Estimate the minimum total normal gripping force for a symmetrical two-jaw external friction grip lifting a part vertically. This is an initial engineering estimate, not a payload rating or an automatic model recommendation.
How the estimate works
Total normal force = mass × (9.81 + upward acceleration) × safety factor ÷ friction coefficient. Each of two equally loaded jaws supplies half this total. Mass is in kg, acceleration in m/s² and force in N. The coefficient of friction and safety factor are inputs you must validate for your part and process.
For example, a 1 kg part at zero upward acceleration, friction coefficient 0.2 and safety factor 2 requires 98.1 N total normal force, or 49.05 N per jaw under these assumptions. These values are an example, not product specifications.
What this calculation does not cover
It does not calculate finger bending, offset moments, torsion, impact, robot rotation, surface damage, form-fit gripping or retention on power loss. The model assumes two opposing vertical contact faces, equal jaw forces and the entered friction coefficient at both contacts. Use the actual worst-case motion and tested surface conditions. Horizontal motion and changing robot orientation require a separate load analysis.
Check travel and finger geometry separately
Confirm the largest part can enter between the fingers and the smallest part can be gripped with clearance from the travel stops. Compare stroke per jaw and total opening on the drawings. Then check finger length, allowable moments, gripper mass and robot payload.
Use the result in a selection review
Before comparing the calculated total force with a product rating, confirm whether the manufacturer quotes force per jaw or total force and at which finger length. Review gripping force definitions, finger design and the model catalog. Send the assumptions and part drawing through our inquiry form for a model review.
How to use the gripper sizing calculator
- Enter the part mass in kilograms and the worst-case upward acceleration in metres per second squared.
- Enter a friction coefficient validated for your contact surfaces and a safety factor selected for your process.
- Select Calculate force estimate and read the total normal force and force per jaw.
- Confirm the product force convention, travel, finger loads and power-loss behavior before testing the actual application.