Instructions

FIGURE 2.2—Mill axis directions in relation to the operator.
Directions of axis movement on a mill
Before we go on, let’s be sure we understand the directions of movement of the three
axes of a milling machine. When programming g-code you will use the Cartesian
coordinate system. In relation to the machine operator, the X-axis moves left/right, the
Y-axis moves in/out and the Z-axis (spindle) moves up/down.
A tip regarding axis direction
It can be a little confusing for a new machine tool operator, because when you
write code you think in terms of the part being fixed and the tool moving, but
when you operate most machine tools the tool is fixed and the table moves.
When using the jog controls, at first it may seem like the axes are moving in the
wrong direction, but when you picture the move in relation to the cutting tool it
makes sense. Programming directions relate to APPARENT TOOL
MOVEMENT. Therefore, a positive move on the X-axis will result in the table
moving to the LEFT (tool appears to move to the RIGHT); a positive move on
the Y-axis will result in the table moving TOWARD you and a
positive move on the Z-axis will result in the headstock moving UPWARD. (A
positive move on the A-axis will cause the rotary table to rotate CLOCKWISE.)
This is the way full-size CNC machines work too.
What is the A-axis?
The 4
th
axis available to you in EMC2 is the A-axis. This axis drives a rotary table and is
programmed in degrees rather than in linear dimensions. Sherline offers an optional 4
th
axis rotary table as P/N 8730. It already has a stepper motor mounted and is ready to plug
in to the A-axis cable coming from the back of your driver box. A 4
th
axis can make some
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