Linear actuator with inverted roller screw and integrated servomotor

Our technology partner Diakont is a specialist manufacturer for compact roller-screw actuators.

The key features of the DA-series are as follows:

• Actuation forces up to 60,000 N
• Actuation speeds up to 833m/s
• Strokes up to 400mm
• Compact, as the servomotor is integrated concentrically around the screw nut
• Integrated encoder
• Higher lifetime than ball-screw actuators

For further information please download the catalogue (on the right) or contact us !

Characteristics of roller screw inverted actuators

Inverted roller screw means: the spindle nut and not the spindle is driven. Our DAXX actuators have a servo motor concentrically mounted around the spindle nut (see picture on the right) and an encoder. The servo motor drives the spindle nut directly via planetary rollers. This rotary motion drives the spindle in a linear direction. The spindle is connected to a piston rod. The linear motion of the spindle drives the piston rod out of the actuator or retracts it.

In the inverted roller screw, the spindle nut is approximately as long as the required travel stroke. Permanent magnets are attached to the spindle nut. Thus the spindle nut becomes the rotor of the motor. The stator (==coil) is mounted concentrically around the spindle nut. Due to this close integration of the components, linear actuators with inverted roller screw are axially shorter than linear actuators with roller screw or ball screw. In addition, weight is saved. Therefore, such actuators are preferred for robotic tasks. Another common reason for these actuators is: tight axial installation space.

If your project requires the shortest possible actuator cylinder and/or a very long service life due to installation space restrictions, the electric actuator cylinder based on inverted roller screw is a good choice.

The most important features of our DIAKONT family are:

• 3 sizes: Flange size 67x67 (DA67), 99x99 (DA99) or 140x140mm (DA140)
• Peak forces up to 60kN
• Strokes up to 450mm, depending on type
• Travel speeds up to 800mm/s possible, depending on type and spindle pitch
• Integrated feedback (resover or encoder incremental or absolute)
• Integrated servo motor

Options:

• Integrated holding brake for DA99 and DA140
• External anti-rotation device
• Oil circulation lubrication
• Force sensor, depending on type
• Lateral force bearing, depending on type
• Safety encoder (encoder safety certified)
• Water cooling, depending on type

For further information please download the catalog (link on the right) or contact us for technical advice.

Normally, the electric actuator is cooled with room air convection cooling. In certain cases, however, water cooling is necessary.
Possible reasons are:

Increased room temperature

A high ambient temperature can be a reason for water cooling. If the sum of self-heating (by spindle and motor) plus the initial ambient temperature becomes too high, water cooling is necessary.

Intensive load cycle

Scenario: there is an ordinary ambient air temperature (e.g. 25°C) and the electric actuator operates at a certain cycle rate. However, the operator wants to increase the cycle rate in order to increase production. He realizes: the installed electric actuating cylinder with room air convection cooling becomes too hot. Solution: water cooling. Depending on the load cycle (force vs. time, speed vs. time), the clocking can possibly be doubled.

The DA99 electric actuator is shown on the right. Clearly visible: the water inlet and outlet as well as the copper pipes that carry the water to cool the housing of the actuator cylinder.

Please contact us to consult your project. With simulation software we can forecast with an accuracy of +/-10% which cycle will be possible at what room temperature.