Four Key Considerations When Choosing a Plastic Granulator

A plastic granulator is one of the most important pieces of auxiliary equipment in any plastics processing factory. It is used to cut and shred scrap and off-spec parts into small granules that can then be recycled back into the manufacturing process. There are many different types of granulators, each designed to handle certain types of scrap and parts. When deciding on which granulator is right for your plant, you should examine four key considerations.

Plastic granulators are designed to chop up and grind large volumes of plastic scrap from production lines, trimming cells, and molding cells. They can be divided generally into two groups: "beside-the-press" models, which are usually used to grind relatively small volumes of sprues, runners, and off-spec parts, and edge trim from film lines for immediate recycling back into the process; and central granulators that are often used to chop larger volumes of scrap from multiple production lines or molding cells.

Central granulators tend to be much larger and more powerful than their "beside-the-press" counterparts, and can be fitted with special feeding hoppers to accommodate long parts like pipes and profiles, wide materials like sheet, or off-spec and startup film rolls that would need to be unwound in order to be shredded. They also often use high-horsepower motors and rotor designs that are optimized for the cutting power needed to chew through heavy, thick-walled and dense scrap. They can be prone to jamming or rotor damage if large, bulky or unevenly-shaped parts are dropped into them too quickly.

In addition to being a very efficient and effective way to reduce the size of plastic waste, granulation is also an environmentally friendly alternative to landfilling and incineration. Because plastic does not biodegrade, it is imperative that we find ways to recycle as much of it as possible. A plastic granulator is an excellent way to do just that, turning waste into usable 3D printing feedstock.

To this end, the authors of this article have designed, built, and tested an open source waste plastic granulator. It can be fabricated for less than $2000 USD in materials and consumes very little energy in operation, drawing only the equivalent of about three to four conventional incandescent light bulbs per hour. This low power draw means that the device can be operated for a very low embodied energy cost. As such, it can accelerate the deployment of distributed recycling by providing a source of inexpensive polymer feed stock for recyclebots and fused particle/granule printers. Full open hardware details including the bill of materials, CAD files, and build instructions for the device can be found at the Open Science Framework. The authors also measured the power usage and particle size distribution of the granulator, and found that it produces a fine, even, and consistent particle size that is suitable for most recyclebots and direct material extruder-based 3D printers. The authors are releasing the design and results of their experiments under an open license to facilitate further research in this important area.recycling machines