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SERVO-DRIVE SERVO ACTUATORS INTRODUCTION

What is a ROLLER SCREW ?

Roller Screw
  • High Efficiency Screw Mechanism
  • Designed in late 1940s
  • Not trivial to manufacture as is a ball screw
  • Many performance advantages to other screw technology
Roller Screw

ROLLER SCREW CONSTRUCTION

Roller Screw Exploded View
A = Screw Shaft
B = Nut
C = Threaded Roller
D = Roller Journal
E = Spacer Washer (Planetary)
F = Retaining Ring
G = Timing Gear (roller)
H = Timing Gear (nut)
I = Retaining Ring
J = Lubrication Access
K = Wiper (seal)

What is INVERTED ROLLER SCREW ?

  • High Efficiency Screw Mechanism
  • Developed in 1990
  • Used in the patented servo actuators
  • The same performance advantages as standard roller screws
  • Design of the mechanism is inverted. , Timing Gears (H) from previous picture are on screw shaft (A).
  • Rotation of Nut produce linear motion of the Screw and allows a construction of compact servo actuator.
INVERTED Roller Screw

Inverted Roller Screw Features

Much less space for Equal Contact Erea

No Conflicting Friction

Adjacent ball bearings within a ball screw have conflicting friction leading to heating and wear. The planetary design of a roller screw does no exhibit this problem. Travel Life Comparison to Ball Screws For similar-sized screw diameters, a roller screw will have many times the expected service life of a ball screw.

More contact points per area

Roller screw provides more contact point to Ball Screw per area.


Planetary design

  • No conflicting friction (heat)
  • More contact points
  • No ballistic effect - dynamic
  • Continuous contact
  • Smooth running
  • Higher rotational speed up to 5000 rpm
  • High acceleration > 1,5 g
  • Higher stiffness through number of parts

Life Time Comparison

Roller Screw Life Time Versus Ball Screw

Testing conditions:

Ball Screw 25x5
Roller Screw 25x5
1000 N Continous Force

Result Life Time:

Ball Screw = 50,5 km
Roller Screw = 762 km

Inverted Roller Screw versus Ball Screw, Hydraulics and Pneumatics

VS. Ball Screws
Higher Load
Minimum 15x life for same size screw
Higher Acceleration
Higher Rotational Speed
Higher Stiffness
VS. HYDRAULICS
Lower maintenance
Less Noise
More Precision
Higher Efficiency
Easier Set up
Higher Repeatability
VS. Pneumatics
Lower maintenance
Less Noise
More Precision
Higher Efficiency
Easier Set up
Higher Repeatability

AC Servomotor - Segmented Stator Technology

Segmented stator
  • Recently introduced segmented lamination motor technology.
  • More efficient than traditional brushless motors.
  • Less heat generation
  • More robust insulation system.
  • Magnets, insulation and potting all provide more thermally robust motor design.
  • 35% torque increase in the same package size.
  • UL Class H compliant, 460 Volt insulation rating
Servo Actuator Cutaway model

Integrated Inverted Roller Screw - Servo Actuator Compact Solution

Servo Actuator Cutaway model
A = Chrome Plated Output Rod
B = Pre-Loaded Angular Contact Bearing
C = Inverted Roller Screw Mechanism
D = Epoxy Coated Aluminium Housing
E = Neodium Iron Boron Magnets
F = Connectors
G = Encoder or Resolver Feedback
H = AC Brushless Servo Motor (segmented design +35% power)
I = Sealed Output Rod

GSM series exist in 4 packages, GSX in 5 package sizes. Compatibility with nearly all major brands of servo amplifiers. Completely sealed. Compact package design. Multiple mounting configurations.

Servo Actuator Applications - Main industrial applications

Level Winding

Motion Simulation

Plastics - Electric Toggle Cylinders


Food industry - Powerfull cutting

Food industry - Fast filling

Wood industry - Saw positioning


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