The efficiency of a gripper’s slide is often provided via a chart that shows jaw length versus force provided. This is an indication of the amount of force actually provided by the gripper versus the theoretical force provided by the pneumatic or electric system. While efficiency is interesting, in most cases it has little to do with the size requirement of a gripper because the slide is equally efficient in both directions. Therefore, if the part is pushing back on the jaw, due to weight or acceleration, the slide will be as efficient or inefficient transmitting this part-created force to the gripper as it is in transmitting the gripper-created force to the part.
Slide efficiency really only comes into play when the gripper jaws are designed so that only a friction grip is provided and “squeeze” is the only thing holding in the part (jaw types and their effect on size requirements are provided in detail later). Typically the slide efficiency charts are only a rough measure of the slide’s torque capability. Therefore, while the charts may be helpful, the better gripper manufacturers now provide torque specifications for pitch jaw and roll of the jaws. Bottom line…ask for torque information when sizing a gripper.