Circle is not smooth

[webcruiser8]

I built a new CNC waterjet gantry table. The motion system includes
linear motion guide, servo motor, and rack/pinion. The problem
I have is that when the table draws a circle, the edge of the circle
is not smooth ( however, circle is closed).

I wish I could up load a picture to show the circle. Could somebody
give me some hint on how to do it? Thanks a lot.

[Weldtutor]

I wish I could up load a picture to show the circle. Could somebody
give me some hint on how to do it? Thanks a lot.

For photo upload, below where you preview your post is a section called additional options.
Click manage attachments
Click browse to find photo on your computer
Select photo
Click upload

Should work.