optionally. The 4th axis is
designated by the letter “U”. The “U” axis function depends on the
builder.