|Machinery to transport pre collated
product into a vertical web of stretch film, wrap the film around the
pack by stretching the film and sealing the film.
No tunnels are normally necessary but it is possible
to install simple heaters to "shrink" the ends of the film into
the familiar shrink wrap appearance. Useful technique when only a band
of film is required around the pack.
The technique of stretch wrapping is limited to speeds
of no more than 15 per minute and product that is reasonably "solid"
and inflexible as forcing the product through the film can distort the
A neat pack can be made by producing "envelope"
sides which are heat sealed.
The stretch wrap machine is one autonomous unit as different
to the shrink wrap process.
Stretch band - Purely a band of film with no overlapping sides.
Envelope pack - Stretch film wider than pack and heat sealed envelope ends.
Full enclosed pack - Stretch film but ends shrunk with simple heaters.
Double band - Useful for packs that split into two.
Various film weights are used as in shrink wrapping.
The "average" cost of a pack is approximately 10% cheaper than
shrink wrap. The actual costs can be calculated from the following formula:
[ (2 x W) + )2 x W] x [L + (1 x H ) ] = sq. mm x cost of film.
If a band only is required the formula is:
(2 x W) + (2 x H) x L = sq. mm 'L' can be any dimension required.