How to choose cutting knife blade of industrial shredders


Shredder blade is a kind of cutter that is equipped with an industrial shredder or granulator. They are machines for crushing waste materials like rubber, tires, wood, paper, polymers, plastic, textiles and so forth. As we all know, industrial waste shredders are playing a critical role in the recycling industry. For one thing, they can save a lot of storage space. Data indicates a shredder can reduce the total volume of processed industrial waste by 30%-50% on average. For another thing, shredders optimize the value of industrial wastes by forming them into granules reaching a recyclable level.

As space is limited, we only pay attention to the cutter part of a shredder. Many variables affect the shredder cutter’s efficiency, such as cutting angle, numbers of knives, cutting velocity, chip load, etc. Above all, A primary factor is If the cutter material is suitable to deal with the industrial waste. That’s always the first thing on your concern.
Materials of shredder cutter out there vary, so do the materials of industrial waste, too. You have to know about the common cutter materials for main sources of industrial waste If you happen to work in the recycling business. ( cement waste is not covered by this article cause, in general, it’s not processed by cutter blade, but anvil hammer)
1.For shredding wood
Common trash wood includes cardboard, paper, solid wood, and plywood board. For brittle wood, such as branches, twig, cardboard, SK5 is a practical and economical option. The steel is a kind of carbon tool steel with nice resistance to wear, but poor plasticity and hardenability. SK5 is often used to make woodworking knives, and sample-sized dies. Its performance is not super outstanding, which results in its cheaper price, compared with other types of wood-processed steels.
However, for high-strength trash wood, such as stumps, plywood boards, and discarded furniture, SK5 is not competent. We’d turn to use high manganese steel, accordingly. High manganese steel is generally used to make a smashing hammer in mining and architecture industry. Its metal hardened depth can reach 10mm-20mm and remain as hard as HB500-550. When working at a high torque, the manganese steel will not be easily deformed or even broken like SK5. In addition to this, the high manganese steel is more affordable, compared with other alloy carbon steel.
2.For shredding plastic
In the plastic industry collectors and recyclers started their business pretty late compared to areas of scrap wood and paper&cardboard. Trash plastic can be generally a huge blend with at least the same amount of possible additives and fillers. They contain not only lower grade plastic but also high-value ones. Thus we need to recognize which type of plastic is in the input mixture.

a.For cutting off plastics of ABS、PE、PP board, etc.
In general, we’d choose alloy carbon steel, such as 65Mn spring steel, T10, and D2 for these plastics. That’s because these carbon steels are with great harden-ability and temper resistance to high impact load. These blade materials are generally utilized on the cut-off blade at lower cutting velocity and large torture. Concern data indicates that when cut-off blades have to bear traction that is more than 270Mpa. In the meantime are required to maintain the hardness of HRC52-55. A cut-off blade made of low-alloy steel will work well under the circumstance, taking credit for its property.

b.For crumbling plastics fragments and granules.
Granulator consists of a fixed cutter and hob cutter. Granulator’s rolling of hob cutters and sifter’s screening at the outlet process together plastic mixture into granules. Hob cutter is the major working part of the whole granulator’s system. The requirements for hob cutter’s heat-treatment hardness is around HRC58-62. Besides, crumbling knives requires to be more resistant to abrasion, high temperature, and impact. Thus, We prefer quenched carbon steel 9CrSi, spring steel 65Mn, or even HSS W18Cr4V. They are fine choices to fabricate all main plastic granules of PVC, PS, ABS, AS, and HIPS.

3.For shredding tyre rubbers
In light of the growing prices for precious metals exist in radial tires as well as raw rubber granule, all types of rubber waste recycling, trash rubber we mostly referred to “black trash” is gradually becoming “black gold” now. Contractors and dealers can easily procure wore tires from automobiles at a very sound price and process them into premium recycled rubber. Recycled tire rubber is not only a cheap but a versatile and environment-friendly material that has a wide range of usage in many places, right from the artificial golf course, to flame-retardant&deadening painting materials.
Take WANROOETECH shredder PNSS as an example. It can firstly cut passenger car tires of up to Ø 800mm into strips of approx. 150 mm- 300mm, then completely smash these pieces int to fine granules. Tire shredder’s hob cutter differs from plastic shredder’s. It consists of many tungsten carbide tips screw fixed and the main cutter body that made of a carbon tool steel. That’s because radial tyres are mainstream of auto-tires, in belt part of which there are many kinds of metal or hardening fiber working as tire cord, such as aramid fiber, Polyamide fiber, or even copper. These hard materials make tire’s strength, hardness, and toughness stronger than general plastic, which means shredding of tyre is hard than shredding plastic, in some degree. And that’s why Zerma have designed two shredders of pre-shred and shred, and choose tungsten carbide(WC) as the material of cutter bit.
b. property of Tungsten Carbide
Tungsten carbide has superior resistance to abrasion and high temperature for processing hard steel like copper and high carbon steel. At normal temperature, its hardness is around 69-81HRC. It still can keep hardness of 60 HRC at 1000℃. Compared to materials with lower properties, tungsten carbide is relatively more expensive. Thus, now shredder producers generally weld, braze or screw fix carbide tips on hob cutter’s body, instead of making the whole cutter body in tungsten carbide. Speaking of reducing cost, nowadays people get their shredders with knives that have larger concave, producing high-quality output, and indexable after worn-out.

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