Too many fines.
 
 
One of the problems of recycling lines are fines.
Doesn't matter which system you have, fines are around and represent a problem.
So, let's see how to get less fines first and how to handle them.
Fines are mainly created by granulators and there is nothing you can do about it.
A little more or a little less but this machine makes fines.
Some more are then created by friction washers and centrifuges.
There are two "fines separators" available on the market:
First one is a vibrating screen that works well if fines are "heavy" and compulsory if fines are wet.
Second one is a fine separator working with air, where fines need to be dry.
This last one works better than vibrating screens with lighter fines and can be more precise and handle more quantities.
In both cases, fines are colleted in a single point and this is a big advantage.
Let's see now how to have less fines around also because fines is material that costs money and you may not want to throw them away. (the money)
Sharp blades make less fines so do not complain with the machine if blades are dull.
After granulator fines may go into a blower and this can make some of the fines as well.
Of course, a lot depends by the material itself because some plastics are soft, that means less fines while rigid plastics (like PS for example) will make a lot whetever you do.
The granulator itself can be the cause of fines; it depends by the configuration of the rotor, if blades are scissor type or flat, the gap between the rotating blades and the grid, the RPM of the rotor, the shape of the holes of the grid and few things like these.
So, once again, check all details before buying a machine.
As I said before, centrifuges can create fines as well.
Easy to understand, the higher the speed of the rotor, the better the drying will be.
Sometimes, centrifuges into a line can be more than one being the ones in the middle of the line normally used for dewatering.
These can run slower to make less fines because if moisture left is 2, 3 or even 5%  it is not big deal while final one should dry well so it needs to run fast.
If you have, for example, three centrifuges into the line, make first two to run slow so they will make a little amount of fines and run the last one as efficiently as possible as far as drying, doesn't matter how many fines you get.
One more, very important item to check is the diameter of the holes of the screen.
The bigger the holes, the better the drying, true.
On the other side, the bigger the holes the more the amount of fines.
Remember that the area of a three millimiters hole is more than twice as much of the two millimiters one that, in other words, means a three millimiters screen will make, at least, three times more fines than a two millimiters one.
 
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