A 360-degree look at resin conveying systems: types, operation, economics, design, installation, components and controls.
This Knowledge Center provides an overview of resin moisture and the drying process, including information on the best drying practices for your manufacturing facility. Screw Extruder Machine
Everything you need to know about plastics compounding technology—from feeding solutions to application profiles and expert advice.
Combat the skilled labor shortage using this comprehensive resource to train your own plastics processing experts.
Deep dive into the basics of blending versus dosing, controls, maintenance, process integration and more.
This Knowledge Center provides an overview of the considerations needed to understand the purchase, operation, and maintenance of a process cooling system.
Learn about sustainable scrap reprocessing—this resource offers a deep dive into everything from granulator types and options, to service tips, videos and technical articles.
While price initiatives for PE and PVC were underway, resin prices had rollover potential for first two months of 2024, perhaps with the exception of PET.
Flat-to-downward trajectory for at least this month.
A mixed bag, though prices likely to be down if not flat for all this month.
Trajectory is generally flat-to-down for all commodity resins.
Flat-to-down trajectory underway for fourth quarter for commodity resins.
Generally, a bottoming-out appears to be the projected pricing trajectory.
Resin drying is a crucial, but often-misunderstood area. This collection includes details on why and what you need to dry, how to specify a dryer, and best practices.
Take a deep dive into all of the various aspects of part quoting to ensure you’ve got all the bases—as in costs—covered before preparing your customer’s quote for services.
In this collection of articles, two of the industry’s foremost authorities on screw design — Jim Frankand and Mark Spalding — offer their sage advice on screw design...what works, what doesn’t, and what to look for when things start going wrong.
In this collection, which is part one of a series representing some of John’s finest work, we present you with five articles that we think you will refer to time and again as you look to solve problems, cut cycle times and improve the quality of the parts you mold.
Gifted with extraordinary technical know how and an authoritative yet plain English writing style, in this collection of articles Fattori offers his insights on a variety of molding-related topics that are bound to make your days on the production floor go a little bit better.
In this three-part collection, veteran molder and moldmaker Jim Fattori brings to bear his 40+ years of on-the-job experience and provides molders his “from the trenches” perspective on on the why, where and how of venting injection molds. Take the trial-and-error out of the molding venting process.
Mike Sepe has authored more than 25 ANTEC papers and more than 250 articles illustrating the importance of this interdisciplanary approach. In this collection, we present some of his best work during the years he has been contributing for Plastics Technology Magazine.
In this collection of content, we provide expert advice on welding from some of the leading authorities in the field, with tips on such matters as controls, as well as insights on how to solve common problems in welding.
Mold maintenance is critical, and with this collection of content we’ve bundled some of the very best advice we’ve published on repairing, maintaining, evaluating and even hanging molds on injection molding machines.
Thousands of people visit our Supplier Guide every day to source equipment and materials. Get in front of them with a free company profile.
Medical-component specialist LightningCath has carved a niche meeting the needs of small to medium-sized entrepreneurs with complex catheter designs … quickly.
Plastics Technology is closing in on its 70th anniversary. Here are some of Editorial Director Jim Callari’s observations to commemorate the occasion.
As with everything else, there are pros and cons, but more of the former. They provide processors higher rates while decreasing the temperature of the extrudate while enabling downgauging.
The drop in plastics activity appears to be driven by a return to accelerated contraction for three closely connected components — new orders, production and backlog.
Beginning the first of this year, 12 states are following EPA bans on potentially damaging cooling fluids. Chiller suppliers have adjusted equipment designs to accommodate the new regulations. Here’s what all this means to processors.
Pairing external big picture training with internal job-specific instruction can help your process technicians meet quality expectations as well as production targets.
In less than a decade in injection molding, US Merchants has acquired hundreds of machines spread across facilities in California, Texas, Virginia and Arizona, with even more growth coming.
Demand for bioresins is growing in molded goods, particularly as a sustainability play to replace fossil-fuel based materials, but these materials are not a drop-in replacement for traditional materials. Molds and hot runners need to be optimized for these materials.
There are many things to consider, and paying attention to the details can help avoid machine downtime and higher maintenance costs — and keep the customer happy.
Flat-to-downward trajectory for at least this month.
Topping five other entries in voting by fellow molders, the Ultradent team talks about their Hot Shots sweep.
Serendipitous Learning Opportunities at PTXPO Underscore the Value of Being Present.
Introduced by Zeiger and Spark Industries at the PTXPO, the nozzle is designed for maximum heat transfer and uniformity with a continuous taper for self cleaning.
Ultradent's entry of its Umbrella cheek retractor took home the awards for Technical Sophistication and Achievement in Economics and Efficiency at PTXPO.
technotrans says climate protection, energy efficiency and customization will be key discussion topics at PTXPO as it displays its protemp flow 6 ultrasonic eco and the teco cs 90t 9.1 TCUs.
Shibaura discusses the upcoming Plastics Technology Expo (PTXPO) March 28-30
Competition will invite participants to help reshape life cycle management in plastics.
Sign up to attend North America’s leading trade show for plastics.
Offerings range from recycled, biobased, biodegradable and monomaterial structures that enhance recyclability to additives that are more efficient, sustainable and safer to use.
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As self-imposed and government-issued sustainability mandates approach, injection molders reimagine their operations.
August 29-30 in Minneapolis all things injection molding and moldmaking will be happening at the Hyatt Regency — check out who’s speaking on what topics today.
Get your clicking finger in shape and sign up for all that we have in store for you in 2023.
Molding 2023 to take place Aug. 29-30 in Minnesota; Extrusion 2023 slated for Oct. 10-12 in Indiana.
Key technologies — such as multicolor molding, film molding and PUR overmolding for both exterior and interior applications — are at the forefront of this transformation. Join this webinar to explore the vast potential of eMobility in molding large components — including those with fiber reinforcements — thereby driving the need for large injection molding cells with a clamping force of up to 11,000 tons. You will also gain insight into Engel's innovative two-stage process, a solution for future recycling processes. This webinar will provide an in-depth overview of challenging applications, production concepts and best practices, including: BMW iX front panel production cell Smart rear panels concept based on IMD and 2C molding Sustainability concepts based on two-stage process Large tonnage equipment for battery moldings
In today's manufacturing environment, robust processes that meet strict industry and regulatory standards are essential. With the advent of servo-driven ultrasonic welding technology, enhancing product quality and maintaining consistency has become remarkably effortless. Discover the fundamentals of ultrasonic welding, delve into vital components within these systems, explore how servo-driven ultrasonic welding enhances weld quality via advanced control features and gain insights into optimizing your assemblies for welding in these high-performing machines. Join Dukane to unlock the potential of ultrasonic welding in modern manufacturing for plastic devices and components. Agenda: Fundamentals of ultrasonic welding Key components in an ultrasonic welding system Using servo-driven ultrasonic systems to control your welding process Designing your parts and components for servo-controlled ultrasonic welding
This webinar will help you make informed decisions to confirm the equipment access stairs in your facility are OSHA compliant and meet the highest standards of safety and ergonomics. Agenda: Identifying opportunities to increase safety in the work place Utilizing space saving stairways Ensuring code compliance for equipment access
4.0, EUROMAP, OPC, OLE, QC, DSN, SQL, VNC, MES, ERP, FTP, CMS, SPI — are you confused by all buzzwords being tossed around in the plastics industry? Not convinced the data collection is necessary? Or are you unsure of how it could be implemented and improve your molding processes? Wittmann has been on the cutting edge of the data collection push for nearly 20 years. In this webinar, take a step back from the idea of the manufacturing facility of the future and discuss what you can do today to improve your process. Using readily-available technology, Wittmann can help reduce downtime, limit scrap and wasted material, and predict required maintenance. Let the experts at Wittmann help you understand: what data can be collected, what that data can be used for, what systems are used, and how to implement them. Agenda: Demystifying the terminology Tracking the material flow and lot information through the material handling system The data available from various auxiliary equipment, such as: dryers, blenders, mold temperature controls and robots Automating the process through changes in the data collected at the machines during production Adding visualization to increase productivity
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The global plastics industry has been navigating through what is arguably the most volatile period in decades. Unprecedented amounts of new production capacity are scheduled to start in North America, Europe, and China in the near term and compete for demand during a period of economic challenges. How will trade flows shift? Will this lead to regional cost disparities and rationalization? Energy transition and sustainability targets continue transforming the plastics market and increasing the competitive landscape. As the market evolves, what impact will new technology, policy, regulation, the growing role of chemicals versus fuel and other factors have on industry restructuring and business models? At GPS 2024, leading global experts will come together to discuss pivotal impacts and initiatives shaping the plastics industry. Join us and participants from across the globe to gain the latest insight and deep analysis as you connect with your peers and industry professionals. This year’s conference will explore the theme Disruptive Global Dynamics Reshaping Plastics and include a full day workshop focused on the Global Plastics Business and Plastics Transition to Circularity, 1.5 days of expert content and numerous networking functions.
Every three years, leaders from almost every major industry gather at NPE to advance their businesses through innovations in plastics. The largest plastics trade show in the Americas, NPE offers six technology zones, keynote speakers, workshops and opportunities to build partnerships.
The 3D Printing Workshop @ NPE2024 – The Plastics Show, is an immersive, half-day workshop focused on the emerging possibilities for part production via 3D printing and additive manufacturing. Presented by Additive Manufacturing Media, Plastics Technology and MoldMaking Technology, the 3D Printing Workshop will build upon a successful model first introduced at IMTS 2014. Attendees will benefit from a program focused on practical applications of 3D technologies related to plastics processing. This event will conclude with a 3D Printing Industry Reception sponsored by Additive Manufacturing Media.
The Society Plastics Engineers (SPE) Extrusion Division and the SPE Eastern New England Section will co-host the Screw Design Conference-Topcon on June 19-20, 2024 @ UMass Lowell in Lowell, MA. This highly technical program will focus upon screw design principles for single and twin screw extruders with wide ranging topics relating to screw designs for feeding, melting, mixing, venting and pumping plastics products and parts. Areas of focus will include screw designs for melt temperature and gel management, gel minimization, bioplastics, recycled materials and foaming. In addition to the technical sessions, a tour of the UMass Lowel Plastics Processing Laboratories will be integrated into Day 2 of the event. This program is not just for screw designers, but to help anyone responsible for any type of extrusion operation to evaluate existing extrusion equipment; and also to prepare for future projects. Price to attend: Less than $1000! Registrations will be accepted in early 2024. Call for papers – To be considered to give a presentation, please submit a talk title and abstract on or before December 15 to: Technical Chair: Eldridge M. Mount III, e-mail emmount@msn.com Corporate sponsorships - A limited # of corporate sponsorships (15) are available on a 1st come basis. Included is a 6’ tabletop display (must fit on table), denotation in all promotional activities, and 1 no charge registration. To become a sponsor contact: Charlie Martin, Leistritz Extrusion, e-mail cmartin@leistritz-extrusion.com, cell 973-650 3137 General information: A reception on Day 1 and a tabletop display area will allow the attendees to meet and discuss state-of-the-art screw technologies with industry experts. The SPE Extrusion Division will issue a “Screw Design Certificate” to all participants who have attended the program. Students are encouraged to attend and will receive a discounted rate. For additional information contact: Program Chair: Karen Xiao, Macro Engineering, KXiao@macroeng.com
Debuting in 2010, the Parts Cleaning Conference is the leading and most trusted manufacturing and industrial parts cleaning forum focused solely on delivering quality technical information in the specialized field of machined parts cleansing. Providing guidance and training to understand the recognized sets of standards for industrial cleaning, every year the Conference showcases industry experts who present educational sessions on the latest and most pressing topics affecting manufacturing facilities today. Discover all that the 2022 Parts Cleaning Conference has to offer!
Presented by Additive Manufacturing Media, Plastics Technology and MoldMaking Technology, the 3D Printing Workshop at IMTS 2024 is a chance for job shops to learn the emerging possibilities for part production via 3D printing and additive manufacturing. First introduced at IMTS 2014, this workshop has helped hundreds of manufacturing professionals expand their additive capabilities.
For many compounding operations, material is fed to the extruder at the feed throat. This is the case when feeding a single polymer or a blend of polymers mixed with solid additives. Some ingredients, however, present a challenge in feeding. Here’s how to solve to them.
In the previous three articles, we discussed the configurability of the twin-screw extruder. Starting with the barrel sections, we’ve discussed how we can assemble the extruder barrel with the functionality that is required for the compounding process. Then we looked at feeding of raw materials through the feed throat and melting the polymers.
For many compounding operations, all the raw materials can be fed to the extruder at the feed throat. This is true when feeding a single polymer or a blend of polymers to be mixed with some solid additives (such as pigments or low levels of fillers) and pelletized. Some ingredients, however, present a challenge in feeding.
Here, we discuss some raw materials that present difficulties when fed to the feed throat. Additives are raw materials that improve or modify the properties of the polymers. Some of these ingredients can create a blockage in the feed throat or prevent the polymer from melting fully, while others can be damaged by the high forces involved during the melting process.
We will look at how to feed these materials directly into the molten polymer for optimum process effectiveness and product performance.
The first materials we will discuss are fibers. Feeding fiber into the feed throat and requiring them to pass through the melting zone can damage the fibers and diminish the property enhancements for which they are being added to the polymer.
Glass, carbon or mineral fibers are commonly added to plastics to enhance the strength of the compounded product. A key characteristic of fiber that enhances the material properties of a compound is the fiber aspect ratio. This is the ratio of the length of the fiber to its diameter.
Processing fibers through an extruder damages those fibers. In the last article, we discussed how the forces generated by the kneading blocks shear the polymer to generate heat. Shear forces are at a maximum during the phase transition from solid to melt. Fibers that are fed through the feed throat and subjected to these same forces would essentially be ground into a powder. The benefits derived from the fibers would be lost as a result of this level of damage.
FIG 1 A side feeder pushes solid materials into the molten polymer in the extruder. Photo Credit: CTI/Volker
To lessen the damage caused by processing, fibers are fed downstream after the polymer is molten via a side feeder.
A side feeder, also known as a side stuffer, consists of a hopper and a set of conveying screws. The side feeder (Fig. 1) pushes the solid materials into the molten polymer in the extruder. A combi-barrel section (Fig. 2) provides the connection for the side feeder and venting of any entrained air with the solids.
Fibers are starve-fed into the side feeder using a standard material feeder in the same manner as material is fed to the extruder feed throat. The fibers are conveyed to the extruder and stuffed directly into the molten polymer in the extruder.
Feeding fiber through a side feeder avoids the shear forces generated during melting. The polymer is melted first and then the fibers are introduced and incorporated after the polymer is molten. The shear forces in an extruder are highest when the polymer changes from a solid to a melt. Fibers enter the extruder directly into the polymer melt and can then be gently incorporated, minimizing attrition.
FIG 2 A combination barrel section connects the side feeder with vents for the entrapped air within the solids. Photo Credit: CTI/Volker
The unit operations involved with side feeding and incorporation of fibers that have to be considered are feeding and mixing. The side feeder connects to the extruder at the combi-barrel. The screw configuration through the combi-barrel utilizes screw elements similar to those used in the feed throat — long lead conveying elements. These conveying elements should have the standard conveying element profile.
The conveying elements should be placed preferably beginning with one screw diameter or more upstream of the figure eight opening in the side of the combi-barrel and continue into the adjacent, closed barrel section downstream. At this point, the pitch of the screw element can tighten up as needed based on the available space for the overall screw design as shown in Fig. 3.
FIG 3 Screw configuration for feeding fibers. Illustration Credit: K. Russell
In general, I do not recommend “SK” type feed elements in this section. The undercut that is beneficial during the feeding of dry, solid ingredients is not wiped the way the rest of the flight is. If you recall, the standard conveying element is self-wiped. The flight from the element on one shaft wipes the flight of the corresponding element on the adjacent shaft. When a feed element is used in a section of the extruder that contains molten polymer, the molten polymer can accumulate in the undercut region. Because there is no mechanism to remove this accumulated polymer, the material can burn creating char that results in gels and black specks.
Once the material is conveyed into the closed barrel section after the side feeder, mixing elements are needed to incorporate the fibers. Gentle mixing is key to minimize any attrition of the fibers. Narrow disc kneading blocks can gently mix the fibers into the molten polymer. Narrow disc kneading blocks provide more distributive mixing compared to wider discs. We will discuss this in more detail in the next article.
A series of forward, narrow disc kneading elements can distribute and incorporate the fibers throughout the polymer. These kneading blocks should immediately be followed by a neutral (90-degree) kneading block. The 90-degree kneading block creates a minor backup of material to ensure the fibers are fully integrated. Some screw designs use only forward conveying kneading blocks to gently mix the fibers, however, this can result in poor incorporation as the fibers may not be fully whetted.
Once the material is conveyed into the closed barrel section after the side feeder, mixing elements are needed to incorporate the fibers.
As the concentration of fibers increases, a reverse pumping kneading block may also be needed to ensure the fibers are fully incorporated. The design of the mixing section for fibers requires attention to balance. The length of the mixing section and whether to use reverse kneading blocks must be balanced against the potential for damage to the fibers. The more work the screw imparts to the material, the greater the potential of fiber attrition.
At the same time, holding back material in the mixing zone by using neutral or reverse conveying kneading blocks creates a gentler mixing action as the amount of material being impacted in that area of the screw is greater. An empty mixing section whips and beats the material more forcefully while a full mixing section cushions the material to some extent.
Another group of materials that require downstream feeding are “low melters.” These are additives with a melting point significantly below that of the polymer. Low molecular weight waxes and fatty acid slip agents are examples of low melting additives. The melting point ranges for three common slip agents used in polyethylene films are shown in the table below. Compare these values with melting points of the polymer, for example, 122– 135°C for PE, and the difference in melt points can be problematic.
In addition, these low melting additives melt quickly with minimal shear, becoming a liquid with very low viscosity comparable to water.
Polymers, on the other hand, require significant mechanical energy in addition to heat and melt more slowly across the entire melting section of the screw. The presence of low melting additives interferes with the melting of the polymers. By their very nature, low melters are lubricants. As a result, the polymer slips through the melting section and may not fully melt. Small pieces of polymer can pass through the melting section as solids, resulting in poor quality of the final compound.
Feeding the low melters downstream enables the polymer to be fully molten before introducing these components. The additives are fed through the side feeder and quickly melted. They are then easily incorporated into the polymer stream.
Figure 4 shows a sketch of a generic mixing section. A key point is the use of reverse pumping kneading blocks to provide increased shear and back-mixing to ensure complete incorporation.
FIG 4 In this generic mixing section, reverse pumping kneading blocks are used to provide increased shear and back-mixing to ensure complete incorporation.Illustration Credit: K. Russell
The final group of additives that we will discuss today are in liquid form. Liquids can be pumped to the extruder and injected directly into the melt. As with low melting additives, liquids are added after the polymer is fully molten. An injection port can be drilled and tapped into a plug for an open barrel or into a separate 1-diameter long injection plate.
The injector consists of a threaded shaft with the same dimensions and threading as used for a pressure transducer or thermocouple. The simplest design is a hollow shaft through which the liquid is pumped. The liquid pressure must be greater than the polymer pressure directly beneath the injector or the polymer can back up into the injector.
For this type of injector, medium pitch conveying elements are best used at the point of injection to ensure the pressure is fairly low while minimizing the potential for pooling of the liquid in the screw root. Injecting directly over mixing elements is preferred but may be difficult depending on the capability of the pump.
A sketch showing a liquid injection set up is presented in Fig. 5. The liquid is pumped through a flow gauge and into the injector. The injector shown here is spring loaded. The pressure generated by the pump must be sufficient to raise the internal plunger opening the outlet of the injector. This arrangement prevents polymer from backing up into the injector by ensuring the liquid pressure exceeds the polymer pressure.
FIG 5 Liquid injection units consists of a threaded shaft with the same dimensions and threading as used for a pressure transducer or thermocouple. Illustration Credit: K. Russell
Once the liquid is injected into the polymer, narrow disc kneading blocks followed by a reverse kneading block or reverse conveying element serve to fully incorporate the liquid into the polymer.
We started this series discussing how the barrel can be assembled and modified to meet the requirements of our process. We’ve now spent three articles discussing how materials are fed to the extruder and melted. In our next discussion, we will look at mixing in a twin screw, the different types of mixing and how the elements function to affect the materials being mixed.
ABOUT THE AUTHOR: Kenneth W. Russell has more than 35 years’ experience working with polymer processing and resin companies. He has expertise in polyolefin polymerization, polymer compounding, reactive extrusion, and film and sheet extrusion. In 2014, he started Optimized Compounds LLC, providing consulting services in reactive extrusion, polymer compounding, product development, process optimization and scale-up with clients worldwide. In 2021, he joined GEM Plastics, a manufacturer of HDPE sheet, providing process engineering, operator and technician training, and materials expertise. Contact: kwrcompounding@gmail.com.
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Pvc Twin Screw Extruder Plastics Technology covers technical and business Information for Plastics Processors in Injection Molding, Extrusion, Blow Molding, Plastic Additives, Compounding, Plastic Materials, and Resin Pricing. Learn More