Hi:

Well, after seeing a "fecking" priest as an avatar, I guess I better respond.( I loved that show..) :-)

Distance tolerance in CV is not exactly as you think, and your formula isnt actually the proper error, ( except in certain circumstances.). Your error is a function

of both acceleration and feedrate, so its a much more complex formula to determine and integrate error. You have to remember than in Mach3, CV is actually

a case of starting the next move, as soon as the previous one starts to decelerate. Low acceleration of any involved axis, will increase error. Increased acceleration

reduces error. Angle limit tells it to not CV at all on angles greater than n , which does help as the larger the angle, the more error is involved for any axis, but

constant stop will mar a surface finish. All a trade-off.

Its quite normal for people to try to be more accurate by lowering accel and feedrate, lowering accel increases error in reality as does increasing feedrate.

To understand this clearly, imagine a 2 move sequence,

G1X10

G1Y10

As the X axis progresses toward 10, it will eventually decide it has to decelerate. The lower your acceleration the sooner this will occur. As soon as it does occur,

the Y axis will begin to move as the X slows. If your picturing this properly, your picturing a circular corner as the X slows and Y accelerates. Now imagine

a faster acceleration, it takes longer before the X HAS to decelerate, the Y wont begin till this happens, so the circular arc at the corner gets smaller. The error

shrinks. Nwo imagine a faster feedrate, same accel. The X must now decelerate sooner as it has more speed to dump, the Y starts earlier and your error

increases.

Imagine the X and Y have a different acceleration, now the corner is an ellipse. Faster the feedrate, the greater the ellipse. The slower the accel the greater the

ellipse ( and the two are additive). So to be fair to your job and error requirements is a two pronged approach,firstly, have accel as high as your axis will allow for.

This is almost always true, keep accel as fast as you can. Secondly, when it comes to feedrate, keep it reasonable, that is to say that if you set Feedrate to 10,000

inches per minutes, and the axis only really gets to 50, then 50 is the proper setting in the code, setting higher than reachable affects error and surface condition

in terms of pockmarks and such. That is the target to reach for. If error is then too much for you, best compromise is to program even lower feedrate, but never higher

than actually reachable on the majority of the code. As accel is much more important than feedrate as it is squared over time,maximizing it is integral to

lowering error and maximizing surface results. Max error of course does increase with higher angles and its not unreasonable to set an angle limit for higher angles,

but its a trade-off, and Ive always found its best to use accel more than angle limit to fight any issues of speed and performance.

Machines vary so its not possible for me to tell you how to set your unit, but take it from me, I speak from some experience in Mach3

, the faster the accel the better,

the slower the feedrate the better ( in terms of error ) . Id set accel so the axis can handle no more without errors or jerking, then adjust feedrate for best results. Always

keep feedrate commands as close to the reachable feedrate if it seems limited, and as high as your material/tool can handle. This minimizes error and makes things smooth.

There is almost never a need to use exact stop, and almost never a need to limit angles to less than 45 degrees. If you do so, your probably fighting yourself. Properly adjusted

angle limit and accel should then simply allow you to slow commanded feedrate to decrease overall finish error without any other tuning. It then follows one simple rule, the faster

you go the greater the error.

Now if you have a machine which just cannot accel fast, set it as high as it will take, then use feedrate for finish..

Just my two cents, for what their worth..

Art