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New technique for radiation free energy saving and more versatile High Frequency welding

Final Report Summary - ENERGY SAVING WELD (New technique for radiation free energy saving and more versatile High Frequency welding)

The overall objective of the ENERGY SAVING WELD project was to develop a new technique for high frequency (HF) welding, based on modern technology, giving better energy efficiency and decreasing electromagnetic radiation. A secondary objective was to automate the frequency adjustment. This will enable tuning for new materials / products and welding of materials with varying thickness. Research on polymers in order to find new polymers that can be welded is also an objective.

The industrial objectives were to:
- reduce the electromagnetic radiation with at least 50 %;
- enable the use of the outstanding HF welding in products that today are stitched or glued and in new innovative products;
- safety secured production with lower risk for burn outs;
- be able to produce smaller and cheaper equipment which will enable more SME:s to invest in the technology.

The economic objectives were to:
- reduce the energy consumption of HF welding equipment with up to 60 %;
- reduce the investment cost for HF welding equipment;
- enhance productivity of the welding equipment with shorter lead times and more efficient weld cycle.

The societal objectives were to:
- minimise the electromagnetic radiation for the operators.

The project was structured into work packages (WPs) as follows:

WP 1: Solid state technology investigation
The major work of WP 1 can be divided in the solid state research and the material research. After some problems in the realisation of the solid state generator at Thales, that also led to that much of the project was delayed the project had to cancel some of the tasks in WP1. Instead of these cancelled tasks it was also decided to put more emphasis on the material research, why a subtask called 1.5b material manipulation was added.

A technical specification of a solid state HF generator has been developed. It describes a generator with an energy efficiency that is theoretically 100 %, but with an expected real efficiency of well over 70 % and possibly up to 85 % compared to the efficiency of today's vacuum tube generators that seldom reach over 50 %.
The material research has proved that apart from the known materials PVC and PU it is also theoretically possible to HF weld fluor polymers, silicone elastomers and PP-based materials.

The analysis of known additives shows the possible strategies to manipulate materials for HF activity. For polyolefin and fluoro polymer materials commercial HF-receptive products and additives have been tested with various results. Additives that would theoretically increase the weld ability did in the practical test not always perform as predicted. The potential of the textile technology, coating and finishing processes for manipulation of materials for HF welding were also investigated and in this work it was concluded that so called welding aids can be used. Welding aids can be high frequency active films or coatings.

WP 2: Automated frequency regulator
A solid state HF generator and auto-matching system have been developed and a prototype has been built. The prototype has been tested with very good results. A concept was developed for a commercial eyelet welding machine and software with human system interface was also designed.

The study on a HF welding and ultrasonic combination shows that adding vibration to the HF welder gives a better weld result than HF only for materials where the HF activity is low, but this feature have not been implemented in the final design.

A new electrode system called a two electrode has also been tested. It shows good welding results and energy efficiency, but had some problems with spark over, why neither this feature was implemented in the prototype welding machine.

WP 3: Analyses, tests, adjustments and new product development
A design concept and a CAD model of a commercial solid state eyelet welding machine have been produced. A prototype machine of a simpler machine was built and tested. The tests showed excellent results and compared to the state of the art vacuum tube generator the energy savings with a solid state generator was up to 81 % and the electro-magnetic radiation was lowered with in average about 39 %. Interesting new products have been identified as possible to manufacture with HF if the materials can be developed or manipulated to get the right characteristics.

The tests results of energy consumption and radiation on the prototype eyelet welding machine is very promising and much better than the objectives of energy consumption outlined for the project. The radiation did not entirely meet the objective, but almost 40 % decrease is still very good. On the polymer research side it looks very promising with several new materials found to be HF weldable and with manipulation and additives identified for increasing the weld ability of several interesting materials.

During the project the following main achievements have been done:
1. A technical specification has been developed for a solid state HF generator that gives a theoretical energy efficiency of 70-85 % compared to the about 50 % efficiency of the vacuum tube generators.
2. Tests with adding vibration to HF welding shows that a combination of HF and ultrasonic welding can give better weld results at shorter weld cycles and also enable welding of polymer materials that are not weld able with HF only.
3. New polymers have been found that are weld able with HF and with added value due to better performances of these materials they can be used for many interesting applications that are stitched or glued today and also in completely new products.
4. A solid state HF generator has been developed for a small machine for welding eyelets
5. An auto-matching system has been developed for the solid state generator system.
6. The generator and auto matching system is much smaller than the vacuum tube generator and its components. This will enable much smaller welding equipment to be developed.
7. The electro-magnetic radiation from the new machine is about 39 % less than from a similar vacuum tube generator machine.
8. The energy consumption of a solid state eyelet welding machine has been proven to be up to 81 % less than for a similar vacuum tube generated welding machine and with maintained welding results.

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