Welding of polymeric films

Welding equipment performs the following facilities to user (fig. 1):

• Making of packages, polyethylene sacks, bags etc.;
• Packaging products into film packs by means of welding;
• Packaging products into thermo-film with its following welding and shrinkage.

Foodstuffs and uneatable products to be packed can be:

• Liquid;
• Spread;
• Free-flowing;
• Solid.

The following kinds of film is often used as polymeric films:

• Polyethylene;
• Polypropylene;
• Polyamide;
• Polyvinyl chloride,

as well as multi-ply combined films based on foregoing, and composition materials:

• Laminar paper;
• Metallized films;
• Laminar foil etc.

Welding equipment differs on the basis of following feature:

a) Constructional execution (fig. 2):

• Table;
• Floor;

b) Kind of formed seam:

• Tear-off linear seam ("string");
• Welded plane seam ("tape");
• Grooved seam ("euro-seam");

as well as combined seams by way of combination above-named;

Power supply type of heating spiral:

• Impact ("string", "tape");
• Permanent ("euro-seam").

Technology of forming Tear-off linear seam ïprovides for the following operations (fig. 3):

• Pressing films to the heating spiral (wire);
• Feeding the heating spiral with current impulse adjustable to the time sufficient for melting and cutting film by the heating wire, which serves as knife;
• Keeping the film in pressed condition, that is necessary for getting cold and consolidation of molten film edges;
• Opening and extraction of cut and welded film.

Technology of forming plane seam (fig. 4) is not actually differing from the Technology of forming Tear-off linear seam. The only difference is that heating spiral of such device (plane tape) adjoins the foil through the heat-resistant glass-wool. At that time on the spot of contact melting of films to be weld is carried out. After getting cold welds repeat the form of heating tape.

Technology of forming Grooved seam (fig. 5) provides for the momentary pressing of films to be weld by the grooved and permanently heated to adjusted temperature jaws of welding device. In this case films are not completely melted and their edges after getting cold retain the grooved form. For making such a seam we recommend to use a multi-ply films because their internal layer of welded surface has smaller melting temperature than external layer of surface that is not welded.