Learn the factors that can help you determine whether a beside-the-press granulator is best for your plastics processing operation. #sustainability
No matter what type of process is the mainstay of your plastics manufacturing operation, every floor manager knows that waste materials generated can be significant. Ideally, those materials are reclaimed back into the process. By grinding the plastic materials down to a size that’s similar to the virgin material, you drastically decrease waste and use less of that new material in the process. Electrical Wiring Pipe Production Line
Regardless of the size of your operation or type of manufacturing process, regrinding of plastic components has the potential to create substantial savings. There are multiple types of size-reduction equipment, including shredders and granulators that can be used to transform the material into a more useable state. The type of machines utilized in a process depend on the material characteristics, size and density. Considering the annual savings over many manufacturing runs, it’s vital that you choose the right type of granulator based on your particular processing operation, type of materials, labor, floor and storage space, and many other factors.
To help get the most from regrinding, plastics processors typically use one of two types of manufacturing-floor configurations and equipment designed for that workflow: a central granulator or a beside-the-press granulator. (It should be noted that Under-the-Press [UTP] granulators are sometimes categorized with beside-the-press granulators, although they are generally located beneath a thermoforming line.) Each approach to regrinding has pros and cons that are specific to each operation, so the burden is on floor managers and manufacturing engineers—with the help of a knowledgeable equipment partner—to determine what works best to meet the company’s needs, limitations, and goals.
Injection molding plant equipped with beside-the-press granulators.
Although a central granulator configuration offers many benefits for those operations that are well-suited for that equipment, this article will focus on beside-the-press (BTP) granulators. We’ll explore the top reasons you might want to choose this type of granulator for your plastic component waste, as well as other considerations.
A beside-the-press granulator is an ideal solution for maximizing your floor space.
Depending on your current floor operations, selecting a beside-the-press configuration may result in substantial materials savings for several reasons. First, by their very nature, beside-the-press granulators offer a tailored solution for the most usable reclaim. It’s vital to work with your equipment supplier to ensure that you determine the best chamber geometry for your applications and type of material. You also want to consider the size of the discharge bin: A larger bin allows for more uptime, which decreases the frequency of bin emptying. When vacuum-takeoff (VTO) is used, a larger bin helps create a buffer for surges in granulator discharge rates.
Second, the beside-the-press granulator can reduce material loss due to inefficient material handling and machine cleanout. While central granulators have their place in many operations, BTP granulators have the benefit of direct throughput from the press, eliminating the need for excessive manual handling and cleanouts that can result in material waste. BTPs can be fed by hand or robot at the press.
Third, regrind materials can be fed directly from the granulator takeoff back into the primary process. This might include an equipment configuration with an evacuation system that sends regrind material back into the process line. It can be completely automated, eliminating manual processes and the resulting material losses and leakage.
Granulating scrap beside the press, instead of at a central location, minimizes handling, storage and possible contamination.
Beside-the-press granulators eliminate the need to collect, store, and process batches in a central granulator workflow. For example, a typical central granulator process might include dedicated personnel responsible for:
• Collecting materials to regrind;
• Depositing them in gaylords;
• Using a forklift to move the gaylords to a dedicated central granulation room;
• Regrinding the materials there using a central granulator;
• Depositing the ground materials back into gaylords; and
• Forklifting ground materials back into the production facility for reuse, or transporting them back to storage (onsite or offsite)
Obviously, all these manual tasks—done repeatedly—present a layer of complexity and increase labor costs. For operations where a beside-the-press granulator is the best fit, the benefits may include an immediate decrease in operational costs without the constant need to handle and transport regrind materials.
In today’s competitive environment, square footage on the production floor comes at a premium. A BTP granulator is an ideal solution for maximizing your floor space.
With a beside-the-press granulator, you can increase production capacity. This gives you the ability to replace former storage space with potential additions to production floor space. The net effect is increased production capacity where material storage previously took place.
Also, you’ll benefit from less storage or material to be processed, as well as decreased storage of regrind material after processing.
With a BTP granulator, the frequency of machine cleanout is minimized because each unit is typically dedicated to one production line. With a central granulation process, the system may need to be cleaned out multiple times a day with material changes from multiple lines. Plus, newer well-designed BTP models can permit accelerated total machine cleanout due to increased accessibility to the cutting chamber. The potential benefit may make machine cleanout up to six times faster.
Also, today’s premium BTP models feature high-quality knives and screens that have increased longevity, reducing consumable parts and decreasing variable operating cost. It’s not uncommon for new granulators to run for well over a year with the original knives and screens and zero downtime. Generally, the knife and screen kits for each BTP granulator are selected for regrinding a specific type of material. This specificity results not only in greater performance but greater uptime and less maintenance.
Safety during servicing is important. Features such as rotor lock; safety interlocks to access the chamber; hopper and chamber lift assist; tipping prevention; and other key features are recommended with any granulator installation. Industry-leading companies use a variety of interlocks to ensure that service work can be done safely:
• Zero rotor-speed detection prevents users from accessing the cutting chamber until the rotor has stopped;
• Hopper lock automatically engages with manual disengagement;
• Rotor lock automatically engages with manual override;
• Chamber lock ensures that the upper chamber is locked via solenoid-activated interlock;
• Discharge-bin lock operates via solenoid-activated network.
Currently, the gold standard for granulator safety is ISO 12100 and Category 3 requirements. This requires that the equipment conforms to the principles of risk assessment and has two sets of redundant safety interlock circuits so that a single fault does not lead to the loss of the safety function. Safety-rated components and reliability are also part of these requirements.
The fewer tasks involved with unloading, cleaning, retooling knives or screens, or any other internal workings of a granulator, the safer your operation.
Plastic manufacturing operations with BTP size reduction will naturally reduce injury risks and increase safety overall by minimizing manual handling of material. Decreased maintenance of knives and screen components mentioned above is also a factor that keeps employees safe. Simply put, the fewer tasks involved with unloading, cleaning, retooling knives or screens, or any other internal workings of a granulator, the safer your operation.
Poor service on a granulator can result in poor-quality regrind with excessive dust and fines. So, accessibility to the cutting chamber, rotors and knives is extremely important. Knives must be kept sharp and clean for best results, and the cutting gap between rotating and stationary knives should be easy to set and maintain. Ease of cleaning is also important, particularly in short-run environments where the granulator must be thoroughly cleaned before moving on to the next material.
Finally, harmful high sound levels are another layer of safety risks every operation must consider as they look to decrease the liability of hearing loss of employees. Not surprisingly, most of the sound generated by a granulator occurs in the cutting chamber. But significant noise can be generated by the drive train as well. A full sound enclosure is designed for maximum noise suppression and will typically lower the decibel level outside the machine by 10% to 30%.
When determining the right beside-the-press granulator for your facility, look for sound-damping features that help make your operation quieter, safer, and more enjoyable for your employees.
ABOUT THE AUTHOR: Andre Adams is the senior product manager for size reduction and material handling at ACS Group. Prior to his current role, Adams spent 15 years as a lead mechanical engineer and product manager for Centrisys Corp. in the water/wastewater reclamation industry. At ACS, he has helped shape and develop strategies for plastics sustainability and circular-economy initiatives. He has worked extensively with key partners such as KW Plastics and Teel Plastics to construct modeling systems, case studies, and white papers to quantify net benefits and best practices that favorably impact profitability. Contact: 262-641-8600; aadams@acscorporate.com; cumberlandplastics.com
The impact of material loss is a key area every plastics manufacturer must address to help ensure profitability and minimize overhead. So, after noticing a considerable amount of material loss, the management team of Teel Plastics, an injection molder and extruder of pipe and tubing in Baraboo, Wis., started tracking and analyzing its regrinding process. Following a thorough review, the team concluded that its central granulator workflow needed to be revisited. The issues and challenges Teel identified included:
• 20,000 to 30,000 lb of regrind materials lost in the grinding process each year;
• A complex workflow that was both inefficient and labor-intensive;
• Manual tasks that required hand loading and handling 5-gal buckets of regrind materials, resulting in plenty of unsafe heavy lifting, bending and twisting by some employees;
• 224 pallets of regrind material taking up 3000 ft2 of valuable production floor space;
• Additional offsite storage of regrind materials was occasionally required, adding handling and transportation costs;
• Inability to meet company sustainability goals for reuse of materials.
“It was not a great process,” says Max Cummings, technical development engineer at Teel Plastics. “We did a value-stream map and found that there were so many moving parts and steps involved in moving regrind materials in and out of the central granulator room. We were touching the materials too frequently—unloading, collecting it into gaylords, forklifting gaylords, storing—so there were a lot of soft costs associated with the workflow. That’s when we started talking to the folks at Cumberland.”
Switching to beside-the-press granulating freed up floor space for production at Teel Plastics, saving about 1000 hr in labor and about $300,000/yr in material.
Looking to minimize the regrind touch points, Teel Plastics management consulted with Cumberland about its current challenges and the possibility of a beside-the-press (BTP) or beside-the-extrusion-line configuration. After an on-site analysis at its Baraboo pipe plant, Teel decided on a test of Cumberland BTP granulators on one of their smaller lines.
The new workflow would allow scrap to be taken directly from the end of the line as it was produced, reground and transported via an evacuation system to the front of the line where it is discharged to a gaylord positioned next to the extruder. As soon as the gaylord was full, it could easily be moved a mere 5 ft to start reusing the scrap right on the line. This immediately eliminated several labor- and time-intensive steps and allowed more scrap material to be reused, cutting down on overall process waste. The company then decided to reconfigure six more lines using a similar BTP workflow.
The next step in the company’s regrind workflow transformation involved eliminating steps and the complexity of the regrind process on the larger lines. Using larger Cumberland FX beside-the-press units equipped with evacuation systems, Teel Plastics was able to reuse regrind immediately within the process, eliminating the need for time-intensive manual steps and costly storage. It also cut down on lost material and cleanup time allowing more materials to be recaptured and used internally.
“Switching to the beside-the-press granulators and reconfiguring our workflow has allowed us to expand and grow without having to hire more people,” says Cummings. Other advantages of the new regrind workflow cited by Teel Plastics management include an increase in manufacturing floor space, freeing up nearly 3000 ft2 of production capacity. Added efficiencies also enabled an increase in the percentage of regrind used in some products, supporting company environmental initiatives.
Also, there was a dramatic decrease in maintenance, due to the Cumberland FX granulators’ long-lasting knife kits. “Every three months we perform a thorough check of belts, blades, safety sensors and more,” says Cummings. “We’ve had a couple of the Cumberland granulators in service for a year now and haven’t had to change the blades yet.”
With the move from a central granulator unit and a complex manual process to BTP granulators and a more efficient workflow with Cumberland FX Series equipment, Teel Plastics has seen tangible results in three key areas:
• Elimination of many manual steps;
• No need to collect, transport, and store regrind material to a central granulator room;
• A more automated workflow significantly reduced the need to manually handle regrind material;
• Offsite transportation and storage no longer needed.
• BTP granulators and collection equipment allow for regrind to be reused immediately on a dedicated line;
• No need for frequent work stoppage for collection and moving of regrind materials:
• Eliminating several layers of manual labor and overhead;
• Cleanout times reduced from 2 to 3 hr down to 30 min, due to easy access to FX Series granulators’ cutting chamber and bin;
• More total material capture and reduced waste to landfill.
• A substantial decrease in the need to handle regrind materials;
• Reduced fork-truck traffic and a less congested manufacturing space;
• Ensure safe access with zero-rotor-speed detection, as well as hopper, rotor, chamber and discharge-bin locks;
• Allows for two sets of redundant safety-interlock contacts, safety-rated components, and short-circuit protection (S12100 Cat 3 certified);
• Lower sound decibel levels—reduced by up to 30%--due to FX Series noise-suppression technology.
Almost all extrusion processes pass melt through wire-mesh screens on the way to the die to provide filtering and improved mixing.
Two recently developed technologies are said to make high-quality PET recycling more economical.
Whether you’re blow molding PET bottles or extruding APET sheet, you’ll produce amorphous scrap in the process. How you handle it will impact your production costs. Re-crystallizing it will help.
Sheet Extrusion Line © 2023 Gardner Business Media, Inc. Privacy Policy [Log On]