Chapter 11 Motion Control Instructions 
11-275 
reference. 
  T is the number of full circles; the path is a length of arc when T=0; the path is the 
corresponding full circles plus the arc length when T is a constant. 
  Different from format 1, format 2 determines a length of circular arc via the start point, 
terminal point and radius. If the input value on the right of R parameter is a positive 
number (R+), the circular arc is a minor arc less than 180 degrees; if the input value on 
the right of R parameter is a negative number (R-), the circular arc is a major arc more 
than 180 degrees. 
  The following full lines are the motion paths when G3 selects R+ and R- and the arrows 
on the arcs refer to the motion direction. 
 
 
  The coordinate relations on different planes: 
 
 
 
Please note the relations among the coordinate planes and I, J, K. Only two of I, J and K exist in one 
circular arc instruction. Which two exist depends on the corresponding plane, e.g. on XY plane, only 
I and J exist. 
The coordinate plane can be set by G17, G18 and G19. The circular and helical motion paths for G3 
on different coordinate planes are shown as below.   
a) XY plane circular arc b) XZ plane circular arc C) YZ plane circular arc
X X Y
I
l J
J K K
R R R
O O O
Y Z Z
Start point
Start point Start point
Terminal point Terminal point Terminal point
Ce nter of 
a circle
Ce nter of 
a circle
Ce nter of 
a circle