DESIGN FOR MOULDABILITY (PART 1)

INTRODUCTION

The aim for the most cost effective solution is to design parts in their finished form, i.e. without the requirement for secondary operations and with no waste of materials.

The main advantages of injection moulding are:

     Production of highly complex parts is possible

     Tight tolerances are repeatable

     Features such as bosses, snap-fits, undercuts and holes can be moulded in

     High quality surface properties are possible

     Automation is easier on long production runs

However, when considering injection moulding there are various design considerations:

     Nominal Wall Thickness – The ‘Goldilocks’ rule should apply – not too thick and not too thin.

     Radii – Sharp corners should be avoided as these increase stress in a moulded part.

     Ribs – Correct rib design is essential to achieve the right balance between strength and aesthetics.

     Bosses – Correct design is essential for optimum strength and appearance.

     Undercuts – To be avoided if possible.

     Coring – Elimination of material from a particular area of the component to reduce wall thickness and material content.

     Draft Angles – To facilitate part removal from the mould.

     Textures, Lettering and Recesses – All design features that can enhance an injection moulded product or component.

     Recesses - Not normally a problem but they can impact on the flow of the plastic.

Each of the above will be discussed in greater detail in future articles.

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