I have made a memorial placque for a passed pet. It has a fancy outside shape and text carved into it. All that cuts out well. There also is a 3"x3" .060" deep pocket to receive a small pictute. The pocket is the last thing to cut...it starts in the middle and cuts ccw till it's done which is at the lower left corner. My problem is the lower left corner radius is correct fot the cutter being used. But the top left and right, and the bottom right are all the same but have a larger radius. Some suggested to change from Constant Velocity to Exact Stop in Mach 3. I did this and my machine time went from approx 7.5 minutes to about 30 minutes in the simulation mode. It really slowed down to a crawl. If I start the placque in Constant Velocity and pause the program just before it starts to cut the pocket, switch to Exact Stop, then resume the program, the pocket cuts out fine and the four corners have the small proper radius. I don't want to have to stop my program. Is there a way to have the program change by itself. Actually I'm not sure exactly what Constant Velocity and Exact stop do. I think the three larger corners are due to the machine not wanting to slow down but maybe not. Thanks for any help.
When in Exact Stop mode, mach3 decelerates to a stop at the end of each move. On shorter moves it may never get up to full speed. When in Constant Velocity mode, Mach3 tries to keep the speed constant. The downside is that you'll get rounded corners. The reason is that for Mach to maintain velocity, when it gets to a corner, one axis starts to accelerate as the other starts to decelerate. The faster your machine can accelerate, the less rounding you'll notice.
In the General Config Window, you can set an angle which will turn off CV if it's exceeded. Not sure what it does, but there is also a distance tolerance setting that you might want to play with.
You can also edit your code to add a G61 to turn off CV before the corners, and turn it back on with a G64.
Not sure if it would help on the rounding, but you might want to try running the beta of Quantum, Mach's successor
Mach3 2010 Screenset
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)