The ARCH command works a bit differently from the MOVP and MOVL commands commonly associated with point-to-point moves.
In order to cut down on cycle time, the ARCH command lowers the total vertical distance traveled before moving the axes by “rounding the corners”. A normal pattern, using either the MOVP or MOVL command, forces the vertical axis to rise all the way before moving the horizontal axes. The ARCH command, on the other hand, begins to move the horizontal axes (1 and 2) before the vertical axis has reached its complete distance of travel.
Before the ARCH command is used, the vertical Z-axis (3rd axis in this case) must be declared as the axis in which the arching is to be performed by using the ACHZ command.
In addition to using the ARCH command, the above diagram shows arch trigger points. ATRG stands for “Arch Trigger” and represents how high up or down the vertical axis must travel before or after the arch move is triggered. By adjusting the ATRG setting in conjunction with VELS and ACCS, the user has very accurate control of cycle and speed.