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BURAN Orbital

Spaceship Airframe

Creation

Automated Technology of Cabin Assembly-Welding for BURAN Orbiter

Ryazantsev V.I., Kovyazina S.I.
The problem of manufacturing the BURAN cabin by assembly-welding is considered. New technology of assembly-welding on the UPSF-2 specialized equipment ensuring reliability, resource and quality of production, reduction time of the production and preparation of manufacture is submitted. Characteristics of the UPSF type equipment are indicated: UPSF-2, UPSF-3-1, UPSF-3-2, UPSF-4 - ensuring assembly-welding of products by dimensions: by a length - 900 (27000 mm); by a diameter - 1600 (4700 mm).

The development of new flight vehicle, the BURAN Orbiter, required the creation and introduction of new science technologies with application of the automated flexible integral equipment. These technologies and equipment maintained reliability, resource and quality of production, growth of productivity, essential reduction of labor input, terms of manufacture preparation and industrial powers.


Assembly - Welding Technology of the BURAN Orbiter

The processes of assembly concern to the most labor-consuming processes of aircraft and machine building industry. Its fraction is the half of total labor input of manufacturing.

Main properties of production resulted from processes of assembly. The use of significant volume of manual work at main assembly operations gets to the creation and introduction of new technologies and equipment.

The welding joint finds wide use for the details and units operated under conditions of vibration loads, difference of the temperatures and vacuum. The welding takes up a leading place among the technological productions of machine building industry and, first of all, of flying vehicles manufacture. The creation of the sealed thin-walled structures of aviation and space vehicles is based on the use of foreign and domestic experience. The firms Siyaki (France), Komatsu (Japan), ESAB (Sweden) create the specialized welding installations supplied with the rotators with horizontal and vertical inclined axes and means of moving of the burners in three mutually perpendicular planes. For manufacture of the sealed welded tanks in the domestic space-rocket industry and machine building industry the PK-12, PK-27, KZ-9909 welding equipment supplied with the rotators with the horizontal axis is used.

This equipment has unit-type-milling heads to carry out the technological processes of milling and welding. Such equipment can not be used for complex automation of the assembly activities.

Creation of the Shuttle’s pressurized cabin was solved by Rockwell International (USA) in another way.

The local automation means were made for every sealed-intricate seam. On the assembly-welding stand, the tool for milling and welding moved along installed guides. Such technology provides creation of the units but can not form the base of flexible integral automation of the assembly processes. Rockwell International for butt joint welding used the traditional technology providing application of keyboard clamping to press the edges to the backing plate. Such lacks are inherent in the specified technology as leaky and irregular pressing of the edges during the welding because of the necessity of increase of length of the heated up joint what is interfered by keyboard clamping. It results in formation in the welded joint of so-called ‘steps’ and, consequently, lacks of penetrations, burn-through, cracks and other welding defects. At manufacturing of the cabin by Rockwell International the up to 28% length of the welds had defects that required repair.

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Figure 1. Main characteristics of the UPSF type units

The task of complex automation of assembly-welding was put for developing of technology and equipment for the manufacture of the BURAN Orbiter’s cabin.

This technology will be able to increase quality of assembly-welding by reduction of defects quantity in the welded joints in comparison with the results of Rockwell International. The tasks on essential simplification and equipment cost decrease due to unification of the number of its elements were also put.

The progressive technology and the structure of the specialized equipment on the basis of computer program control machine was designed by NIAT NIAT (Mrs. S.I Kovyazina, Mr. Hristoev U.Ya, Vainshtein I.V., Ryazantsev V.I.) for providing high and stable quality of gasket-welded structures and decreasing of labor input of their manufacture. This equipment covered all the type sizes of made products (with diameter of the circumscribed circle from 200 up to 7000 mm at practically unlimited length) including UPSF-2 (programmed welding-milling installation).

The UPSF-2 installation allows on one workplace under the unified program to make:

  • assembly of butt onboard planes with the inspection of accuracy of edges pressing to the elements of the equipment;
  • milling and sharpening end faces of the welded edges under the program;
  • welding with the application of special heads;
  • scraping bright, hardening and dressing of the welds;
  • quality inspection of the welded joints directly in assembly-welding equipment.

The UPFS-2 installation includes moving portal with a crosspiece as cantilever. On one side of crosspiece the cross-sectional carriage with a slider and rotary milling head are located, and on the other - cross-sectional carriage with a slider and rotary welding head. Under the crosspiece along the line of moving, the rotary element with forward stock is fixed on the machine, and with back stock having a capability of moving along the frame. Forward and back stocks are equipped with rotary faceplates.

The portal, cross-sectional carriages, vertical sliders and rotary heads (around horizontal and vertical axes) motion are automated by two devices of programmed control, such as the VECTOR of 8600-type. The portal (across the frame), cross-sectional carriages and the sliders moving is implemented with the help of closed gear units and turn of the heads around of their axes and the rotator faceplates with the help of gear worm units. As the network member the direct current motor with built-in brakes controlled by converters are used. The main characteristics of the UPSF type installations are given in Tab. 1.

The application of the UPSF-type functional complexes will allow by the radical image to change the technological process of assembly, mechanic machining under welding and welding of intricate spatial designs.

During welding the arc interval 0,2 ± 0,005 mm are supported along length of a weld of any geometrical shape at the expense of programming of X, Y, Z coordinates. The accuracy of the tungsten electrode passage axis along the axis of the joint of any shape is ± 0.1 mm. The data on longitudinal sag after welding are in Tab. 2.

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Figure 2. Longitudinal sag

Note:
1. * - with stretching the seam. 2. Samples of 1201 alloy of 6-mm thickness.

The application of the UPSF-2 unit resulted that the accuracy and quality of the executed operations didn't depend on the qualification of the welder or miller but quality of equipment and program record and play.

Specialized heads was designed and made for the fulfillment of all technological operations of assembly-welding process on the UPSF-2. They are used for milling straight-line and figured end faces of the details under welding, for mechanized edges scraping under welding, for welding with application mobile local clamping, for the mechanized impact dressing after welding.

All these heads have unified landing places and can be located on any unit of UPSF type.

Experiments showed that two-roller clamping gave best results among UPSF units. Each roller is fixed under an angle to the billet and has a capability of moving together with the sliding bearing. The pressure is transmitted to the preparations from the power gear through the sliders and rollers. The welding head is rigidly fastened to one of the rollers. It provides mechanical copying of the surface at differences from 0 up to 5-mm. The tracking on the altitude at differences of 3-1250 mm is reached at the expense of programmed coordinate on the UPSF installation.

The deformations at welding depend on the processes of heating and shortening at cooling. There are various ways to decrease the residual deformations: tension of the billet, rolling along the seam or near-seam zone, impact dressing etc. The experiments on welding with use of the roller clamping showed that the tension along the axis of the weld was the most effective one; it allowed to lower residual deformations by almost three times.

The cabin of the BURAN Orbiter was manufactured on the UPSF type with use tension member, roller clamping and welding on direct current of the straight polarity. The assembly-welding technology with UPSF-2 application allowed to lower labor input of manufacturing of the cabin in 1,5…3,5 times. In addition, it allowed to reduce quantity of the defects, to improve quality and to increase durability of the welded products in 1,5 …3 times in comparison with the traditional technology.

The UPSF-2 unit is shown in the Figure.


Conclusions

The introduction of the advanced assembly-welding technology of the BURAN Orbiter’s cabin with using of UPSF-2 unit showed next results:

  • For the first time in the world, the problem of integrated automation for the bulky welded hermetically sealed production of airspace industry and economy was solved. That allowed ensuring practically flawless arc welding of high-strength aluminum alloys on machines units with the use of mobile local clamping and tension system. That guaranteed quality of high-performance hermetically sealed welded joints with the minimal deformations and stresses at the high level of mechanical properties. The experimental researches are carried out and the engineering bases of the automated flexible integral technology of assembly-welding on the UPSF-2 type multifunctional machine units are created. Experience on UPSF-2 unit operation allowed to develop the UPSF-2-1, UPSF-3-1, UPSF-3-2, UPSF-4 specialized facilities. Their manufacturing was organized. The wide introduction of the developed technological processes and specialized equipment and tool was done in the manufacture of flying vehicles and advanced aerospace system at 15 enterprises of Russian Federation, as well as at HOMATEK, ZEPPELLIN (Germany) companies.

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Figure 3. The welding-milling unit with rotator and computer program control of UPSF-2 type

Later, the perfection of the developed complex in view of the requirements to new range of products is possible by way:

  • increases of units’ sizes;
  • automation of the adjustment- assembly-clamp processes under welding;
  • expansions of functionality with reference to the new materials (carbon composite material, thermal insulation materials).