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An axis between device and lifting attachment that rotates the part about one or more axes. What matters is where the axis sits: through the centre of gravity, a few newtons of hand force turn the whole way and the part stays put in any intermediate position. Off centre, the load has to be held – the commonest sizing error in turning tasks.
Parts rarely arrive in the position in which they are needed. The rotation unit sits between device and gripper and brings the part into its installation position: about the vertical axis to align it, or about a horizontal axis to swivel or turn it. Several axes can be combined.
Rotating about the vertical axis is uncritical because weight produces no moment there. Every rotation about a horizontal axis is demanding.
For a horizontal axis of rotation: M = m · g · e. The moment is weight force times the distance e between the axis and the centre of gravity of part and gripper. If the axis passes through the centre of gravity, the moment is zero – the part can be turned by hand and stays in any position.
An example shows the sensitivity: 80 kg with an offset of only 50 mm produce about 40 Nm. On a handle with a 0.4 m lever that is roughly 100 N of hand force – too much for continuous work. And the load tries to return by itself to the position in which the centre of gravity is at the bottom.
The hand-operated rotation unit is the simplest and most sensitive solution but requires an axis close to the centre of gravity; detents or a brake fix the end positions. Pneumatic rotary actuators turn between fixed stops, throttled and with end-position cushioning. Electric drives with a gearbox allow any intermediate position and a controlled speed.
If the parts change, and with them the centre of gravity, an adjustable axis position helps, or a drive that takes the residual moment.
An eccentrically suspended load stores energy. If the drive fails, it must not swing back. This is ensured by a self-locking gearbox, a brake that closes without power, pilot-operated check valves on the rotary cylinder or positive locking of the end positions.
Speed matters just as much: an uncushioned rotation ends at the stop with a shock that loads gripper and device and endangers the operator.
The gripper behind the rotation unit usually needs compressed air, vacuum or signals. With a limited angle of rotation, guided hoses and cables are sufficient. If rotation is to be continuous, a rotary union is needed – it belongs in the design from the start because it determines space, weight and the number of channels available.
What Entracon offers here is on the matching page.
See what we offer| Drive | Characteristic | Suits |
|---|---|---|
| Manual | sensitive, simple, no energy | axis through the centre of gravity, uniform parts |
| Pneumatic | fixed end positions, robust | 90 or 180 degree swivel, hazardous areas |
| Electric | any position, controlled | changing centre of gravity, high moments |
Almost always because the axis of rotation does not pass through the combined centre of gravity of part and gripper. Even a few centimetres of offset produce a moment on heavy parts that can no longer be controlled by hand.
From the centre of gravity of the part, taken from CAD or by weighing, and the centre of gravity of the gripper. The axis is placed through the combined centre of gravity; for part families, for the most frequent or heaviest case, with adjustment for the others.
As a rule not on its own. During rotation the direction of force at the gripper changes, and a friction grip can slip. Rotated loads are gripped by shape or secured by positive locking.
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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