Filter
Top Products
MNA1MLSDM00EN, V2.01, 07.2009
PAS4•S9 Glossary
Portal axes with ball screw drive 87
9 Glossary
9.1 Terms and Abbreviations
Axis body The axis body is a high-strength, torsion-resistant aluminum precision
profile.
Ball screw drive The ball screw drive converts a rotary movement into a linear move-
ment. It consists of a ball screw, a ball nut with the ball recirculating el-
ements and the bearing balls. A ball screw drive has a very high
efficiency. It allows for high-precision, stiff feed movements and gener-
ates high feed forces at high positioning accuracy and repeatability.
Ball screw pitch The pitch of the ball screw shaft relates to the distance covered by the
carriage per revolution of the ball screw. The greater the pitch the higher
the maximum velocity.
The following applies to the ball screw pitch:
• High pitch requires high driving torque
• High pitch results in high velocity
• High pitch causes high inaccuracy
• High pitch implies little self-locking
Breakaway torque The breakaway torque describes the driving torque required to over-
come the static friction and that initiates the transition to sliding friction.
Buckling load Buckling is the loss of stability of the spindles when the max. permissible
feed forces whose line of application is along the spindle axis are ex-
ceeded. Exceeding the buckling load is expressed by a quickly increas-
ing change in the shape of the spindle with a deviation to the side.
Cantilever axis In the case of a cantilever axis, the carriage is stationary while the axis
body moves. Portal axes work the other way round.
Critical speed of the ball screw If the critical speed of the ball screw is exceeded, deflection of the ball
screw and resonance will occur. This will seriously affect the service life
of the ball screw drive. Ball screw supports are installed in longer ball
screw axes to increase the critical screw speed and thus the perform-
ance data.
Drive element The drive element of the linear axis is a ball screw drive.
Feed per revolution The feed per revolution is the distance the carriage covers per motor rev-
olution.
Linear guide The linear guide consists of the guide carriage and the profile rail.
Load torque The permissible load torques are calculated based on the service life of
the carriage guide. If the load torque exceeds the specified values, the
service life of the axis will be reduced.
Modulus of elasticity The modulus of elasticity is used to describe the tendency of a material
to deform along an axis when opposing forces are applied along this
axis; it is the ratio of tensile strain and tensile stress. The higher the
value, the stiffer the material.
Mounting position The linear axes can be installed in any desired position. However, all ex-
ternal forces and torques must be within the ranges of permissible val-
ues.