The most common automated stretch systems are turntable wrappers. The goods are loaded onto the turntable and the film end is secured to the load and the table begins to rotate. The film roll is mounted on a carriage that moves slowly up and down a mast as the table rotates and the film is wrapped evenly around the load.
More sophisticated turntables have programmable functions that the operator can use to vary the rotational speed of the turntable, the vertical travel speed of the film carriage and the tension of the film. Other programs include the addition of extra reinforcing layers at the head, base and middle of the pallet, wherever reinforcement is needed, and to pause at the top of the pallet so that the edges of a protective plastic top sheet can be trapped between the pallet head film layers.
Some automated stretch wrappers feature ‘power pre-stretch’, which stretches the film by up to four times its original length between it leaving the roll and being applied to the load. Once again, the benefits are increased load stability and a truly significant decrease in film usage without loss of performance.
Other features to look out for when choosing a turntable wrapper include
- Automatic table orientation
A boon if access to the wrapper is restricted, this always stops the turntable rotation at exactly the same point from which it started, so that a pallet truck or forklift can remain in place to remove the load when wrapping is complete
- Pin puncture
If air bubbles are trapped between the layers of film they prevent the film from creating a bond and the wrap will be weaker. A film puncture pin function automatically perforates the film at regular intervals as it comes off the roll so that trapped air has a means of escape.
- Soft wrapping
One advantage of automated stretch wrapping – consistent film tension – can also be a disadvantage as the tension is determined by the speed at which the film is applied. The corners of a rotating rectangular object will be further from the centre of rotation than the centres of the object’s sides, so the application speed will be higher at the corners, resulting in higher film tension at the corners.
Unless the load is extremely sturdy, this extra pressure can cause contents such as corrugated cartons to collapse, but reducing the overall pressure will mean that there is insufficient support at the side centres.
Soft wrapping takes this into account and reduces the pressure at the corners so that it is more even at every point of the perimeter.
A more recent development of the turntable wrapper is the robotic stretch wrapper. This typically offers many of features of advanced turntable wrappers such as power pre-stretch, soft wrapping and programmable wrap patterns, but brings the wrapping to the load rather than vice versa.
Not all palletised loads are compatible with a turntable. They may simply be too bulky, or too heavy, or too unstable to be moved with a fork truck until they have been secured with stretch wrap film. This is where the robotic wrapper comes into its own.
It is brought to the palletised load with a manually-controlled tiller and a guide wheel is lightly pressed against the pallet base, or against the load if this overlaps the pallet. The film end is secured to the pallet and the robotic wrapper is activated. Requiring very small clearance room around the pallet it will automatically orbit the pallet, its film carriage moving up and down to apply the film evenly. At the end of the programmed wrapping cycle it will automatically cut the film to detach itself from the pallet and the operator can manoeuvre it away from the pallet.
Southgate supply the Optimax range of PSW turntable stretch wrappers and RSW6 robotic stretch wrapper through their network of approved distributors throughout the UK and across Europe:
- PSW001 Optimax basic turntable stretch wrapper
- PSW002 Optimax turntable with variable powered pre-stretch
- PSW003 Optimax turntable with variable powered pre-stretch and integrated weigh scales
- PSW004 Optimax turntable with fixed 200% power pre-stretch
- PSWR loading ramp for Optimax PSW001 and PSW004 turntables
- PSWR-2 loading ramp for Optimax PSW002 turntable
- PSWR-3 loading ramp for Optimax PSW003 turntable
- RSW6 Optimax robotic pallet stretch wrapper
For further information call 01553 69 29 69 or email firstname.lastname@example.org.