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Popular manufacturing process for plastic products and here we explain how product design considerations must be made.


  • Allows excellent surface finish, repeatability and speed.
  • Mould decorations can be integrated into the actual moulding process, eliminating the need for a separate printing process
  • Colouring is possible
  • Inserts and snap-fits can be moulded to aid assembly


  • Tooling costs are very high, depending on the number of cavities and complexity of the design
  • Large parts take longer to solidify and thus can increase mould cycle times

Design Considerations:

  • High volume production runs only
  • Mould cycle times depend on the size of the part
  • Warping and shrinkage can occur after the part is ejected from the mould cavity, ribbing can help reduce these effects
  • Stress can occur at sharp corners and draft angles
  • Draft angles should be at least 0.5o
  • The melted plastic must inject into the thickest section and finish at the thinnest
  • Wall thickness should be uniform (ideal) or within 10%
  • Uneven wall sections cause the part to warp
  • Ribs should not exceed 5 times the height of the wall thickness, so use many shallow ribs instead


Injection moulding machine. Source: http://www.crabdev.co.uk/comp%20manufacturing.htm

 Source: Manufacturing processes for design professionals; Rob Thompson [2007]