The knowledge about scrap-shredder:

Here we introduce some knowledge about scrap-shredder to you, we hope that it is helpful for your business.

Material Type
Each type of material is best reduced by a certain type and configuration of scrap-shredder.
Different materials have their own physical characteristics which determine how they will react to the reduction process .
Ductile Materials
Ductile materials are not easily fractured but tend to tear into long strips. They are best reduced by shearing to ensure small particle size. Examples are cloth, rubber, soft plastics, paper, cardboard, or soft metals.
Friable Materials
These are materials that are easily fractured (the opposite of ductile) or broken into shards. Examples are stone, glass, cast metals, hard plastics, or wood. Shredded friable materials tend to come out as small pieces rather than the long strips.

Three Ways to Shred
Tearing material to reduce it to smaller particles depends on three actions.
This action involves the actual cutting of material. As in scissors, shearing efficiency depends on the sharpness of the cutting edges working against each other and the tolerance of the space between them. Harden has developed technology (such as ACLS and hardened alloys) to maintain this tolerance and sharpness, ensuring a clean cut even after long operation.
Tearing involves pulling the material with such force that it comes apart. Some materials like fabric, soft metals, plastics, and tires, are more tearable than others. Purpose-built tearing reducers (such as Harden’s Primary Waste Reducers) are good for reducing mixed waste where small, uniform particle size is not important.
Some materials are brittle, such as glass, hard plastics, and certain metals, and tend to be broken or shattered in a scrap-shredder when the cutters aren’t sharp or are loose. Unlike tearing, when something breaks it releases energy explosively, sometimes propelling the shards upwards into the faces of the fascinated onlookers. Always wear eye protection.
Optimum Action
All three actions, shearing, tearing, and breaking are present when a scrap-shredder is being used. However, when the cutters are kept sharp and the tolerances tight, the dominant and most efficient reduction action should be shearing.

Shredder Types
Harden makes four basic types of high-torque scrap-shredders, each coming in various sizes and driven by either electric or hydraulic power units.
Medium-speed, single-shaft, rotary grinder. Recommended for uncontaminated wood, paper, hard plastics, and brittle materials where small, uniform particle size is vital.

Low-speed, high-torque, two-shaft, shear shredder. Recommended for metals, soft plastics, tires, product destruction, or any diverse and contaminated materials where particle size variation is allowed.

Low-speed, high-torque, four-shaft shredder. Especially suited for applications such as electronic scrap, tire shredding,alternative fuel production, and reduction of contaminated materials where uniform, small to medium particle size is desired.

Low-speed, high-torque, multi-material reduce. A high-capacity solution ideal for construction and demolition and for volume reduction of bulky waste containing metal and abrasives. Particle size is coarse.

Batch Feeding
Batch feeding involves dropping large masses of material into the hopper, either by some sort of grapple or loader. Batch feeding is common with appliance destruction, demolition work, or bale processing.

While batch feeding is simple and straightforward, it can also be inefficient. If not properly sized for the job, batch fed shredders are more likely to clog or take on more than they can shred at one time.

Meter Feeding
Meter feeding involves introducing material to the hopper in a steady, controlled stream, usually by conveyor. If a material can be meter fed, the scrap-shredder can monitor its own intake and operate more efficiently. Meter feeding can result in fewer reversals or shut downs.

Low-Speed, High-Torque Advantages
Harden’s expertise comes from low-speed (15-30 RPM), high-torque, rotary shear technology.

Low-speed offers some significant advantages:
1. Less material preparation. Unlike high-speed grinders, low speed scrap-shredders don’t require uncontaminated material.
2. Almost anything can be thrown into a low speed scrap-shredder. They are much harder to damage than high-speed machines.
3. Very low vibration means no special foundations are required.
4. Lower dust and noise means a safer work environment.
5. Lower risk of projectiles ejected from the cutting chamber.
6. Lower maintenance and operating costs than high-speed.
7. Longer life to the cutters and entire equipment.
8. Higher online reliability, less down time than high-speed grinders.
9. Lower power requirements.

Cutter Hardfacing

For most scrap-shredder applications Harden’s standard cutter hardness is suitable. However, when certain applications require a harder, sharper edge, the cutters are hardfaced. This is done by welding alloys to the cutter edges.

Harden uses proprietary alloys to hardface their cutters. The alloys are rated up to a hardness level of HRC 58-66, with 61 being average. The advantage of hardfacing is that the cutter keeps its edge longer. And it is ideal for making clean cuts of ductile but abrasive materials such as tires, carpet, and nylon.

Patented Ram Assist
Harden’s patented design that assists the scrap-shredder to work smarter and more efficiently.

Often bulky and light materials can “bridge” or float on top of the cutting table of scrap-shredders. Harden’s Patented Ram Assist pushes the material into the scrap-shredder, allowing the cutter hooks to get a better grab on the material.
Smart Ram
The Harden Ram Assist is not just a brute plunger like you would find on other manufacturers’ scrap-shredders. Our Ram Assist is integrated with the scrap-shredder controls so it senses when it is needed and by how much, applying just the right amount and duration of force to help the scrap-shredder grab it’s material effectively.

Harden provides ram configurations for a wide variety of both vertical and horizontal feeding systems for its scrap-shredders.


Harden has created unique screen designs that aid in controlling particle size.
Harden’s unique screen design on its scrap-shredders, not only efficiently control particle size, they actually aid in the shredding action.

Our scrap-shredder screens are concentrically aligned with the rotating cutter shafts, so as the cutters interact with the screen face, they are able to tear and pull cut material apart.

For example, in tire shredding, this screen/cutter interaction allows an Harden scrap-shredder to liberate embedded metal bead and sidewall wire in preparation for crumbing. Easy Installation and Maintenance.

Shaft Design
Harden scrap-shredders come with both Hex or Round/Keyed shafts. Each has its advantages.

Hex Shafts
Hex Shafts are still considered by many to be stronger than round/keyed shafts. If it weren’t for the wear and maintenance problems caused by loose cutters slipping across the hex face, they would still be preferred by many users.

Harden solved the loose cutter problem with the ACLS (Advanced Cutter Locking System), which keeps cutters and spacers tight on the shaft, eliminating wobble. Now both round/keyed and hex shafts are available on Harden shredders.

Round/Keyed Shafts
Traditionally shredders were mounted with hex-shaped shafts, which were preferred for high torque applications. However, both hex shafts and cutters tend to wear down as the cutters become loose, and eventually the entire shaft and cutters would need to be replaced.

Harden’s solution to this is the Round/Keyed Shaft. This type of shaft actually locks the cutters onto it and performs very well under high loads. A tremendous economic and maintenance advantage of the round/keyed shaft is that when it becomes worn, you only need to replace the key and not the entire shaft and its cutters.

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