Planetary screw assemblies from Rexroth: by 3Yk4i0U

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									Product Feature: PLSA
Planetary screw assemblies from Rexroth:
Moving heavy loads more quickly in smaller spaces                                                        March 2012




PLSA Planetary Screw Assemblies from Rexroth offer space -saving alternatives for high -load
machine applications


There is a demand for increasingly high performance when it comes to
electric presses and injection-molding machines. That puts more demand
on the axis mechanics, which have to move increasingly heavy loads.
Rexroth meets these demands with its new planetary screw assemblies. At
a static load capacity of up to 475kN, they can also handle extreme loads
and require very little installation space. The new planetary screw
assemblies create a new, robust drive solution, especially well-suited for
use in pressing, plastic injection-molding machines and in the paper and
steel industry. Although they are compact in size, they can traverse heavy
loads quickly and efficiently—a task which typically required hydraulic
cylinders until now.

Even if many products are getting smaller and smaller, the forces needed during
production are on the rise. In numerous industry sectors of intermediate and
heavy mechanical engineering, manufacturers can use the new planetary screw
drive solution to process higher quantities of workpieces, resulting in increased
productivity. With the new system, for example, manufacturers might add a

                                                                                                    Contact for Journalists:
                                                                                                    Bosch Rexroth Corporation
                                                                                                    Susan Strauss
                                                                                                    2315 City Line Road
                                                                                                    Bethlehem, PA 18017
                                                                                                    Telephone (610) 694-8352
Bosch Rexroth Corporation, Corporate Communications, 14001 South Lakes Drive, Charlotte, NC 28273   Susan.Strauss@boschrexroth-us.com
www.boschrexroth-us.com
Product Feature: PLSA
higher number of moulded parts to a single cycle in large plastics processing
machines—a considerable improvement in process efficiency. Increased use of                              March 2012
high-strength steel also calls for higher forming force. That’s where traditional
ball screw drives reach their limits.

The substantial increase in load capacity from the newly developed planetary
screw assemblies now extends the application range of electromechanical drives
considerably upwards for heavy applications. In the planetary screw assemblies,
planetary rollers rotate inside a nut parallel to the axis around a screw. The
numerous contact areas lead to a higher load capacity compared to ball screws.
That means that planetary screw assemblies can manage heavier loads. They
achieve higher static and dynamic load capacity with the same dimensions.

Same load, smaller space

The smallest size in the product range has a 20mm screw diameter and even a
lead of 5 mm provides a dynamic load capacity of 55kN. The largest size
increases dynamic load capacity to 220kN and static load capacity to an
impressive 475kN. By comparison, a Boeing 747 barely generates between
206KN and 296KN of thrust during takeoff.

The high power density of planetary screw assemblies makes it possible in to
use smaller sizes to generate the same amount of force. That means smaller
installation space, making it possible to replace gantry drives with a compact
single drive.

High Efficiency

Rexroth applies the principle of synchronization to its new drive units, in which
the nut holds the planetary rollers in two raceways, keeping them at a distance.
The toothed ends of the planetary rollers mesh with the toothed shim locked
inside the nut. The thread has geometrically-structured sides that roll into the nut
without slippage. This enables the assembly to achieve a high level of
repeatability and positioning accuracy even with minimal movement. Planetary
screw assemblies can reach travel speeds of up to 1.5 m/s (90 m/min), thereby
meeting increased dynamic requirements for shorter machine cycle times.
What’s more, noise emissions are significantly lower compared to ball screw
assemblies. In ball screw assemblies, the balls are continuously fed back

                                                                                                    Contact for Journalists:
                                                                                                    Bosch Rexroth Corporation
                                                                                                    Susan Strauss
                                                                                                    2315 City Line Road
                                                                                                    Bethlehem, PA 18017
                                                                                                    Telephone (610) 694-8352
Bosch Rexroth Corporation, Corporate Communications, 14001 South Lakes Drive, Charlotte, NC 28273   Susan.Strauss@boschrexroth-us.com
www.boschrexroth-us.com
Product Feature: PLSA
through the return channel into the loaded area. That generates higher noise
levels.                                                                                                  March 2012

Tolerance class T5 in roll-forming process

The product range initially includes five sizes with screw diameters of 20, 30 and
48mm and leads of 5 and 10mm. Cut exactly to the millimeter, the PLSA can be
provided in custom lengths up to 3000 mm. In manufacturing the screws,
Rexroth uses a precision roll-forming process, a technology with much shorter
processing times than grinding. Over the past few years, the manufacturer has
advanced this processing technology with ball screw assemblies so that the
company can now offer planetary screw assemblies with a T5 tolerance class, as
well. That means the maximum permissible travel deviation is only 23 µm per
300 mm of travel. Although screw assemblies in T7 and T9 tolerance classes are
not able to reach ultra-precision accuracy requirements, they are still able to
provide a high degree of precision.




Rexroth supplies the planetary screw assemblies ready-to-mount with the
appropriately machined ends. Included in the portfolio are different bearing
assemblies in angular and deep-groove ball bearing types for fixed and floating
end-bearings. This variety of options provides the engineer with substantial
design flexibility, making it easier to apply the right parts to meet the job
requirements.

Nuts with and without preload

Compact, cylindrical single nuts and flanged single nuts for all tolerance classes
with a limited axial backlash of maximum 0.03 mm provide a high degree of
freedom when it comes to design. The split flange single nuts cover applications
requiring greater precision with preload. This allows backlash-free movements in
the T7 and T5 tolerance classes.

Planetary screw assemblies are often used in very harsh environments. That
poses a particular challenge when it comes to reliable sealing. Contact seals in
all sizes reduce the amount of dirt that can enter the nut system and make sure
that the system does not experience premature failure as a result of

                                                                                                    Contact for Journalists:
                                                                                                    Bosch Rexroth Corporation
                                                                                                    Susan Strauss
                                                                                                    2315 City Line Road
                                                                                                    Bethlehem, PA 18017
                                                                                                    Telephone (610) 694-8352
Bosch Rexroth Corporation, Corporate Communications, 14001 South Lakes Drive, Charlotte, NC 28273   Susan.Strauss@boschrexroth-us.com
www.boschrexroth-us.com
Product Feature: PLSA
contamination. These highly-effective seals help to keep the lubrication
preserved within the nut, extending the life of the assembly, and minimizing the                           March 2012
costs of maintenance and machine downtime.

With the new planetary screw assemblies, Rexroth provides a compact, robust
drive solution, one that can also transfer high amounts of force, previously the
exclusive domain of hydraulics, for example in servo presses and plastics
machines. What’s more, they also offer additional options in applications in which
ball screw assemblies were previously the only choice. They reduce the amount
of required installation space and provide a long service life thanks to high load
capacities.

Bosch Rexroth AG is one of the world’s leading specialists in the field of drive and control
technologies. Under the Rexroth brand name, the company supplies more than 500,000 customers
with tailored solutions for driving, controlling, and moving. Bosch Rexroth is a partner for Mobile
Applications, Machinery Applications and Engineering, Factory Automation and Renewable Energies.
The company provides customized solutions tailored to the needs and specifications of each
individual market. As The Drive & Control Company, Bosch Rexroth develops, produces, and sells
components and systems in over 80 countries. As part of the Bosch Group, Bosch Rexroth and its
34,900 associates generated approximately 5.1 billion euros ($6.8 billion) in revenue in 2010.
To learn more, please visit www.boschrexroth-us.com




The Bosch Group is a leading global supplier of technology and services. According to preliminary
figures, more than 300,000 associates generated sales of 51.4 billion euros ($71.5 billion) in the
areas of automotive and industrial technology, consumer goods, and building technology in fiscal
year 2011. The Bosch Group comprises Robert Bosch GmbH and its more than 350 subsidiaries
and regional companies in some 60 countries. If its sales and service partners are included, then
Bosch is represented in roughly 150 countries. This worldwide development, manufacturing, and
sales network is the foundation for further growth. Bosch spent more than 4 billion euros ($5.5
billion) for research and development in 2011, and applied for over 4,100 patents worldwide. With
all its products and services, Bosch enhances the quality of life by providing solutions which are
both innovative and beneficial. Further information is available online at www.bosch.com and
www.bosch-press.com.




                                                                                                      Contact for Journalists:
                                                                                                      Bosch Rexroth Corporation
                                                                                                      Susan Strauss
                                                                                                      2315 City Line Road
                                                                                                      Bethlehem, PA 18017
                                                                                                      Telephone (610) 694-8352
Bosch Rexroth Corporation, Corporate Communications, 14001 South Lakes Drive, Charlotte, NC 28273     Susan.Strauss@boschrexroth-us.com
www.boschrexroth-us.com
Product Feature: PLSA

Reader Inquiries:
                                                                                                         March 2012
info@boschrexroth-us.com




                                                                                                    Contact for Journalists:
                                                                                                    Bosch Rexroth Corporation
                                                                                                    Susan Strauss
                                                                                                    2315 City Line Road
                                                                                                    Bethlehem, PA 18017
                                                                                                    Telephone (610) 694-8352
Bosch Rexroth Corporation, Corporate Communications, 14001 South Lakes Drive, Charlotte, NC 28273   Susan.Strauss@boschrexroth-us.com
www.boschrexroth-us.com

								
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