DRAFT INTERNATIONAL STANDARD© ISO 2019 – All rights reservedISO/DIS 22705-1:2019(E) 63Part 1: Cold formed cylindrical helical compression springsSprings — Measurement and test parametersRessort — Mesures et paramètres de test — Partie 1: Ressort hélicoïdal de compression cylindriques formé à froidSprings — Measurement and test parameters — Part 1: Cold formed cylindrical helical compression springsE2019-11-14(40) EnquiryISOISO/ International Standard 2019ISO 22705‑ISO 22705‑1ISO/DIS 22705-1 DIN Springs2 227 2Überschrift 2Überschrift 1 0 STD Version 2.9p40 4D:\3rd meeting - 2019-11-14 Nagoya\Draft\ISO_CD_22705-1_(E)_markup.docx ISO/TC 227

Date:   2019-11-14

ISO/DIS 22705-1:2020(E)

ISO/TC 227/WG 2

Secretariat:   DIN

Springs — Measurement and test parameters — Part 1: Cold formed cylindrical helical compression springs

Ressort — Mesures et paramètres de test — Partie 1: Ressort hélicoïdal de compression cylindriques formé à froid

Warning

This document is not an ISO International Standard. It is distributed for review and comment. It is subject to change without notice and may not be referred to as an International Standard.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to provide supporting documentation.

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Contents Page

1 Scope 1

2 Normative references 1

3 Terms, definitions, symbols and abbreviated terms 1

3.1 Terms and definitions 1

3.2 Symbols and abbreviated terms 2

4 Environmental conditions 4

5 Qualifications of the person(s) performing the work 4

6 Geometries of guiding and supporting devices 4

7 Measuring and testing equipment 4

8 Measurement and test parameter for technical cold formed cylindrical compression springs 5

8.1 Free length (L0) 5

8.2 Outside diameter (De) 8

8.3 Internal diameter (Di) 12

8.4 Total number of coils (nt), number of active coils (n) and coil direction 16

8.5 Applied end coils 20

8.6 Solid length (Lc)/solid force (Fc) 21

8.7 Spring load (F) 23

8.8 Spring pitch/distance between the coils 25

8.9 Grinding surface/angle 27

8.10 Perpendicularity (e1) 29

8.11 Parallelism (e2) 31

8.12 Shear-off burr 33

Annex A (informative) Calculation of spring rate R 35

A.1 General 35

A.2 Type of characteristic 35

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).

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This document was prepared by Technical Committee ISO/TC 227, Springs.

A list of all parts in the ISO 22705 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Springs — Measurement and test parameters — Part 1: Cold formed cylindrical helical compression springs

This document specifies the measurement and test methods excluding dynamic testing for general characteristics of cold formed helical compression springs made from round wire.

The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 3611, Geometrical product specifications (GPS) — Dimensional measuring equipment: Micrometers for external measurements — Design and metrological characteristics

ISO 13385‑1, Geometrical product specifications (GPS) — Dimensional measuring equipment — Part 1: Design and metrological characteristics of callipers

ISO 16249, Springs — Symbols

ISO 26909, Springs — Vocabulary

For the purpose of this document, the terms and definitions given in ISO 26909 and the following apply.

3.1.1

spring

mechanical device designed to store energy when deflected and to return the equivalent amount of energy when released

[SOURCE: ISO 26909:2009, 1.1]

3.1.2

compression spring

spring that offers resistance to a compressive force applied axially

Note 1 to entry: In the narrow sense, a compression spring indicates a helical compression spring.

[SOURCE: ISO 26909:2009, 1.2]

3.1.3

coil spring

coil-shaped spring

[SOURCE: ISO 26909:2009, 3.11]

3.1.4

helical compression spring

compression spring made of wire of circular cross-section, wound around an axis with spaces between its coils

[SOURCE: ISO 26909:2009, 3.12, modified — limited to wires with circular cross-section]

3.1.5

cold formed spring

spring formed at ambient temperature

[SOURCE: ISO 26909:2009, 1.12]

3.1.6

active coils

total number of coils less the inactive end coils

Note 1 to entry: This is the number of coils used in computing the total deflection of a spring.

[SOURCE: ISO 26909:2009, 5.70]

3.1.7

test parameter

parameter with a tolerance for which there is an immediate conclusion after test (OK or not OK)

Note 1 to entry: Test can be done without measurement (i. e. with go/no-go gauges)

Table 1 includes symbols, units and abbreviated terms in accordance with ISO 16249 and used throughout this standard.

Table 1 — Symbols and abbreviated terms

The spatial distribution and equipment of the facility shall permit a reliable implementation of the measurements and tests.

Measurements and tests should be carried out at ambient temperature in a normal workshop environment.

Special tests (e.g. in air-conditioned rooms or other special environments) shall be agreed upon between the manufacturer and the customer.

Measuring and testing equipment should be subject to regular inspection.

The measurements and tests shall be carried out by a person who has been instructed/trained in the use of the measuring and testing equipment, as well as regarding methods and test requirements.

The qualifications or additional knowledge and skills should be documented in appropriate qualification or training documents, depending on the requirements.

If guiding and supporting devices (mandrels, guide sleeves, ring groove, etc.) are used, the properties (geometry, material, etc.) shall be agreed upon between the manufacturer and the customer to include special cases such as snapping end coils, buckling, bulging, etc. The alignment of guiding and supporting devices is aimed to improve the reproducibility of the measures.

Suitable measuring equipment shall be selected. Measuring equipment shall conform to ISO standards, if such are available (e. g. ISO 3611 and ISO 13385-1).

If there is a customer requirement, the methods and measuring equipment shall be agreed on separately.

The free length L0 is a measurement and test parameter.

L₀ is the length across the entire spring body when no load is applied and only for the case that both ends are ground (see Figure 1); other cases should be agreed upon between the manufacturer and the customer.

Figure 1 — Free length (L0), for the case that both ends are close and ground

The following measuring equipment can be used:

— micrometer gauge;

— calliper;

— dial gauge/indicating calliper;

— electronic measuring sensor;

— manual/automatic force gauge;

— optical measuring instruments/protractor/measurement microscope/camera systems;

The following testing equipment can be used:

— attributive gauges ("GO/NO GO" gauges)

The characteristic shall be evaluated at ambient temperature as delivered.

The measurement can be carried out without contact using optical procedures, capacitive or electrically by contact (with minimal force) or by contact with the measuring surfaces (at a known/unknown measuring force). Preferably, the measurement should be carried out over the entire face (see Figure 2 and Figure 3). If this is not possible, then a second measurement can be carried out with a 90° offset. In this case, it shall be clarified whether the maximum value, the minimum value or the average value is to be specified.

When there is a spring self-weight effect, the measurement of free height should be agreed upon between the manufacturer and the customer.

Figure 2 — Method of testing the free length (L₀) with gauges (examples)

If the customer specifies a setting length for the test spring, the setting condition for the test spring shall be agreed upon between the manufacturer and the customer.

Springs that are not preset shall only be measured after the force test, or they shall be set to the length Lmin (Fmax) before the test. If no load or force is specified, measurement can be done without any preliminary test.

Figure 3 — Method of measurement of the free length L₀ with calliper (exemplary)

The test direction is in the axial direction to the finished spring. When measuring equipment is used that induces a measuring force, then the applied force should not deflect the spring.

When optical measuring equipment (camera systems) is used, the measurement axis is perpendicular to the spring axis.

The outside diameter is a measurement and test parameter.

D_e is the value of the outside diameter through the whole spring body (see Figure 4).

Figure 4 — Outside diameter (De)

The following standard measuring equipment can be used:

— micrometer gauge;

— calliper;

— dial gauge.

Alternatively, optical measuring equipment can be used.

The following testing equipment can be used:

— test sleeve;

— special gauge (part-based);

— snap gauge.

The shape and dimension of all testing equipment shall be agreed upon between the manufacturer and the customer.

The characteristic shall be evaluated at ambient temperature as delivered.

Note about special cases: Tests for coated and set springs should be agreed upon between the manufacturer and the customer.

a) Variable measurement (e.g. calliper)

The measurement is performed at several locations on the product, at least at the beginning, in the centre (Figure 5 and Figure 6) and at the end of the spring. The measurements at the end is performed in two perpendicular directions of the spring, except if calliper jaws useful length is greater than free length of spring. Each measured value shall be within the tolerance. The maximum value shall be documented.

Key

Figure 5 — Method of measurement of the outside diameter D_e with calliper (examples)

Key

Figure 6 — Method of measurement of the outside diameter D_e with dial gauge (examplary)

b) Attributive testing (good/bad/test sleeve, see Figure 7)

The spring shall fall through the test sleeve due to its own weight at De,max (see Figure 7a).

The spring shall not fall through the test sleeve due to its own weight at De,min (see Figure 7c).

Figure 7 — Method of testing of the outside diameter D_e with test sleeve (examples)

a) Variable measurement (calliper)

The measurement is performed at several locations on the product, at least at the beginning, in the centre and at the end of the spring. The whole spring body is to measure. The characteristic shall be evaluated at ambient temperature as delivered and not under load.

b) Attributive testing (good/bad/test sleeve)

The test is carried out over the entire length of the spring. The test sleeve length shall correspond to at least the clearance between 2 and a maximum of 4 coils.

For the purpose of testing geometrical deviations (enveloping circle, curvature), a test sleeve with the length and diameter for cylindrical springs can be agreed upon between the manufacturer and the customer.

The internal diameter Di is a measurement and test parameter.

D_i is the minimum value of the internal diameter through the whole spring body (see Figure 8).

Figure 8 — Internal diameter (Di)

The following measuring equipment can be used:

— calliper.

Alternatively, a micrometer screw or optical measuring equipment can be used.

The following testing equipment can be used:

— test pin;

— special gauge (part-based), e. g. GO/NO GO gauge.

The shape and dimension of all testing equipment shall be agreed upon between the manufacturer and the customer.

The characteristic shall be evaluated at ambient temperature as delivered.

Note about special cases: Tests for coated and set springs should be agreed upon between the manufacturer and the customer.

a) Variable measurements (e.g. calliper)

Two measurement per end (in two perpendicular direction per end) of spring, except if calliper jaws useful length is greater than free length of spring (in this case, only two measurements in perpendicular directions (see Figure 9). Each measured value shall be within the tolerance. The maximum value shall be documented.

Figure 9 — Method of measurement of the inside diameter (D_i) with calliper (exemplary)

b) Attributive testing (GO/NO GO on test pin, see Figure 10)

The spring shall fall over the test pin due to its own weight at Di,min (see Figure 10c).

The spring shall not fall over the test pin due to its own weight at Di,max (see Figure 10a).

Both of the above mentioned criteria shall be met, regardless of which side of the spring is attached to the test pin.

Figure 10 — Method of testing the inside diameter (D_i) with test mandrel (examples)

a) Variable measurement

The measurement is carried out at the beginning and at the end of the spring.

In the spring centre, the inside diameter of spring Di can only be determined by calculation.

b) Attributive gauges (GO-, NO GO-gauges)

The test is carried out over the entire length of the spring (L0).

For the purpose of testing geometrical deviations (enveloping circle, curvature), a test gauge can be agreed upon between the manufacturer and the customer.

The total number of coils and the coil direction are test parameters. The number of active coils is a theoretical calculation value.

Total number of coils (n_t) is the number of wire rotations/coils around the spring axis (see Figure 11).

Key

Figure 11 — Total number of coils (nt)

Number of active coils n is a theoretical calculated value that cannot be measured geometrically. The number of active coils can only be counted approximately.

The number of active coils n is the total number of coils n_t less the number of inactive coils (see Figure 12).

Definition of inactive coils:

a) with the end coil in contact, the number of turns is determined from the end of the wire to the last contact point with the subsequent coil.

b) with the coils contacting in the spring body between the end coils, the number of coils in each case is determined from the first to the last contact point of two adjacent (consecutive) coils.

Key

Figure 12 — Number of active coils (n)

Depending on the winding direction during the coiling process the spring can be coiled clockwise or anti-clockweise (see Figure 13).

Figure 13 — Coil direction

The following test equipment can be used:

— visual inspection;

— test template;

— optical test.

The characteristic shall be evaluated at ambient temperature as delivered.

All tests are carried out on the unloaded spring.

Total number of coils nt:

The wire coil rotations shall be counted from one end of the wire (spring end) to the other. Therefore, the end of the wire in each case is the maximum point in the run-off direction of rotation (see Figure 11).

In case of open flat ends, and with open coils in the spring body, n = nt.

Depending on the spring holding condition, there are cases of n ≠ n_t

The coil direction can be clockwise (right-handed) or anti-clockwise (left-handed) (see Figure 13).

The entire spring body shall be considered (see Figure 14).

Key

Figure 14 — Methof of measurement of the total number of coils n_t with test template (exemplary)

The contacting end coils are a test parameter.

This is the condition of the spring ends. The end coils can be in contact (closed) or not (open) (see Figure 15). A minor gap is permissible if it is not relevant to the spring behaviour and cannot result in spring locking.

Key

Figure 15 — End coils

The following testing equipment can be used:

— visual inspection;

— optical test.

The characteristic shall be evaluated at ambient temperature as delivered.

The test is carried out on the unloaded spring.

The number of turns from the wire end to the last contact point of two adjacent (consecutive) coils shall be determined.

The respective end coils of the spring shall be considered.

The solid length Lc is a measurement and test parameter.

The solid force Fc is the theoretical spring force at solid length, which is not used during measurement and testing.

If the number of coils is open for production margin, this shall be taken into consideration or agreed upon when indicating the solid dimension.

The length and the corresponding force of the spring between two parallel test surfaces, in which all coils contact in at least one point (see Figure 16).

Figure 16 — Solid length (Lc)

The following measuring and testing equipment can be used:

— spring load tester (manual or powered);

— calliper;

— dial gauge;

— block gauge;

— optical test.

The characteristic is evaluated at ambient temperature as delivered.

The spring shall not exceed a defined solid length Lc, i.e. the solid length Lc shall be less than or equal to a specified value.

Measurement method for the determination of solid length Lc:

The spring shall be compressed until all coils contact each other in at least one point (see Figure 17).

Figure 17 — Method of testing the solid length (Lc) with a spring load tester (exemplary)

A test force shall be agreed on with the customer on demand.

Geometries of guiding and supporting devices (mandrels, guide bushings, ring groove, etc.) shall possibly be agreed upon between the manufacturer and the customer to include special cases such as snapping end coils, buckling, bulging, etc.

The entire spring body shall be considered.

The two highest points are measured in axial direction.

The spring load F is a measurement and test parameter.

F1, F2,… are the assigned spring loads to the lengths of the loaded spring L1, L2,…. or the assigned deflections s1, s2,….

The spring load is an axial force in the direction of compression (see Figure 18).

Figure 18 — Spring load (F)

In order to test the force, a suitable, calibrated force and test gauge shall be used, which has been checked regularly between the calibrating intervals and adjusted to the required tolerance. This can be:

— spring load tester (manual or powered);

— force measuring sensors (relationship between deformation and force) in part-specific test equipment;

— beam balance (balancing weights).

The characteristic is evaluated at ambient temperature as delivered.

Unless otherwise specified, springs that are not preset are measured under force between two parallel plates, first at Lmin (Fmax), then unloaded and then measured by decreasing lenghts to Lmax (Fmin). The spring is relieved between the individual measurements.

If the manufacturer considers the use of a mandrel to be required for the spring force test, then it shall be used.

When testing with a mandrel, the spring shall fall over the test pin due to its own weight at Di,min.

If the customer specifies a setting length for the test spring, the setting condition for the test spring shall be agreed upon between the manufacturer and the customer.

Geometries of guiding and supporting devices (mandrels, guide bushings, ring groove, etc.) shall possibly be agreed upon between the manufacturer and the customer to include special cases such as snapping end coils, buckling, bulging, etc.

The entire spring body shall be considered.

The spring pitch/distance between the coils is a measurement.

NOTE The (functional) spring characteristic with the corresponding tolerances should rather be defined than specifying the spring pitch/distance between the coils.

The spring pitch (p) is the distance between two consecutive coils in the neutral axis.

The spring pitch (p) can be calculated with the distance between coils and the diameter of wire (d):

p = d + distance between coils

Figure 19 illustrates the difference between distance between coils and spring pitch.

Key

Figure 19 — Difference between spring pitch and distance between the coils

The following measuring equipment can be used:

— calliper (with the corresponding dimension);

— optical measuring instruments/protractors.

The resolution of the measuring equipment shall be observed.

The characteristic is evaluated at ambient temperature as delivered.

The measurement can be performed without contact (optical) or with minimal force application (manual check).

The measurement should be performed perpendicular to the spring axis.

Coils to be defined between the manufacturer and the customer.

Furthermore, the measuring point should be precisely defined, since there are partly different distance between the coils in the spring.

The grinding surface is a measurement and test parameter, for which the angle between the beginning and the end of the grinding surface is indicated in degrees (see Figure 20 and Figure 21).

The inspected properties are the grinding surfaces of the coil ends.

Key

Figure 20 — Applied and ground spring ends

The following testing equipment should be used:

— visual inspection

— template

— projector

— protractor

The following measuring equipment should be used:

— projector with reflected light and protractor.

In case the grinding angle is determinated by using a template, see Figure 21.

Key

Figure 21 — Method of testing the grinding angle with a template (exemplary)

The characteristic is evaluated at ambient temperature as delivered.

Visual inspection: grinding surface

Profile projector: grinding angle with reflected light and protractor.

The test is performed at the ground end coils of the spring.

The perpendicularity e1 at contacting and ground coil ends.

The perpendicularity e1 is a measurement and test parameter.

e1 is the variation of squareness from the vertical spring axis in mm.

Figure 22 illustrates the characteristic of the perpendicularity e1.

Figure 22 — Perpendicularity (e1)

The following measuring and testing equipment can be used:

— profile projector;

— height gauge or fixture with dial gauge;

— 3D camera systems (optical measuring system);

— steel square and feeler or pin gauge;

— protractor.

Special test procedures shall be agreed on between the manufacturer and the customer.

The characteristic is evaluated at ambient temperature as delivered. The test is only applicable for closed and ground springs.

The perpendicularity e1 is determined at both spring ends. The larger of the two measurement values shall be used.

a) e1 feeler gauge or dial gauge or pin gauge:

The ground spring is held, ground end against a flat surface, and lower coil against a square, while turned until the maximum offset between the lower and upper coil diameter is reached (check). The conformity to a maximum e1 acceptable value is then determined using a feeler gauge.

b) e1 profile projector:

The measurement is carried out using the coordinate system of the profile projector, without stops or devices. After orientation on the flat surface (glass plate) of the profile projector, the spring is turned to its maximum perpendicularity. This can be in the X and Y direction. The measured distance between the centres of the first and of the last coil diameter is e1 (depending on the light incidence of the profile projector, applied perpendicular to a magnet).

c) e1 camera systems:

The e1 measurement is similar to that using the dial gauge; however, the measurement values are determined optically. The measurement using optical measuring instruments is device-dependent and shall be described/be agreed upon with the customer on a case-by-case basis.

The test location is on the applied and ground end coils.

Parallelism e2 at contacting and ground end coils.

Parallelism e2 is a measuring and test parameter.

e2 is the variation of parallelism of the spring bearing surface in mm.

Figure 23 illustrates the characteristic of parallelism.

Figure 23 — Parallelism (e2)

The following measuring and testing equipment can be used:

— profile projector;

— height gauge or fixture with dial gauge;

— 3D camera systems (optical measuring system);

— load testing machine and feeler or pin gauge.

Special test procedures shall be agreed between the manufacturer and the customer.

The characteristic is evaluated at ambient temperature as delivered. The test is only applicable for closed and ground springs.

The parallelism e2 is determined at both spring ends. The larger of the two measurement values shall be used. To determine e2, the ground area opposite to the reference has to be considered just for ground angles about ‑30 °.

a) e2 dial gauge:

The value e2 shall be measured using a height gauge or a fixture with a dial gauge. For this purpose, the measuring device is positioned on the ground surface of the end coil and the difference between the minimum and maximum value is determined as the spring is turned around the spring axis.

The force applied on the dial gauge shall not deflect the spring. If possible, the measuring head of the dial gauge should be guided in the radius of the spring when turning the spring.

b) e2 profile projector:

For e2, the spring shall be horizontally placed on the glass plate and secured against rolling. The alignment is made by means of the coordinate system. Therefore, one coil end is aligned perpendicular to the glass plate. The difference between the maximum and the minimum value of the plane surface of the spring end is e2.

c) e2 camera systems:

The e2 measurement is similar to that using the dial gauge; however, the measurement values are determined optically. The measurement using optical measuring instruments is device-dependent and shall be described/be agreed upon with the customer on a case-by-case basis.

d) e2 feeler or pin gauge:

A spring shall be placed between two parallel surfaces, which have a clearance of L0 to this spring. The greatest distance between the top plate and the spring can now be determined with the feeler gauge.

The test location is on the ground spring bearing surfaces.

The shear-off burr is a test parameter.

The inspected property is the burr resulting from cutting off at both ends of the spring and on the inside and/or outside (see Figure 24).

Figure 24 — Shear-off burr

The shear-off burr cannot be measured. Evaluation is carried out by test. This test is the assessment of the sharp edge (subjective evaluation).

The following testing equipment can be used:

— test pin and test sleeve;

NOTE Only the burr projection regarding De or Di or the exceedance/undercut of the minimum or maximum tolerance can be determined with the test pin/test sleeve.

— magnifying glass;

— projector;

— stereoscopic microscope;

— camera.

Unless otherwise agreed between customer and manufacturer, assessment is done with naked eye.

The characteristic is evaluated at ambient temperature as delivered.

One of the following test methods shall be applied:

— visual inspection;

— magnifying glass;

— projector test;

— microscope;

— camera test.

The shear-off burr should be taken into account when testing with a mandrel or sleeve. The shear-off burr shall not exceed/undercut the tolerances of the inside and outside diameter.

Tests are carried out at the points where the wire is cut off/sheared.

1. 
   (informative)
   
   Calculation of spring rate R
   1. General

The spring rate R [N/mm] is a parameter and is determined by calculation.

Instructions regarding force and length measurement shall be observed.

• 1. Type of characteristic

ΔF is the increase in force corresponding to a reduction in length ΔL or the increase in deflection Δs.

The spring rate calculation is between two points only, and does not define the whole travel of the spring. Furthermore, the rate of a compression spring will not be constant, in particular close to the free or solid lengths.