Circular Interpolation Concepts & Programming Part 4 (Unknown R)

The 4th part of Circular Interpolation Concepts & Programming series explains how cnc program for an arc can be made if arc Radius (R) is not directly given.

Program an Arc only Arc Center is given

To program an arc when only the arc center is given (the radius is unknown) use the address letters I and J

• I – relates to the address X and is the incremental value and direction (+/-) from the start point of the arc in the X axis to the arc centre.
• J – relates to the address Y and is the incremental value and direction (+/-) from the start point of the arc in the Y axis to the arc centre. Program an Arc only Arc Center is given

In this figure the procedure is very clear to calculate I and J values. From the point where arc is started always look to wards arc midpoint.  If the arc is less than a quadrant than you must find out the both I and J values.

`G03 X (End Point) Y(End Point) I J`

For CNC Lathe Machinists
Fanuc Circular Interpolation G02 G Code Example