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The force per unit area at the contact between gripper and part. It decides whether a mount leaves marks: thin-walled plastic parts, cardboard cores, fresh concrete and lacquered surfaces take little. The answer is rarely less force – that is needed to hold – but more area: larger jaws, softer pads, additional contact points.
Contact pressure, also called surface pressure, is the force acting perpendicular to a contact face divided by that area: p = F / A. It is given in newtons per square millimetre (MPa). The same force can be harmless or destructive – depending on the area it lands on.
An example: 2,000 N of clamping force on a jaw of 40 by 50 mm gives 1 N/mm². The same force on a jaw of 80 by 100 mm gives 0.25 N/mm² – a quarter, without the grip being any weaker.
The formula assumes that the force rests evenly on a flat face. For a pin in a bore the projected area is used, that is diameter times bearing length. If a round part rests on a flat face, or a thin mandrel in a large core, the bodies touch along a line only; local pressure is then many times the average.
Even a large, rigid jaw does not automatically bear over its whole face: if the part is uneven or the jaw is not aligned, it bears on one edge only.
Permissible contact pressure depends on the material, the wall thickness and whether a mark counts as damage. Solid steel tolerates a lot; thin-walled plastic parts, cardboard cores, foams, fresh concrete, wood and painted or polished visible surfaces little. With hollow parts, the wall dents long before the material yields at the surface.
There is therefore no universal limit. Dependable figures come from the manufacturer of the part or from a trial on the real part with the intended jaw.
A clamping gripper needs force to hold by friction – and that very force creates the pressure. Less force is rarely the answer, because holding force is then missing. The levers lie elsewhere:
Contact pressure is not only a clamping issue. It also decides whether the saddle of a C-hook crushes the inner wraps of a coil, whether a mandrel damages a cardboard core and whether a fork under a rim deforms the rim. In all these places the support is rounded, widened or padded until the pressure suits the part.
What Entracon offers here is on the matching page.
See what we offer| Contact | Pressure | Example at the gripper |
|---|---|---|
| Area contact | low, even | shaped jaw on a flat face, support shell in a core |
| Line contact | locally high | round part on a flat jaw, thin mandrel in a large core |
| Point contact | locally very high | edge or tip on a curved face |
| Edge bearing | uneven | rigid jaw on an uneven or tilted part |
Force divided by the bearing area: p = F / A. For pins and mandrels the projected area of diameter times bearing length is used. The result is an average; with line or edge contact, local pressure is considerably higher.
By more area and better seating: larger or contour-matched jaws, soft pads, pivoting mounts. Less clamping force helps only if part of the load is carried by positive locking at the same time.
Reference tables give guide values for engineering materials, but they rarely apply to the actual part – thin-walled, coated, with a visible surface. The part manufacturer’s figure or a trial is dependable.
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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