Because the sun gear in a hybrid unit is pre-aligned within the gearhead rather than affixed to the motor shaft, these gearheads can be used in contouring applications like a glue-dispensing nozzle for affixing a windshield to a car. Motion of the nozzle as it comes after the seam between a windshield and its own window frame should be perfectly smooth; otherwise a ripple in velocity alters the bead diameter and causes messy glue app.

Smooth motion, this means the absence of torque and velocity variations (ripple), is servo motor gear reducers essential in contouring applications. But, it is difficult to consistently achieve smooth motion where the sun equipment is mounted on the motor shaft. A good slight misalignment in the sun gear (motor shaft runout or coupling inaccuracies) could cause rough procedure and noise.

Many servo controllers use software compensation, and their success depends on knowing the lost movement of the entire system. This details is usually obtainable from the gearhead manufacturer.
Contouring applications usually involve end-effectors or tool-points that adhere to mathematically defined paths. Sealant and bonding machines, drinking water and flame cutters, laser beam welders and cutters, movement managed cameras, and CNC machine tools are good examples.

Software compensation is achieved by commanding the electric motor to move beyond the apparently desired position by a quantity equal to the system’s dropped motion, thereby bringing the strain to the truly desired position. For example, consider a servomotor, gearhead, and leadscrew combination in a pick-andplace robot. If 100,000 encoder counts equals 1.0 in. of linear movement and the system has 0.1-in. dropped motion, then the controller tells the engine to go 110,000 encoder counts to obtain 1.0 in. of motion, hence compensating for the 0.1-in. lost motion.

Backlash is the excess space between two adjacent equipment teeth and its engaging tooth; lost movement may be the total looseness or movement at a reducer’s result shaft when the insight shaft is fixed. Lost motion includes backlash, plus losses from bearing looseness, tolerances and fits, and shaft and gear tooth compliance.
Servo controllers can be programmed to compensate for backlash and dropped movement in planetary gearheads. This technique compensates for backlash even where an application requires accuracy much better than the minimal backlash of the gearhead.