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Plastic mouldings Plastic mouldings

Summary

  • Failure mode Impact damage and pulling of hoses can cause breakage.
  • Durability feature Use of impact resistant grades of plastic for example ABS.
  • Cost

Good practices

  • Good practicesImpact resistant plastics
  • Good practicesTest new designs

Bad practices

  • Bad practicesAvoid notches
  • Bad practicesFlimsy parts

Key facts

  • 28% of vacuum cleaners failed to meet customers’ expectation of a 5-year lifetime.
  • Which? surveys show that the most common faults are loss of suction, blocked filters and brushes.

Icon key

  • Failure mode Failure mode
  • Durability features Durability features
  • Cost saving Cost saving
  • Low cost Low cost
  • Cost neutral Cost neutral
  • High cost High cost

Key failure modes

Vacuum cleaners are susceptible to impact damage that can cause cracks or breakage of plastic parts.

Hoses of cylinder cleaners may be used to pull the vacuum cleaner along, stretched to reach awkward places and bent around sharp corners.  Latch mechanisms of upright cleaners experience repeated stress cycles which can cause fatigue fracture failure.

Early life

  • Impact damage can cause breakage of external plastic parts.
  • Hoses will break early if they are not sufficiently robust to withstand normal use and likely abuse.
  • Hoses are flexible plastic tubes reinforced with either metal wire or a harder plastic wire. The plastic needs to be sufficiently thick to prevent it from being damaged by foreseeable misuse.

Later in lifetime

  • Repeated use of flexible hoses will eventually cause stress fatigue fracture. The length of time for this to occur will depend on the hose design and choice of materials.
  • Latches of upright cleaners also suffer from stress fatigue and can fail before the expected lifetime of the cleaner if the design is unsuitable.
  • Choice of plastic type also affects the susceptibility to fatigue failure.

Specification for improved performance

The specification below provides the recommended improvements needed to improve product durability. They are ranked from bronze to gold based on the effectiveness of the change in improving durability, with bronze being the minimum and gold being the maximum.

No damage after bump test; 40,000 oscillations – no damage

  • No observable damage after “bump test” and cleaning head impact test. Some vacuum cleaner manufactures drop cleaners repeatedly from 1 meter onto a hard surface to ensure no damage occurs.
  • The EU Eco-design Regulation for vacuum cleaners requires that hoses are usable (i.e. not damaged) after 40,000 oscillations under strain. Designing these so that cylinder cleaners can be moved by pulling hoses will prevent early failures.

Drop tests; test latch mechanism; 51,000 hose oscillations

  • No observable damage after “bump test” and cleaning head impact test. Some vacuum cleaner manufactures drop cleaners repeatedly from 1 meter onto a hard surface to ensure no damage occurs.
  • Avoid “notches” and use a stress fracture resistant polymer such as ABS, PC/ABS or HIPS.
  • Reliability can be specified by the number of open/close mechanisms of the latch; e.g. 5 cycles per week for 10 years is 2600 cycles. A result of no cracks observable at end of test is required.

62,000 hose oscillations

Testing to demonstrate performance

  • Plastic mouldings – Test methods in EN 60312-1:2003, sections 6.5 (Impact resistance of cleaning heads) and section 6.7 (Bump test). Also consider using a drop test.
  • Hoses –  Test methods in EN 60312-1:2013, sections 6.6 (Deformation  of hose and connecting tubes), 6.8 (Flexibility of the hose) and 6.9 (Repeated bending of the hose). No damage for 40,000 oscillations.
  • Latch mechanism – No standard test method exists and so agree with supplier an in-house test method that the cleaner must pass.

Cost implications

Improved reliability of components can reduce early returns and improve brand reputation which, in turn, can lower business costs and increase long-term sales.

To calculate overall cost savings for your business, use the WRAP cost/benefit analysis tool (currently in draft form and available on request).

Saving

Neutral

Low cost

Use impact resistant grades of plastics

Use, for example, ABS, PC/ABS or HIPS for mouldings to avoid impact damage and cracks due to cyclic fatigue.

High cost