fluid robot movement

I have a robot path that I need to be extremely fluid. It is a 6-axis 6600, S4C. Picture a pen as the tool, that is writing a letter “J”, axis 6 is parallel to the “paper” at all times. The path is a straight line, tangent to an arc, then after about 90 degree arc travel, another straight line segment. The catch is that axis-6 must rotate thru the arc so that the tooling plate stays perpendicular to the robot path. I must have constant velocity thru the entire move, no decel at the transition points. Can anyone suggest a technique or settings to achieve a completely fluid movement?