Does Low Constant Pressure Injection Molding Work?

By Jan H. Schut

It could be the most unusual new development in injection molding in the past 20 years, developed by household products giant Procter & Gamble Co., Cincinnati, OH (us.pg.com). According to P&G patents, the technology consists of retrofitable controls and software for aluminum injection molds with pressure sensors and special cooling, which P&G claims increase productivity more than 50% on existing injection molding machines. P&G set up a subsidiary, Imflux Inc. (imflux.com), in May 2013 in Hamilton, OH, to develop and build the retrofits and aluminum molds and requires packaging suppliers to use them if they want to mold for P&G.

Productivity gains are in material savings, not faster cycle time. Imflux U.S. Pat. Applic. # 20160096303 says its proprietary control software and in-mold sensors “deliver a 20-25% average throughput benefit” on existing presses and tools. Using aluminum molds increases throughput another 20-25% because of aluminum’s high thermal conductivity. Imflux patents describe molds made of aluminum alloys like QC-10 from Arconic Inc., formerly part of Alcoa (www.arconic.com), which are 4.5 times more thermally conductive than tool steel (92.2 BTU/ft/hr/ft sq/F for QC-10 vs. 20.2 for P20 tool steel).

Cycle time for Imflux low pressure molding is reportedly roughly the same as for high pressure injection molding, but divided very differently. Where conventional high pressure injection molding spends about 10% of cycle time filling, 50% packing, and 40% cooling, Imflux technology spends 90% of cycle time filling, only 10% cooling (U.S. Pat. # 882829), and little or no time on pack and hold. P&G touted the Imflux technology loudly four years ago when it was introduced, but has said next to nothing about it since it went commercial.

Imflux says its low constant pressure injection molding with aluminum molds

increases throughput by more than 50% on the same size or smaller press
uses 25% less resin than conventional molding because of thinner walls
reduces cold runner volume by 50% (and doesn’t need hot runners)
can mold non-traditional part designs, not previously thought possible
can substitute lower cost materials in the same mold with better surface quality
uses melt temperatures below resin spec for new co-injection possibilities

THE IMFLUX BACK STORY

Imflux came out of an unusual 10-year period of outside collaboration and growth at P&G under high-profile CEO Alan George “A.G.” Lafley, from 2000 to 2010. Lafley, who has a Harvard M.B.A., brought Harvard-trained innovation consultants into P&G, proclaimed P&G “an innovation factory,” offered “innovation college” courses, and set up a FutureWorks division to incubate new technology. Imflux president and CEO, Nathan Estruth, and V.P. of Customer Operations, Jared Kline, both came out of P&G’s FutureWorks division.

P&G claims Imflux invented its low, constant pressure molding technology, but that’s not strictly true. It’s based on technology invented in the 1990s by Milko Guergov, president and founder of Intellimold/MGV Enterprises Inc., Ann Arbor, MI, and acquired by P&G around 2010. By 2012 P&G had registered the Intellimold trademark and process in Imflux’s name, but never marketed it as Intellimold. After P&G acquired Intellimold’s intellectual property, Guergov consulted with P&G to adapt his process to thin-wall packaging. Guergov’s name, spelled “Gergov” by P&G, is on several Imflux patents (U.S. Pat. # 8980146 and # 9481119) along with P&G inventors.

Guergov had previously sold his Intellimold patents and process in 2000 to Textron Automotive Co., which Guergov says used it commercially to injection mold parts ranging in size from small components to whole bumper fascia. The patents traveled a lot after that. Guergov’s U.S. Pat. # 6019918, for example, on “Gas-assisted injection molding with controlled internal melt pressure” was assigned in February 2000 to Guergov, then in May 2000 to Textron, then back to Guergov’s M&C Advanced Processes Inc. in December 2001 before Textron’s automotive trim division was acquired by Collins & Aikman Corp. in January 2002.

The patent was then assigned back to Textron in 2003, to Collins & Aikman in February 2005, and back to Guergov’s MGV Enterprises LLC in April 2005 ahead of Collins & Aikman’s Chapter 11 bankruptcy in May. By 2007, Collins and Aikman had gone out of business, and by 2008, Guergov had let Patent # 6019918 lapse by failing to pay the annual maintenance fee. By 2011, however, the patent had bounced back and belonged to P&G, which assigned it to Imflux in 2014.

P&G CEO Lafley, meantime, had retired in 2010, but was called back by P&G’s board for two more years as CEO, starting in May 2013, just as Imflux opened for business. In Lafley’s second stint as CEO he focused not on innovation but on productivity, which also suited Imflux. In October 2013, P&G CFO Jon Moeller told an analyst conference call that Imflux would save the company $150 million/year in material cost and $50 million/year in capital cost. At the same time “Advertising Age” indirectly quoted P&G’s recently replaced CEO Robert McDonald saying Imflux would save P&G a billion dollars a year by “using less plastic and different raw materials.”

In 2013 P&G’s Imflux got a 60% eight-year Ohio tax credit, reportedly worth about $2.6 million from the Ohio State Development Services Agency for investing $50 million in Imflux over the next eight years and creating 221 new jobs by December 31, 2016. Imflux, however, missed the job creation deadline. A photo of “The Imflux Team” on its website in June 2016 showed only around 70 employees. On December 20, 2016, Imflux’s CFO filed for a two-year extension to December 31, 2018. “The Imflux Team” photo on the company’s website in June 2017 shows around 122 employees, so jobs are growing, but more slowly than expected.

Imflux team

Imflux missed the deadline for an Ohio tax credit for creating 221 new jobs by Dec. 31, 2016 and got a two-year extension. “The Imflux Team” photo on its website in June 2016 showed around 70 employees and a year later only around 122, so jobs are growing more slowly than expected.

By 2017, Imflux’s website says its “current global operation (has) hundreds of installs across three continents.” The installations are presumably at P&G packaging suppliers. Two P&G subsidiaries that do their own injection molding, Braun GmbH and Gillette, may also use Imflux technology for thin wall molding because R&D employees of both Braun in Germany and Gillette in the U.K. are named on some Imflux patents.

Imflux also offers retrofits to outside customers in non-competing areas like medical and automotive and gives seminars in Hamilton on the technology – all under non-disclosure agreements. No outside users have been announced. P&G senior manager of global company communications, Jeff LeRoy, says Imflux customers are confidential and that which P&G brands use Imflux technology is considered proprietary.

HOW DOES IMFLUX LOW PRESSURE MOLDING WORK?

How did P&G convert the not-very-successful 20-year-old Intellimold process into a viable molding process for thin-walled packaging? Intellimold patents describe pressurizing molds with about 200 psi of shop air to control mold filling at constant low pressure. Imflux patents (U.S. Pat. # 8828291 and 9272452) describe molding at low constant pressure of 3000-6000 psi, which is 5-10 times lower than conventional injection pressures of 15,000-30,000 psi. What Intellimold and Imflux appear to have in common is control of mold filling based on maintaining constant pressure in the mold, not on achieving high injection speed.

Imflux’s patented control technology (U.S. Pat. #8980146 and #9321206) claims to alter injection pressure if plastic viscosity changes, so multiple cavities can be filled without short shots or flash. Imflux U.S. Patents # 9289933 and # 9481119 describe a “fluid pressure regulating valve and pressure relief valve” as part of this pressure control, while U.S. Pat. #8911228 describes a “non-naturally balanced feed system” for multi-cavity injection molds with different runner lengths.

The high thermal conductivity of aluminum molds combined with low molding pressure apparently allows co-injection with “more control over the relative velocities of the materials being introduced,” says Imflux patent application WO # 2013126667. The application describes flowing a very thin (0.1 mm) surface layer of a high strength polymer like EVOH or PP together with a layer of an environmentally friendly polymer like PLA, starch and/or postconsumer recycled plastic and achieving overall wall thickness of less than 0.5 mm.

US08591219

Aluminum molds often don’t have cooling lines. Imflux U.S. patent # 8591219, however, describes aluminum molds with fixed mold plates through which coolant flows. Coolant then goes through a condenser and is sprayed onto an upper mold surface.

Another Imflux patent describes a “simplified evaporative cooling system” (U.S. Pat. # 8591219) with cooling lines in a support plate and projections that allow mold cavities to snap in. U.S. Pat. Applic. # 20150064303 describes “simplified cooling with exotic cooling fluids” in channels in the mold support plate for high output injection molding of consumer products. Other patents describe using “hazardous, dangerous or expensive coolants.”

Imflux low pressure molding also apparently allows higher length/thickness ratios for thin wall molding. U.S. Pat. Applic. # 20130221575 on “Method for Operating a High Productivity Injection Molding Machine” shows low pressure molding of parts with up to 240 L/T vs. 100-200 L/T for high-pressure, conventional injection molding.

US20130221575

In U.S. Pat. Applic. # 20130221575, Figures 5A-5D show a cavity filled by conventional variable pressure injection molding. Figures 6A-6D show cross sections of a thin-wall injection mold cavity filled by Imflux’s constant pressure “high productivity” injection molding.

But analyzing the patents is all guesswork. Imflux technology remains a closely held secret known to dozens of major packaging companies and probably hundreds of processors under non-disclosure. Is it fully commercial? Is it working as well as P&G expected? Does it work with some polymers and not others? Is any company using it voluntarily or is it installed only at P&G subsidiaries and suppliers? Why hasn’t P&G presented actual production data?

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In case you missed it at ANTEC 2017

By Jon Evans

Medical polymers

Several advanced medical polymers were showcased in the technical sessions at ANTEC 2017. Suneel Bandi from EVONIK gave an overview of the company’s range of high-performance polyamides. These include flexible polyamides, bio-based polyamides and transparent polyamides for use in catheters, balloons, surgical instrumentation and drug delivery devices. Tony Walder from Lubrizol introduced its new class of non-softening thermoplastic polyurethanes (TPUs). These possess all the benefits of conventional TPUs, including low temperature flexibility, excellent abrasion resistance, high tensile strength and good processing characteristics, but don’t soften in the body.

Trachea Tube

Cheryl Weckle from Trinseo unveiled several new polycarbonate grades that can tolerate multiple cleanings using aggressive disinfectants, which are required for preventing hospital-acquired infections (HAIs). According to Weckle, these grades boast a superior combination of toughness, easy processing, color stability and durability. Foster Corporation is taking a different approach to tackling HAIs, by developing silver-based antimicrobial additives that can be incorporated into polymer melts. Lawrence Acquarulo, founder and CEO of the company, spoke about the effectiveness and efficiency of this additive when added to polycarbonate, TPU and acrylonitrile butadiene styrene (ABS).

Many plastic medical devices are very small or possess very small features that require special fabrication processes, such as micro molding and 3D printing. Alex Maroon from MTD Micro Molding spoke about the challenges of micro molding bioadsorbable polymers, which require a much more extensive and specialized approach than conventional thermoplastics. Roger Narayan, professor in the joint department of biomedical engineering at the University of North Carolina and North Carolina State University, described using a 3D printing process called two photon polymerization to fabricate features less than 1µm in size, which could be useful for medical devices.

Additive manufacturing

Also known as additive manufacturing, 3D printing has proved to be an ideal process for producing complex parts from plastic. This is especially the case for a form of 3D printing known as fused filament fabrication (FFF), in which plastic is printed as a thin, molten filament. But 3D printing is not without its difficulties, because the process can have over 100 unique variables and settings, all of which can affect the properties of the printed component.

Several of the presentations at ANTEC 2017 described efforts to understand the effects of these variables and settings. Steven Kreuzer from Exponent presented an empirical method utilizing a statistical design of experimental technique and standardized mechanical testing that can expose the trends and variable interactions in 3D printing. Omar Ahmed Mohammed from Swinburne University of Technology in Australia described his study into the effect of operating conditions on the mechanical properties of parts printed by FFF from polycarbonate/ABS, especially on their creep deformation behavior. This allowed him to determine the best process parameters to use for practical purposes.

New device

Other speakers presented their work on novel plastic materials for 3D printing. Joamin Gonzalez-Gutierrez from Montanuniversität Leoben in Austria spoke about developing a magnetic plastic material for 3D printing, based on incorporating strontium ferrite powder into the plastic filament, and the effect that different concentrations of the powder had on the plastic’s mechanical and printing properties. Martin Spoerk, also from Montanuniversität Leoben, spoke about incorporating glass spheres into polypropylene, which led to a reduction in shrinkage and an increase in the crystallization temperature.

Bioplastics

One of the most popular current plastics for 3D printing is the bioplastic polylactic acid (PLA), which was the subject of numerous presentations at ANTEC 2017. Several speakers described their efforts to modify PLA’s physical properties by creating blends with other plastic materials or incorporating additives. Svenja Göttermann at the Institut für Kunststofftechnik in Germany gave a presentation on her work looking at the effect of adding various different chemical modifiers to PLA, in order to induce crosslinking, chain extension or grafting by means of reactive extrusion on a twin-screw extruder. She achieved the best results with organic peroxide, which improved the melt strength and crystallization rate and led to foams with a closed-cell structure and low density. Margaret Sobkowicz at the University of Massachusetts, Lowell, described developing a blend of PLA and polyamide for use with a novel, high-speed twin-screw extrusion process.

lubricant eye drops

David Grewell from Iowa State University spoke about his work on welding PLA, using ultrasonic welding for rigid PLA samples and impulse welding for PLA films. For ultrasonic welding, weld distance and velocity had the greatest effect on weld strength, while for impulse welding heating time and temperature had the greatest effect.

Another biomaterial that received much attention at ANTEC 2017 was cellulose. Kim Nelson from American Process, which offers five different varieties of nanocellulose products, revealed how this natural nanomaterial can increase the strength of various materials, including conventional and biodegradable plastics, polyurethane foams and cement. This can help in the development of lighter plastic components, as required by industries such as aerospace and automotive.

Automotive

Ways to lighten the materials used in vehicles was the subject of many other presentations at ANTEC 2017. Omar Faruk from the University of Toronto in Canada reported the development of an automotive oil pan made from a material comprising 20% recycled carbon fiber and 80% recycled polyamide, which was 15% lighter than a conventional oil pan. Matthew Thompson from Advanced Composites spoke about evaluating the effect of several other options for reducing the weight of injected-molded parts, including composite density reduction, wall thickness reduction and foaming.

car lighting switch

Lightweighting can also be achieved by simply replacing metal components with plastic versions, and Luigi Alzati from IMERYS Graphite & Carbon spoke about using graphite-containing plastics as potential replacements for metal heat sinks in vehicles. The company has tested several commercially-available graphite grades in polyolefin plastics and found that that crystallinity, average particle size and aspect ratio are the three main factors that promote thermal conductivity.

Still, plastic parts cannot replace all the metal components in vehicles, and so plastic and metal parts will need to be bonded together for the foreseeable future. The junction between plastic and metal parts is a site of high potential risk, however, providing a potential pathway for the ingress of water, air, and other materials that may adversely affect the plastic-to-metal bond. Andy Stecher from Plasmatreat provided details on its new, cost-efficient plasma sealing technology for obtaining a tight seal between metal and plastic components that is resistant to outside elements.

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Looking Forward to ANTEC 2017?

By Jon Evans

Materials

New material advances are leading to the development of novel polymers with a range of impressive properties. Last year, the US company Gelest reported the development of a silicone-based elastomer with unprecedented elongation and shape recovery abilities. The silica nanoparticle-reinforced material can be stretched almost 50 times its original length before breaking, allowing a 2-yard piece to stretch the length of a football field. Gelest envisions a wide range of applications for this elastomer in areas such as microfluidics, implantable medical devices, elasto-mechanical devices, diaphragms, and optical and electronic interconnects and devices.

More recently, Gelest unveiled its new SIVATE A610 activated amine functional silane, which improves adhesion, speeds reactivity and increases bond strength in packaging, polymer, micro-electronics and curing applications. Gelest is offering SIVATE A610 for use as a tie-layer between organic and inorganic substrates in multi-layer packaging, a coupling agent for high speed epoxy adhesive bonding, phenolic resins, polyurethanes and polyamides, and a primer for high-speed UV-acrylated urethane cure systems.

OCSiAl TUBALL CNTs.jpg

Luxembourg’s OCSiAl is offering its TUBALL brand of single-walled carbon nanotubes as an additive for enhancing the electrical and thermal conductivity as well as other physical and mechanical properties of plastic materials. For example, Euro Accent Saba, a manufacturer of waste treatment systems, has used the carbon nanotubes to produce anti-static fiberglass plastic tanks for storing and transporting oil waste.

Meanwhile, specialty coatings company Novatic has employed TUBALL carbon nanotubes to produce novel anti-static and static dissipative polyurethane coatings, which it recently launched. Adding just 0.01% by weight of carbon nanotubes produces polyurethane coatings with uniform and permanent conductivity, enhanced mechanical properties and higher corrosion resistance.

Testing

Developing polymers with a greater range of properties places more demands on the instruments required to test them. US company Thermo Fisher Scientific offers a range of analytical instruments specifically designed for testing polymers and production processes. These include: the HAAKE MARS rheometer platform, which combines dielectrical analysis with Rheo-Raman spectroscopy for investigating structural changes on the molecular level under shear or deformation; and the Process 11 parallel twin-screw extruder, a benchtop instrument designed to simulate and optimize production processes with as little as 20 grams of polymer per hour.

In addition, many of Thermo Fisher Scientific’s more general analytical instruments can also be applied to polymers. Examples include the Nicolet iS 50 Fourier transform-infrared spectrometer for determining chemical composition and the DXR2xi Raman imaging microscope for high-performance chemical imaging.

Fellow US company TA Instruments develops instruments for thermal analysis, rheology and microcalorimetry. These include the newly-launched SDT 650, a simultaneous differential scanning calorimeter/thermogravimetric analyzer able to measures changes in energy as a function of time and temperature while concurrently measuring sample weight changes. The company has also recently launched three new dilatometers – DIL 820, DIL 830 and ODP 860 – which can measure dimensional changes in a polymer specimen brought about by dynamic thermal events at a resolution of up to 1nm.

TA SDT 650 (002).jpg

Yet another US company, Testing Machines, focuses on developing instruments for measuring physical properties. These include a new coefficient of friction tester, the Model 32-76, which measures both static and kinetic coefficients of friction using the horizontal plane method. There are also new versions of its digital micrometer series, the 49-86 and the 49-87, for accurately testing the thickness of very thin materials, including plastic films and nonwovens.

Machines

Several manufacturers of extrusion machines are exhibiting at this year’s ANTEC, showcasing their latest technologies. Germany’s Reifenhäuser recently launched the latest generation of its Reicofil line for the production of spun-bond, melt-blown and composite nonwovens. Known as RF5, this new generation is faster, more productive and more energy efficient that the preceding RF4 generation, and can produce filaments that are 20% thinner. It also boasts the latest in digitalization technologies, allowing more intuitive operation, continuous process and quality monitoring, predictive maintenance and detection of anomalies.

US company ENTEK has developed a new co-rotating twin-screw extruder, the QC3-33MM, which is designed for small lots and incorporates many of the company’s Quick-Change, Quick-Clean and Quality Control features. These include self-aligning and keyed screw-gearbox couplings to facilitate fast and fool-proof screw installation, a lock and key feature on splined shafts to prevent screw timing errors, and a new extruder frame design that deflects dust and keeps the machine clean under the hood.

Coperion ANTEC 2017.jpg

Germany’s Coperion has also developed a new twin-screw extruder, the STS Mc11, which offers a range of new features. These include a manifold with coaxial solenoid valves, improved heat covers, quick-release clamps to facilitate easy replacement of the feed hopper and a die head specifically developed for masterbatch applications. Coperion also recently launched the UG 750W underwater pelletizer and a deflector elbow for material transport that can prevent the build-up of angel hair.

Meanwhile, US company Parkinson Technologies has developed a new slitter rewinder within its Dusenbery brand. The DC4 offers faster speed, higher capacity and easier thread-up, and boasts exceptional web handling accuracy by maintaining consistent web strain throughout the finished roll structure.

Software

Software plays an increasingly important role at every stage of the plastic production process, from design to simulation to production control to data analysis. As a wholly-owned subsidiary of Altair, many of US company solidThinking’s design tools are now available through Altair’s HyperWorks suite. The latest release of this suite came out in March and includes several new functionalities in areas such as model-based development, nonlinear structural analysis, modelling and meshing, and lightweight design and optimization.

Just a month earlier, solidThinking announced the release of the latest version of its Envision data analytics tool, which the company says offers a complete set of capabilities for industrial analytics and the ‘internet of things’. This allows companies to obtain data from multiple sources, combine and collate it, and then display it in the form of continuously-updated reports, dashboards and charts.

Taiwan’s CoreTech System (Moldex3D) offers a dedicated design module for its Moldex3D simulation tool for plastic injection molding. Known as eDesignSYNC, this module helps to accelerate the design and manufacturing process for both plastic parts and molds through greater simulation accuracy and efficiency. It includes functions such as Result Advisor, which can speed up problem detection by offering users a quick summary report of potential design problems, and Batch Run, which allows multiple designs to be analysed with different process settings at the same time.

Moldex3D.jpg

In March, the company issued the latest release of Moldex3D, Moldex3D R15.0, which offers enhanced performance, accuracy and efficiency to streamline simulation workflow and provide faster turnaround times. New features include runner meshing technology that better captures the intended geometric shape of the runner design and delivers more accurate predictions, and simulation capabilities for in-mold decoration and polyurethane chemical foaming processes.

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‘SSSP’ Technology Is Finally Commercial

By Jan H. Schut

Solid State Shear Pulverization, which chills a co-rotating twin-screw extruder below the softening temperature of plastic rather than allowing it to melt, is finally commercial after more than 20 years of R&D. Zzyzx Polymers LLC, Allentown, PA (www.zpolymers.com), started up in January 2015 reportedly using the first commercial SSSP technology, according to a paper originally submitted to the Society of Plastics Engineers ANTEC 2016 conference (www.4spe.org), but not actually given. The ANTEC paper on “Commercialization of Solid-State Shear Pulverization: a Novel Polymer Processing Technology,” by Philip Brunner (co-founder of Zzyzx), Mark Tapsak, and Mike Janse, says the process has been successfully scaled up to pilot plant size for the first time.

In the SSSP process the twin-screw barrel is chilled so that tri-lobe compounding screw elements crush the polymer in its rigid state, breaking molecular bonds instead of melting the polymer. Repeated crushing turns mixed, unwashed plastics like multilayer and metalized film waste, for example, into a pinkish powder, which can be remelted and have significantly higher properties than its component polymers.

SSSP research began in the former Soviet Union in the 1980s and was continued in the 1990s by Klementina Khait, and later John Torkelson, both professors at Northwestern University, Evanston, IL (www.northwestern.edu), and by professor Katsuyuki Wakabayashi at Bucknell University, Lewisburg, PA (www.bucknell.edu). Both university labs use 25-mm twin-screw extruders from Berstorff (www.kraussmaffeiberstorff.com) with barrels modified for cooling medium (anti-freeze) to roughly -7 °C at Northwestern and -12 °C at Bucknell. But high energy cost and a two-extruder process kept SSSP from being commercialized.

SSSP Figure 1

This schematic shows Solid State Shear Pulverization in a 70-mm twin-screw extruder barrel, which is first chilled to crush mixed plastic to powder, then heated to pelletize the powder. An SSSP-modified machine doing trials at Berstorff in 2003 shows ice on screws and barrels.

Brunner’s PhD dissertation and several subsequent patent applications (U.S. Pat. Applic. # 20150131399) under Torkelson were the basis for spinning the company from Northwestern in 2013 under the name NuGen Polymers LLC. Brunner’s dissertation on “Overcoming Sustainability and Energy Challenges in Polymer Science via Solid State Shear Pulverization” models energy and cost saving from combining SSSP twin-screw extrusion directly with pelletizing in one extruder. It reportedly would use a tenth as much energy as having two extruders: one to pulverize, the other to pelletize. On a lab scale SSSP used 1-10 kw·hrs of energy per kg of material, while the scaled up, in-line extruder uses 0.25-0.40 kw·hrs/kg, Brunner’s ANTEC paper says.

The ANTEC paper describes screw speeds of 200 rpm for a mixture of PE and HMWPE with throughputs over 180 kg/hr at an energy cost of 5-7 cents/kg on a 70-mm SSSP machine. The paper exaggerates that this cost is in line with conventional melt twin-screw extrusion technologies and the SSSP process is now as energy efficient as twin-screw melt compounding.. A 70-mm co-rotating twin-screw extruder for melt compounding would produce 300 kg/hr of masterbatch and 1500 kg/hr or more of engineering plastics. So even if energy cost is comparable, output of 180 kg/hour is low for the capital cost of the machine. The ANTEC paper also describes throughput of only 145 kg/hour for PCR laminated film and 100 kg/hour for waste film containing PVC.

SSSP Figure 2

Zzyzx Polymers’ full-scale SSSP extruder successfully recycled samples of (A) PE/HMWPE at 180 kg/hr for energy cost of 0.26 kw·hr/kg; (B) postconsumer laminated bags at 145 kg/hr for 0.35 kw·hr/kg; and (C) mixed film waste with PVC at 100 kg/hr for 0.40 kw·hr/kg.

Recent patent applications from Zzyzx (U.S. # 20150065616 and especially # 20150131399) describe cooling channels in the extruder shafts and elements as well as in the barrel.  Patent application # 20150131399 says that “systems and methods for controlling the temperature of a solid-state screw extruder may include providing an extrusion screw that incorporates one or more screw shaft channels. The shaft channels may be configured to conduct a flow of a heat conducting medium along a length of the shaft.” If channels are drilled in the shafts, that would weaken them and hurt throughput. But the patent application notes that “shaft channels may be incorporated into an exterior surface” of the shaft, which wouldn’t weaken anything.

NuGen Polymers got $150,000 National Science Foundation grant in 2013, through a Small Business Innovation Research Phase I grant (Award # 1248336). In 2014, under the Zzyzx name, the company was approved for a $150,000 loan from Ben Franklin Technology Partners of Northeastern Pennsylvania, but didn’t accept it. Instead, in 2015, Zzyzx was funded by another larger $737,640 National Science Foundation grant over two years through a Small Business Innovation Research Phase II grant (Award #1434826), plus another $203,000 from the NSF in supplements. That $940,640 of NSF support allowed Zzyzx to set up a 70-mm diameter SSSP twin-screw extruder for the first time.

This pilot scale machine became “a nine thousand lb calorimeter,” Brunner’s ANTEC paper explains, allowing them to measure and control key processing parameters including coolant flow rate, coolant temperature, and heat removal for the first time. The big surprise was that the scale-up was more successful than expected, says Zzyzx CEO Michael Janse. Unexpected efficiency meant that Zzyzx didn’t need to operate cold extrusion in the same extruder with melt extrusion, which involved an extremely steep thermal gradient for a single machine and limited throughput, Janse explains. The patent application for the one-extruder process (U.S. Pat. Applic. # 20150051339) was also somewhat awkwardly shared by Northwestern and Bucknell.

Another $150,000 grant in 2016 came from the Closed Loop Foundation, part of the Closed Loop Fund (www.closedloopfund.com) set up by a group of large consumer products companies to support plastic recycling. “It will help us purchase the equipment needed to scale up our technology for testing in a plastic processing facility,” Janse said in a statement. The Closed Loop grant was primarily sponsored by S.C. Johnson & Son Inc., Racine, WI (www.scjohnson.com), which was looking for a way to support postconsumer recycling of film including its Ziploc bags from municipal collection. The Allentown Economic Development Corp., Allentown, PA (www.allentownedc.com) also incubates Zzyzx in its Bridgeworks Enterprise Center.

SSSP Figure 3

Zzyzx CTO Mark Tapsak (left) and inventor Philip Brunner (right), in its incubator site in 2014. Thanks to a $940,640 of grants in 2015-2016, Zzyzx now has a 70-mm pilot line there. Another $150,000 grant this year could support the first customer installation.

Zzyzx is definitely the first commercialization of SSSP technology, but it’s not the first time that SSSP has been scaled up. Material Sciences Corp., Canton, MI (www.materialsciencescorp.com), supported R&D on an SSSP-modified, 65-mm Berstorff twin-screw extruder in 2003, according to Material Sciences’ 10-K filing Feb. 28, 2003. Reportedly the work was successfully completed at Northwestern and available for license with a patent assigned to Material Sciences Corp., which was interested to apply the powdered plastics to metal coating, but the technology wasn’t used at the time.

Currently Zzyzx is running trials for customers and trying to determine how its technology can best be used for closed loop recycling. Since the twin-screw machine is modular, Zzyzx could either license the technology to customers with a difficult waste stream, or toll recycle difficult waste for customers.

In 2016, Brunner left the company. This leaves no one at Zzyzx with PhD level experience with SSSP, which may hamper development but for now it’s too soon to tell.

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‘Exjection’ Molding Comes into Its Own

By Jan H. Schut

At least two commercial technologies combine extrusion with injection molding to fill molds with much lower pressure than conventional injection molding. One was recently introduced by Extrude to Fill LLC, Loveland, CO (www.extrudetofill.com), which melts plastic electrically without turning the screw (see blog September 13, 2016). The other was introduced nearly 10 years ago by IB Steiner, a plastics engineering firm in Spielberg, Austria (www.exjection.com), called Exjection, which uses a sliding mold cavity.

The two technologies are completely different. Extrude to Fill has an unusual extruder that works with conventional injection molds. Exjection has an unusual mold that works with conventional injection molding machines. The results, however, are very similar. Both technologies use less expensive, smaller barrels, lower clamp tonnage, and much less energy than equivalent conventional, high-pressure injection molding for substantially lower production cost. Exjection’s moving molds cost more than conventional injection molds, but overall production costs are 20-30% less, IB Steiner says.

But savings and efficiencies aren’t why first customers choose either one. Both were commercialized to mold parts that couldn’t be molded otherwise. IB Steiner’s Exjection (U.S. Pat. # 7910044) was originally developed for the aircraft industry to mold long thin parts for commercial planes with ribs, holes and other features out of PEI and PC to meet fire codes. But the compounds were too viscous for long flow paths, and molding with multiple nozzles would have left weak weld lines.

FILLING A PARTIALLY OPEN MOLD

The solution was a long partially-enclosed mold (up to 3 meters) with all functional details like screw bosses and snap-fit hooks contained in a nearly enclosed cavity. The cavity is filled through an open slit in the top as it slides past a fixed injection nozzle in the short upper mold. The upper mold has a heated supply zone (about 130 mm), followed by the nozzle, then a cooled calibration zone (about 260 mm). The sliding cavity also splits in half length-wise for undercuts and part ejection.

“A sword-shaped bar under both the supply and calibration zones on the fixed nozzle side of the mold partially seals the otherwise open cavity to retain injection pressure. The supply zone corresponds to an extrusion die, and the calibration zone to a calibration unit,” explains Gottfried Steiner, CEO and head of engineering at IB Steiner. By the time the mold cavity moves out from under the calibration zone into open air, the exposed plastic is hard.

Exjection

Exjection’s horizontal sliding cavity, with all the molded features on a part, slides under a short fixed upper mold with a heated supply zone, fixed nozzle, and cooled calibration zone. By the time the mold slides out into the open air, the surface of the plastic part is hard.

IB Steiner took three years to develop the concept with sister company Hybrid Composite Products GmbH, also in Spielberg (www.hcp0.com), which molded the first Exjection parts on an injection molding machine from Engel Austria GmbH, Schwertberg, Austria (www.engelglobal.com). Together with Engel they developed special software to control carriage speed to get the right pack pressure under the nozzle. Fill pressures range from 50 to 300 bar depending on melt viscosity and part thickness, but higher pressure can be used if part geometry and viscosity require it, IB Steiner says.

Engel introduced the technology at the K 2007 show in Germany running 1-meter long ABS strips with a Y-shaped cross section, 1.2 mm thin walls, and molded end caps on an Engel e-motion 200/55 Exjection machine. Arburg GmbH & Co. KG, Lossburg, Germany (www.arburg.com), showed Exjection next in 2008 during in-house Technology Days and at Fakuma on an Arburg A375V Exjection machine. The technology was written up at the time, but little has been reported since. Published patent applications, however, show impressive advances—notably two approaches to rotating mold blocks that can make either continuous long parts or high volume discrete parts, which Steiner described in an in-house presentation for customers last January.

 

COMMERCIAL APPLICATIONS AND NEW TECHNOLOGY

IB Steiner now has nearly two dozen licensees, some in commercial production, most still in development for a variety of applications. The first licenses were for aircraft lighting and trim parts, reportedly commercial by 2009, according to an Engel press release in 2010 after IB Steiner won an Austrian government award for Exjection technology. Aircraft parts were done for Boeing Co., Chicago, IL (www.boeing.com), and Airbus Industrie, Toulouse, France (www.airbus.com), developed with Stuekerjuergen Aerospace Composites GmbH, Rietberg-Varensell, Germany (www.stuekerjuergen.com), which has one Exjection machine, and with Hybrid Composite, which has two in operation.

ENGEL/Stuekerjuergen

IB Steiner’s long sliding Exjection mold was commercialized to mold aircraft and lighting parts like these, which couldn’t be molded conventionally, but it’s now being developed for high volume applications for cost saving and better part quality. Top photo: Stuekerjuergen; Bottom photo: ENGEL.

Several European companies also commercialized long Exjection building products including Vossloh-Schwabe Lighting Solutions GmbH, Luedenscheid, Germany (www.vossloh-schwabe.com), a unit of Panasonic Lighting in Europe. Vossloh-Schwabe commercialized 1.5-meter LED lighting strips by 2014, simulating the sliding mold with an existing MoldFlow program for mold filling, which sequences multiple nozzles. Vossloh-Schwabe posted a video of Exjection molding on their website (www.youtube.com/watch?v=UV0w79IeGaA).

Besides giving licenses, IB Steiner also develops and patents technology jointly with customers like patent-applied-for (U.S. Pat. Applic. # 20150273747) “elongated hollow parts” for urinary catheters, under development for four years with Hollister Inc., Libertyville, IL. (www.hollister.com), a maker of medical supplies. The driver is the cost saving of replacing an injection molded connector and extruded thin-wall tube, which require assembly, with a one-piece molded catheter 40 cm long.

By 2008 IB Steiner had also gone beyond horizontal sliding molds with a new concept for “Endless Exjection,” which rotates cavities past one or two fixed injection nozzles. Steiner partnered with SaarGummi International GmbH, Bueschfeld, Germany (www.saargummi.com), a maker of automotive seals, to develop a continuous elastomeric seal carrier (U.S. Pat. 8900499), with cavities rotating on a chain like molds for corrugated pipe. Z-Werkzeugbau GmbH, Dornbirn, Austria (www.z-werkzeugbau.com), built the moving molds with 12 cavity segments. SaarGummi trials were done at Arburg’s customer center on a hydraulic two-component Arburg Allrounder 570S, molding the seal carrier at 7-8 m/min.

Arburg’s Selogica controls alternate the two injection units to create continuous flow into the “endless” part. “While the first injection unit is injecting melt, the second one is metering,” Steiner explains. “Then they switch over, and the second injection unit is injecting while the first is metering.” But SaarGummi’s elastomeric seal carrier program didn’t go ahead in the end because of a design change. SaarGummi declared bankruptcy in 2010 and was acquired by Chongqing Light Industry and Textile Holding Group in Chongquing, China in 2011, after which Exjection R&D at SaarGummi stopped.

To date Arburg and Engel have built more than 10 Exjection machines with IB Steiner since 2007, including two “Endless Exjection” machines. Steiner has three on-going development projects for Endless Exjection, all for mass production. So a decade after Exjection was introduced to mold long thin parts out of materials that couldn’t be molded otherwise, it’s under development for high-volume applications in medical, construction, and even packaging. Its advantages today are efficiency, cost saving, and better part quality for both individual and continuous parts.

Endless Exjection

IB Steiner developed “Endless” Exjection in 2008 for SaarGummi with 12 rotating cavities on an injection molding machine. The part wasn’t commercialized because of a design change, but Steiner now has three development projects with rotary Endless Exjection for mass production.

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Unusual ‘Extrusion’ Molding Is Commercial

By Jan H. Schut

Low-shear, low pressure “extrusion” molding machines developed by Extrude to Fill LLC, Loveland, CO (www.extrudetofill.com), a 2014 start-up, have been commercially molding tiny acoustic parts since 2015. Extrude to Fill’s process melts plastic without motion using electric heater bands in a thin-walled extruder barrel using conduction, not compression or friction between screw and barrel. The screw turns only to fill molds.

Melt temperature is controlled with sensors in the barrel and torque on the screw. A PID control loop uses those measurements to determine viscosity each time the cavity is filled. “You tell the machine what you want the output to be in terms of mold pack pressure, and let it run its algorithm to assure accurate plastic temperature and viscosity to produce the desired part,” explains Extrude to Fill CTO and co-founder Richard Fitzpatrick.

“Cycle time is the same as for conventional high-pressure molding, dictated by part cooling,” says Fitzpatrick, who worked almost 20 years on the process. “Fill time will last a second or half a second, similar to traditional injection molding. But where traditional molding pressure starts high and drops down; we start at 500 pounds and build up. Either way 500-3000 pounds is the final pressure in the mold cavity. Because of this build-up to the final pack pressure, we require less clamp tonnage than traditional machines—usually ½ to 1 ½ tons of clamp pressure per square inch (of mold surface).”

 

Extrude to Fill

Extrude to Fill’s machines melt plastic with electric heater bands in a thin-walled barrel without motion, not with compression and friction between screw and barrel. They come in two sizes—with ¾-inch and 1-inch screws, which turn only to fill molds, not to melt.

FIRST COMMERCIAL “EXTRUSION” MOLDING

Extrude to Fill’s first commercial customer, Aurisonics Inc., Nashville, TN (fender.com), a maker of high-tech audio equipment, wanted to mold tips for ear buds out of temperature-sensitive Class 6 medical grade thermoplastic elastomer instead of typical two-part silicone. Plunger-shaped tips are thick at the center, thin around the edge and couldn’t be molded out of TPE conventionally, Aurisonics’ president, Dale Lott says. The advantage of TPE tips is that they “deform in response to heat from the user’s ear,” says Aurisonics’ patent application (U.S. Pat. Applic. # 20160173971), so they’re more comfortable than silicone tips, which itch.

Aurisonics bought its first machine in 2015, molding 30 and 50 durometer TPE audio tips in up to four cavities and 13-second cycles. “The machine really enabled my business to grow. Our needs went from 100s of tips a month to 1000s a week,” Lott says. Aurisonics, which was acquired in 2015 by acoustic guitar maker Fender Musical Instruments Corp., added a second machine in 2016 for up to eight cavities and ordered two more machines this year to mold larger audio components.

Extrude to Fill offers machines in two sizes with either vertical or horizontal mold opening. Both sizes were originally designed for aluminum molds. The small machine is for 6 x 9 inch molds with up to 30-gram shots and a 3/4-inch screw 20 inches long (26.6 L/D). Aurisonics uses the small machine with vertical mold opening and a customized shuttle table and mold cavity. The operator inserts parts of the ear bud device before molding. After molding, the operator removes the core with parts, removes tiny undercuts by hand, and puts a clean core in. Aurisonics builds its own aluminum molds with inserts and undercuts.

Aurisonics Rockets

Extrude to Fill’s first commercial customer, Aurisonics, has two small, vertical Extrude to Fill machines now and two more on order, molding tiny high tech acoustic parts out of TPE, which couldn’t be molded conventionally.

A year ago Extrude to Fill built the first prototypes of the larger machine with both horizontal and vertical opening platens for aluminum molds to mold parts for another customer and do additional development. The large machine is for 15 x 15 inch molds with up to 200 gram shots and a 1-inch screw 28 inches long (28 L/D).

Potential customers for the large size, however, wanted to be able to use steel molds as well as aluminum, so Extrude to Fill redesigned the platens, integrating them into the machine frame to support heavier molds. The company has just built the first commercial large machine for horizontally opening steel molds, which will be delivered in November, and has four more on order for wire and cable and electronics to be delivered in the first quarter of 2017.

 

HOW ‘MELTING WITHOUT MOTION’ WORKS

Extrude to Fill machines have four temperature zones: a chiller on the initial feed zone followed by three heat zones: preheat, melting, and a heater band on the nozzle before the mold. The 2-3-inch long feed zone is chilled to control the start of melting. Then in the 3-4-inch preheat transition zone, pellets soften and merge, but don’t melt, forming a soft seal that moves forward and keeps melted plastic from flowing backward when the screw stops. Depending on polymer, plastic can be held in the barrel at melt temperature with the screw stopped. PP and PE don’t degrade if held at melt temperature, where ABS, nylon and some other resins do over time, Extrude to Fill’s Fitzpatrick says.

Next comes a 9-inch melting zone where screw geometry changes to short flights that roll melted plastic to get uniform temperature. The screw can be made of brass alloys or coated tool steel and can be heated. It’s driven by a three-phase motor: 1 h.p. for the small machine, which plugs into a 110-volt wall socket; 3 h.p. for the larger one, which needs 208 volts single-phase. The last zone has a patent-pending nozzle which closes with a needle-type valve, preventing formation of a cold slug of material. When the carriage moves forward, the screw retracts, opens the valve, and fills the mold. Instead of an injection or metering zone determining shot size like conventional injection molding, Extrude to Fill machines pump plastic continuously and on demand. There are runners and gates, but less mold cooling is required than for conventional injection molding.

Extrude to Fill describes lots of advantages to this process. Because of low pressure and sheer, it doesn’t degrade plastics. Because it doesn’t compress plastic under high force, it uses 85-90% less energy than conventional molding. Because of low friction, it can mold materials that are hard or impossible to mold conventionally like 50% glass-filled nylon or 75% stainless-steel-powder filled metal injection molding feedstock. Temperature control is more precise. It also has more control of part weight and can mold 100% regrind or recycle with consistent part weight despite variations in melt flow index.

Extrude to Fill isn’t the only electrically heated injection molding process. Hot melt adhesive and lab injection molding machines also melt with electric heat, not friction. But hot melt potting machines are limited to low temperature polymers, and lab machines are limited to very tiny shots. Extrude to Fill’s machine isn’t limited in either way.

Conventional injection molding machines can also use low pressure and resemble extrusion, like “intrusion molding,” in which plastic is first continuously extruded at low pressure into a mold, then packed with a final injection shot. (See an ANTEC 2010 paper on “Improvement of Injection Molding Machine Capacity by Intrusion Technique” by Abbas Mokhtarzadeh and Avraham Benatar of SABIC Innovative Plastics.) There is even licensed “Exjection” technology (U.S. Pat. # 7910044) from IB Steiner, a plastics engineering firm in Spielberg, Austria (www.ibsteiner.com), introduced in 2008, which can be used with conventional injection molding machines. Exjection combines extrusion with injection to mold long or continuous parts. But these processes still melt with compression and friction.

So Extrude to Fill is genuinely different, and more developments are coming. Extrude to Fill’s machines have tiebars now, but will eventually be tiebarless. Air-actuated clamp and carriage drives will be replaced by servo motors. For larger parts and higher cavitation, multiple extrusion molding machines can be used together in a patent-pending multi-port array. Extrude to Fill hasn’t built one yet, but that will be fun to watch!

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New Shapes for Conformal Cooling

By Jan H. Schut

Conformal cooling channels in injection molds have been built by additive manufacturing, or 3-D printing, developmentally since the late 1990s using successive thin layers of metal. Unlike conventional straight drilled cooling lines, conformal cooling channels curve around deep shapes in a mold, equidistant from the mold surface, which is the source of heat. They can only be built by additive manufacturing and are designed with cooling line requirements secondary only to part and parting line requirements, unlike traditional drilled cooling lines which are located where space is available late in the design process.

Conformal cooling, however, was limited by the capabilities of the early metal powder welding process, which used metal powders coated with polymer binder, then evaporated out the binder leaving porous metal, and infiltrated the porous space with bronze. Since about 2006, direct additive manufacturing of pure metal powders became possible with the integration of fiber lasers into metal printing vs. the original CO2 lasers. 3D Systems Inc., Rock Hill, NC (www.3dsystems.com), also added a compaction step to make a dense metal powder bed before laser melting thinner layers—20 microns vs. about 100 microns before.

All that makes “100% metal mold inserts possible with reasonably smooth surfaces, providing a rock solid tool for mold makers,” explains Scott Young, engineering manager at Bastech Inc., Dayton, OH (www.bastech.com), a service bureau for additive manufacturing since 1994 and a reseller for 3D Systems. Bastech has built molds using additive metal manufacturing since 2000 and using pure metal additive manufacturing since 2015.

 

GOING BEYOND ROUND CHANNELS

Conformal channels themselves, however, haven’t changed much in two decades of development. Primary cooling channels can transition to small capillary channels and back to primary trunk lines again to get cooling closer to the mold surface or to cool small mold details. Capillary channels can be closer together than large channels. (The cross section of the supply channel has to be equal to or greater than the sum of the cross sections of the capillaries, and the cross section of the return line has to be equal to or less than the sum of the cross sections of the capillaries.) But conformal cooling channels themselves are still typically round like drilled water lines.

 

Conformal Cooling Figure 1

State-of-the-art conformal cooling channels like these from 3D Systems and Renishaw show round channels like traditional drilled cooling lines. But round may not be the most efficient shape. Triangle, star and X-shaped channels all have more surface area and cool better. Left photo: 3D Systems; Right photo: Renishaw;

 

Graphics for advanced state-of-the-art conformal cooling from 3D Systems; EOS GmbH in Kraillingen, Germany (www.eos.info); and Renishaw PLC in Gloucestershire, U.K. (www.renishaw.com), three suppliers of metal-powder-based additive manufacturing systems, invariably show only round channels. But round may not be the best channel shape, according to a recent study by Bastech, presented at the AMUG 2016 conference (www.additivemanufacturingusersgroup.com) in April in St. Louis, MO. Bastech compared cooling efficiency of round, square, diamond, tear drop, triangular tear drop, and triangular channels, based on surface cooling area calculated from channel perimeter. So for channels with the same length and volume, the channel with the longest perimeter will have the most surface area and cool best.

Using 3D System’s Cimatron 13 software, Bastech compared a round channel with a 1.374 inch perimeter to the other shapes and found that a tear drop has a 1.454 inch perimeter; square has a 1.474 inch (rotating the square into a diamond shape has the same perimeter but is structurally stronger in a mold); triangular tear drop has a 1.574 inch; and triangular has a 1.587 inch. So a triangular channel cools 16% more efficiently than a round one. “More important, triangular channels have a long flat surface that can be oriented to parallel the mold surface,” Bastech’s Young points out.

Conformal Cooling Figure 2

Bastech simulated five cooling channel shapes—round, square, tear drop, triangular tear drop, and triangle–rotating some shapes for better mold strength and orientation to the mold surface. Triangular channels have 16% more surface area than round, which are the least efficient.

THE ‘X’ FACTOR

The most complex conformal channels Bastech has built so far were done this year for a mold core for an in-house promotional product, a 5-inch-tall cold drink sleeve. The 8-inch high mold core, also presented at AMUG 2016, is cooled by two inter-twined helical flow channels with X-shaped cross sections (X’s have even more surface area than triangles). The supply side channel splits to start one helix at the base of the core and the other helix and the top, creating counter flow, shorter channels, and more even cooling. The helical channels then reconnect into the return line to exit the core.

 

Bastech AMU page 16

Bastech built this highly unusual conformally cooled mold core with two X-shaped helical cooling channels. One runs straight to the top of the core and coils down. The other coils up, intertwined with the first for counter flow, shorter channel length, and better cooling.

 

 

Recent patent literature also mentions additive metal manufacturing of alternative cooling channel shapes. Star-shaped cooling channels are described by Siemens AG (U.S. Pat. # 8922072) and “triangular, rectangular, square, semi-circular, and ellipsoidal” channels by General Electric Co. (U.S. Pat. Applic. # 20140202163), both to cool heavy machinery, not injection molds. 3D Systems discussed the concept of star-shaped cooling channels at an electronics trade show in January this year, but without showing simulations.

Star-shaped channels, however, would be difficult to build by additive metal manufacturing “because unsupported structures shouldn’t overhang by more than 45 degrees,” notes Maximilian Boulter, manager for additive manufacturing at Renishaw’s LBC Engineering service bureau in Pliezhausen, Germany (www.renishaw.com), “though the angle is dependent on a few things like material, size, and angle toward the recoating wiper.” The X shape is also difficult to build. “The X pattern would have been doomed in a single helix, but a double helix gave us enough pitch to create the shape,” Bastech’s Young explains.

Cleaning and maintenance, however, are issues with non-round channels, notes Mads Jespersen, a partner at FlowHow ApS, Sydiylland, Denmark (www.flowhow.dk), a consultant on conformal cooling. Jespersen calculated how much steel was needed for a mold core not to collapse with wear over time and filled all the open space with cooling water. “That made some weird but very effective cooling channel shapes,” he says.

He then simulated the flow rate of cooling water using Moldex 3D software from CoreTech System Co. Ltd., Chupei City, Taiwan (www.moldex3d.com), which includes computational flow dynamics (CFD). CFD showed potential areas in the cooling channels with no flow. The risk with ‘no flow’ areas is that “these irregular channels, while effective, would also be sensitive to corrosion and deposits and impossible to clean without use of chemicals and the risk of damaging small features in the cooling channels,” Jespersen says. He concludes that “conventional round channels may be the best solution to minimize the cost of cleaning, spare parts, and break downs.”

Instead of increasing the surface area of the channel with alternative shapes that may be hard to clean later, cooling can also be improved by turbulent flow. FlowHow’s Jespersen simulated and built unusual “fish net” structures with additive manufacturing in combination with round channels to increase turbulent flow where more cooling is needed.

Like FlowHow, Bastech also used additive manufacturing to reduce the mass of metal in molds, but it wasn’t to increase cooling water volume. It was done because less metal in the mold means faster mold start up and shorter additive manufacturing time. “We only need 0.25 inches of tool steel for mold walls, plus an inch or so for the cooling channels. Everything outside of that we don’t need,” Bastech’s Young explains. For the drink sleeve core instead of a solid metal mold, Bastech built a structure of trusses and supports, leaving diamond shapes of metal out and removing roughly 25% of the metal. The drink sleeve core took only 38 hours to build vs. 42 hours for CNC programming and machining to build the same core out of solid tool steel with conventional spiral baffles.

An earlier important study on conformal cooling was done internally by Lego Group, Billund, Denmark (www.lego.com), in 2010. Lego used Moldex3D software and MSC Nastran finite element analysis software from MSC Software Corp., Santa Ana, CA (www.mscsoftware.com), to simulate and build three different cores for Lego blocks: one out of  standard tool steel, one with an Ampco bronze cooling insert, and one with conformal cooling. The study found that cycle time went down to 13.1 seconds for cores with the bronze insert and conformal cooling vs. 23.2 seconds for standard tool steel, but conformal cooling made better parts with less warpage than bronze inserts. Temperature differences between actual mold inserts and simulation were reportedly within 5%. Lego is now believed to have built more conformally cooled production molds than any other company in the world.

Conformal Cooling at LEGO

Conformal channels don’t have to be big. A 2010 study done at Lego using Moldex3D software and MSC Nastran FEA software, compared conformal cooling and bronze inserts to standard tool steel. Both inserts cut cycle time almost in half, but conformal cooling made better parts.

 

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