Industries That Use Radio Frequency Welding
Radio Frequency (RF) welding/sealing consists of a technology that has been widely used for over 60 years. RF welding describes a bonding process used by manufacturers of flexible products where the specifications require the fabrication of an item from two or more pieces of plastic materials by fusing the materials together. RF welding requires the use of polar molecularly structured materials. During the RF welding process, the energy causes the molecules to “scramble” at a level that is deep enough to make the molecules from one layer of material co-mingle with the molecules from a previously independent layer of material. The process creates a quality, durable, airtight and leak-proof seam.
RF welding goes by a number of other names, including dielectric bonding, low dielectric welding, electronic heat high frequency welding, medical radio frequency sealing, package heat sealing, bar sealing, package high frequency sealing and other monikers. The advantages of radio frequency welding include:
1. The process uses the material as a heat source to facilitate sealing from the inside out.
2. Energizing the field generates the heat, which allows for greater control over the amount of energy applied to the material over the complete cycle — preventing degradation of the material.
3. RF tooling runs cold — which means when the machine switches off, the material remains under pressure and the heating stops. The operator can instantly heat, weld and cool the material under compression and exert more control over the weld, which leads to stronger welds that are more durable.
4. The process produces clean welds because creating the weld only requires the material — eliminating the need for adhesives or the generation of by-products.
Many manufacturers employ RF welding as the preferred process for sealing polyurethane and PVC-coated fabrics. Radio frequency welding is the process of fusing two or more pieces of flexible material together using radio frequency electromagnetic waves. This process fuses flexible materials together to create airtight and leak-proof seams, which are essential traits of inflatable products.
Industries and Applications of High-Frequency Welding
Radio frequency welding uses have gained wide acceptance in industries that need an effective process for sealing polymer films. Count automobile sun visors/tops/doors, inflatable rafts, inflatable toys, seat cushions, bladders of footballs, dust filters and sheet protectors among the most common products fabricated with RF sealing methods. The industries and applications suitable for radio frequency welding include:
Radio frequency welding has evolved into a popular choice for companies in the medical and pharmaceutical industries, which requires a fabrication process that’s flexible. Keeping products and materials that are exposed to humans clean is critical for achieving better patient outcomes. Consequently, the concern for contamination makes it critical to produce seams that are durable, strong, airtight, watertight and leak proof. The RF welding medical device must have seams that can maintain sterility. Medical RF welding services create the following types of products:
- Containment bags for intravenous drugs, blood and saline
- Pressure cuffs for blood pressure machines
- Mattress covers that prevent contamination
- Oxygen bags
- Dust covers
- Bags for storing and keeping medical tools sterile
Increasingly, more companies in the medical and pharmaceutical industries are moving to radio frequency welding technology because of its reliability. In comparison, chemical bonding processes, which require the use of harsh chemical adhesives, can become defective over time and with exposure to extreme temperatures.
Military operations require the use of products that have strong, durable seams and reliability. With the use of military RF welding equipment and materials that can be similar or a combination of different materials, the products have the ability to resist tears and pressure points, prevent the leakage of fluids and gases or resist extreme variances in hot and cold temperatures. The military applications of RF welding include:
- Fuel tanks
- Water tanks
- Inflatable bladders for liquid or gas
- Hazmat or containment systems
- Weatherproof covers for weapons and vehicles
- Submersible weapons containment bags
- Pre-conditioned air hoses for aircraft
Radio frequency welding may provide a viable solution for custom product configurations required for the protection of different types of equipment from potential damage. The high standards for military applications require the right materials and an impermeable seal to ensure that the products resist wear and tear during military operations and withstand prolonged periods of use.
The automotive industry has assimilated radio frequency welding into its manufacturing process for a variety of products, including mechanic work stations, spray paint booths for workers, car wash curtain walls and other products with strong seams. These seams can withstand the rigors of day-to-day use for a broad range of applications in this environment, which makes using automotive RF welding machines an attractive option. Easy cleaning of the seams contributes to indoor air quality by reducing mold build-up on the seams.
Similar to other industries, companies in the recreational field can benefit from the versatility offered by RF welding, whether for indoor or outdoor applications. A few good examples of radio frequency welding uses for recreational applications are the huge vinyl curtains used in indoor tennis in schools, gymnasium and sporting complexes, park districts and country club facilities. These products separate courts and playing fields, protect people from fast-moving balls and objects, cordon off baseball batting cages and block the wind and other elements.
Radio frequency welding uses also apply to many applications required for companies in the sectors of government, education, construction, packaging and handling, retail, transportation and other industries.
Considerations for the RF Welding Design Process
Before you can begin the production process, you must gather the key information in order to facilitate an accurate and expeditious product assessment.The design process can be very involved and complex. The first step in product design is the understanding of the intended application and functionality specifications for the product.
If possible, find example of the products, including photographs. Identify the required features of the product for the end-use environment and any regulatory agency guidelines required for product, where applicable. Other steps in the design process include:
- Decide Product’s Intended Function — The first facet in determining if your product is RF weldable is to identify its intended function to determine if it can benefit from radio frequency welding. Pressure is a factor when assessing the use of an RF weld. A product that must contain highly compressed air and interior pressure that exceed certain levels will fail the criteria for RF welding because some welds will fail under the intense pressure. Products that must withstand abrasion require heavier reinforced fabric to endure RF welding. The product may also need to meet material ratings as specified by agencies such as FDA, USDA, NSF, NFPA or other specific ratings.
- Determine Dimensions — You will also need to consider the dimensions of the products that need RF welding. Radio frequency plastic welding machines operate like a punch press or printing press, which could be a problem for large products. The largest custom RF welding machines have the capability to weld mattresses. Make sure that you choose an RF welding company that has the equipment to work efficiently with your product. Large products like landfill liners, truck tarps or tent tops may require up to hundreds of bar welds to form the long seams and edge hems.
- Configure the Product — Generally, radio frequency welding consists of a two-dimensional process. However, designers can create more complex products with perpendicular seams — the key determinant being the configuration of the product. The process employed to fabricate three-dimensional products consist of two-dimensional steps, completed one at a time. Nonetheless, if you cannot configure a three-dimensional product utilizing a progressive two-dimensional process, the complexity of the product may make it unsuitable for RF welding.
- Create Drawings — You will need to develop professional drawings for your product. The best way to convey the concept of your product is with CAD drawings. Although the drawings do not need to be three-dimensional, they will need to communicate the product you would like to manufacture.
- Contact a Company That Specializes in RF Welding — Make sure to choose a company that is able to work with your materials and meet your product’s requirements before you take further steps moving ahead with manufacturing products that use radio frequency welding. Discuss the specific needs for your project, such as size, functionality, material preferences, production methods, production schedule and deadlines.
- Develop a Prototype — You will need a prototype of the product, which provides a starting point for determining if the design will work or seeing features that the designer may need to rework or change. The prototype may or may not meet all the requirements of the final product.
- Establish Tooling Die Requirements — Once you’ve chosen your preferred material and fabrication methods, you will need to establish if any tooling or dies are needed to manufacture the product. Tooling can represent a significant portion of the project and needs to be addressed during the early stages of planning.
- Rework the Design — Once you evaluate the prototype to determine what works and what does not work, you have the information you need to determine if you need to rework the design or the material or improve functionality. After you complete this step in the process, you can proceed to the production of the finished product. This part of the process can require multiple reworks and requires patience and focus on the end objective for the finished product.
Now that the product design meets the specifications, it is time to move forward with the production run. Collaboration with a radio frequency welding expert that can evaluate your product requirements and provide recommendations and manufacturing options will ensure that you have a quality product that will meet or exceed your expectations.
Material Selection for RF Welding Applications
RF welding technology offers a variety of ways to provide a permanent bond of flexible products. During each stage of the project, from developing a workable production model to bringing your product to market, it is important to have the guidance of an experienced and knowledgeable RF welding professional. Procuring an RF welding expert early in the process increases the probability of having a successful outcome for your product. To fabricate flexible products, you must choose the correct material — one that has polar molecular properties, which give it high weldability. RF weldable materials are typically heavy but very pliable and are able to withstand temperature variances and meet certain expansion or form requirements.
Products that provide protection for a person or something else require strong-welded and heavy-stitched seams, which last over the long lifespan of the product. You will need access to a large volume of material resource information, and with the assistance of an RF welding expert, choose the best material for manufacturing your product. You can combine many of these materials to improve product design, increase functionality or expand your product line. Critical properties the material must possess include pliability for the intended function, stability and durability.
The most common material options for flexible product fabrication include:
- Vinyl Materials — By far, Thermoplastic Polyurethane (TPU) rates as the most popular choice of vinyl substrate for flexible products. The TPU category of materials includes nearly any type of polyurethane plastics that possess flexible properties, including shear strength, transparency, elasticity and resistance to oil, grease and abrasion. TPU materials allow manufacturers to choose radio frequency welding to weld vinyl textiles and seal vinyl seams for containment, inflation and contraction properties, and to make air, liquid and vapor leak-proof seals.
- Coated Fabrics — Another material option for weldable products consists of woven or knitted fabrics, which have a layer of urethane on one side that makes the material RF weldable. To create a good weld, the coating needs to have a minimum thickness of three to five mil or.003” to .005”. The ability to add a coated fabric offers tremendous possibilities for fabric-like materials that are weldable with the radio frequency welding/high-frequency welding process. The wide selection of urethane-coated fabrics provides a viable option when looking for materials. Many larger material supplies will offer a custom coating, lamination or a fabric/film combination. It is important to make sure you select the right material and the best option for textile seam welding.
The material selection process also includes choosing a buffer material, which has a variety of functions. A buffer acts as electrical and thermal insulation, serves as dielectric enhancement and compensates for small irregularities in the die surface. As a thermal insulator, the buffer can modify the position of the peak temperature point and make the weld more efficient. This is necessary because the die platens conduct the heat produced by the application away from the RF field, which produces a temperature gradient within the plastic film.
Material options for buffers include polyester and silicone rubber. To prevent arcs across the platen plates, the RF welding operator must use the buffer with tear seal tools as a voltage barrier.
RF Welding Machines, Tools and Processes
Radio frequency welding machines come in a variety of equipment in a variety of power ranges, sizes and shapes. The choice of tooling depends on the type of product slated for manufacture and the quantity of product desires. The types and sizes of RF machines depend on the tool contact area and the thickness of the materials. Tool makers use brass, steel and aluminum to create dies used in radio frequency welding. The type of die chosen for your project will depend on a variety of factors, including cost, design complexity and durability. Steel die cost less but are prone to rusting and arc pits and are difficult to repair.
Brass dies cost more but have high durability and are easy to repair. Aluminum dies — sometimes called magnesium dies — are low-cost tools that are easy to fabricate. They work well for complex patterns but require more power than brass tools in order to achieve similar bond strengths.
During the manufacturing process, the operator positions two sections of the material that require the table press, which applies pressure to the surface area of the materials. Driven by dies, when the sealing process occurs, the table press comes together and RF waves are transmitted through the small area between the table and die — where the sealing takes place. The radio frequency excites the molecules, which move around and become hot. Applying heat and pressure helps mold the pieces in the die.
- Textile Sealing — The most commonly used feature of RF welding, textile sealing offers the flexibility needed to ensure the functionality of the product. It is also the strongest and most durable seam possible for flexible products. The process employs radio frequency welding to soften the molecules in the materials and reconfigure them. The next step requires the use of pressure to fuse the materials back together to create a big, one-piece seam that is just as strong or stronger than the original piece.
- Sealing Tape — This option provides an effective method of RF welding that uses a separate layer of urethane positioned between the two non-RF weldable materials. Typical in the form of tape and should only be used as a last option. The placement and positioning of the urethane tape between the materials make this process labor intensive resulting in high labor costs
Radio frequency welding processes have multiple operating variables that include RF field frequency, down-stroke pressure, power and cycle time. Experienced RF welding operators understand the factors that enable them to achieve superior welds for the same material combinations using a wide range of settings.
Contact a Reliable Supplier/Manufacturer
Establishing a partnership with an experienced, trusted and reliable supplier and manufacturer can help you optimize the productivity of your RF welding and heat sealing operation and increase revenues and profits. Whether you need new RF Welders, used RF sealers, used RF Welders or remanufactured RF Welding equipment, contact us to purchase a product or service.