Metal v plastic: a debate that continues going round

In his article in Gear Technology magazine, Senior Editor, Jack McGuinn argues that plastic gears are still ‘a work in progress’. Even given the variety of materials that can be added to plastic to overcome its deficiencies. His article linked below elaborates on this as well as compiling a ‘good/bad’ list….

The pros and cons of the materials are listed as follows….

Plastic – the good…

  • Elimination of machining operations; capability of fabrication with inserts and integral designs
  • Lightweight
  • Reduction in shock, noise and vibration
  • Parts uniformity
  • In many applications, no or very little lubrication; self-lubricating in some cases (nylon)
  • Corrosion-resistance.
  • More forgiving tolerances than with metal gears
  • Relatively simple production, with no pre- or post-production

…..And the bad

  • Material cost can be markedly higher than basic metal gears, especially if custom poly materials are used
  • Difficulty in wedding plastic gears with metal shafts
  • Often less strength than similar metal gears
  • Problems with high tolerances vs. metal gears
  • Not as dimensionally stable as metal gears in that plastic gears are adversely affected by temperature and humidity conditions

Follow the link here for a fuller appraisal of the issues.

Although, the article above acknowledges the many benefits of plastic, a more favoured analysis of its application appears in a much older article in Gear Solutions which can be viewed here.

Certainly as the usage of plastics develops in conjunction with other materials, its prevalence within the industry will increase.