straight corners in rhino and mach3 but radiused when I machine. Help!

[steve webster]

I just switched over from using a shopbot control box to a Gecko g540 set of drivers.
Right now the software I am using is Rhino 4.0 SR6 build 09/07/09 , Madcam  4.1 build 09/08/28 and Mach3 version 3.042.029.
I am post processing with MACH-3-INCH.TXT.  This is my first experience with using Mach 3.
My problem is that at every square corner I am getting a tapered radius about 1/2 by 1/8" long .
This happens on every corner as the cutter approaches the corner.
This does not show up on the rhino drawing or the cut simulator in madcam , nor the simulator in mach 3 but is there on every piece I cut .
Any body have a clue what might be the cause of this. Here is the g code
Steve Webster

[Sam]

Have a read here...  http://www.machsupport.com/docs/Mach3_CVSettings_v2.pdf

[Sam]

Upon a better look at your file, and a quick load into Mach, it appears that you don't have corners in the code. They are indeed rounded. There is a possibility that you are not zoomed in close enough to actually see they are rounded in your cad program. Another thing that I notice is that your arcs are really only a huge amount of tiny lines. This is a common mistake made. You should do a bit of investigating and find out what you need to do in your software to output arcs. That particular part could have been made with less that 20 or so lines of code, and the motion from the machine would be soooo much smoother. Sorry for sending you off to read about something that wasn't your problem in the first place, however, it is a very informative piece that everybody should know about.

[steve webster]

Hi Sam
Thanks for the reply. I now have straight corners. Changed the look ahead to 300 units and decreased the cv distance tolerance units to 5.
This may be extreme. I don't know as I am new to mach 3.
Gerry on cnc zone suggested trying running in exact stop mode (g61)to see if I this gave me square corners.Choppy and slow on the arcs but perfect corners.
His suggestion was that if this worked than I needed to increase my rate of acceleration and than go back to cv mode.
This worked perfectly so now smooth curves and straight corners.
Thank you both

[Sam]

Glad to hear you have it sorted. Happy cutting.

[ger21]