Design Guide Topic 1

Corner Breaks

• Fillets and radii improve plastic flow, prevent stress concentration under loads and increase component strength.
• Fillets and radii as small as .030" can make marked improvements.
• Corner breaks can reduce damage when a bulk handling process is used.
• Chamfers protect holes from damage, and improve plastic flow.

Draft

• Required to eject component from tool cavity.
• Greater draft is needed for internal features due to shrinkage, typically 0.50" - 2.00" per side.
• Draft for external features is usually .000" - l.00" per side depending on configuration.

Uniform Wall Section

• Uniform wall sections provide predictable shrinkage, improved plastic flow, reduced porosity and uniform cooling.
• When wall thickness variations are necessary, they should be as gradual as possible.

Ribs

• Increase strength by distributing loads over a larger area of the component, while allowing for reduced wall sections.
• Improve metal flow, increasing integrity, stability and density.
• Provide good locations for ejector pins

Thin Walls

• Walls can be cast to .040" (1.0 mm) with smaller areas as thin as .020" (0.5 mm).
• Thin walls cool more rapidly than thick sections.
• Reduce costs by reducing plastic volume and shortening cycle times, thus increasing production rates.
• Thin walls produce a hard outer skin which offers higher impact and fatigue strengths.