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A gripper with two jaws moving in parallel, clamping a part from outside. It is the simplest and most robust design and tolerates positional variation. Because it holds by friction, clamping force is sized from the friction coefficient and every acceleration occurring in the sequence – not from weight. A check valve keeps the clamp closed on pressure loss.
A parallel gripper clamps the part between two jaws that move towards each other in parallel. It holds by friction: clamping force presses the jaws on, and the friction force at both contact faces carries the weight. Because the jaws move in parallel, contact stays flat over the whole stroke – unlike tongs, whose jaws pivot.
For two jaws and a load held vertically, the starting point is F = m · (g + a) · S / (2 · μ). F is the clamping force per jaw, m the mass, g gravitational acceleration, a the highest acceleration in the sequence, S the safety factor and μ the friction coefficient between jaw and part.
An example: 40 kg, friction coefficient 0.2, additional acceleration 2 m/s², safety factor 2. This gives a clamping force of about 2,400 N per jaw – six times the weight force. The calculation shows why the friction coefficient is the most sensitive value: if oil or dust halves it, the force required doubles.
The jaw decides friction and contact pressure. Rubber or polyurethane pads raise the friction coefficient and protect the surface, but they wear and lose effect with oil. Serrated or hardened jaws grip securely but leave marks.
Where geometry allows, the jaws are matched to the contour – as a V-block for round parts or with a lip that reaches under a rim. The shape then helps to carry, and the clamp only has to centre the part.
Pneumatic parallel grippers are the most common type. If pressure drops, the clamp must be maintained: by a pilot-operated check valve on the cylinder, by a spring that closes without pressure, or by a self-locking mechanism. Electric drives hold by self-locking or a brake.
Opening under load is prevented, for example by sensing whether the load has been set down or by two-hand actuation.
A parallel gripper needs two opposite, accessible faces and a part that tolerates the clamping force. Thin-walled containers dent, soft parts deform, painted surfaces show marks. If the load is rotated or tilted, the direction of force at the jaws changes – a positive-locking safeguard is then required.
What Entracon offers here is on the matching page.
See what we offer| Jaw | Effect | Suitable for |
|---|---|---|
| Smooth, metallic | low friction, high clamping force needed | robust parts with some positive locking |
| Rubber or PU pad | higher friction, lower contact pressure | painted and delicate surfaces |
| Serrated, hardened | secure grip even with oil | castings, forgings, blanks |
| V-block | centres, carries partly by shape | round parts, shafts, tubes |
| With under-grip | positive locking under rim or collar | containers, crates, flanged parts |
Because friction delivers only a fraction of clamping force as holding force, and lifting, braking and slewing add accelerations. At a friction coefficient of 0.2, two and a half times the weight force per jaw is needed even without any reserve.
The least favourable one occurring in operation – for oily, wet or dusty parts, not for the clean sample. A trial with real parts and the intended jaw gives a dependable value.
With a correct design, nothing: a pilot-operated check valve, a closing spring or a self-locking mechanism maintains the clamp. Whether this works is tested at the periodic inspection.
One short conversation usually settles more than three quotations. Call or write — you will reach an engineer directly.
Start typing – for example “balancer”, “SAP” or “pipe stress”.
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