Chapter 22
Compression Springs According to DIN EN 13906-1-2002

    22.1   Start the Calculation Module
    22.2   General Information
    22.3   Input Possibilities
    22.4   Spring Geometry Selection
    22.5   Material Selection
    22.6   How to Change the Unit System
    22.7   The Button ‘Redo’ and ‘Undo’
    22.8   Message Window
    22.9   Quick Info: Tooltip
    22.10   Calculation Results
    22.11   Diagrams
    22.12   Documentation: Calculation Report
    22.13   How to Save the Calculation
    22.14   The Button ‘Options’
    22.15   Calculation Example: Compression Spring According to DIN EN 13906-1, Edition 2002

22.1 Start the Calculation Module

Please login with your username and your password. To start the calculation module for compression springs, please click the menu item ‘Spring calculation’ on the left side and then select ‘Compression spring’.

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Figure 22.1: General overview

22.2 General Information

Spring is a mechanical device designed to store elastic energy when deflected and to return the energy when relaxed. The compression spring offers resistance to a compressive force applied axially.

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Figure 22.2: Compression spring

22.3 Input Possibilities

22.3.1 Input of Spring Force and Spring Deflection

The calculation of the compression spring is based on DIN EN-13906-1. Forces and deflection or a combination of both parameters can be defined for the calculation. Other parameters for the spring geometry (e.g., length, diameter, coils) can be entered manually or can be selected from the geometry database according to DIN 2098. If you manually enter the parameters, you can define an individual compression spring. The depending values will be automatically calculated.

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Figure 22.3: Input fields for spring force and deflection

For the entry of forces and deflections there are the following possibilities:

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The entry of forces

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The entry of deflection

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The entry of forces and deflections

The input fields that are dependent upon one another are color-coded to simplify the connection of force, deflection and length. Click the input field and the corresponding input field will turn yellow. It makes it easier for you to see how these values relate to each other and how they change.

22.3.2 Transverse Loading

If an axially loaded spring with parallel guided ends is additionally perpendicular to its axis, transverse deflection with localised increase in torsional stress will occur (DIN EN 13906-1: July 2002, p. 10).

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Figure 22.4: Spring under simultaneous axial and transverse loading

Enter either force or deflection in order to consider transverse loading.

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Figure 22.5: Transversal spring

22.3.3 Coils

Enter the number of active coils \(n\). The manual entry allows the dimensioning of individual compression springs. Activate the option ‘unsprung’ and enter a value for the number of unsprung coils.

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Figure 22.6: Coils

Enter either a value for the coils \(n\) or the spring rate \(R\). The input fields are color-coded. If you enter a number of active coils, the spring rate is automatically determined and input field turns yellow. In case you define the spring rate, the input field for the coils turns yellow.

Please Note: Click the button ‘Options in order to consider the wire diameter tolerances. The listbox provides the tolerances according to DIN 2076 B/C and DIN 2077. Selecting the entry ‘User-defined’ allows you to define an individual wire diameter tolerance.

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Figure 22.7: Tolerances

22.3.4 Spring End Types

Select the following spring end types:

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Figure 22.8: Selection of spring end types

22.3.5 Support of Spring End Types

Some springs have the tendency to buckle. The critical spring length at whick buckling starts is known as the buckling length \(L_{k}\). The spring deflection up to the point of buckling is known as the buckling spring deflection \(s_{K}\). The influence of the seating of the spring ends is taken into account by means of the seating coefficient \(\nu \).

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Figure 22.9: Representation of spring end types

For the support of spring end types the following options are available:

Please Note: Select the option ‘Own input’ and enter your own supporting coefficient \(\nu \) of the spring end type.

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Figure 22.10: Seating of the spring end

22.3.6 Load

Before starting the calculation, it should be specified whether they will be subjected to static loading, quasi-static loading or dynamic loading. The calculation is possible for both dynamic and static/quasi-static loading. A static loading is:

Quasi-static loading is:

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Figure 22.11: Load

In the case of compression spring dynamic loading is loading variable with time with a number of load cycles over \(10^{4}\) and torsional stress range greater than 0.1 \(\times \) fatigue strength at:

Depending on the required number of cycles \(N\) up to rupture it is necessary to differentiate between two cases as follows:

22.3.7 Input of Lengths and Diameters

Enter the values for the length and diameter. The input fields that are dependent upon one another are color-coded. Click the input field and the corresponding input field will turn yellow. It makes it easier for you to see how these values relate to each other and how they change.

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Figure 22.12: Lengths and diameters

22.4 Spring Geometry Selection

You can either enter the spring geometry with length, diameter and coils directly into the input fields or you can choose the geometry from the spring geometry database according to DIN 2098. The spring database makes it possible to quickly find the spring that will meet your requirements. Start with defining the loads and click the button ‘Spring geometry database’.

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Figure 22.13: Button ‘Spring geometry database’

The database provides a list of all spring geometries that can be used for your application. Please choose a compression spring and click the ‘OK’ button.

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Figure 22.14: Spring geometry database

Please Note: The option ‘Show only geometries that are applicable for the entered values.’ is enabled by default. If you want to display all geometries, simply remove the checkmark from its box and select a spring geometry. Confirm with the ‘OK’ button.

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Figure 22.15: Option is activated

22.5 Material Selection

Select an appropriate material directly from the listbox. Clicking the button ‘Material’ opens the material database. In case there is no material that will fulfill the design requirements, then simply define your individual material.

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Figure 22.16: Button ‘Material’

Please select the material from the list. You will get detailed information on the material. The two cursor keys ‘Up’ and ‘Down’ of your keyboard allows you to navigate through the material database, so you can compare the different material properties with each other.

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Figure 22.17: Material database

22.5.1 Define Your Own Material

In case there is no material that will fulfill the design requirements, then simply define your individual material. You will find the entry ‘User-defined’ in the listbox. If you select this option, the input fields will be enabled, so that you can enter your own input values or add a comment. Depending on the manufacturing process (e.g., hot rolled or cold coiled springs), the calculation of the tolerances is determined according to DIN 2095 or DIN 2096. In addition, the eigenfrequency of the spring is calculated.

In order to confirm your inputs, click the button ‘OK’. Please be advised that changing the material will delete your defined inputs and you have to enter the inputs again.

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Figure 22.18: Add own values

22.6 How to Change the Unit System

eAssistant provides two unit systems: the metric system and the U.S. customary unit system. You can quickly switch between the units. To select the unit system, click the button ‘Options’ and decide for a unit. It is also possible to change the unit by clicking the label field. When you click the label field, a context menu will open providing all available units within the unit system. The change should take effect immediately. All settings will be saved to the calculation file. As soon as you select a unit, the current field value will be converted automatically into the chosen unit.

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Figure 22.19: Change the unit

22.7 The Button ‘Redo’ and ‘Undo’

The button ‘Undo’ allows you to reset your input to an older state. The button ‘Redo’ reverses the undo.

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Figure 22.20: ‘Redo’ and ‘Undo’ button

22.8 Message Window

The calculation module provides a message window. This message window displays detailed information, helpful hints or warnings about problems. One of the main benefits of the program is that the software provides suggestions for correcting errors during the data input. If you check the message window carefully for any errors or warnings and follow the hints, you are able to find a solution to quickly resolve calculation problems.

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Figure 22.21: Message window

22.9 Quick Info: Tooltip

The quick info feature gives you additional information about all input fields and buttons. Move the mouse pointer to an input field or a button, then you will get some additional information. This information will be displayed in the quick info line.

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Figure 22.22: Quick info

22.10 Calculation Results

All important calculation results will be calculated during every input and will be displayed in the result panel. A recalculation occurs after every data input. Any changes that are made to the user interface take effect immediately. Press the Enter key or move to the next input field to complete the input. Alternatively, use the Tab key to jump from field to field or click the ‘Calculate’ button after every input. Your entries will be also confirmed and the calculation results will displayed automatically. If the result exceeds certain values, the result will be marked red.

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Figure 22.23: Calculation results

22.11 Diagrams

You get a graphical representation of the load-deflection and Goodman diagram. Click on the diagram to see the full image and details. The Goodman diagram is displayed only for the dynamic load.

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Figure 22.24: Load deflection and Goodman diagram

22.12 Documentation: Calculation Report

After the completion of your calculation you can create a calculation report. Click on the ‘Report’ button.

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Figure 22.25: Button ‘Report’

You can navigate through the report via the table of contents that provides links to the input values, results and figures. This calculation report contains all input data, the calculation method as well as all detailed results. The report is available in HTML and PDF format. The calculation report saved in HTML format, can be opened in a web browser or in Word for Windows.

You may also print or save the calculation report:

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Figure 22.26: Calculation report

22.13 How to Save the Calculation

When the calculation is finished, it is easy to save the calculation. You can save your calculation either to the eAssistant server or to your computer. Click on the button ‘Save’.

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Figure 22.27: ‘Save’ button

Before you can save the calculation to your computer, you need to activate the option ‘Local’ in the calculation module. A standard Windows dialog for saving files will appear. Now you will be able to save the calculation to your computer.

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Figure 22.28: Windows dialog for saving the file

In case you do not activate the option in order to save your files locally, then a new window is opened and you can save the calculation to the eAssistant server. Please enter a name into the input field ‘Filename’ and click on the button ‘Save’.

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Figure 22.29: Save the calculation

22.14 The Button ‘Options’

Click the button ‘Options’ in order to change the default settings.

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Figure 22.30: ‘Options’ button

Here are the default settings that you can modify:

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Figure 22.31: Options

22.15 Calculation Example: Compression Spring According to DIN EN 13906-1, Edition 2002

22.15.1 Start the Calculation Module

Please login with your username and your password. To start the calculation module for compression springs, please click the menu item ‘Spring calculation’ on the left side and then select ‘Compression spring’.

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Figure 22.32: Calculation module

22.15.2 Input Values

A cold coiled compression spring 4 x 32 x 120 is made of patented cold drawn spring steel wire

Wire diameter \(d\) = 4 mm

Diameter \(D\) = 32 mm

Coils \(n\) = 8.5

Length of the unloaded spring \(L_{0}\) = 120 mm

is alternately loaded with

Spring force \(F_{1}\) = 300 N

Spring force \(F_{2}\) = 500 N

We are looking for the spring rate \(R\), the corrected shear stress \(\tau _{k2}\) for the spring force \(F_{2}\) = 500 N and spring deviation \(s_{h}\).

22.15.3 The Calculation

Enter Spring Forces

Please start to enter the spring forces \(F_{1}\) and \(F_{2}\). During entering the spring forces, the corresponding spring deflections are automatically determined and will be highlighted in a different color.

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Figure 22.33: Input of spring forces
Enter Coils and Wire Diameter

Enter the number of coils \(n\) as well as the wire diameter \(d\). The settings for the spring ends, the support of spring as well the load will not be changed.

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Figure 22.34: Input of coils \(d\) and wire diameter \(d\)
Enter Spring Length and Spring Diameter

Enter the spring length \(L_{0}\) and the spring diameter \(D\).

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Figure 22.35: Input of length and diameter
Material Selection

Click the button ‘Material’ to open the material database and to find the required material for the compression spring.

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Figure 22.36: Button ‘Material’

Select the following material from the listbox: patented cold drawn wire DH according to EN 10270-1: 2001, shot peened, \(N =10e^{7}\).

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Figure 22.37: Select the material

22.15.4 Calculation Results

All important calculation results, such as the static and dynamic utilization of the permissable stress, the spring deviation \(s_{h}\) and the utilization of the permissable spring deflection \(s_{n}\), will be calculated during every input and will be displayed in the result panel. A recalculation occurs after every data input. Any changes that are made to the user interface take effect immediately. Press the Enter key or move to the next input field to complete the input. Alternatively, use the Tab key to jump from field to field or click the ‘Calculate’ button after every input. Your entries will be also confirmed and the calculation results will displayed automatically.

Spring Rate \(R\)

The spring rate \(R\) is = 9,363511 N/mm and is displayed above the input field for the wire diameter.

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Figure 22.38: Result for the spring rate
Shear Stress for the Spring Force \(F_{2}\)

The calculation report provides the result for the shear stress. Click the button ‘Report’ to open the calculation report. The shear stress \(\tau _{k2}\) for the spring force \(F_{2}\) is = 636,62 N/mm\(^{2}\).

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Figure 22.39: Result for the shear stress
Spring Deviation \(s_{h}\)

You will find the value for the spring deviation \(s_{h}\) in the result panel. The spring deviation \(s_{h}\) is = 21.36 mm.

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Figure 22.40: Result for the spring deviation

22.15.5 Documentation: Diagrams and Calculation Report

Diagrams

The results are clearly displayed in the diagrams. Click on the diagram to see the full image and details.

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Figure 22.41: Diagrams
Calculation Report

After the completion of your calculation, you can create a calculation report. Click on the ‘Report’ button.

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Figure 22.42: Button ‘Report’

You can navigate through the report via the table of contents that provides links to the input values, results and figures. This calculation report contains all input data, the calculation method as well as all detailed results. The report is available in HTML and PDF format. The calculation report saved in HTML format, can be opened in a web browser or in Word for Windows. You may also print or save the calculation report:

22.15.6 How to Save the Calculation

When the calculation is finished, it is easy to save the calculation. You can save your calculation either to the eAssistant server or to your computer. Click on the button ‘Save’.

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Figure 22.43: Button ‘Save’

Before you can save the calculation to your computer, you need to activate the checkbox ‘Local’ in the calculation module. A standard Windows dialog for saving files will appear. Now you will be able to save the calculation to your computer.

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Figure 22.44: Windows dialog for saving the file

In case you do not activate the option in order to save your files locally, then a new window is opened and you can save the calculation to the eAssistant server. Please enter a name into the input field ‘Filename’ and click on the button ‘Save’.

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Figure 22.45: Save the calculation

Our manual is improved continually. Of course we are always interested in your opinion, so we would like to know what you think. We appreciate your feedback and we are looking for ideas, suggestions or criticism. If you have anything to say or if you have any questions, please let us know by phone +49 (0) 531 129 399-0 or email eAssistant@gwj.de.