General technical notes and information Planetary Screw Assemblies

Description

• Cylindrical single nut with backlash or preload (ZEM-E-S)

Product description

Planetary Screw Assembly – Definition

Rexroth planetary screw assemblies offer design engineers many opportunities to solve transport and positioning tasks with a driven screw. At Rexroth you will be sure to find exactly the kind of tailor-made products you need for special applications.

Structural design:

Both the screw and the nut have an identical multi-start profile with a flank angle of 90°. The planets have journals at both ends, which are lodged in holes bored in the guide discs. The toothed ends of the planets engage with the internal gear rims of the nut. The planets have single-start threads and crowned flanks that roll without slipping along the nut threads.

At each end of the nut there are internally geared rims which engage with the external gearing on the planets. Guide discs inside the gear rims support the planets’ journals and ensure that they are correctly spaced. The discs also prevent coarse dirt from working its way into the nut.

Versions:

• Cylindrical single nut with backlash or preload (ZEM-E-S)

• Flanged single nut with backlash or preload (FEM-E-S)

Precision Screws PSR

Bosch Rexroth has a long tradition of manufacturing precision screws. Offered in many sizes and in unmatched quality, these have been an integral part of our ball screw assembly product range for years.

We have now transferred this tried and trusted manufacturing technology to the screws of our planetary screw assemblies.

For users, this results in many advantages, including the following:

• Identical quality to Rexroth ball screw assemblies

• Fast delivery

• Attractive prices thanks to cost-effective manufacturing

Overview of formats

ZEM-E-S	FEM-E-S

Alignment of the screw assembly in the machine

A gauge with a self-aligning contact pad is available from Rexroth for the easy alignment of the screw assembly.

The dial gauge is not included in the scope of delivery of the screw assembly.

Two pads of different lengths are available which can be used depending on the screw lead:

• Part number R3305 131 19, length 33 mm for leads < 20

• Part number R3305 131 21, length 50 mm for leads > 20

Overview of screw ends: Screw ends, forms for a left or right screw end

Basic version		with keyway
002
112		122
132		142
212		222
312
412
512		522
532		542
612		622
712		722
812		822
832		842
912		922
932		942

End machining of end-face

Z centering hole DIN 332-D	S hex socket

Identification system for short product names PLSA / ordering data

Technical data

Rigidity in the area of the nut unit Rnu

See the corresponding tables for rigidity values.

The values given for dynamic drag torque are proven practical indicators for the nut preloading.

Preload and rigidity of the nuts

Frictional torque of the seals
Seal torque of the nuts

Legend

Fields of application

Project planning information

Notes on buckling

The effective buckling length lc of the screw is the maximum unsupported screw length in the direction of the force’s flow between the nut and the fixed bearing (centerline-to-centerline distance) or between the nut and the screw end.

For buckling load calculations, the nut is taken into consideration as a bearing.

For “nut fixed,” the following conditions must be met:

• zero-backlash nut,

• rigid attachment of the nut to the linear guide,

• the nut unit is not subjected to moment loads, i.e. a linear guide absorbs any arising moments,

• no distortive stresses due to external factors (for example, temperature).

If one or more of the conditions for “nut fixed” are not met, the appropriate coefficients for “nut floating” must be used instead.

End fixity III occurs in applications with driven nuts, for example, when the nut is stationary and the screw rotates. The nut can then be regarded as a fixed bearing.

End fixity VI only arises when the nut is not supported by any linear guide.

Mounting

Mounting direction of nut types

Definition: The centering diameter on nuts with a flange points to the right end of the screw. The mounting direction for cylindrical nuts is freely selectable (symmetrical).

1) Centering diameter D1

2) Symmetrical keyway

Maintenance

Information

Certification

Safety Instructions

Required and supplementary documentation

For further instructions and information, please refer to the documentation for this product.

You can find PDF files of these documents on the Internet at www.boschrexroth.com/mediadirectory.

We would also be happy to send you the documents that you want.

If you are unsure about using this product, please contact Bosch Rexroth.

Downloads

	Planetary Screw Assemblies Manual | R320103883 | 2011-06-01 | English, French, German, Italian | PDF | 974k Product Groups: Linear Screw Assemblies
	Catalog screw assemblies Catalog | R999001185 | 2021-04-01 | English | PDF | 30.7MB Product Groups: Ball Screw Assemblies, Planetary Screw Assemblies Only available as PDF - Ball screw assemblies BASA/Planetary screw assemblies PLSA