High-frequency welding

What is HF/RF welding
How high-frequency welding works
Suitable materials
Advantages

What is high-frequency welding

High-frequency welding (HF welding, also known as dielectric sealing is a proven joining process in plastics processing. It enables the Durable and precise joining of thermoplastics through the use of a high-frequency electromagnetic field.

Typically, a frequency of 27.12 MHz a globally approved standard range that delivers optimum results with consistent quality.

The process is characterised by the fact that No external heat source such as hot air, heating wedge or heating cartridge is required. Instead, the heat is generated directly in the materialThis is achieved by causing the molecules to vibrate and heat up through molecular friction. Under pressure, the materials fuse at the joining zone and, after cooling, form a Homogeneous, resilient weld seam.

How does HF welding work?

  • Electromagnetic fieldAn HF generator produces an alternating field in the range from 13.56 to 40.68 MHz.

  • Molecular motionThe dipole molecules (e.g. in PVC or TPU) are constantly realigning themselves, which generates heat in the material.

  • PlasticisationThe material becomes soft and mouldable at the seam.

  • Print phaseThe parts are joined precisely under mechanical pressure.

  • Cooling downWhen cooled under pressure, the joint solidifies and forms a high-strength, airtight and watertight weld seam.

Suitable materials

Not every plastic can be welded. The following are particularly suitable polar thermoplastics with a high dielectric loss factor:

  • PVC (polyvinyl chloride) - Soft and hard

  • TPU (thermoplastic polyurethane)

  • PA (polyamides)

  • PET & PETG (polyester)

  • TPO (thermoplastic olefins) - with additives or modifications

  • Special composite materials and coated fabrics

Other plastics such as PE (polyethylene) or PP (polypropylene) are only suitable to a limited extent, but can also be processed using additives or special welding aids.

Advantages of high-frequency welding

HF welding offers a number of advantages over alternative processes (e.g. hot air, hot wedge or ultrasonic welding):

  • High seam strength - Weld seams achieve up to 70-100 % of the base material strength.

  • Airtight and watertight - Ideal for products that require tightness.

  • Gentle on materials - Heat is only generated at the seam, surfaces remain protected.

  • Precision & repeatability - consistent results even in series production.

  • Versatility - for multi-layer materials, three-dimensional moulds and contour welding.

  • Clean process - No adhesives, solvents or open heat sources required.

  • High energy efficiency - Energy is channelled specifically to where it is needed.

Typical areas of application

The process is used in numerous industries, e.g:

  • Automotive industryInterior panelling, protective films, carpet and headliner components, air ducts.

  • Medical technologyBlood and infusion bags, sterile packaging, protective equipment, bandages & orthoses

  • Packaging industryBlister packaging, technical films, flexible multilayer packaging.

  • Outdoor & DefenceTarpaulins, tents, protective clothing, inflatable boats, flotation devices, emergency equipment.

  • Building & InteriorStretch ceilings, pool liners, insulation materials.

  • Advertising & LeisureBanners, sun protection, inflatable advertising media.

Process parameters - decisive for quality

The welding result is essentially determined by four parameters:

  1. Power / current - influences the speed of heating.

  2. Pressure - ensures that the materials are evenly bonded.

  3. Welding time - determines how long the energy is applied.

  4. Cooling time - stabilises the seam and prevents deformation.

Through modern Control and monitoring technologies these parameters can be precisely set and monitored. Automated systems thus enable Repeatable results in industrial series production.

Future-proof technology

Schirmacher welding machines are constantly being further developed and are designed for long-term requirements. With a Unique control of the high frequency, specialised toolmaking and optimised generators we offer maximum process stability and quality. Thanks to these technologies, our systems are not only customised for today's applications, but are also future-proof for new materials, increasing quality requirements and integration into automated production processes.