Breviary Technical Ceramics






7.5 The Design of Parts

7.5.1 Basic Rules

  • Aim for simple forms and dimensioning that is suitable for manufacturing
    o adapt the design to suit the forming process of the green body,
    o make the forming process and sintering processes easier,
    o split complex forms into several simpler pieces,
    o avoid over-specifying surface properties and unnecessarily close tolerances.
  • Avoiding stress concentrations
    o minimise notch stresses,
    o apply forces over large areas,
    o avoid sudden changes in cross-sectional area,
    o avoid corners and sharp edges.
  • Minimise tensile stresses
    o specify cross-sections appropriate to the expected loading,
    o convert tensile stress into compressive stress through appropriate construction,
    o include compressive pre-stressing,
    o arrange for forces to be applied in a manner suitable for ceramics
  • Avoid material accumulations
    o pay attention to keeping wall thickness as uniform as possible,
    o separate the nodes in the design,
    o avoid sudden changes in cross-section,
    o design for good densification.
  • Minimise final finishing
    o specify the shape of the green body and the green body machining, leaving only very little working allowance for final finishing,
    o prefer green machining to final finishing,
    o allow only small and limited machined surfaces,
    o only specify requirements that are absolutely necessary,
    o define non-machined roundings and chamfers.
  • Pay attention to manufacturing-specific details
    o ease removal from the mould,
    o avoid undercuts,
    o choose the most favourable forming process for the green body,
    o avoid thin walls and bridges,
    o aim to keep the component proportions suitable for manufacturing,
    o create clear seating and fastening facilities for subsequent machining
    o pay attention to special requirements of the individual manufacturing steps such as:
       - wet and dry pressing,
       - extrusion
       - sintering and
       - glazing.


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