May. 19, 2025
Machinery
This article will take an in-depth look at shredding machines.
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The article will bring more detail on topics such as:
Principle of Shredding Machines
Types of Shredding Machines
Applications, Advantages and Standards of Shredding Machines
And much more...
This chapter will discuss what shredding machines are, their design, construction, and how they function.
A shredding machine is equipment utilized for shredding. Shredding machines are used to reduce the size of materials. While most online sources define the shredding machine as "equipment used to shred documents as a privacy measure to avoid identity theft," shredding machines can be of many forms depending on the material being shredded.
There are shredding machines designed to handle material shredding across a span of recycling uses, including recycling plastic, recycling scrap metal, e-waste, recycling wood, and tire-shredding or recycling.
The shredding operation produces raw materials to be re-introduced into manufacturing, as well as complete products like landscape mulch. Many terminologies are utilized to describe size reduction machines, including grinders, granulators, chippers, and hammer mills. Overall, their main purpose is to reduce the size of a given material.
The design and construction of shredding machines involves:
Equipment Components
Shredding machines consist of feed shafts (for industrial applications), a feed zone into which materials are placed, crushing gears or slicing blades, a motor to spin the blades, and a chute (also for industrial) which transports the materials onto a conveyor for more handling or into a container for disposal.
Most shredding machines have screens to catch reduced material that is too big for the finished products. For thoroughness, the caught material is put back through the shredding machine as many times as possible until it is broken down to size.
Shredding Machine Design and Customization
When designing a shredding machine, a number of factors are taken into consideration, including the material to be shredded, the volume of material to be shredded, the area in which the shredder will operate (on a farm, in an office, outdoors, indoors, etc.), the available space set apart for the machine, the frequency at which the shredding machine will be utilized, and client budget.
Cutter Geometry
The size and shape of hooks on cutters differ according to the kind of material they are required to grab. Commonly, the bigger the hook, the more material can be grabbed. With some materials, this will improve the rate of production. But it is imperative that the hooks grab no more than the shredding machine can shred at a time, or else there will be regular redos and slowing down of production. Many shredding blades are made of tool steel and carburizing steel, but other applications use molybdenum, chromium, and manganese low alloy steels.
Shaft Geometry
Shaft design consists mainly of the calculation of the proper shaft diameter to ascertain satisfactory rigidity and strength while the shaft is conveying power under different loading and operating conditions.
The material utilized for the shaft must have the following characteristics:
It must have high strength.
It must have decent machinability.
It must have decent heat treatment characteristics.
It must have high wearing resistance properties.
Carbon steel is primarily utilized for the shaft, but when high strength is needed, alloy steel like nickel-chromium, nickel, or chrome-vanadium is used.
Electric or Hydraulic Drive
Electric Drives – This is the system that rotates the blades; it varies in size depending on the type of shredding machine. It may be DC in small shredders like paper shredders to 3 phase AC induction motors in metal shredders. Commonly, electric shredding machines require less space, are simpler to use and maintain, and are much more energy-efficient than hydraulic shredders. They are also cost-effective. Electric shredding machines are proper and adequately powered for processing many materials.
Hydraulic Drives – They perform the same job as electric drives. Hydraulic drives are at times better for more heavy-duty reduction like in tire shredding. They are also better for reducing materials that undergo frequent overloading from batch feeding. As a result, they are only found in industrial shredders. Hydraulic drives also provide better shock load protection from unshreddables.
Situations in which a hydraulic drive system is appropriate:
Batch fed materials
Feed including unknown or unsorted materials
Materials that are exceedingly difficult to shred
Process needing stricter particle size control
System has to meter shredded pieces to downstream equipment
System needing regular starts and stops
Shredder needing a lower voltage start or soft start
Depending on the application, a shredding machine’s design might be small, hand-feedable, and placed in an office or home, or it might occupy a commercial shredding plant, shredding thousands of kilograms of material by the hour.
There are three ways to shred discussed below:
Shearing Material in Shredding Machines
Shearing includes the actual cutting of materials. As with scissors, the efficiency of shearing is dependent on the sharpness of cutting edges operating against each other and the tolerance of space between them. Technology like ACLS and annealed alloys maintain this sharpness and tolerance, ensuring clean cuts even after a long working time.
Tearing Material in Shredding Machines
Tearing includes pulling the materials with such a force that they come apart. Some materials such as fabric, soft metals, tires, and plastics are more tearable than others. Purpose-built tearing reducers are great for shredding mixed waste material where small, constant particle size is not prioritized.
Fracturing Material In Shredding Machines
Some items are brittle, such as hard plastics, glass, and particular metals, and tend to be shattered or broken in a shredding machine when the cutters are loose or not sharp. Unlike with tearing, if something breaks it releases explosive energy and at times may even propel the shards into nearby personnel. Eye protection must always be worn.
Optimum Shredding Action
All three actions–tearing, shearing, and fracturing–are available when a shredding machine is being used. However, when cutters are kept finely sharp and tolerances are tight, the main and most efficient shredding action is shearing.
Material Types Shredded
Each kind of material is best shredded by a certain kind and setting of the shredder. Different items have individual physical properties that determine how they react to the shredding process.
Ductile Material – Ductile material is not fractured easily but is apt to tear into long strips. They are best shredded by shearing to guarantee small particle size. Examples are paper, cloth, soft plastics, rubber, soft metals, or cardboard.
Friable Materials – This is material that is easily fractured (the opposite of ductile material) or broken into shards. Examples are glass, stone, cast metals, wood, or hard plastics. Shredded friable material is apt to come out as small parts rather than long strips.
Some of the considerations when choosing a shredding machine include:
Type of Material to be Shredded
Different kinds of shredders excel at shredding specific materials. A tree branch is typically shredded utilizing a high-speed chipper. Plastics are frequently shredded in a granulator (spinning knife blade), but big plastic shapes are at times put through a shredding machine as a first step before granulating. When organizing to shred cars, this kind of application is generally done using a hammer mill. Though shredding a variety of waste products may need adaptability with a less amount of dust and noise, then a twin-shaft shredding machine may be the optimal solution.
Desired Output
Understanding the size of output requirement will aid in determining the kind of equipment to install. Some companies require the items to be separated, while others may require shredding once again and grinding. A single-pass shredding machine will cost less but if the items need to be shredded to a very minuscule size and compressed then compaction machinery may be required.
Shredder Capacity
Choosing an industrial shredding machine to cater to the correct capacity is vital to the success of every installation. Capacity is generally expressed in kilograms per hour and is alluded to by the physical dimensions, weight (matter density), and amount to be shredded. The capacity might be restricted by the shredding chamber size.
Carefully check the capacity rating before procuring the machine and allowing for some extra capacity. Using a shredding machine with a maximum capacity very close to the required capacity may lead to short service life. However, oversizing a shredding machine by a huge margin may lead to excessive power usage and take up a lot of floor space.
Feed Type
Two simple feed types are common: automatic and manual. Manually fed shredding machines usually feature a hopper and function by either hand-feeding the items or utilizing a forklift to load the items in. Automatic conveyors or feeders help optimize shredding machine performance by supplying a regular and constant supply of items to the shredder.
Operational Considerations
Safety, portability, and noise are concerns when choosing a shredding machine. A suitable location for a shredder must be selected because it is not simple to move machinery weighing close to a ton or more. Depending on the items, dust and other airborne debris may be an environmental danger. Noise is another aspect to consider since some shredding machines (like hammer-mills) make more noise than others.
Shredder Maintenance and Repairs
Shredders undergo a great deal of strain, and maintaining them is necessary to keep them operating efficiently. Cutters, hammers, or blades will wear out under normal usage and need adjusting, sharpening, or eventually replacing. Repairs, maintenance, and ease of acquiring replacement parts must be considered when choosing a manufacturer. Access location for maintenance must always be evaluated when figuring out where to place any equipment including a shredding machine.
>> The Ultimate Guide to Shredding Plastics
The different types of shredding machines include:
A cardboard shredding machine is an industrial or commercial recycling machine that instantly recycles and repurposes cardboard waste material into packaging material. These cardboard shredding machines can make cushioning netting, chips, flat netting, or strips.
A cardboard shredding machine operates almost like a paper shredding machine for discarded cardboard boxes. The machine upgrades cardboard waste material into eco-friendly and high-quality cardboard void fill material, like strips, chips or netting, or packaging material. Cardboard shredding machines are user-friendly, very simple to operate, and safe to use. The machine is switched on using a switch. A piece of cardboard is grabbed and fed via the shredding machine’s front opening. The converted cardboard is dropped out of the back of the shredder.
With a cardboard shredding machine, cardboard waste is quickly converted into packaging material. This cardboard is eco-friendly and saves on waste-carrying expenses and the need for purchasing packing materials. A cardboard shredding machine produces void fill materials in different sizes and shapes to protect goods in transportation while at the same time reconstructing and reusing cardboard waste material in an environmentally friendly way.
A paper shredding machine is electronic equipment used to shred (usually sensitive or confidential) paper documents into indecipherable particles. The shredding machine shreds documents using a set of spinning cutting blades spun by an electric motor.
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The size of the output pieces depends on the kind of paper shredding machine. Shredding machines are categorized into strip cut, cross cut, and micro-cut shredders. A shredding machine can turn documents into tiny paper shreds or long strips as tiny as confetti. The output of paper shredding machines is covered in the authorized security levels of DIN .
Not all paper shredding machines produce the same cut. In other words, this means not every shredding machine makes the same particle size. That is why paper shredding machines are categorized into three types to distinguish them from each other:
Strip Cut
A strip cut (also known as ribbon cut, straight cut or spaghetti cut) shredding machine is a simple paper shredder for reducing non-confidential documents. It reduces paper vertically in narrow long strips that are fairly readable.
This type of shredding machine has the advantage that it can shred easily and quickly because of the individual cutting mechanism.
The drawback of a strip cutting shredding machine is that it offers less data protection compared to a cross cut or micro-cut paper shredder. The characteristics of strip cutting are:
Low security level
Use for non-sensitive documents
Spaghetti-like narrow long vertical paper strips
Vertical cuts only
Approximately 39 strips per size A4 shredded document
Security level: DIN P-2, DIN P-1
Cross Cut Shredder
A cross cut (or confetti cut or diamond cut) shredding machine is a paper shredder for reducing confidential documents. It reduces paper diagonally from two corners into short pieces that are barely readable. The P-4 or P-3 security level of cross cut shredding machines gives them the ideal security level for eliminating personal sensitive information or general private documents in the workplace. Its characteristics include:
Medium security level
Use for shredding confidential documents
Narrow and short paper shreds
Diagonal cuts from two corners
Approximately 400 pieces per shredded size A4 document
Security level: DIN P-4*, DIN P-3
Micro Cut Shredder
A micro cut, particle cut, or security cut shredding machine is an advanced paper shredder for reducing highly confidential documents. It reduces paper diagonally from two corners into square shaped pieces that are almost unreadable. Its characteristics include:
High security level
Use for shredding highly confidential documents
Small square shaped paper particles
Diagonal cuts from two corners
Approximately 3,700 pieces per shredded size A4 document
Security level DIN P-5* or more
A plastic shredding machine is equipment used to reduce plastic into tiny pieces for granulation. Unlike plastic granulators, shredding machines are designed particularly for large plastic waste, such as car bumpers, drums, pipes, and other products too big for granulators.
In the operation, big plastic products are fed into the shredding machines. Moving at slower speeds than granulators, blades break the plastic apart into smaller chunks. These particles are then collected, cleaned, and treated in cleansing and recycling plants prior to being granulated and delivered to manufacturers.
This machine offers several advantages in addition to reducing plastics that are utilized as raw materials for other products such as storage containers, packaging bags, toys, and consumer electronics. The different applications of plastic shredding machines include the plastic industry, catering industry, laboratories, manufacturing units, pharmaceutical companies, biomedical waste management plants, food processing facilities, nursing homes, cardboard manufacturing units, healthcare facilities, and supermarkets.
Hard drives are full of confidential data, from financial information and customers’ social security numbers to nuclear weapon plans. Hard drive shredding is a generally used method to physically destroy a hard drive. A hard drive shredder crushes the hard drive so that criminals will be less motivated to try to retrieve the data stored on the shredded remains, but it doesn’t destroy it. Shredding a hard drive is inadequate for present day technology; an up-to-date hard drive keeps 600 000 data pages on a 2 mm wide shred particle. That is a particle tinier than a grain of rice!
A common fallacy is that shredding media makes the data unrecoverable. However, physically destroying or shredding the media does not eliminate data from the disk platters since data is stored magnetically. Data is recoverable from larger particles of a shredded drive with the usage of tools and applications available on the Internet. Even smaller particles of shredded hard drive can be read with the usage of magnetic force microscopes.
Tire shredders are shredding machines that are capable of reducing tires into a constant particle size. This type of shredder can also be utilized for a wide range of materials such as aluminum, plastics, paper, and cables. The tire shredding is capable of reducing tires and hence making recycling of tires easier. The end result, the tire waste, may often be sold.
A chipper shredder, also called a wood chipper, shreds twigs, branches, and leaves into compost and mulch material, helping in keeping landscapes looking their best. Chipper shredders vary from light duty electric equipment to heavy-duty gasoline-powered machines that can chop branches more than a few inches in diameter.
A chipper shredder features a chute that receives branches for chipping. A spinning blade or array of blades chops them down into wood chips. The shredding mechanism handles small debris, such as grass and leaves. As material is being fed into the shredding machine hopper, it is shred by a separate array of hinged blades also known as hammers or flails. Some bigger shredding machines can manage small twigs. Once the machine shreds or chips the debris, the reduced material is discharged into a collection bag or onto the ground.
The shredder hopper and the chipper chute help separate a user from the shredding and chipping mechanisms. Some models come with a tamper or paddle to feed debris so that hands are kept clear of the machine.
Metal shredders are equipment utilized for reducing a wide range of scrap metal. They are often used in metal recycling applications and scrapyards to shred the waste into consistent shapes and dimensions for disassembly and further processing.
They come in many sizes, from small shredders capable of reducing coins and tin cans to large models which can work at 10,000HP and shred up to 4,000 tons of metal a day. These bigger machines shred products such as automobiles as a step of the end-of-life car recycling process, big drums, and almost every other kind of scrap metal.
This chapter will discuss the applications, benefits and standards applied in shredding machines.
Some industrial applications for shredding solids include the reducing of foods, pharmaceuticals, pallets, rubber, steel, furniture, plastic drums, construction debris, containers, tires, corrugated boxes, labels, packaging, and other big materials. Industrial shredding machines are also utilized for the reduction of documents, x-rays, media like hard disk drives, and other electronic devices to safeguard the privacy of individual people and corporate information.
Municipal applications involve recycling centers and smaller shredding machines with many cutting teeth for thorough reduction for usage in wastewater treatment plants. The recycling business has found a lot of uses for shredding machines like shredding tires for recovering rubber. These recycled rubbers are found in various products and applications including hot melt asphalt, playgrounds, basketball courts, and shoe products.
The rubber is also used in civil engineering applications for backfilling, the partial-grade insulation of roads and for energy as "Tire Derived Fuel". Scrap wood is reduced for recycling and utilized for the manufacturing of many kinds of wood products like particle paper and board. Plastic bottles are shredded and recycled into polyethylene terephthalate (PET) plastic pieces for the manufacture of new bottles. Recycling or reutilizing all of these items through shredding minimizes environmental waste, maximizes corporate profitability, and minimizes carbon emissions.
Shredding machines play a crucial role in a lot of applications including recycling, manufacturing, solid waste reduction, wastewater treatment, security, gas and oil production, the transportation and making of bio-solids, and more. Shredding provides a mass of advantages in addition to the obvious size reduction. Shredding machines are utilized for shredding materials that produce products or fuel, safeguarding business intelligence by eliminating confidential documents or products, recycling of products or waste materials, and reducing solids to make sure that other processes or equipment run smoothly. Corporations, municipalities and government agencies all employ shredders.
Increase Security – The main advantage of a good shredding is the increase in information protection for a business. Modern businesses should work to guarantee that their sensitive data will not be exposed to the wrong parties. From both competitive and regulatory perspectives, it is crucial that businesses put their private data far from the access of unauthorized personnel. A good shredding machine can help do just that.
Reduce Waste Volume – By shredding documents and other media, the size of the waste output by a business is also reduced. This will make waste management much more efficient and can minimize the costs when waste removal is charged by volume.
Minimize Costs – Investing in a personal shredder will also bring abundant cost savings when paying individual third party suppliers to handle the shredding. Good quality shredding machines are becoming better and cheaper for any size of business. The long-term difference between a personal shredding machine and paying for shredding services is quite massive. Having a personal shredder on site also increases security, removing the need to send sensitive information out to be destroyed.
Increase Efficiency – Having a personal shredder can also greatly increase efficiency in a business. With a personal shredding machine, there is no need to wait for long durations between visits from dispatches to third-party or suppliers’ individual shredding services. There will no longer be any need to manage, organize, and store documents and other items which are set to be shredded. With a personal shredding machine, documents and other types of sensitive data can be destroyed immediately.
These are some of the basic benefits which a shredding machine can bring to a business, but there are many more based on the type and scale of shredding machine selected.
The following are some of the drawbacks associated with machine shredders:
There is risk of injury with rotating, sharp cutting blades. The injuries could be fatal with some types of shredders; for instance, metal shredders and chipper shredders.
Noise pollution is associated with tire and scrap metal shredders.
Operating a shredder takes time (and hence money). For paper shredders, the time cost is more noticeable when papers must be shred on a daily basis, taking up time for other tasks.
For hard drive shredders, the data is not destroyed. Even on particulate shreds, there are thousands of pages of information which can be recovered in labs.
To ensure operator safety, it is recommended that employers train their operating personnel in responsible shredding, loading and unloading. The best materials on safety standards and safe working areas are from OSHA. As a governmental division, OSHA is probably the most noteworthy work safety administration in a country. Customers must make sure that their manufacturer provides OSHA certified machines.
In addition, most industries such as metal recycling comply with OSHA regulations. So care must be taken to know what safety and compliance standards apply in an industry for their respective machine.
Based on the intent of use, shredding machines can be categorized as industrial shredders or consumer shredders. A paper shredding machine normally falls in the class of consumer shredder since it is mainly used by consumers.
Industrial shredders are generally heavy duty and high-volume machines utilized to reduce such recycling material streams as plastic, e-waste, wood, and paper. Industrial shredders are fitted with different types of cutting systems like horizontal shaft design, vertical shaft design, single shaft, two shaft, three shaft, and four shaft cutting systems.
There are various factors to consider before choosing a suitable shredding machine. Collecting all the important information to compare against the shredding machine specifications will aid in shortening the process of comparing the equipment to the requirements. For recycling, the necessary permits must be at hand. Seeking knowledge and advice from a trustworthy company is a great start, and asking for a demonstration using a sample will approve the shredding machine’s effectiveness. Visiting a manufacturer’s website to check the company’s background and going through some case studies to learn how other companies have used shredding machines to solve operating difficulties is also a good start. The last step of the equation is figuring out the budget. Keep in mind that some machines, though initially less expensive, can be inferior in quality and in actuality are costlier in the long term to use and maintain.
Plastic Shredders
Shredders are employed in recycling for size reduction and volume reduction purposes. They are often used to break down large and bulky items into smaller, manageable pieces. Shredders use a tearing or shearing action, and they may have rotating blades or other mechanisms to shred materials into various sizes. While the resulting pieces may not be as uniform as those from granulators, shredders are effective in reducing the volume of materials.
There are a few main types of plastic shredders :
These have a single shaft with hammers or blades attached. The shaft rotates inside a screened chamber to shred the materials. They are relatively compact and inexpensive shredders suitable for low to moderate capacity recycling operations.
These utilize two parallel shafts with interleaving hammers or blades that grab, shear, and tear apart plastic fed between them. The dual shaft design provides more shredding power and throughput.
Cutter design and the arrangement of cutters on the shafts play a key role in determining shredding efficiency. The load on a shredder is primarily determined by the number of cutter hooks that are “engaged” at any particular point in time. The more hooks engaged, the higher the load. To manage the load in a shredder you need to manage the number of engaged hooks and this is done in a couple of ways.
The number of hooks on a cutter can be varied – single, dual, triple, six. The offset – or the degrees until the next adjacent hook, can also be varied. This enables the creation of spiralling of the hooks which is suitable for some applications – but not for all materials. Other applications require larger open gaps to enable large objects to enter the cutting zone. The correct use of equal speed and differential speed shafts is also essential to manage the load and create open areas. At Brentwood we design a cutter arrangement specifically to suit your materials and throughput requirements.
Brentwood’s cutters are manufactured from a nickel based alloy and case hardened to 60 Rockwell. This produces a cutter with excellent durability and superior shock tolerance so the cutter can withstand high impact loads which may occur when an unshreddable item enters the cutting chamber. Brentwood cutters are also repairable. We can hard face the cutting edges and regrind to specification several times over the life of a cutter. This greatly reduces the cost of ownership of a Brentwood shredder.
The overall length of the cutting chamber also has an impact on the throughput of a shredder. Longer cutting chambers can increase production rates where the input material is flowable and can move in the cutting chamber. Too long a cutting chamber however can increase load beyond the shredders limit and place higher levels of stress on the shafts.
Cutting chamber width – and more particularly, the distance between the shaft centres plays a crucial role in determining if a material can be effectively grabbed by the cutters. If the shaft centres are too close for a particular sized input material, then bridging may occur or the shredder may have difficulty in grabbing the material.
At Brentwood, we offer customised cutting chamber lengths to enhance throughput on certain materials and to allow longer items – such as pallets and IBC’s to be effectively shredded.
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