Harmonised lead screws and lubrication-free lead screw nuts in
trapezoidal threads extend service life by 30%.

Motion plastics specialist igus
has refined the classic trapezoidal thread, achieving a 30% service life
extension – a huge increase for a well-established mechanical part. Thanks to a
special geometric interaction between the lead screw nut, which requires no
lubrication or maintenance, and the metal lead screw, dryspin technology
promises a long service life, improved efficiencies, reduced wear and quieter
operation. And now dryspin lead screw technology is available in eight new
sizes.

Trapezoidal threads have been
classical mechanical engineering designs for decades. The machine elements
convert rotary motion into linear motion – in applications such as window and
door drives, format adjustments in production plants and laboratory technology.
However, almost every classic design has the potential for improvement.
“We have tackled a market standard and are able to say that we can do even
better,” says Robert Dumayne, drytech director at igus UK. The igus design
relies on an optimised interaction between the metal lead screw and the plastic
lead screw nut geometries.

30% longer service life, 82%
efficiency

Both the nut’s thread flanks and
the width of the lead screw are larger than those of classic trapezoidal
thread. This is a small change, but it has big consequences: enlarging the
thread flank means that more high-performance plastic is used for power
transmission. This means more material that is tribologically optimised, i.e.,
reducing friction and wear. “The asymmetry has enabled us to extend the service
life so that it is about 30% longer than that of symmetrical trapezoidal
threads”, Dumayne says. He adds “Optimising the flank
angle also increases the amount of energy supplied that is actually used. We
have flattened the flank angles of the lead screw nut and lead screw, this
gives us above average efficiency – up to 82% at high pitches.”

Lead screws work almost
silently and without vibration

The new dryspin thread technology
is not only durable and efficient, but also quieter than many conventional
trapezoidal threads, because the tooth flanks are not angular but rounded,
reducing the contact area between lead screw nut and lead screw. This leads to
less vibration, which can take the form of rattling or squeaking. Dumayne says:
“The rounded tooth flanks allow the lead screws to move without vibration
and almost silently. The lead screw manufacturing tolerance is tighter than
that specified in DIN 103 7e, ensuring more precise operating
behaviour and allowing for much higher speeds in the application.”

Eight more installation
sizes added to the dryspin lead screw portfolio

igus began to establish its own
lead screw technology on the market in 2013, initially as an alternative to
high helix threads. Now there are eight new installation sizes – both
harmonised lead screws and lead screw nuts, including dimensions with low pitches
that enable quick one-to-one replacement of installed trapezoidal threads.

The new lead screws are available
with pitches of 6.35×6.35 RH, 8×40 RH, 10×3 LH, 12×25 LH,
14×4 RH, 16×5 RH, 18×4 RH and 20×10 RH. They are made of
stainless steel or aluminium, and the lead screw nut material can be selected
from seven high-performance plastics and several geometries – from a
cylindrical design with flange or spanner flats to a version with spring
pre-load.