Can a pellet screen separate mixed resin types?

Not when their sizes overlap. Screening classifies physical size rather than resin composition.

Plastic Pellet Screening

Separating fused pellets from usable product

Plastic pellet screening removes oversized fused pieces and separates smaller fragments from the wanted pellet band. A multi-deck screen can provide distinct oversize, accepted-pellet and fines outlets. Pellets of different resin types can have the same dimensions, so a screen cannot sort them reliably by chemistry or colour. Grade segregation starts with separate storage and clean handling equipment.

Linear Vibrating Screen on a white background — Linear Vibrating Screen

Pellet shape and fines

Cylindrical, rounded and irregular pellets contact the mesh differently. A long thin piece may pass an opening in one orientation but be retained in another. Soft or warm pellets may adhere or deform, creating a different problem from dry rigid pellets. Fines can cling to surfaces and appear again downstream when deposits are disturbed.

Material / observation	Separation / cause	Equipment / action
Fused pellets	Oversized joined pieces	Separate at the upper size cut
Small fragments and fines	Below the wanted pellet size	Collect separately from accepted pellets
Different resin grades	Similar size but different composition	Prevent mixing; screening cannot identify resin chemistry

Illustrative sample of plastic pellets and oversized fused pieces — Material illustration: plastic pellets and fused pieces

Why usable pellets appear in oversize

Excessive bed depth or uneven feed limits contact with the openings. Blocked openings and an aperture unsuited to pellet geometry can produce the same symptom. Inspect a reject sample and the deck before adjusting the machine. Linear and gyratory screens spread a suitable pellet feed across the screening surface; clean discharge partitions prevent the separated fractions from mixing again.

Gyratory Screen on a white background — Gyratory Screen

Prevent grade carryover in closed conveyors

An enclosed pipe chain conveyor moves suitable pellets through a tube route, but closure does not guarantee that the route empties completely. Inspect bends, the discharge and drive or tension housings for retained pellets during a grade change. Screw conveyors also require attention to trapped pellets and friction where the resin is susceptible to damage. Compare the fines level before and after transfer to identify handling-generated fragments.