There is a lot
of jargon related to ballscrews, some familiar and some less so. Ballscrews
suppliers don’t often explain what it all means so here we will run through a
few of the terms associated with these products that you should know if you
have any dealings with applications using ballscrews.
Backdrive, Backlash and Creep
to the action of converting thrust motion back into torque motion. It can
reduce the efficiency of an application, though its effect can be reduced with
a self-locking mechanism. Backlash refers to the movement of a screw and nut
from its original position. Creep is similar to backlash, but is caused by the
vibrations and shocks from heavy loads, whereas backlash is not caused by such
Critical Speed and Speed
speed of revolving screw shafts refers to the frequency speed of vibrations
caused by the screws’ revolutions. The frequency of the generated vibration will
depend on the size and shape of the screw shafts.
Speed is the
measurement of the speed of linear movement within ballscrew assemblies,
usually measured by RPM (revolutions per minute).
How the ends of each
screw is supported is called end
fixity. The three most common types of end fixity are free, supported and
fixed. The end fixity of a screw is a crucial part of screw and nut drive
systems. The screw end’s rigidity will determine how much resistance to column
buckling there is and how limitation is placed on the rotational speed of the
screw drive system. The different types
of end fixity has a significant bearing on natural frequency vibrations.
assemblies using continuous screw rotation without linear movement are known as
freewheeling. Freewheeling ballscrews differ from traditional ballscrews in
that the balls are arranged and contained within the nut housing. Instead of
re-circulating the balls back to the opposite side of the nut, the balls of a
freewheeling ballscrew continuously re-circulate throughout the nut housing.
generated between a screw and its nut is friction, or resistance to movement. There
are different types of friction, with ballscrews typically creating a rolling
friction. There is also the sliding friction generated by many lead screws and
ACME screws in particular.
Pitch refers to
the axial measurement between the threads of ballscrews,
though it can also refer to the amount of full rotations a screw makes in order
to produce a particular measurement of movement betwixt the nut along its
Shafts and Threads
The shaft is the
part of the screw that contains the threads, while the threads are the raised
helical rib that goes around the screw’s shaft.
Stroke, Thrust and Torque
Stroke is the
measurement of a ballscrew system’s linear motion or thrust, with the thrust
itself being the linear movement created by the torque produced from ballscrew
assemblies. Torque refers to the rotational
movement of a ballscrew system that converts into thrust.If you require any of the products resulting from
ballscrews manufacture – then contact
YB Components who are the UK’s
leading ballscrews suppliers