Shin Etsu Silicones of America Open House: Liquid Injection Moulding Systems Review
Shin-Etsu Silicones of America (SESA—A US subsidiary of Shin-Etsu Chemical Co Ltd, Japan), held its LIMS (Liquid Injection Molding System) Technical Center open house in Akron, Ohio, USA, on Monday, October 7 2013. The open house event provided an integrated platform showcasing the new facility that recently premiered under the leadership of Shin-Etsu’s LIMS Process Engineer Craig Lustek. A world class line-up of material and equipment suppliers profiled LSR advancements via interactive presentations including: Shin-Etsu Silicones, ARBURG, Inc, Elmet North America, Inc, Albright Technologies, Inc, and SIGMA Plastic Services, Inc.
At the epicentre of the event, a LIMS demonstration featured equipment and materials from presenting suppliers including: ARBURG’s injection moulding machine, Elmet’s 4-cavity mould and dosing System, and Shin-Etsu’s LIMS liquid silicone rubber. Notably, the moulding demonstration focused on the center’s 110 ton, all-electric horizontal liquid injection moulding press from Arburg, and production processes of a 4-cavity nasal mask with robotic demould.
According to Lustek, “The goal of the LIMS Technical Center is driving the design of new LIMS products and providing full-scale process development of LIMS materials. Additionally, we provide value-added support for new and existing customers with training, moulding trials, prototyping, production start-up, and process improvements.”
The following is a synopsis of key advancements and considerations for today’s integrated LSR market applications as presented during Shin-Etsu’s open-house exposition:
SHIN-ETSU SILICONES OF AMERICA, INC (Akron, OH)
Presentation: Liquid Silicone Rubber Properties, Applications, and Innovations
Presenter: Eric Bishop: North American Marketing Manager
Shin-Etsu Chemical Co Ltd is the largest chemical company in Japan and is in its 60th year of manufacturing silicone products worldwide−producing over 4,000 different silicone products. Its subsidiary, Shin-Etsu Silicones of America, Inc (SESA), recently celebrated its 25th year in the USA and has over 130 employees with annual revenue in excess of $200 million. Additionally, SESA has established a large scale organo silane plant in Freeport, TX and a Cosmetic Application Laboratory (CAL) in Totowa, NJ.
Following this corporate overview, Shin-Etsu’s North American Marketing Manager, Eric Bishop, provided a detailed profile on the key advantages of LSR including (but not limited to): a wide range of thermal stability (-60°F−400°F), non-conductive thermally and electrically so it’s a great insulator, the elastomeric molecule has the ability to expand and elongate naturally without additives and has a wide range of elastomeric hardnesses (5-to-80: Shore A), boasts high tear strength properties, is chemically inert (ideal for health care products), is a translucent material but can also be colored with dispersions, has a low surface energy so objects don’t stick to it (ideal for the bake ware market), and meets USP Class VI and ISO 10993 regulatory standards for biocompatibility.
Given this myriad of property benefits, Bishop highlighted emerging LSR market applications that included growth in the healthcare, infant feeding, and consumer markets for products such as straws, baby bottle nipples, and valves for sippy cups—which has drawn some significant production back to the USA.
Key SESA product lines in the booming health care market include their standard KE1950 workhorse material and the KEG2000 Series for newer applications. The KEG2000 products offer “Dynamic Viscosity”—exhibiting higher viscosity under low shear stress (pumping and shut-off) and lower viscosity under high shear stress (injection). Thus, customers benefit from faster mould filling and minimal flash. The products are visibly clear and range in hardness from 20-to-75: Shore A, and tensile and tear strength have been maximised for physically demanding applications. Additionally, the products are FDA, USP Class VI, and ISO 10993 compliant.
Bishop also focused on broadening the unique properties of their Select-Hesive LIMS KE2090 Series that provides primer-less adhesion to a variety of thermoplastic resins. Suitable for insert over-moulding or 2-shot moulding, the products are specifically engineered to adhere to the thermoplastic substrate (plastic inserts) but not to the metal surfaces of the mould. With hardness ranges of 5-to-70: Shore A, the series also has outstanding bond strength performance under extreme conditions of high temperature (120°C), high humidity (85°C/85% RH) and thermal cycling (-40°C to 120°C).
KE2090 is also tested to comply with USP Class VI and ISO 10993 regulatory standards for biocompatibility—ideal for healthcare applications such as respiratory masks, diaphragms, handles, gaskets, etc. According to Bishop, “The KE2090 series is essential for anything that is being assembled with a silicone seal that could be potentially over-moulded and thus bypass that step to improve manufacturing efficiency.”
With proven strong adhesion to higher temperature thermoplastic resin substrates such as PEEK, PSU, PPSU, and PEI−a next generation product in the series will soon be introduced that will bond to ULTEM and nylon-12 materials.
ARBURG, INC (Lossburg, Germany / Elgin, IL)
Presentation: Multi-component silicone moulding and integrated robotics
Presenter: Marko Koellmer / Area Manager-Sales & Engineering
ARBURG, INC is a pioneering manufacturer of injection moulding machines for plastics processing, has been involved in the processing of liquid silicone since 1980. With several thousand LSR (Liquid Silicone Rubber) applications having already been realised worldwide, LSR processing is now one of ARBURG’s core areas of expertise. An interdepartmental team of LSR specialists also ensures expert consulting at all times—from the requirements-based specification of its ALLROUNDER injection moulding machines and applications technology, to customer consulting of moulded parts and mould design.
Marko Koellmer, ARBURG’s US Area Manager, Sales & Engineering, focused on creating added value by combining multi-component technology with LSR processing and automation to achieve optimal cost efficiency. According to Koellmer, “Based on standard solutions for processing several components, machine technology from ARBURG can be adapted precisely to the relevant injection moulding task. Whether you require single or multi-component LSR moulding, the modular product range includes a choice of drive concepts with a multitude of clamping forces (14-620 tons) and injection units. The injection units can be flexibly/precisely arranged to suit the mould and process technology requirements.”
Automation solutions include the integration of 6-axis robotics for complex demoulding/extensive postmoulding operations—making complete turnkey systems easily achievable. With a focus exclusively on the best customer-specific solution; there are no fixed concepts limiting process-engineering possibilities. ARBURG’s ALLROUNDERS and efficient SELOGICA machine control are ideally suited to produce solutions for applications requiring a combination of thermoplastic and LSR.
For multi-component moulding, a combination of injection units can be orientated in a choice of configurations to meet the requirements of the mould and part design. A common arrangement of injection units is the L-configuration; in which one injection unit injects through the fixed platen in the standard manner (eg thermoplastic), and the second unit injects from the rear of the machine into the cold-runner (eg LSR). The cylinder modules can be exchanged individually. In addition to the robotic system, all of the system peripherals including temperature control units, the ARBURG THERMOLIFT dryer and conveyor, and the LSR dosage system and mould heating system—are integrated in to the machine and can be operated centrally.
ELMET NORTH AMERICA INC (Lansing, MI)
Presentation: Technical developments in fully automatic LSR moulds/dosing systems
Presenter: Ryan Cutler / Technical Sales-Operations Manager
Austria-based ELMET has been a professional in tool making and mould making since its inception in 1996: with local presence as ELMET North America, Inc since 2002. With approximately 1/3 of its global business based in the USA, its core business is fully automatic injection moulds for LSR with cold runner technology. The company’s spectrum of expertise includes designing, manufacturing, and automating LSR, HTV, Rubber and TPE injection moulds, valve gate nozzle technology, patented dosing systems, and LIMS peripheral devices for elastomer processing. Additionally, the company can provide turnkey ready moulding machines for the production of high-quality elastomer parts.
According to Elmet’s Technical Sales-Operations Manager, Ryan Cutler, “A key technical challenge for LIMS processing is the two-component material dosing. Proper conveyance of two compressible liquids, with each one having their own differing viscosity while also changing viscosities due to shear, temperatures, or additives—all while controlling and monitoring the 1:1 ratio situation.” Noting the parallel challenge with the injection moulding machine, Cutler stated, “It is imperative to inject the mixed silicone into the cavity with the right pressure, speed, and volume to avoid overfilling/underfilling the cavity—particularly when sometimes there are up to 256 individual cavities.”
Ultimately, the dosing system must be capable of exact dosing the levels of A/B, plus a third component. As waste reduction is critical, exact control of A/B levels guarantees making both barrels empty at the same time. The end result is that dosing accuracy, via proper dosing equipment, saves money during production.
Notably, amongst ELMET’s line of dosing equipment, they have developed a patent regulated dosing system. The system ensures that the remaining material (waste), per change of drum kit, is a maximum of 1%. Dosing units with a conventional dosing system do have a remaining material of approximately 5% to 4% difference; or equal to 18 kilograms of waste per change of drum kit (using 200 kg / 55 gallon barrels).
Emphasis was also placed on the importance of the cold runner and valve gate nozzle which is directly gated into the LSR part (medium and larger parts, thin wall parts, critical parts and critical industries).
According to Cutler, “For applications such as LSR, HTV and rubber, the main advantage lies in the continuous and direct adjustment of each valve gate nozzles respective motor. This allows easy optimisation of the filling rate for each cavity during the moulding process. The external control unit only needs to be connected with the cold deck when either setting is changed or data sets are put into the cold deck. Therefore, one control unit can save the data of various project-oriented moulds and thus be reproducible.”
ALBRIGHT TECHNOLOGIES, INC (Leominster, MA)
Presentation: Alternative methods of prototyping liquid silicone parts
Presenter: Matt Bont, Senior Project Engineer
Established in 1995, Albright Technologies specialises in manufacturing prototypes and low volume production silicone components for medical, pharmaceutical, consumer goods, and military applications. With extensive silicone moulding experience, the company assists customers with silicone material selection, prototyping, and design for manufacturability and scalable moulding methods.
According to Albright’s Senior Project Engineer, Matt Bont, “Ultimately, with any type of prototyping you are trying to solve a problem and achieve feasibility—from concept to parts. Whether it’s testing a design just to see if it works, or pitching and idea—key questions must be answered to get the optimal prototype with the best results.”
These investigative parameters may include (but are not limited to): design testing (fit, form, and function), clinical trials, regulatory testing, budget/cost assessment, scale required to complete testing (1, 10, 100, 10,000 parts, etc), and project timeframe.
Balancing material selection and product application for prototyping is valuable. LSR is injection and compression friendly, the viscosity is low, and the mechanical properties are good−but often middle range. Typical applications for LSR prototypes include: strain reliefs, gaskets, seals, diaphragms, thermal/electrical insulators, etc. In the case of RTV material, it has a low temperature cure (some as low as room temperature), low viscosity, and a wide range of mechanical properties. Therefore, RTV is ideal for applications such as coating/encapsulating heat sensitive electronic products, pourable mouldings and castings, etc.
Each process for moulding prototypes including injection, compression, transfer, and 3D printing has its advantages/disadvantages depending on the goals, geometry, material, and application.
The dimensional tolerance and lead time for all processes depends on the complexity of the part and size. Compression moulding is the most flexible, the moulds are simple and fast to make and modify. Materials are rapidly changed without having to purge but moulding requires more operator interaction. Prototype injection moulding offers greater production rates, automated control benefits, and process validation advantages but requires more complex moulds and startup time. Transfer moulding represents a medium between injection and compression moulding with more control of shot size. Lastly, 3D plastic printing is inexpensive compared with traditional moulding but have limited accuracy and materials which often does not represent the end design.
In conclusion Bont stated, “We typically deliver 5-15 day turnaround times for our prototypes and many low volume production applications. Successful prototyping starts by understanding the design intent, prototyping goals, process limitations, cost and time constraints and then building on knowledge gained throughout the development process.”
SIGMA PLASTIC SERVICES INC (Schaumburg, IL)
Presentation: Evaluating material behavior, part and mould design, and injection process before building the mould.
Presenter: Matt Proske / Vice President
SIGMA Plastic Services, Inc, a subsidiary of MAGMA GmbH—Germany's largest developer of CAE software, focuses on combining physics, technology, and innovation in process simulations to reduce development and production costs.
With a core competence in plastics, SIGMA uses a worldwide network of industrial and scientific partners to provide advanced virtual injection moulding LSR software. The company’s latest 3D injection moulding simulation software, SIGMASOFT, analyses the entire process; filling, curing or solidification, post ejection cooling, and the entire mould with multiple consecutive production cycles.
According to SIGMA’s Vice President, Matt Proske, “3D LSR simulation is a lot like a flight simulator for pilots—you want to avoid test flights which are costly (fuel, aircraft damage, airport fees). The technology allows manufacturing engineers to test moulding trials virtually, and develop a complete mould by taking into account the entire process. By virtually injecting moulded parts, you can speed up tool making and make better decisions before you start cutting steel.”
The goal is to simulate the entire process over multiple/consecutive cycles to establish a realistic model. The entire process must be modeled accurately therefore, you must consider the entire mould and production cycle. The 3D simulation includes the entire tool, heaters, cooling lines, mould materials, complete processes, post-curing, etc.
Ultimately, considering the thermo-physical properties of key mould elements (cold plate, hot plate, valve gate, core pins, cavity, etc) allows engineers to understand the physics behind heat flow and the steel to make a quality, cost effective part. Proske noted that, “This includes the heat up cycle, maximum temperatures, temperature distribution, set points, etc. We are very comprehensive, so we know what happens at the beginning of filling, the end of filling, curing, where do you put venting, thermocouples, what is the pressure and temperature influence on viscosity, what are the intra-cavity mould temperature differences, etc. The bottom line is that we want to know what areas are going to create problems.”
Proske noted that the kinetics of each project is different depending on the type of materials you are using and the material data set. Additionally, if the customer doesn’t have the LSR material data set, material data measurement services can be acquired cost-effectively from outside partners.