Advanced silicone technology makes the future possible
When it comes to relatively new production concepts, liquid silicone rubber injection molding is one of the most flexible.
The world is becoming increasingly digitally connected and smart solutions are everywhere. In automotive the buzz is all about E-mobility and advanced driver assistance systems. The development of the fully connected and ultimately the fully autonomous car are even taking precedence over greater efficiencies of combustion engines in some cases.
In the field of healthcare and medical technology, the trend is for personalized health monitoring and treatment of acute and chronic ailments with the help of smart wearable medical devices. In industrial engineering, Industry 4.0 is one of the most talked about subjects.
Even our homes are becoming wired through advanced and sophisticated electric and electronic equipment and appliances. Devices that allow you to control your heating from your phone or smart fridges that order your food for you are the embryos of the fully connected home.
However, without polymer technology this evolution would not be possible, as plastic and rubber components sit at the heart of this virtual revolution. The challenge though is for polymer experts to come up with, at an ever more rapid pace, new, intelligent and innovative solutions to facilitate the advancement of a fully connected society.
In this new manufacturing landscape, innovation leaders are becoming the partners of choice to original equipment and device manufacturers who wish to take advantage of the digital trend.
In a world where each technological innovation seems to more rapidly come into use than the last one, speed of development is of the essence. Polymer suppliers that are able to not just produce parts to specifications provided by a customer, but who can actively participate and support with design input from early concept stage, will come to the fore.
When it comes to relatively new production concepts, liquid silicone rubber or LSR injection molding is one of the most flexible. As a raw form of silicone material, LSR enjoys a relatively young history of about 40 years with the first pioneers in specialized tool and process engineering starting in the late 1970s to early 1980s.
Multi-component injection molding has been a well-established process within the plastic molding industry for many years. It’s been used successfully to produce combinations of two or more dissimilar thermoplastics (TP), combinations of TP and thermoplastic elastomers (TPE) or TP with elastomers and other forms of polymers, including multi-color options of all of the above.
Following from these established processes, advanced two component or 2C LSR technology opens new horizons within the field of technical seals and parts. It allows the combination of LSR with an increasing range of engineered and high performance thermoplastic materials into components that integrate multiple elements and functions.
The results are fully bonded and robust hard-soft or soft-soft components that can be produced for high volume, often safety critical applications; where a combination of extreme precision, faultless performance, outstanding quality and long-term economical solutions are crucial.
Ultimately, associated with this innovative process is an ‘out-of-the-box’ approach to design and manufacturing concepts, in particular, tool, process and automation engineering. This means that the ‘so far thought impossible’ can be achieved in the production of ever more complex and miniature multi-component parts. The spheres in terms of component sizes is moving from micro to nano-part weights.
Liquid silicone rubber, as with all forms of silicone, is an extremely versatile material that lends itself to a broad range of application conditions across a wide temperature spectrum from -58° F to +482° F. Due to its platinum cure system, it enjoys the highest purity, making it an excellent choice where food or potable water compliance is required, as well as biocompatibility.
The material also demonstrates excellent electrical and damping properties, ozone resistance and favorable mechanical properties. In addition, LSR offers several distinct processing advantages. Fast curing speed and low viscosity make it suitable for highly complex part geometries and co-injection with engineered or high performance thermoplastics, 2C LSR technology.
2C LSR technology is available in two principal process methods, either one-stage or two-stage. The more common and basic is the two-stage method. In this, a thermoplastic component is molded at stage one. In stage two, the thermoplastic component is over molded with LSR. This method is appropriate for lower quantities with mostly manual handling throughout the process.
The one-stage method is a technically more advanced 2C LSR concept and process where injection of thermoplastic and LSR are made in parallel in one tool and on one injection machine. Ideally this process is fully automated in a flash-less, waste-less tooling concept with completely integrated automatic quality control. This process method is recommended for high quantities of typically 500,000 plus parts per annum.
The advanced one-stage method of 2C LSR offers many advantages for designers and engineers. There is increased latitude in design by integrating multiple components into one fully-bonded high precision hard-soft or soft-soft component solution. The design of LSR seals or gaskets can be easily adapted to mating components within the tightest dimensional tolerance constraints of 0.1mm, with a high precision, flash-less finish instead of having to adapt mating hardware to standard seal or gasket geometries.
In terms of the component itself, this can be lighter weight due to a singular component design and through the possibility of replacing metals with an engineered plastic. The process also enables a higher level of hygiene. Potential dead space where media can be trapped, possibly causing contamination, can be eliminated in a one-piece part.
In manufacturing, risks and costs associated with secondary assemblies can be avoided, such as potential leak paths from poor assembly. The single assembly can also lower costs by reducing the number of components in the customer’s supply chain.
In fact, the 2C LSR injection one-stage molding process in the only robust and cost-effective way of combining an engineered or high performance thermoplastic and silicone component. Alternatives are gluing or assembly of loose parts. Both potentially introduce additional process steps that can cause variability in process and quality as well as extra direct, indirect and possibly hidden costs.
Looking specifically at digitally connected applications, in automotive and industrial engineering one of the main areas of use of LSR is for sensors and actuators with electronic, mechatronic, and optical components on the principles of LIDAR (Light Detection And Ranging), radar and sonar technology. In these, LSR enjoys increasing attractiveness in the form of sealing, damping or protecting elements in connection with highly sensitive electronics packages. Instead of considering the sealing element as an isolated part, 2C LSR technology allows the integration of a seal directly into part of a sensor housing.
In household appliances, one application is in luxury shower installations where indirect LED lighting is incorporated into the shower. This is made possible with a combination of LSR and thermoplastic materials and innovative part and tooling design to guarantee both water spray and lighting effect while ensuring good sealability for the intended life of the product.
Wearables in healthcare began as a lifestyle product for mostly leisure and general fitness purposes. This has changed to them having a more medical focus for critical health monitoring in the form of novel medical devices. These are manifested as portable or wearable devices which digitally monitor and medicate patients with chronic ailments such as diabetes, COPD, asthma or pain.
2C LSR technology enables multi-component solutions with LSR as a fully biocompatible choice with excellent haptic properties and possibilities to integrate sensors or sensing, electrically or magnetically conductive elements.
2C LSR technology also offers excellent solutions in the growing field of personalized medical devices such as prefilled syringes, pump systems or inhalers. The challenge with such devices and therein advantages with 2C LSR technology is the need for the highest precision and absolute reliability over millions of parts, plus the requirement for the smallest of components in the range of not just micro, but even nano weights.
Undoubtedly some people may fear the coming of the digitally connected society, while others will relish it. Inevitably, however, we will not be able to halt the growing and rapid adoption of smart technology. And for those who are pleased to see the revolution, they should be thankful for advanced polymer technology that is truly helping make the future happen.