Heating Elements in Sealing Machines

Refuse Sacks – How Do They Do It?

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Refuse sacks are made from low density polyethylene (invented in 1942), a soft, stretchy, and water and air proof material. In its raw state polyethylene is a mass of small resin pellets or beads and it is only through the process of extrusion that the hard beads are converted into bags of plastic.

The hard polyethylene beads are heated to a temperature of 200 degrees centigrade with the subsequent molten polyethylene then put under high pressure and mixed with agents that provide colour and make the plastic pliable. The prepared plastic polyethylene is blown into one long tube of bagging, which is then cooled, collapsed, cut to the right individual length, and sealed on one end to make a refuse sack.

The job of the sealing machine is simple yet effective. In the typical side-sealing arrangement, an item or set of items travel, usually down a conveyer belt, toward the machine. When manufacturing refuse sacks, a folded sheet of polyethylene film, having two layers, is fed into the sealing machine. The machine has a side sealing mechanism, which typically comprises several sets of belts to hold and guide the film, sealing/heating elements fuse or weld the two layers together and a cutting element removes the excess material.

And so, as the item passes by the side sealing mechanism, this open edge is sealed by welding the two layers together, the plastic is cut and the waste is removed and discarded. The resultant tube then continues down to the final heating element (the end sealing mechanism), where seals are made in pre-determined distances along the plastic.

Refuse sacks at your service!

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