UCCNC Users Manual, page 21

Interpolation mode selection:
This parameter selects how the trajectory planner executes the motion.
There are two modes, the exact stop mode and the constant velocity mode.
These two different modes can be also selected executing the G61.1 (exact stop mode) and G64
(constant velocity mode). When these codes are executed the selection on the screen changes
accordingly. When a G64 code gets executed the parameters for this command are read from this
screen settings.

Exact stop mode:
This is a trajectory planning mode. In this mode the trajectory planner follows
the motion path positions exactly. The machine axis accelerates at the beginning of each segment
and deccelerates at the end of each segment. This interpolation mode is adviced to set if close
tolerance parts are manufactured. The position error is always zero with this interpolation mode.

Constant velocity mode:
This is a trajectory planning mode. In this mode the trajectory planner is
interpolating to the set feedrate, in other words the trajectory is planned looking ahead in the motion
path and trying to keep the feedrate constant on the set feedrate.

For this mode to work some additional parameters needs to be defined which are discussed in the
followings. The constant velocity mode is adviced to be used when high speed machining is
nessessary for example 3D artworks are machined. This mode can also be used for close tolerance
parts machining, but the tolerance parameters for this mode must be set correctly to force the
motion planner to not make higher position errors than what is allowed for the workpiece.

There is always a tradeoff between machining speed and precision. The higher the allowed
machining errors are set the faster the job will be finished, because the motion planner has more
space for optimising the motion, however the less the workpiece precision might be.

Search, read, and you will find.

Cheers
Roger