Denford Software & Machines

I am attempting to turn the bottom of an egg.

Everytime I program the lathe, I get a "bad arc end point" message.

I have a cylinder that is 45mm diameter and 60mm long. The datum is set on the right edge.

I want to end up with an arc on the right side of the cylinder from x-7.5 z0 to x0 z-20 (where the datum, x0z0 is the right edge). I know that I can't cut the whole thing in one pass, so I'm trying to take off 1mm at a time--meaning arc from x-1 z0 to x0 z-20, then arc from x-2 zo to x0 z-20, etc.---until reaching x-7.5 z0 to x0 z-20.

When I get this side done, I'll turn the piece and cut the top.

Here's what I've tried:
g3 x0 z-20 i1 k20 f150

g3 x0 z-20 i-1 k0 f150

None of the other variations on this command in the help file make any sense to me.
I am trying to finish this before my seniors graduate (soon.) Please help.
Thank you,

- should that x be negative on your machine? that's x past the centre line
where ever your centre is Z (K) will be negative

I presume there's a line above this one, ie, the start point? G02 & 3 tell the machine where to go to and where the centre is.

I agree with Whizz - your X coords should be positive.

Also, try programming your arcs using radius (R) instead of circle centre(I,K)

Using R and the CNC will calculate the Cirle Centre for you.
Using I and K and you must calc the exact centre point else the CNC will complain

G01 X10 Z0
G02 X20 Z-5 R5

Note also that the X axis programming is a diamemter value (you program the diameter you want the billet to be, not the distance you want to tool to move) so this example will produce a 90 degree arc