Extrusion filtration of plastic scraps

The first one coming up with an easy way to filter polymer scraps gets rich in no time.
There are many filters around, each one (almost) good for each application but, still, with lots of limits.
When twenty years ago a German company came up with the very first "back-flush" self-cleaning screenchanger, it was a kind of revolution and everybody was under the impression filtering of polymers wasn't an issue any more.
Wrong.
Till this moment there is nothing really very smart.
The choice of the right filtration system should be according the following parameters:
- Cost of the operator to handle it
- Cost of the screens
Of course, operator is needed if screens need to be changed often or, with continuous cleaning screenchanger, how often operator should intervene to remove the polymer automatically discharged.
In both ways, operator is needed.
The cost of the screens, that apply to slide or rotating plate screenchangers, is another important issue, from cost point of view.
In fact very many recyclers spend an incredible amount of money just to buy screens.
All this means, from our point of view, that if the filtration of polymer is too expensive, you better work on the line that's before the extruder and try your best to remove contamination before it gets to the extruder.
Running some numbers, you may find out you can buy and maintain another piece of equipment in your recycling system with the money you spend for the screens.
Without forgetting you will have a better quality product if contamination is removed before extrusion, less wearing of screw ..................