杜邦POM齒輪設計(英文)(pdf 16頁)

DELRIN? acetal resins and ZYTEL? nylon resins are used in
a wide variety of gear applications throughout the world.
They offer the widest range of operating temperature and
highest fatigue endurance of any thermoplastic gear material,
accounting for their almost universal use in nonmetallic
gearing.
The primary driving force in the use of plastic vs. metal
gears is the large economic advantage afforded by the
injection moulding process. In addition, cams, bearings,
ratchets, springs, gear shafts and other gears can be
designed as integral parts in a single moulding, thus eliminating
costly manufacturing and assembly operations.
Tolerances for plastic gears are in some cases less critical
than for metal gears because the inherent resiliency
enables the teeth to conform to slight errors in pitch and
profile. This same resilience offers the ability to dampen
shock or impact loads. The use of ZYTEL? nylon resin as
the tooth surface in engine timing chain sprockets is an
outstanding example of this latter advantage. In this case,
timing chain life is extended because nylon dampens
somewhat the transmission of shock loads from fuel ignition.
ZYTEL? nylon resin and DELRIN? acetal resin have
low coefficients of friction and good wear characteristics,
offering the ability to operate with little or no lubrication.
They can also operate in environments that would be
adverse to metal gears. A summary of the advantages and
limitations of plastic gears is given in Table 8.01.……
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