Products: ACR9600, ACR9630, ACR9640
Each new call to MC_MoveVelocity, MC_MoveAbsolute, MC_MoveRelative or MC_MoveAdditive will set the velocity of the axis to whatever value is in the Velocity input of the FB. Just changing the value of Velocity input without a new rising edge of the Execute input will NOT change the velocity on the fly.
If the axis is in motion from a MC_MoveVelocity block (continous move), change the Velocity input AND toggle the Execute input to change the velocity on the fly. When a move is in progress from any one of the MC_Move function blocks, then use the MC_Writeparameter function, with ParameterNumber=60. ParameterNumber=60 refers to the ACR Jog Velocity Setting parameter