# Thread: Circular interpolation Fanuc O-M

1. ## Circular interpolation Fanuc O-M

Hello I need an example line of code to do a G03.

I have a Fanuc O-M controller.

I want to make a 1.25" circle with the with a .75" endmill.

Can not figure out how to calculate the I & J value or the order to put them in.

Thanks,
CD

2. I and J are the distance in X and Y that the center point exists relative to the start point. For example, if you have a point at X.5 Y2. where a circle starts and the circle center is at X.75 Y2., your code would look like:

G01 X.5 Y2.
G03 X.5 Y2. I.25 J0

because the center point is .25 from the start point in X, and no distance from the start point in Y. Hope this is understandable.

I'm not giving you the answer for two reasons. First, the teach a man to fish thing, and second, I don't know where your circle exists on your coordinate system. Good Luck!

3. I and J are the distance to center of the Arc in X and Y. Fanuc will read I and J as incremental distance.

So if you start your arc at 3 O'clock... "I" would be minus "J" would be 0(zero)

If you start your arc at 11 O'clock.."I" would be positive and "J" would be negative

4. Quick sample codes for you...

starting at 9 O'clock

(G41)G1X-1.0 Y0 F... (feed in to edge of circle)
G3 X-1.0 Y0 I1.0 J0 ( do full circle, X and Y end points can be left out)
(G40)G1 X-1.5 (move away)

5. ## Circle Milling

http://www.kentechinc.com/tip7.html

Look for the free circle milling code generator on that page ... it will come in handy for ya.

Real World Machine Shop Software at ... www.KentechInc.com

6. Let me jump in.
Is it must I J? If not you can alway just used simple R instead it's just work as good.

7. CNCRIM is right just use R

I=the distance from the centre point of circle to the start in X with direction
J=the distance from the centre point of circle to the start in X with direction

Simple.

PM me and i'll send you a sheet explaining it all.

8. But, cannot make a complete circle with R method. The reason is that, for the same start and end points, infinite circles are possible, all with the same radius. In such a case, the circle would need to be made at least in two halves, if R method is desired to be used.
While both methods can be used, selection should generally be based on how dimensions are specified on the drawing.

9. Originally Posted by sinha_nsit
But, cannot make a complete circle with R method. The reason is that, for the same start and end points, infinite circles are possible, all with the same radius. In such a case, the circle would need to be made at least in two halves, if R method is desired to be used.
While both methods can be used, selection should generally be based on how dimensions are specified on the drawing.
what are you talking about? if you want to make an arc more 180deg all you need is put a munis sign in from of the number like R-x.xxxx.
Will make complete 1" circle.
G1X0Y.5
G3Y.5R-.5

10. See the attached figure.
For the coincident start/end points, infinite circles are possible, all with the same radius. Possibly the machine would make one, which may or may not suit you.

11. Originally Posted by sinha_nsit
But, cannot make a complete circle with R method. The reason is that, for the same start and end points, infinite circles are possible, all with the same radius. In such a case, the circle would need to be made at least in two halves, if R method is desired to be used.
While both methods can be used, selection should generally be based on how dimensions are specified on the drawing.
WRONG

Again i agree with CNCRim

12. Have you looked at the figure posted by me?
It is not that a complete circle cannot be made. But the question is: which circle (see the figure)?

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