Robot Gripper Actuator Calculator

How the single-actuator gripper works

The actuator pulls a central crosshead along a guide. Two equal-length connecting rods join the crosshead to jaw carriages on a transverse guide. As the actuator retracts, the crosshead moves away from the jaw guide and pulls both jaws inward by equal amounts. Extending the actuator opens the jaws.

The jaws stay parallel because their carriages slide rather than rotate. The fixed frame and guides carry the sideways forces from the rods; those forces must not bend the actuator shaft. The animation is a top view of this horizontal mechanism.

Measurements to enter

• Open and closed jaw gaps: measure between the opposing gripping faces. Each jaw moves half the change in gap.
• Connecting-rod length: measure between its two pin centers. Both rods have the same length.
• Jaw-pin offset: measure outward from a gripping face to the connecting-rod pin on that jaw carriage.
• Required force per jaw: enter the normal force that one jaw must apply to the workpiece. This is not the workpiece weight or the sum of both jaw forces.
• Drive resistance: enter additional measured resistance at the actuator, such as guide drag. Efficiency and the design factor allow for transmission losses and a chosen sizing margin.

Choose the grip force from the actual workpiece, contact pads and handling motion. Holding a part by friction also depends on its surface condition and acceleration; this calculator does not infer that force from payload weight.

Force and stroke calculation

Let g be the jaw gap, o the jaw-pin offset and L the rod length. The distance from the centerline to either jaw pin is a = g/2 + o. The crosshead distance from the jaw guide is h = √(L² − a²). Required actuator movement is the change in h between the open and closed positions.

For a normal force N at each jaw, the ideal actuator pull is F = 2Nh/a. The sizing force is (ideal pull + drive resistance) × design factor ÷ (efficiency/100). The calculation is quasi-static: it does not add inertial loads.

The force calculation applies the entered per-jaw force across the selected travel to find the largest actuator demand. In use, gripping force develops when the jaws contact the workpiece. The tool excludes rod angles within 5° of either the actuator axis or the jaw guide, where the linkage approaches an extreme mechanical ratio.

Choosing and installing the actuator

Super Duty is the starting actuator family. Compare the required pull force and travel with the exact model, then check its retracted and extended mounting lengths. Changing the actuator changes the illustrated actuator geometry; it does not change the entered jaw and rod dimensions.

Use end-of-travel limits to keep the crosshead within the selected jaw range when an actuator has spare stroke. Confirm the model's pull rating, mounting details, duty cycle and controller. Provide a rigid frame and adequately rated jaw guides, crosshead guide, pins and rods.

Position alone does not control gripping force. Use suitable force or current limiting for the workpiece, and guard the jaw and linkage pinch points.