Shrink wrap
Shrink film packaging serves as the outer packaging of goods; it must partly meet a wide variety of criteria:
- on the one hand it is with polyethylene - foil in the area of shipping pallets - logistics as well as the wood packaging ( laminate flooring , glued panels , lining) as " transport packaging , to allow" common to provide a safe, fast and easy transportation to customers. Polyethylene film is used here because it is inexpensive and easy to dispose of.
- the second application is “sales packaging ”: for this, polyolefin film (also known as “fine shrink film”) is used. This packaging can be found e.g. B. CDs , DVDs , puzzles , technical articles, etc. Polyolefin films consist of a plastic mix of polyethylene , polypropylene and other ingredients; their demand for the German market is estimated at approx. 6800 tons / year.
Function of a horizontal flow wrapping machine
Continuous operation with side welding
The product is fed to the forming shoulder via belts or a finger conveyor chain. A half tube is formed there that is slightly larger than the product to be packaged, and at the same time the products are lined up at the correct intervals. Now the half tube filled with products is transported to the side welding station by means of a suction belt. The side sealing station welds the film to the open side of the half tube and at the same time cuts off the waste strip. This is wound up and recycled . The product is then conveyed to the transverse seal, where the front or rear seam is made. In this case the transverse weld works continuously, i. H. the cross weld moves synchronously to the product during welding and moves back to the next gap after welding. After the product is completely welded, it runs into the shrink tunnel. Temperatures between 120 degrees and 250 degrees Celsius prevail in the shrink tunnel, depending on the speed and the type and thickness of the film. The machines' packaging output ranges from 300 cycles / hour (small machines) to 15,000 cycles / hour (high-performance machines).
Intermittent operation with continuous side welding
The machine works on the same principle as described above, but the machine stops to seal the bags on the front.
Continuous working method with overlapping above or below
Here the product is typically only transported to the forming shoulder with a finger conveyor chain. Here, however, the half tube is shaped in such a way that the film comes from above or below and is then placed around the product over a distance of approx. One to two meters. A film overlap of two to five centimeters remains at the top or bottom. This overlap is then sealed to create a closed pouch. The cross welding works here in the same way as with the side welding machine . It is not absolutely necessary to shrink the bag because the bag can be made extremely tight. The packaging capacity of the machines is between 4,000 and 15,000 cycles per hour.
