Cylinder crankcase

The cylinder crankcase, also known as the engine block, is the central element of the combustion engine. Depending on the vehicle model and engine size, different models and sizes are available, from the 2-cylinder series engine to the 12-cylinder engine in V-configuration. In the automotive sector, aluminium alloys are mainly used due to the weight advantage. For the cylinder bore, this requires the use of cast sleeves or wear-resistant Coatings to ensure a high mileage. In machining, this often involves mixed machining with aluminium and cast iron and the use of extremely abrasive coatings. The higher combustion pressures in modern engines increase mechanical and thermal loads, resulting in more stringent quality requirements for the features to be machined.
Cylinder crankcase with numbering

Key features

  1. Cylinder bore
  2. Water pump bore
  3. Crankshaft bearing bore

  • A tool used for roughing a cylindrical bore

    1. Pre-machining – cylinder bore

    Pre-machining includes boring cylinder bores with sturdily designed indexable insert tools. They handle high and fluctuating stock removal. Depending on the workpiece material, PCD-tipped or coated HM indexable inserts are used to ensure
    long tool lives and high precision.

  • A tool used for finishing a cylindrical bore

    2. Finishing – cylinder bore

    Fine boring tools bring the bore to the exact dimension for subsequent coating or liner use. The tools are designed for high stability and feeds. They also produce the required dimensional accuracy and surface quality.

  • A tool performing finishing of a cylinder liner surface.

    3. Finishing – cylinder bore Surface

    After coating or liner fitting, the final machining of the bore surface takes place. Precise fine boring tools ensure dimensional and shape accuracy, have cutting compensation, and enable contact-free retraction from the bore.

  • A tool performing a honing relief.

    4. Honing relief

    Honing relief is mostly produced with special milling or actuating tools. The complex transition geometries and mixed machining that sometimes occur require coordinated tool and cutting material selection.

1. Cylinder bore

PROCESS CONDITIONS
  • Fluctuating casting and stock removal situations
  • Wear-resistant coatings (TWAS coating) are sometimes included in the components
  • Partly mixed machining through the use of different materials
    -> aluminium crankcase and grey cast iron cylinder liner
  • Machining with poor accessibility due to component size
  • Diameter tolerance before honing of up to 40 μm
Two tools for roughing and finishing

Blind Bore

1. Pre-machining
Boring tool
 
  • Stable and cost-effective tool design with indexable inserts and easy-to-adjust cartridges, including for fluctuating component stock removal.

2. Finishing
Fine boring tool with EA System
 
  • Compact multi-blade tool design for maximum feed rates and easy adjustment.

On the left a compensation tool and on the right an adjustable fine boring tool for machining

Cylinder Bore Surface with Sleeve

3. Finishing
Compensation tool (Machining centre)

  • Cutting compensation through face-side serration can be implemented automatically and directly in the machine. Cutting-edge lifting through positional offset and special tool design enable contact-free retraction.

or


Actuating tool (Custom machine)

  • Depending on the machine type, the inserts are retracted and actuated in a defined manner using a drawbar, adjusting spindle or rotary drive. This enables contact-free retraction and precision blade readjustment.

On the left a circular milling cutter and on the right an adjustable boring tool

Cylinder Bore Surface

4. Honing relief
Circular milling cutter (Custom machine)

  • Multi-blade tool design with maximum flexibility in the selection of indexable inserts.

or


Actuating tool (Custom machine)

  • Defined blade actuation through drawbar/push rod. Flexible contour possible.

2. Water pump bore

PROCESS CONDITIONS
  • Multi-stage bore with defined radius transitions
  • Diameter tolerances in H8 range
  • Circularities of 10 – 20 μm
A PCD step boring tool

1. Semi-finishing
PCD step boring tool
 
  • Optimised PCD insert geometry for controlled chip breaking and with interchangeable solid carbide drill for efficient use of cutting edges on boring stages.

3. Crankshaft bearing bore

PROCESS CONDITIONS
  • High coaxiality of the individual bearing journals to each other
  • Repeated cutting due to the interrupted cut
  • Mixed machining for fine machining through bearing shells
  • Diameter tolerances of 0.2 mm
  • Surface specifications of Rz 3.2 μm
  • Circularity < 3 μm
Machining of the crankcase (crankshaft bearing bore) using a precision line boring bar

Maximum productivity with one-shot solution

1. Pre- and finishing machining
Precision line boring bar

  • Optimum coaxiality on the component due to additional bearings opposite the machine spindle, including for long component lengths.

Two fine boring tools – the left one for roughing and the right one for finishing.

Ultimate process reliability with 2-step process

Pre- and Finishing
Fine boring tool
 
  • Pre-machining stage and additional micro-machining at the finishing stage for the highest quality requirements and process reliability.