Electrified drives

Machining requirements and features of different housing types

Highly integrated housing

Highly integrated electric motor housing

Description: Highly integrated, complex housing with stator mount, transmission mount and connection for the power electronics. High functional integration saves assembly costs. Compact design. Complex cast housing as a result.

FEATURES

• Stator incorporated directly in the housing or via a stator carrier / cooling jacket
• Stator bore with stages and flat surfaces as functional surfaces
• A bearing bore of the rotor is integrated coaxially with the stator bore in the housing
• Positioning of the second bearing cover via dowel pins or fitting surfaces; second bearing bore must be coaxial
• Bearing bores of transmission stages integrated in the housing; high concentricity and positional accuracy are required
• Cooling channels partially integrated in the housing
• Complex cast aluminium housing

MACHINING REQUIREMENTS

• Elaborate contour trains with several diameter levels ( high cutting forces and large machining volume)
• Mixed processing (-> chip separation / removal)
• Interrupted cuts (-> contacting, cooling circuit)
• 15°-30° flat lead-in chamfers (-> flow chip formation and high radial forces)

Pot-shaped housing

Pot-shaped electric motor housing

Description: To reduce the complexity, in particular to implement a simpler construction of the cooling jacket, pot-shaped or bell-shaped housings or stator supports are used.

FEATURES

• As an intermediate housing for integration in the overall system
• Stator bore with stages and flat surfaces as functional surfaces
• A bearing bore of the rotor is integrated coaxially with the stator bore in the housing
• Positioning via fitting surfaces on the outer surface
• Cooling channels as ribs on the outside
• Thin-walled, susceptible to vibration
• Tension problematic

MACHINING REQUIREMENTS

• Extremely thin-walled parts (-> ap corresponds to wall strength)
• Outer cooling ribs must be machined
• Pot or bell shape (-> promotes vibrations, special clamping concepts and vibration dampers)
• 15°-30° flat lead-in chamfers (-> flow chip formation and high radial forces)

Tubular housing

Tubular electric motor housing

Description: The simplest design of motor housings is tubular. The length of the housing and thus the electrical machine can be varied comparatively easily for different powers. As a result, the installation effort increases due to the low level of functional integration.

FEATURES

• No rotor bearing bores integrated in the housing
• Two bearing covers to hold the rotor
• Positioning of the two bearing covers over fitting surfaces for coaxiality of the bearing points
• Minimal complexity
• Practically rotationally symmetrical
• Thin-walled, susceptible to vibration
• Tension problematic

MACHINING REQUIREMENTS

• More stable components usually with an internal cooling structure
• Extruded profiles also possible (AlSi1 -> flow chips)
• Without clamping straps (-> special clamping concepts)
• Partly with fits on both sides in IT6 tolerance

Hybrid housing

Hybrid transmission housing and hybrid module/intermediate housing

Description: Integration of the electrical machine into the existing transmission architecture using disk-shaped hybrid modules or intermediate housing. Space neutral structures are also implemented with partially pot-shaped housings as slide-in parts.

FEATURES

Hybrid module/intermediate housing

• Mainly incorporation of the stator
• No rotor bearing with disc shape
• Rotor bearing integrated with pot shape

Hybrid transmission housing

• Extreme length-diameter ratios
• Thin-walled, susceptible to vibration
• Elaborate contour trains
• Interrupted cut

MACHINING REQUIREMENTS

Hybrid transmission housing

• IT6 tolerance
• High demands on coaxiality and stage dimensions
• Restricted maximum weight and moment of tilt

Pre-machining

Pre-machining

The use of an ISO boring tool is particularly suitable for pre-machining. This method allows high cutting speeds and feed rates to remove material quickly and economically. Under specific conditions, for example with precisely pre-cast parts and corresponding machine conditions, the first roughing operation can be omitted.

Semi-finishing

Semi-finishing

During semi-finish machining, the complex contour train of the electric motor housing is prepared. This is done in such a way that the complete contour with chamfers and radial transitions are produced in the required quality during finish machining. This step allows the housing to be shaped optimally. Depending on spindle power and stock removal, it may be necessary to split the semi-finish machining into two steps.

Finishing

Finishing

In the final step, the stator drilling is precisely machined with a fine boring tool that has finely adjustable indexable blades and guide pads.

External Machining stator housing

External machining of stator housings for electric motors is a demanding task. These housings, which often come in tubular or pot-shaped designs, are crucial for the efficiency of the electric motor. Several challenges have to be overcome during the process. The thin-walled aluminium housings with integrated ribs for the cooling circuit require the highest precision in terms of diameter accuracy, shape and position tolerances. The concentricity between different diameters is of huge importance.

Machining solutions for...

Basic

Prototype solution with standard tools

• High flexibility
• System for pre- and finish machining
• Modular design
• Standard troughs from Ø 87 - 1000mm 
• Fine boring clamp adjustable in the µm range
• Easy handling

Pre-machining

• Helix milling cutter

  with ISO indexable inserts

  • Coated ISO indexable inserts made of carbide or PCD-tipped indexable inserts
  • Reduced cutting forces
  • Standard product
  • HSK extension for different machining depths

• ModulBore

  Boring head with bridge module

  • Pre- and finish machining system
  • Modular construction
  • ISO cartridges

Finish machining

• ModulBore

  high level of flexibility during boring and fine boring

  • Pre- and finish machining system
  • Modular construction
  • Standard range from ø 87 mm – 1000 mm
  • Fine boring cartridge adjustable in the µm range
  • Easy to handle

Performance

Series solution with HSK-63 / HSK-100

Process-safe solution with adapted performance and requirement spectrum

• Three-stage process (pre-, semi-finish and finish machining)
• Particularly light tools
• Large components on compact machines
• Optimal solution for small and medium quantities

Pre-machining

• Helix milling cutter

  with ISO indexable inserts

  • Coated ISO indexable inserts made of carbide or PCD-tipped indexable inserts
  • Reduced cutting forces
  • Standard product
  • HSK extension for different machining depths

• PCD form cutter

  contour machining the bottom of the bore

  • Brazed cutting edge
  • Special contours possible
  • Can optionally be used with HSK extensions

Semi-finish-machining

• Precision boring tool

  with ISO indexable inserts

  • Tool shape adapted to magazine changer
  • Coated ISO indexable inserts made of carbide or PCD-tipped indexable inserts

• Precision boring tool

  single-stage or multi-stage

  • ISO cartridges
  • PCD-tipped ISO indexable inserts
  • Tool body made of aluminium

• Precision boring tool

  single-stage or multi-stage

  • ISO cartridges
  • PCD-tipped ISO indexable inserts
  • Tool body made of aluminium

Finish machining

• Fine boring tool

  with guide pads

  • PCD-tipped indexable inserts
  • Finely adjustable
  • Guide pads made of PCD
  • Tool shape adapted to magazine changer

• Fine boring tool

  in lightweight construction made of steel

  • PCD-tipped indexable inserts
  • Cermet indexable inserts for machining of steel bearing bushes
  • Finely adjustable and temperature stable
  • Guide pad technology with EA system

Expert

Series solution with HSK 100

Highly productive for large diameters

• Three-stage process (pre-, semi-finish and finish machining)
• Large machining diameters > 220 mm
• Highest performance and precision
• Ideal process for high volumes and short cycle times

Pre-machining

• ISO boring tool

  aluminium construction

  • PCD-tipped indexable inserts
  • ISO cartridges
  • Single or multi-stage design

Semi-finish-machining

• Precision boring tool

  Aluminium construction

  • PCD-tipped indexable inserts 
  • Design as welded construction or with tool body made of aluminium

Finish machining

• Fine boring tool

  in lightweight construction

  • PCD-tipped indexable inserts
  • Cermet indexable inserts for machining of steel bearing bushes
  • Finely adjustable and temperature stable
  • Guide pad technology

• Actuating tool

  for u-axis-systems

  • Suitable for machining of housing variants
  • To compensate for insert wear