Film

 

 

Bales of film scraps, generally contain many foreign materials and different contaminants. Scrap bales need to be opened and sorted not only for this reason, but removing of wood, foamed materials, an entire piece of carton, steel or other metals that you will find inside is compulsory if what you're looking for is a pellet good for film application.

Therefore, manual sorting will not be good only to protect your shredder but also for the quality of your final product.

Because you should expect everything and because we're talking about dirty material, we strongly suggest to go with a single shaft shredder rather than a granulator to save maintenance first and consequently (a lot of) downtime.

If you'll need a small size flake because of your force-feeder, you can always go into a granulator at the end of the line because, after material is clean and dry, your blades will last forever.

The  material is shredded, using a grid of about 50 mm in order to not create lots of fines during washing and drying.

Even if it is true shredder delivers material constantly, we like to go into a buffer silo anyway to be sure the quantity of flakes we feed to the line is what we want and, just in case, operator should state how much material goes to the line and not the shredder itself.

Buffer silo extraction screw speed can be adjusted to deliver to the line what operator think is the best for the efficiency of the line. (because it is a screw conveyor, dosing will be by volume and not by weight, remember it)

From the shredder we go to a special pre-washing machine which will accept oversize pieces without jamming, and, by friction in presence of water, will release most of the dirt.

This stage is very important ,or better compulsory, if the material is agro-film, silage film or stuff like that.

 Separation into a sink float tank to get rid of the sinkable material will follow, followed by a treatment with an horizontal centrifuge to dry the flakes. This type of machine will also further clean plastic film flakes by friction created by an highly spinning rotor.

Now, if the quantity to be processed is max 500kg/hr (about 1000lbs.)one sink float tank and a centrifuge will do the job, otherwise to process a double quantity you should add another set. 

The last step will be drying with an horizontal centrifuge specially designed for thin film.

 

Production rate besides contamination will strongly be affected by thickness of the film that is a real issue.

This is an important data indispensable to configure the line ,and must be known, because it is what states the throughput of the line.

In other words, if you feed a 40 micron average thickness film and you get, let's say, one ton per hour, with exactly the same line you'll get 750 Kg/hour with a 30 micron film, 

500 Kg/hour with a 20 micron and so on.

On top, problems (cutting and drying) will increase proportionally with the decrease of thickness so, not only you get less production but your machinery will not perform as well as they are supposed to.  Drying will also be affected by thickness as residual moisture in the same surface, will be higher for example in a 20 micron than in a 40 micron one.

 

It is customer responsibility to show what will be the worse scrap coming to the line and to specify what is needed.

This means if the scrap characteristics change, the line will perform differently, may be better, may be not, up to what  is fed into the line. In other words, the quality could be lower than expected, throughput too low and so on, all resulting in a very expensive operation.

Generally speaking, if very poor quality material is fed in, a very poor quality material will be obtained from the line .

 


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