Electron beam welding machines in ISI: past&present

E-beam welder ES-2 manufactured and installed in ISI, Brno

The Institute of Scientific Instruments (ISI) of the Czechoslovac Academy of Sciences (CSAV) was founded in 1957 as successor of so-called „Scientific Workshop“. In 1960 the founders, together with three Laboratories of CSAV in Brno, moved to a new site on Kralovopolska street.

The very first experiment with thermal effects of electron beam in ISI was made in about 1963 by Eng. Karel Hladil who used an old electron microscope for this experiment.

The real technological applications of electron beam in ISI have been made by Eng. Ladislav Zobač in the years 1964 through 1966, which resulted in the design of electron beam welder ES2 after 1968.

The „birth“ of electron beam welder ES2

Fig. 1: Multipurpose vacuum furnace (ES1)Fig. 1: Multipurpose vacuum furnace (ES1)

Practically applicable electron gun for electron beam welding (slightly modified gun of electron microscope) has been incorporated into a „multi-purpose“ vacuum furnace designed by Eng. Ladislav Zobač in about 1964. The electron gun in this equipment had only 250 W, limited by the parameters of the power supply,(50 kv, 5 mA). The results of experimental electron beam welding realized in 1964–65 in this equipment have been published in Slaboproudý obzor (1. To this publication responded in 1968 strongly Eng. Jiří Bušta from the Institute of Nuclear Research (Řež). He organized a venture which resulted in participation of those interested in the new technology, on development and manufacture of 5 electron beam welders, namely:

  • Eng. Ladislav Zobač, Institute of Scientific Instruments (UPT) Brno.
  • Eng. JIří Bušta, Institute of Nuclear Research (UJV) Řež.
  • Eng. Jiří Sika,Factory of Nuclear Energetics (ZJE) Bolevec.
  • Mr. Mrázek,Factory Tesla-Opočno.
  • Eng. Vladimír Ustohal, Military technical Academy (VTA AZ) Brno.

These participants met at the end of 1968 and agreed to contribute, each according to his possibilities, to the design and manufacture of 5 electron beam welders:

Eng. Zobač pledged to design and prepare the documentation for the manufacture of electron gun, the working chamber, work-piece manipulator and parts of vacuum system (diffusion pump and vacuum valves).

Eng. Bušta promised to take care of design and manufacture of control electronics in UJV.

Eng. Sika pledged to take care of vacuum chambers in Škoda-Plzeň.

Mr. Mrázek promised to manufacture the vacuum systems in Tesla-OPočno.

Eng. Ustohal promised to take care of financial coverage of 5 electron guns in UPT.

The high voltage power supply (50 kV/1,5 kW), part of an X-ray equipment, purchased each participant in Chirana-Modřany.

All these preparatory actions have been realized within 1969, without any official contracts, just as „gentlemen agreements“ . With the technical assistance of ISI, each one of the participants assembled and put in operation one welder, marked ES2. Another two ES2 welders have been manufactured later in Energetické strojírny-Brno, one for the Nuclear Plant in Jaslovské Bohunice, Slovakia, and the other for a research institute (VUSE-Běchovice). The stories of all these seven welding machines may be, for someone, quite interesting, but do not find place in this paper. We shall follow the fate of only one of them, which is still used, after more upgrades, in ISI Brno.

Fig. 2: Original design of E-beam welder ES2Fig. 2: Original design of E-beam welder ES2

Applications and upgrades of ES2 in ISI between 1970 and 1990.

Since its „birth“ in 1970 the ES2 welder in ISI has been intensely used, first of all of course, to cover all the needs of the three scientific departments in ISI. It also helped to solve technological problems of many other institutions. In this way, and also by experimental applications of electron beam heating, extensive knowledge of electron beam technology has been accumulated.

To satisfy the broad variety of demands, the ES2 welder had to be continuously improved. First upgrades of ES2 electronics have been made by Eng. J. Husták. They concerned particularly the the beam control system. Very useful was the implementation of scanning mode providing better control of the welding process and other options. e.g. visual inspection of welds at higher magnification (up to 30×) immediately after welding, before venting the working chamber.

The other parts of ES2 have also been continuously developed. First of all the recent electron gun, a derive of electron microscope gun, has been replaced by a new construction. With the power of 50kV/30 mA the beam supplied by this gun could penetrate 10 mm deep in stainless steal. The beam could be, on the other hand, made fine enough to weld the metal sheets only 0,02 mm thick.

The welder ES2 has also been continuously provided with various aids (jigs) needed for fixation of work-piece parts, work-piece cooling aids, vacuum chamber extentions, etc. Thanks to the conception of the welder, with these extentions we have been able, in rather small working chamber (60 cm in diameter, 50 cm long) to weld tubes several meters long. All the time since its installation in ISI in 1970, the ES2 equipment covered not only all the needs of Electron Optics and Cryogenics departments in ISI, but also satisfy the demands for electron beam welding of many external institutions. Much valuable knowledge and experience has been gained through this activities.

EB welders in ISI after 1991

Renovation of ES2

Fig. 3: Modified e-beam welder ES2(D)Fig. 3: Modified e-beam welder ES2(D)

In 1991, after Eng. Ladislav Zobač retired, his college Eng. Jan Dupák took over the EB welding activities. First of all he continued with the ES2 upgrades. He, with his co-workers exchanged step by step: the electron gun 2, the pumping system, control electronics, high voltage power supply, work-piece manipulator and added some new options. Frankly speaking, only the vacuum chamber (hence the conception of the welder) remained unchanged. It deserves to be renamed , e.g. to ES2D (D for Dupák). The modified welder works in ISI up to now (see Fig. 3).

Desk-top electron beam welder SES-1

Fig. 4: E-beam welder SES-1 installed in ISI, and its designer  Dipl. Eng. Jan DupákFig. 4: E-beam welder SES-1 installed in ISI, and its designer Dipl. Eng. Jan Dupák

After ES2 renovation Mr. Dupák constructed a brand-new EB-welder, SES-1. His leading idea was apparently to build a „handy“, versatille EB machine for welding of small components. Inspired evidently with proved conception of ES2 he chose a cylindrical working chamber of small dimensions (235 mm in diameter and about 125 mm long), oriented horizontally and provided with three identical mounting openings, so enabling to position the electron gun vertically or horizontally (left or right). He designed a new electron gun, which can provide a fine electron beam with the power up to 2 kW. The high vacuum pumping system comprises one membrane pump and two turbomolecular pumps, one for electron gun and the other for working space evacuation. All three pumps are simultaneously switched on for evacuation, and switched off for venting. No vacuum valves, except for venting, are needed. The pumping time is 2–3 minutes, the venting takes about 30 seconds.

Micro Electron Beam Welder MEBW 60/2

Fig. 5: E-beam welder MEBW-60/2Fig. 5: E-beam welder MEBW-60/2

Fig. 6: MEBW-60/2 control software GUIFig. 6: MEBW-60/2 control software GUI

The SES-1 „desk-top“ welder attracted attention of the manager of a German firm FOCUS GmbH, Mr. Merkel, and he expressed his intention to include this welder into its production program. After he confirmed his interest and made a contract with ISI in 2007 to deliver one prototype and complete production documentation the recent SES-1 had to be thoroughly renovated.

Only minor changes and improvements have been made in electron gun, the working chamber and manipulator. The frame of the welder and bench have been made more practical and better-looking.

The electrical equipment of the welder has been totally changed. The power unit (the high voltage supply) has been reconstructed and made more reliable. The power limit was increased up to 2 kW.

Fig. 7: Photo engraved on stainless steel sheetFig. 7: Photo engraved on stainless steel sheet

The control and monitoring electronics has gone through essential changes. It was consistently digitalized, which provided very useful new features and possibility of computer control. The most useful proved to be the implementation of the „scanning mode“, in which the welder is operated as a scanning electron microscope. That, e.g. provides the possibility to inspect the weld seam at 30× magnification right of the weld has been made. The control software allows image acquisition, arbitrary shaped welding (“Draw-a-weld” mode), micro-engraving techniques (see Fig. 6), surface heat treatment and other functions.

The MEBW 60/2 is now produced in Germany by FOCUS GmbH under licence, with custom working chambers and manipulators.