Film Winding

The film hose coming from the extruder can be further processed more in an onward production stage. To do this, the film rolls - which often hold several kilometres of film - are placed in so-called manufacturing machines (also called sachet welding machines). The film is unwound, cut with hot knives, and welded into the desire sachet or bag sizes using welding terminals (the principle of this technique is the same as in household film welding equipment, with which deep freeze goods etc. are shrink wrapped). This can ofen produce not just one, but 4, 5 or 6 sachets at once - depending on sachet size. Modern manufacturing machines can produce 200 or more welds (cycles) per minute, i.e. the manufacturing system output is over 1,000 sachets per minute.

 

As the size of the sachet to be manufactured is known before production, the film width and thickness in extrusion must be pre-set. Should the required formats no longer be maintained during film production, then the desired sachet format can no longer be produced.

The film must be recycled.

 

If printed goods are to be produced, the film is printed in an additional stage after extrusion. Here, the film roll is unwound by a printing machine and runs past several rotating print stamps. A negative of the image to be printed is fixed in advance in a rubber plate on the print stamps. Each print stamp applies a different colour to the film. As the printing machine is set up such that each print stamp prints inside the print of the previous stamp, the motif to be printed is formed at the end. The final motif becomes more recognizable after each stage, until the deisred image is finally visible.

 

The film is rewound on the other side of the printing machine and it finally arrives at the manufacturing machine as described above. Here, the system must be set such that the motif always appears in the centre of the sachet/carrier bag and no carrier bag is produced with half of the image at the top, half at the bottom and white in the centre. Our customers would not want that.

 
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