Technical Analysis: Why Blade Mills Fail on PCBs
Discover the “Screen Paradox,” overheating issues, and why Impact technology outperforms traditional methods.
Comparative Analysis: Blade Mill vs. Impact Technology (IM Series)
In PCB recycling, a common mistake is treating circuit boards like standard plastic, using blade granulators. PCBs are abrasive composites (Copper + Silicon), and applying cutting-based technology introduces structural inefficiencies that Impact technology addresses at the source.
Blade Mill (Incomplete Cutting):
Blades apply shear forces to cut the material. When processing a composite, cutting reduces particle size but does not separate layers. The result is “sandwich” fragments—copper or other metals still bonded to plastic—making downstream recovery difficult and less profitable.
IM Impact Mill (Selective Liberation):
The system exploits the different elasto-plastic behavior of materials. Ballistic impact fractures the brittle inert fraction (fiberglass) while plastically deforming the ductile metals.
Result: Materials exit the mill already physically separated (delaminated), optimizing density table performance and metal recovery.
Using blades on PCBs forces operators into a trade-off known as the “Screen Paradox”:
Scenario A – Wide Screen (> 8–10 mm):
To avoid overheating, wide holes are used. The blade cuts but does not liberate the metal, producing mixed material with low commercial value.
Scenario B – Fine Screen (< 4 mm):
To free the copper, fine screens are used. This leads to process collapse:
Phenomenon: Friction generates heat spikes that exceed the epoxy resin’s softening point.
Damage: Resin melts instead of pulverizing, binding copper and clogging the screens, causing machine downtime.
IM Solution:
Impact milling works by collision, not sliding friction, keeping temperatures controlled. The resin remains crystalline, and even fine screening avoids melting or clumping.
Blade Mills (Accelerated Wear):
PCBs contain fiberglass (silica), a highly abrasive material. Blade edges wear down within hours. A dull blade tears instead of cutting, dramatically increasing energy consumption and heat generation.
Impact Mill (Durable Performance):
High-chromium alloy hammers rely on mass and inertia, not sharpness. Crushing efficiency remains consistent over time, reducing maintenance cycles and operating costs.
IM crushers work on a different principle: the energy is released upon impact. How it works: the material is accelerated and collides with the walls. This releases the plastic through mechanical impact, allowing the metals to "agglomerate" through plastic deformation.
Result: Since there is no friction and no prolonged wear, the valuable coatings ("flash") usually remain embedded in the heavy metal or are crushed so that they can be recovered in later separation steps or additional chemical processes. In all cases, nothing is lost and the commercial value of the metal mixture produced increases significantly.
