DESIGN DEVELOPMENT FOR INJECTION MOULDING

Before going too far down the design route it is necessary to establish end-use requirements.  This is probably the most important stage because if the specification is incomplete then the product or component may not be suitable for the application.

There are a number of good reasons to choose plastics:

  • Different appearance – plastics provide for a wider variety of shapes and colours
  • Improved performance – Longer life, easier to handle, corrosion resistance
  • Weight reduction
  • Cost reduction
  • Fewer components – reduced assembly cost
  • Easier and/or faster assembly

END USE REQUIREMENTS

End use requirements fall into the major categories of functional, aesthetic and manufacturing related.  More specifically the following are factors to consider:

  • Any special strength characteristics.  When considering loading, for example, it is vital to be clear on the type of load, the rate at which the load may be applied, duration and frequency.
  • Life expectancy.
  • Environmental.  This can include exposure to chemicals/ UV light, temperatures, relative humidity.  Not forgetting any conditions that may apply during assembly and storage, such as exposure to paints, solvents, adhesives and even household cleaners.
  • Aesthetic requirements including surface finish.
  • Assembly with other parts.
  • Dimensional requirements.  It is necessary to specify critical dimensions and flatness, all with realistic tolerances.
  • Cost considerations – maximum cost for the product or component to be viable.  Part of this calculation is likely production quantities.
  • Legal requirements including food contact, flammability and any dimensional standards, e.g. for plumbing fittings.
  • Need for recyclability.

FREE DESIGN GUIDE

A checklist is provided at the back of the Rutland Plastics Design Guide and many of the above points covered in greater depth in other articles.