Mold and Temperature Control
A magnetic separator is equipment that uses a permanent magnet to capture iron-bearing (ferromagnetic) metal particles in the material flow and remove them before they reach the screw, barrel and mold. It comes in different geometries for free-fall, pressurized line and conveyor belt applications. It does not hold non-magnetic metals such as aluminum, copper and stainless steel; an all-metal separator is required for those.
Separation performance is determined by three things: the magnet material and its gradient, the thickness of the material layer (the distance to the magnet) and the flow speed. The upper part of a thick layer never sees the magnet; that is why grate and drawer types split the flow into thin layers.
A neodymium magnet gives the highest pull force but loses strength above 80 °C; on hot lines such as a dryer outlet, samarium-cobalt or high-temperature neodymium types are used. Magnet strength can drop quietly over time; periodic pull force measurement is required.
Austenitic stainless steel (304/316) is not magnetic and is not caught. For stainless fragments coming from blade and screen wear, an all-metal separator working with inductive detection is required.