High-frequency welding

What is HF/RF welding
How high-frequency welding works
Further information
Typical areas of application

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 permanent and precise joining of thermoplastics through the use of a high-frequency electromagnetic field.

Typically, this is done at 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 material by causing the molecules to vibrate and heat up through molecular friction. Under pressure, the materials fuse at the joining zone and form a homogeneous, resilient weld seam after cooling.

How does HF welding work?

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

» 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.

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

» High weld strength – welds achieve up to 70–100 % of the base material’s strength.

» Air- and watertight – ideal for products that require a tight seal.

» Gentle on materials – heat is generated only at the seam, whilst surfaces remain protected.

» Precision & repeatability – consistent results even in series production.

» Versatility – for multi-layer materials, three-dimensional shapes and contour welds.

» A clean process – no adhesives, solvents or open heat sources are required.

» High energy efficiency – energy is directed precisely where it is needed.

The welding result is essentially determined by four parameters:

» Power / Current – affects the rate at which the device heats up.

» Pressure – ensures that the materials bond evenly.

» Welding time – determines how long the power is applied.

» Cooling time – stabilises the seam and prevents distortion.

Modern control and monitoring technologies allow these parameters to be precisely set and monitored. Automated systems thus enable repeatable results in industrial series production.

Typical areas of application

Future-proof technology

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