Shredder Screens, Baskets & Screen Plates

Inspect the screen first, because it is cheaper to check and more often the cause. Look for bell-mouthing — holes that have worn conical and enlarged on the inner face — and for blinding, where softened plastic has plugged the apertures. If holes have grown more than about 10% over nominal, the screen is already passing oversize particles and should be replaced regardless of knife condition. In practice the two wear together: a dull knife pushes material against the screen instead of cutting it, and a blinded screen recirculates material that grinds the knife edge. Replacing only one usually means a second shutdown within weeks.

Blinding is almost always a heat problem, not a hole-size problem. When knives are dull or the rotor-to-screen gap has opened, material is smeared and worked rather than cut. Frictional heat softens the polymer, which then extrudes into the apertures and sets. Fitting a larger screen usually makes the coarse fraction unacceptable without fixing the cause. The durable fixes are sharpening or replacing the knives, restoring the correct rotor gap, and — for heat-sensitive polymers like LDPE and PP film — reducing feed rate or adding cooling. A thicker plate makes blinding worse, not better, because each hole becomes a longer channel to clear.

The limit is set by ligament width, not by open-area percentage. As a working rule, keep the ligament at or above 0.4× the hole diameter for clean plastics and at or above 0.6× for feed that may contain metal, stone or other hard contamination. A 20 mm hole with an 8 mm ligament gives roughly 46% open area and survives contaminated feed; the same hole with a 4 mm ligament reaches about 63% open area but will crack between holes under impact, typically starting at the discharge edge. On abrasive streams we would rather increase plate thickness and accept slightly lower open area than chase throughput with a thin ligament.

Because a screen fails differently from a blade. A blade needs edge retention and works in compression at the cutting edge; a screen is a perforated structural member absorbing continuous impact across a large span. Hardened to HRC 58–62, the ligaments lose the ductility they need to absorb shock and crack rather than deform. A cracked screen is far more expensive than a worn one, because fragments entering the rotor can destroy an entire knife set. We specify S355J2 for clean plastics, Hardox 400/450 for mixed post-consumer feed, and Hardox 500 or selective hardfacing for severely abrasive material — all chosen for toughness first.

Yes, and this is how most of our screen orders start. Send photographs of the worn screen with a tape measure laid across the hole pitch, plus the machine make and model and, where possible, the overall arc length and end-plate detail. We produce a manufacturing drawing for your written approval before any steel is cut. One important detail: we take hole geometry from the unworn edges rather than the enlarged centre holes, so the new screen restores your original particle size instead of reproducing the worn condition.

Yes. Screens, counter knives, knife holders, clamping bars and spacers are all manufactured in-house and routinely shipped together, which is how we recommend ordering them. Replacing the screen while leaving worn counter knives in place means the new screen blinds faster, and a single consolidated shipment reduces both freight cost and the number of production shutdowns.