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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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