Electron beam welder machines in ISI: past&present

The Institute of Scientific Instruments (ISI) was founded in 1957. From the very beginning, analytical electron-beam devices, particularly electron microscopes, were designed and produced here. Later technological applications of the e-beam have been developed too.

First technological instrument was a multifunctional vacuum furnace made at group leaded by Dipl. Eng. Ladislav Zobač in 1965, see Fig., with a round working chamber evacuated by a rotary and a diffusion pump (designed also in ISI). The furnace had three different heat-sources: an infra-red heating (molybdenum direct-heated basket), a HF induction heating and a low power e-beam gun (50 kV/5 mA). Possible applications were vacuum soldering/brazing, vacuum remelting and e-beam welding.

More about furniture in paper article1.

Fig. 1: E-beam welder ES-2 manufactured and installed in ISI, Brno Fig. 2: E-beam welder ES-2 clone made in Tesla Opočno

The last option led to development of the first specialized e-beam welder in ISI (see Fig. 1), that has been later produced in cooperation with other companies (e.g. former Tesla Opočno – see. Fig. 2) in years 1969–70. Beam power was up to 1.5 kW, electrons energy was 50 keV. The electronics, developed mainly in ISI, had progressive features including e-beam viewing system (scanning-electron-microscope mode) and oscillating beam mode. This welder was used for variety of tasks, including welding of vacuum components:

• pipes, valves, membrane bellows, feed-throughs etc.,
• cryogenic devices like helium cryostat components and many others.

Fig. 4: E-beam welder SES-1 installed in ISI together with its designer, Dipl. Eng. Jan Dupák Fig. 3: Modified e-beam welder ES-2

In 1990s the welder was redesigned, especially its e-gun2, electronics, manipulator and vacuum system. The modified welder with medium-size chamber works in ISI up to now (see Fig. 3).

A desktop electron beam welder SES-1 shares the same e-gun and electronics (see Fig. 4). This instrument, which has small chamber volume about 7 litres, is intended for piece production especially for instrumentation and vacuum technologies.

Fig. 5: E-beam welder MEBW-60/2 Fig. 6: MEBW-60/2 control software GUI

The recent e-beam welder MEBW-60/23, see Fig. 5, is SES-1 descendant. The e-gun, working chamber, stage and workbench were considerably improved and allow reliable operation up to 60 kV/2 kW. New electronics, including high voltage power supply, is completely digitized now. Remote control by common personal computer is possible (see. Fig. 6). The control software allows image acquisition, arbitrary shaped welding (“Draw-a-weld” mode), micro-engraving techniques and other functions. The MEBW is now produced by FOCUS GmbH under licence, with custom working chambers and manipulators.

The article is html version of the paper article4.

1. 1. Zobač, L. - Dupák, J. - Kachlík, J. - Krejčí, Z. - Ustohal, V.  Víceúčelová vakuová pec s indukčním, elektronovým a odporovým ohřevem. Slaboproudý obzor, , roč. 28, 1965, p. 146–152.
2. 2. Dupák, J. - Vlček, I. - Zobač, M.  Electron gun for computer–controlled welding of small components. Vacuum, , 62, 2001, p. 159–164, ISSN 0042-207X.
3. 3. Vlček, I. - Zobač, M. - Dupák, L. - Dupák, J. - Kapounek, P.  Prototyp stolní elektronové svářečky MEBW–60/2. Jemná mechanika a optika, , 53, 2008, p. 27–29, ISSN 0447-6441.
4. 4. Zobač, M. - Vlček, I.  Electron Beam Welding in ISI Brno: Past and Present. Recent Trends (11th seminar), Brno: ÚPT AV ČR, 2008, p. 109–110, ISBN 978-80-254-0905-3.