A Typical Injection Molding Process

Polymers commonly used for injection molding include

• Polystyrene (PS)
• Acrylonitrile Butadiene Styrene (ABS)
• Polyamide (PA)
• Polypropylene (PP)
• Polyethylene (PE)
• Polyvinylchloride (PVC)
• Other short fiber reinforced plastics

1. Use uniform wall thicknesses throughout the part. This will minimize sinking, warping, residual stresses, and improve mold fill and cycle times.
2. Use generous radius at all corners. The inside corner radius should be a minimum of one material thickness.
3. Use the least thickness compliant with the process, material, or product design requirements. Using the least wall thickness for the process ensures rapid cooling, short cycle times, and minimum shot weight. All these result in the least possible part cost.
4. Design parts to facilitate easy withdrawal from the mold by providing draft (taper) in the direction of mold opening or closing.
5. Use ribs or gussets to improve part stiffness in bending. This avoids the use of thick section to achieve the same, thereby saving on part weight, material costs, and cycle time costs.

• Ribs
• Boss
• Counter bore/sink
• Inserts
• Self-Tapping Screws
• Snap Latches
• Living Hinge

• Incomplete Fillings:
  • not enough resin to fill the mold completely
  • inadequate injection stroke
  • low injection rate
  • low injection pressure
  • resin viscosity too high
  • exotic geometry
• Surface Imperfections:
  • moisture or air bubbles in the resin
  • temperature too high causing resin decomposition
  • not enough pressure to fill the mold completely
  • dirty mold
• Burned Parts:
  • temperature too high
  • polymer trapped and degraded in the nozzle
  • slow chilling cycle
• Warped Parts
  • uneven mold surface temperature
  • design flaws
  • parts removed from the mold too early

• Low costs in mass production
• High precision
• Complex parts. Geometries only limited by mold manufacturability.

• High initial setup costs

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