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    dihw MAGAZIN

    Feature articles from research and industry from the basis of the comprehensive editorial content about specific usage and application of tools with superhard coatings.

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    Continuous process for electromobility

    Internal and External Machining of the Stator Housing

    With increasing numbers of electric vehicles, not only very
    precisely manufactured parts are required, but also the most
    efficient production possible. One part that is particularly
    demanding in terms of machining is the motor housing for the
    electric motor. MAPAL has already established a three-stage
    solution for machining the stator bore. The precision tool
    manufacturer now presents a large tool for external machining.

    • Tyrolit
  • Three-stage solution for the stator bore
    In the pot-shaped version of the motor housing, the stator
    carrier housing is inserted into the main housing as an
    intermediate housing. Typical diameters for the thin-walled
    aluminium part are between 200 and 240 mm on the inside and
    between 240 and 260 mm externally. Concentricity of the
    various bearing and mounting diameters is critical to the
    performance of the electric motor, which requires very precise
    machining within tight tolerances.
    The first of three steps for machining the stator bore is pre-
    machining with a boring tool. The blank has casting bevels that
    result in cutting depths of up to 6 mm to be removed. For this
    purpose, special indexable inserts with a supporting arc shaped
    land are used to avoid vibrations. This also ensures that small
    chips are produced, which can be easily removed. In the
    subsequent semi-finish machining, the complex contour path of
    the electric motor housing is pre-machined in such a way that
    the complete fine machining with chamfers and radial
    transitions can be produced to μm accuracy with the finishing
    fine boring tool. The tools are individually designed for the
    respective customer depending on the stock situation,
    machinery and clamping setup. Different steps in the housing
    are taken into account with the cutting-edge positions of the
    tools, as are cast-in or pressed-in steel bushings for bearings.
    While the majority of the workpiece is machined with PCD,

    carbide cutting edges are used for the steel area.

    World first for external machining
    On the outside, the part features a helical circumferential
    groove. Because the coolant later flows through this groove
    after it’s been inserted into the outer housing, the stator carrier
    is also known as the “cooling jacket”.
    MAPAL is presenting new external machining tools at the EMO
    in Milan. They are among the more unusual tools. After pre-
    machining, a bell-shaped tool takes over the complete finishing
    of the outside. The specifically designed lightweight tool is
    equipped with indexable inserts and guide pads and was
    provided with bars in the right places to save as much weight as
    possible and to get rid of chips through large openings. The fine

    machining tool promises high roundness and accuracy.

    Complete machining on machining centre
    Internal machining is possible very quickly and accurately with
    the boring tools. In addition, the outside can also be machined
    in the same clamping setup without moving. The machining
    centre solution caters to customers who are embracing the
    transformation to e-mobility with existing machinery geared to
    machining large cubic aluminium housings.
    Those who start their production on a greenfield site can, of
    course, choose which machining strategy is best for them.
    MAPAL has developed an alternative machining solution in a
    joint project with a machine manufacturer. In this case, the

    process was rotated 90 degrees for use on vertical lathes.

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