About the CV mode confusion in Mach 3:
I've heard several people mentioning that they had problems using it. I know I did awhile back when I tried to pocket squares and the corners at opposite ends kept getting rounded. Here is what I found out;
The CV mode attempts to keep the cutter moving at the last commanded feed rate throughout all movements below the set CV rate (in this case 180). What that means is that if the next
move is more than 180 degrees relative (in this example) to the current cutter path then the machine is commanded to full stop (absolute mode) before the next move is made.
The problem arises when there is, say, a 90 degree movement perpendicular to the current path of the cutter. In order to make the 90 degree move, the software will attempt to "round-out" the move in an attempt to keep the feed rate constant. This is not what we want since the corners of a square pocket would be rounded. This happens because (in our example) more than a 180 degree movement has not
been commanded, just a motion 90 degrees relative to the last path.
Important: Remember that the CV mode also acts on the Z axis as well.
It would seem, at first glance, that to turn CV mode off would be the best option but I have found that all this does is put the machine in "absolute stop" mode at the end of each line segment (think segmented circle here). This would then cause the machine to ramp up and down on each itty-bitty little line segment, a huge waste of time since the machine spends more time ramping up and down when it really should be moving in a continuous motion.
The solution (or at least it works great for me) is to enable
CV mode and change the setting to 45 (degrees; works for me). Now, any movement greater than 45 degrees to the last cutter movement will come to a complete stop, change direction and ramp. Anything less than that will be one smooth motion (Continuous Velocity).
It took me awhile to figure out but my productivity has shot up and the wear on my machine drastically reduced since there are far fewer start-ramp up-go-ramp down-stop cycles of the mass of the gantry. Give it a try on your next project, especially one where you know how long it takes to cut and you'll be amazed at the productivity gains (and smoothness of your machine).