Bit won't square 2 opposite corners of a rectangle

Post Reply
User avatar
wdwkr53
Posts: 41
Joined: Sun Aug 01, 2010 11:13 pm
Model of CNC Machine: 8020 Extrusion

Bit won't square 2 opposite corners of a rectangle

Post by wdwkr53 »

I have noticed that when I try to speed up a pocketing or profiling job, the machine consistently rounds the top right and bottom left corners of a rectangle. I have to slow it down to get a "square" cut. But no matter how fast I go, it always comes to the exact corner of the top left & bottom right corners. It doesn't seem to make a difference if I am setting the speed fast in the setup or push it faster with the % button. My speeds vary from 100-150 ipm on.25" endmill. Any thoughts?

User avatar
Mike-S
Vectric Wizard
Posts: 1123
Joined: Mon Jun 13, 2011 6:45 am
Model of CNC Machine: Joe's Hybrid 4x4 (but 3x3)
Location: Hayesville, NC

Re: Bit won't square 2 opposite corners of a rectangle

Post by Mike-S »

it always comes to the exact corner of the top left & bottom right corners
If it always happens there, you may have something loose in the machine that shows up as the direction changes.

ger21
Vectric Wizard
Posts: 1592
Joined: Sun Sep 16, 2007 2:59 pm
Model of CNC Machine: Custom DIY
Location: Lake St Clair, MI, USA
Contact:

Re: Bit won't square 2 opposite corners of a rectangle

Post by ger21 »

If your using Mach3, it's your CV mode settings.
Gerry - http://www.thecncwoodworker.com

4DThinker
Vectric Wizard
Posts: 1701
Joined: Sun Sep 23, 2012 12:14 pm
Model of CNC Machine: CNC Shark Pro, Probotix Meteor 25" x 50"

Re: Bit won't square 2 opposite corners of a rectangle

Post by 4DThinker »

Look up G-Code G64. If you have a G64 with nothing after in either the post processor header or your machine's setup file then your machine will try to keep up feed speed while sacrificing accuracy. If you add a P followed by a fraction the bit will slow down as it needs to keep close to the programmed coordinates (less the fraction). So:
G64 says keep up speed even if it means rounding off corners.
G64P0.001 says stay within .001 of the programmed coordinates.

4D

ger21
Vectric Wizard
Posts: 1592
Joined: Sun Sep 16, 2007 2:59 pm
Model of CNC Machine: Custom DIY
Location: Lake St Clair, MI, USA
Contact:

Re: Bit won't square 2 opposite corners of a rectangle

Post by ger21 »

G64P0.001 says stay within .001 of the programmed coordinates.
This depends on the control that you're using. All controls handle CV modes differently.
Gerry - http://www.thecncwoodworker.com

Post Reply