Parallel gripper design: fingers, force, and part access

Start where the fingers touch the part

A parallel gripper can have the right nominal force and stroke while its fingers make the application unreliable. The contact location, shape, material, and access path determine how the part is captured and released. Start the design review with the part and its next operation, then work backward to the gripper body.

List the permissible gripping surfaces, cosmetic restrictions, variation between parts, and orientation at pickup. Identify surfaces covered by coolant, oil, dust, or packaging. For a machine-tending application, include the chuck, fixture, machine door, and unloading path. A finger that grips perfectly on a bench may not reach the same location inside the machine.

Check the finger limits separately from grip force

Request the exact gripper manufacturer’s finger-design limits and mounting drawing. Robotiq’s custom-fingertip guidance identifies mounting and overhang constraints for its specific grippers. Those dimensions should not be transferred to another model. Ask your supplier to review the proposed finger geometry and load cases against the selected product.

The Zimmer MATCH selector lists finger length alongside force, stroke, weight, and other properties. That is a useful reminder to compare more than a force number. Require the design review to include finger mass, offset contact, acceleration, and forces from the process. Document whether the gripper locates the part, merely holds it, or must resist an external operation.

Separate holding from accurate location

A shaped pocket can help establish a repeatable contact pattern, but it must accommodate the actual tolerance range and allow reliable release. A soft pad can protect a surface while introducing deformation or wear that changes the held position. Decide which surfaces provide location and which provide retention rather than leaving that relationship implicit.

For a hypothetical family of cast parts, ask for trials using the smallest and largest permitted contact features, not only a nominal CAD model. Include representative casting variation and contamination. Record whether each part seats fully, whether grip detection distinguishes an empty close, and whether release leaves the part correctly positioned in the receiving fixture.

Review clearances through the entire stroke

Check fingers open, fingers closed, the part present, and the part absent. Evaluate insertion into trays, clearance around adjacent parts, and access for fasteners. Include the sweep of the gripper body and robot wrist. The safe clearance question is three-dimensional and continues during acceleration, approach, placement, and recovery.

Compare required travel with the available stroke definition: per-jaw travel and total opening are easy to confuse. Festo’s gripper range includes different mechanical arrangements and actuation options, so confirm the exact geometry rather than relying on a generic “parallel” label. Our actuation comparison addresses the separate choice of how the fingers are driven.

Use a prototype to answer specific questions

A prototype should test the unresolved contact and access questions, not simply reproduce the CAD model attractively. Decide which properties of the prototype represent production and which do not. A printed finger can help examine space and contact, but its material and build quality may not represent the strength or wear of the final tool.

Have the responsible designer approve the trial method and operating limits. Keep the acceptance record focused on secure capture, acceptable marking, stable part position, reliable release, and recoverable failures. After the final material or geometry changes, repeat the relevant checks. A successful early demonstration is evidence about that configuration, not every later revision.

Release a complete tooling package

• Dimensioned fingers and interfaces, with revision-controlled drawings.
• Named contact materials, replaceable pads, and fastener requirements.
• Reviewed force, moment, mass, and clearance limits for the chosen gripper.
• Part-present detection and agreed responses to incomplete grips.
• A trial report covering part variation, release, wear checks, and maintenance.

Add the gripper, fingers, adapters, and carried part to the robot payload discussion. Selecting the arm and designing the fingers should inform each other. A complete tool package lets the production team reproduce the intended grip after maintenance instead of improvising a replacement on the shop floor.

Match the fingers to a FAIRINO configuration

A FAIRINO quotation becomes more useful when it includes the proposed grip and the complete carried load. Use the FAIRINO model comparison to explore load and reach starting points, then bring finger drawings and representative parts for application review. We recommend selecting the arm and tooling together so the tool does not consume an unplanned share of capacity or working space. Follow the FAIRINO buying checklist and request a FAIRINO cell quote that identifies tooling and validation responsibilities.