RF Welding Performed at Hi-Tech Products
RF Welding (Radio-frequency welding), also known as dielectric welding and high-frequency welding, is a plastic welding process that utilizes high-frequency electric fields to induce heating and melting of thermoplastic base materials. An electric field is applied by a pair of electrodes after the parts being joined are clamped together. The clamping force is maintained until the joint solidifies. Advantages of this process are fast cycle times of a few seconds, automation, repeatability, and good weld appearance. Only plastics which have dipoles can be heated using radio waves and therefore not all plastics are able to be welded using this process. Also, this process is not well suited for thick or overly complex joints. The most common use of this process is lap joints or seals on thin plastic sheets or parts.
RF Welding Compatible Materials
The Radio Frequency heating mechanism relies on a dipole in the molecule in order to generate heat and therefore the plastics used in RF Welding are limited to those whose molecules contain an electrical dipole. Permanent molecular dipoles can form due to differences in electronegativities between the atoms of a molecule. Negative charge is shifted toward atoms with higher electronegativity, resulting in more negatively charged regions surrounding more electronegative atoms, and positively charged regions surrounding less electronegative atoms. Because polyethylene consists of symmetric mer groups, no dipole forms, and polyethylene cannot be joined using radio-frequency welding. Like water, polyvinyl chloride (PVC) consists of asymmetrically distributed atoms of differing electronegativities, with a resulting dipole moment. Because of its strong dipolar moment (and other properties) PVC is considered an excellent material for radio-frequency welding. In addition to polarity, properties that contribute to good radio-frequency weldability are high dielectric constant, which reduces resistance to current flow; high dielectric strength, which prevents arcing through the joint members during welding; and high dielectric loss, which is a factor that describes the amount of heat generated by an electric field.
Some plastics commonly welded with dielectric heating include:
- Polyvinyl chloride (PVC)
- Chlorinated polyvinyl chloride (CPVC)
- Polyurethane
- Nylons
- Cellulose acetate
- Ethylene-vinyl acetate (EVA)
- Polyvinylidene chloride (PVDC)
- Polyethylene terephthalate (PET)
Radio-Frequency Welding Applications
The most common application for radio frequency welding is sealing thin sheets of polar thermoplastics such as PVC. RF Welding is commonly used for medical items such as blood bags, disposable clothing, blood pressure cuffs, and packaging for certain items. RF welding is most typically used in the construction of products that require a watertight or airtight seal. A welded seam or insertion tube sealing process creates seals that can withstand various types of requirements for certain liquid types or air pressures. An example of this would be for the medical industry, where ensuring the seal is airtight and fluid-tight is crucial. Some other products that typically use RF Welding include beach balls, airbeds, life jackets, book covers, and loose-leaf binders.
Hi-Tech Products Specializes in Medical RF Welding Applications
- Negative pressure wound therapy devices
- Minimally invasive surgery access ports
- Patient and equipment drapes
- Hospital bed surfaces
- Fluid containment
- Compression therapy garments
- Inflatable dissection balloons
The RF Welding Process
Dielectric heating causes the parts that are in intimate contact to melt, and the liquid polymers diffuse into each other at the interface. Diffusion and solidification of the joint occur while pressure is maintained for a specified time.
Hi-Tech Products expertly controls the many parameters used to control the welding process and insure a high quality weld.
- Weld time – duration electric field is applied
- Power – electric field power into the joint
- Clamp pressure (or collapse distance) – limit of squeeze pressure (or limit of squeeze distance) parts are pressed together
- Hold time – duration pressure is applied after power source is turned off
- Die temperature – temperature of dies
- Number/sequence of cycles – modification of welding process to perform multiple cycles in sequences to maximize weld quality
The parameters listed are often interdependent, and a process window must be developed to tune the process for acceptable weld quality.
Is RF Welding the Best Welding Process for your Product?
RF welding vs. gluing, sewing, or hot air.
Sewing – RF welding provides a more consistent, air and liquid tight seal than sewing. When sewn seams are stressed, the thread takes the pressure and could break. RF welds provide a much stronger seam or bond by evenly distributing stresses throughout the material.
Gluing – Gluing can provide an air or liquid tight solution, however glued seams are subject to failure once the gluing has worn out. RF Welding is a better manufacturing process as gluing takes much longer than RF welding and often uses hazardous solvents that are harmful to the environment.
Hot Air Method – The hot air method applies heat to the outside of the materials being bonded to melt them and create a bond. This method is restricted by material thicknesses. Thicker materials will not melt in the middle and bond, while outside layers will be over heated or burned. RF welding heats the parts being bonded from the inside out and is the best method for forming air tight seams.
Why choose Hi-Tech Products for your RF Welding?
Competitive pricing and High Quality – Medical RF Welding processes are conducted in a certified cleanroom in our Tijuana Mexico facility, offering competitive labor rates with US engineering. Our Tijuana facility, with ISO 13485:2016, and ISO 9001:2015 certified quality systems, offers extensive cleanroom assembly and packaging capabilities to compliment the RF Welding process.
RF Welding Expertise – You will want to choose a manufacturer that understands the many factors that affect the strength and seal quality created by RF Welding. Weld thickness, material thickness, tooling layout, and machine control are some of the most important factors in creating a good weld or seal. RF Welding can create very robust hermetic seals. Welds are subject to pull tests, leak tests, and optical tests to determine that the correct conditions and highest weld quality has been achieved.
Hi-Tech Products is capable of RF Welded the many materials used in manufacturing medical devices and medical packaging. Whether your product requires PET, PETG, PVCs, Thermoplastic Polyurethanes (TPU), LDPE/EVA, or Open Celled Polyurethanes; we are prepared to accommodate your product manufacturing requirements.
Hi-Tech Products is much more than an RF Welder.
Most products require multiple manufacturing processes to complete their production and reach the marketplace. Hi-Tech Products not only offers RF Welding, but also a full spectrum of die cutting and converting capabilities. Hi-Tech provides expert guidance from prototype through clinical trials to final production parts as well as OQ / PQ validation.
For over 35 years, Hi-Tech Products has been a top manufacturer of die cut components. Hi-Tech’s many capabilities, including medical RF Welding, are performed in certified cleanrooms in FDA registered facilities. Hi-Tech Products has extensive experience with medical device assembly, packaging, and manufacturing; producing medical devices for wound care, diagnostics, microfluidics, and the latest in wearable sensor technologies.
See more about RF Welding and the many other Hi-Tech Products capabilities
