Web Goblin cnc has begun

[JAZZCNC]

Jonathan I am using USBCNC not Mach3. It has something called look ahead feed built in to it. I think this looks ahead of the block you are running and looks at the program to see what is coming up. It then tries to calculate the optimum speed for those upcomming blocks to keep the machine moving smoothly, well thats what I got out of reading the manual anyway!

Mach also use's look ahead.
CV (constant velocity) and Exact stop are Gcode commands which basicly tell the control software how to react.
If your code outputs G61 then the look ahead won't apply because it's been forced into exact stop mode and look ahead only works in CV mode.

If your code breaks arc's down into tiny lines(like lots of software does) then this will have the affect of jerky movements, it will also have the affect of stopping and starting between arcs and straight lines as exact stop accelerates and deaccelerates point to point, this affects cut quality badly. (Plus it's bloody annoying)

Exact stop will not round tight corners like CV does at high feeds but it can cause the machine to run very slow and quite rough as it accellerates then deaccelrates between each point.
As you can imagine at high feeds this will hammer the machine and motors as it flys upto the corner at high speed then jumps on the brakes for the tight bend.!!

I think if you check there will be settings within USBCNC to help control CV's angular distance where it changes for tight radius and controls rounding at high feeds.

But I think even USBCNC can be put into exact stop mode so G61 will apply basicly cancelling look ahead and CV mode. . . . . Worth checking out.!!