My circles aren't circles, but hexagons

[ArnieB]

Hi all, fairly new here, have just finished building a CNC router and it has been fun.  Right now I just have fixed a pen to the z axis and have been doing the drawing thing as I'm testing.  Everything in general is looking quite good
and most test runs are producing very acceptable results.  However, i have noticed that anytime it comes to recreating a  circle, I instead get a hexagon.  Curves and arcs for designs come out as they should but a complete circle always comes out as a hexagon.  This is in a 1 inch to 3 inch size, I haven't tried say a 6 inch circle yet.   Just wondering if anyone else has had similar results and what was done to rectify the situation.  Squares come out square, triangles come out as they should, just a circle issue.  I still have a lot of learning to do and so far have found nothing similar going thru the forum.  Lots of issues with being out of round etc, but this is repeatable every time.  Anyone have a suggestion?
Thanks in advance.
Arnie

[ger21]

Can you post the g-code for one of your hex circles?

[Tweakie.CNC]

Hi Arnie,

Which drawing program are you using to create you GCode ?

Drawing programs (such as Sketchup for example) have various resolution levels which can be set and these directly affect the smoothness of the finished circles.

Tweakie.

[ArnieB]

Hi Tweakie,
I was using Coreldraw X5 to draw these designs.  I did stumble across some other posts on the forum last night about how coreldraw can cause problems with circles and also that there is an app. that will help smooth out the issue.   I used a cad program last night also and did a few circles and other designs and it looks like that was the problem.  Corel causes circles not to come out as drawn but the cad program worked perfectly.
My thanks to Ger21 and yourself for the quick replys.  I should have read a little more and then tried the test before I posted I guess. 
Thanks again.