Because the sun gear in a hybrid unit is pre-aligned within the gearhead rather than affixed to the electric motor shaft, these gearheads can be utilized in contouring applications such as a glue-dispensing nozzle for affixing a windshield to an automobile. Motion of the nozzle since it follows the seam between a windshield and its window frame must be perfectly smooth; or else a ripple in velocity alters the bead diameter and causes messy glue application.

Smooth motion, which means the lack of torque and velocity variations (ripple), is important in contouring applications. But, it really is difficult to regularly achieve smooth motion where the sun gear is mounted on the motor shaft. Even a slight misalignment in the sun gear (engine shaft runout or coupling inaccuracies) can cause rough operation and noise.

Many servo controllers use software compensation, and their success depends upon knowing the lost movement of the whole system. This information is usually offered from the gearhead manufacturer.
Contouring applications generally 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 controlled cameras, and CNC machine tools are good examples.

Software compensation is accomplished by commanding the motor to move beyond the apparently desired position by a quantity add up to the system’s dropped motion, thereby bringing the strain to the truly desired position. For instance, consider a servomotor, gearhead, and leadscrew combination in a pick-andplace robot. If 100,000 encoder counts equals 1.0 in. of linear motion and the machine has 0.1-in. lost motion, then your servo gear reducer controller tells the engine to move 110,000 encoder counts to obtain 1.0 in. of motion, thus compensating for the 0.1-in. lost motion.

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