GEC Alsthom and automated assembly

Citation

(1998), "GEC Alsthom and automated assembly", Assembly Automation, Vol. 18 No. 2. https://doi.org/10.1108/aa.1998.03318baf.005

GEC Alsthom and automated assembly

GEC Alsthom and automated assembly

Three RX130L robots assemble alternator stators; a large scale application

Keywords Assembly, Automation, Energy industry, GEC Alsthom

The cell that is presented here has been designed by The Automated Assembly Department of GEC Alsthom Systems and Services.

The product

Stators assembled by the three RX130 L robots are the fixed part of alternators that are supplied to local power plants (Plate 5). They are made by staking thousands of magnetic steel sheets (electric sheets) that are arranged in torus. Each electric sheet ties in with a variable dimensions area (up to 1m × 1m roughly), according to the stator pattern. Once the stator is assembled, it is a cylindrical set of:

• •

  outside diameter: 1.5 to 3m;

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  height: 1.5 to 5m;

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  gross weight (including implements): up to 240 metric tons.

Application

Electric sheet stacking accomplished by the robots is done on a hydraulic elevating platform, of 7 metres stroke, located in a pit, keeping the work area at roughly 1.2 metres above the floor level.

Electric sheets (supplied on a wooden pallet) are unstacked and rejogged mechanically before being assembled by three RX130 L robots. Three robots are needed in order to cover the entire torus surface and to ensure the required production cycle of an electric sheet fixed every 1.25 seconds. Thus, a complete stator assembly can take several days.

Plate 5 Three RX130L robots assemble alternator stators

As the stator is being assembled, the hydraulic platform's downward movement is synchronized to the robot's work cycle.

Installation benefits

Compared to the previous assembly procedures the customer was using, this installation allows:

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  Deletion of intermediate handling when assembling the stator.

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  Suppression of stacking mistakes. Width verification is done automatically by the robots with correction if necessary.

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  A high precision cell (±0.2 mm radius) that not only deletes all manual rework operations but improves the finished alternator's efficiency as well.

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  Preparation of specific electric sheet bundles (edges) during tooling set up and heavy handling operations.

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  Switching from one stator model to another by:

  ­ setting up appropriate tooling;

  ­ sheet loading;

  ­ robot program selection

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  reducing down time and increasing market reactivity.

RX robot choice

Sheet loading on the elevating platform is done with a rounded movement in order to avoid air concentration (buffer) and thus sheet sliding which would jeopardize the required precision.

The movements require the use of a six-axis robot:

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  The application requires both very high speed and very high precision.

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  Easy programming and flexibility of the cell allow a constant adaptation to the assembly of specific stators dedicated to each customer (total dimensions, sheet number, sheet specifications).

The three robots are mounted on horizontal tracks to allow finished stator extraction and new tool settings on the elevating platform, with regards to safety regulations.