I am having a problem regarding velocity and acceleration figures, how to reduce the time can anybody help?

 What I am trying to do is ,I cut the same job 3 times with different feeds: 100 IPM, 125 IPM, 150 IPM but the total time taken for all 3 setup is 40 min. There is no
difference in time. Is there anything which I am doing incorrectly.

is there something related to motor tuning tab?

PLEASE HELP

IF the Gcode you are using is a lot of small moves MACH may not be able to get to TOP Feedrate as called. If that is the case going UP on Feedrate does not speed up the job.  On jobs like that Acceleration is the key to going faster.

Just a thought, (;-) TP

Actually i m using photovcarve for photo engraving with 2.5mm deep cut and in all the feeds time is the same...

Thank for the replies, what i was trying to do is increasing the velocity per units setting in motor tuning tab and not changing the acceleration setting.

What is the good setting or ratio between velocity and acceleration setting in mach3.

Will increasing the acc settings will also reduce time?

There is no such thing as a " good setting" it will all depend on your machine, what motors etc.
Faster acceleration will allow your machine to reach the programmed feed much quicker so will almost certainly reduce cycle time, especially when code with small moves is used. It can be quite a dramatic change and can often cut cycle times drastically thus it is often much better to have less Velocity in motor tuning if it allows you to have greater acceleration.
As an example when I had a Bridgeport with steppers I could get 2500mm/min rapids but only an acceleration of 40mm/s/s.  I reduced the Velocity to 2200mm/min and that allowed me to get the acceleration to 120mm/s/s and that halfved the cycle time on some jobs.
 Hood