Tiêu chuẩn iso 03408 3 2006

Microsoft Word C035023e doc Reference number ISO 3408 3 2006(E) © ISO 2006 INTERNATIONAL STANDARD ISO 3408 3 Second edition 2006 06 15 Ball screws — Part 3 Acceptance conditions and acceptance tests V[.]

Classification

The tests are graded in six standard tolerance grades (see Table 1) in conformance with ISO 286-2:1988, Table 1

Increasing requirements on accuracy and function

Geometrical tests

Tolerances on specified travel (e_p) for useful travel (l_u), as determined by tests E 1.1 and E 1.2, are directly adopted from ISO 286-2:1988, Table 1 For useful travel lengths (l_u) of 3150 mm or more, the values of e_p were calculated through linear extrapolation, ensuring accurate tolerance calculations for extended travel ranges (refer to Table A.1).

Tolerances on travel variation, v up , in micrometres, within useful travel l u were evaluated using the following equations:

⎯ Grade 5: v up = 0,018⋅l u + 18,4 where l u is the geometrical mean, in millimetres, of the extreme lengths of each step of measured travel given in Table A.1: u u max u min l = l ⋅l

Run-out tolerance and orientation tolerances were determined from experience

4.2.2 Evaluation of the measuring diagrams

To assess the actual mean travel deviation within the useful travel, both precise mathematical methods and quick, graphical techniques can be employed Mathematical approaches offer high accuracy for detailed analysis, while graphical methods provide a simple and efficient approximation suitable for everyday evaluations Combining these methods ensures reliable assessment of travel deviations, enhancing overall transportation efficiency.

The graphical method gives the minimum travel variation

The actual mean travel deviation, e a , is given by the formula e a = +a b γ with

This formula calculates the actual mean travel deviation relative to the nominal travel, taking into account each measuring point’s specific deviations The variables include γ, the angle of rotation or travel, and γ_i, the angle of rotation at each measuring point Similarly, e and e_i denote the deviations at the overall and individual measuring points, respectively The sum over all measuring points (n) ensures an accurate assessment of travel deviations, which is essential for precise mechanical and engineering analyses.

4.2.2.3 Graphical method [see Figure 3 a) and b)]

The evaluation of the actual mean travel deviation from the deviation diagram involves drawing tangent lines at multiple upper peaks, such as l₁ and l₂, and repeating the process for lower peaks like l₃ Next, the largest deviations parallel to the ordinate, such as e₁, e₂, and e₃, are determined, selecting the smallest among them (e₂ in the example) Finally, a straight line is drawn through this minimum deviation point, parallel to the corresponding peak line (l′₂ parallel to l₂ in the example), to analyze the mean travel deviation accurately.

The actual mean travel deviation, denoted as e_a, represents the central line between the parallel lines l₂ and l′₂, ensuring accurate alignment in travel measurement The bandwidth within the useful travel, represented as v_ua, is the distance between these parallel lines (e₂), measured parallel to the ordinate, indicating the effective range of travel These concepts are essential for precise navigation and performance assessment in transportation systems.

2 angular measuring instrument (permissible error = 10”)

4 travel measuring instrument (permissible error = 1 àm)

NOTE For the excess travel, see Table A.3 a Travel deviation

Figure 3 — Determination of the actual mean travel deviation, e sa or e 0a

General

The typical tolerance grades for positioning and transport ball screws are given in Table 2

Table 2 — Typical tolerance grades for positioning and transport ball screws

Type of ball screw Standard tolerance grade

The test according to Table 3 shall apply, depending on the type of ball screw considered [positioning (type P) or transport (type T) ball screw]

The basic measuring principle is illustrated in Figure 2

Travel deviations per reference length

Travel compensation c for useful travel l u Specified by user C = 0

Permissible travel variation v up within useful travel E 2 —

Permissible travel variation v 300p within 300 mm travel E 3 E 3

Permissible travel variation v 2πp within 2π rad E 4 —

Tests and tolerances to the ball nut displacement are relative to the ball screw shaft

A pitch-to-pitch measurement may be carried out using a measuring ball by touching the ball track of a non- rotating ball screw shaft For the measuring intervals, see Table A.2

The travel variation v ranges over 2π radians, determined through nine measurements—eight at 45° intervals per revolution—or continuously within a single thread at the start, middle, and end of the useful travel, provided this method is specified by a prior agreement This standardized approach ensures accurate assessment of travel variation in accordance with ISO 2006 standards.

Travel deviation and variation

Checking of the mean travel deviations, e sa and e 0a , within the useful travel, l u : a) for the specified travel, l s ; b) for the nominal travel, l 0

Tolerance on specified travel e p àm

Observations and remarks a) e sa = àm b)

The travel compensation c shall be specified by the user c = e 0a = àm

Checking of the mean travel deviation e 0a , within the useful travel, l u :

Tolerance on specified travel e p àm Standard tolerance grade

Checking of the travel variation v u within the useful travel, l u :

Travel variation v up àm Standard tolerance grade

Observations and remarks v ua = àm

See Figure 2 The variable v ua represents the smallest distance, measured parallel to the ordinate, between two lines that are parallel to the mean travel path This measurement effectively envelops the actual travel deviation over the useful travel distance, providing a precise assessment of travel consistency.

Object: Positioning or transport ball screw

Checking of the travel variation v 300 within an axial travel of 300 mm:

0 1 3 5 7 10 v 300p àm 3,5 6 12 23 52 a 210 a a Only for transport ball screws.

Observations and remarks v 300a max = _ àm

Figure 2 illustrates that the minimum distance, labeled as v 300a, is measured parallel to the ordinate and represents the shortest separation when a template moves along the actual travel deviation This distance is aligned parallel to the mean travel, which encompasses the real travel deviation over the measured segment, providing critical insights into the precision of template movement in relation to the travel deviation.

Checking of the travel variation v 2πp within 2π rad:

Observations and remarks v 2πa max = àm

See Figure 2 The smallest distance, measured parallel to the ordinate, is 2πa and is observed when a template is moved along the actual travel deviation, parallel to the mean travel This distance corresponds to one full revolution of the useful travel, or 2π radians, capturing the maximum deviation over that travel segment.

Run-out and location tolerances

Object: Transport or positioning ball screw

Measurement of radial run-out, t 5 , of ball screw shaft outer diameter for ascertaining straightness related to AA′ per length l 5 :

Observations and remarks t 5a = _ àm t 5max a = àm

Test instructions Reference to test code ISO 230-1:1996, 5.612.2

Place ball screw in identical V-blocks at points A and A′

Set dial gauge with measuring shoe at the distance l 5 perpendicular to the cylindrical surface

Rotate the ball screw slowly while recording the changes in the measurements at specified measuring intervals

NOTE 1 Optionally, measurement by supporting the ball screw shaft at both centres can be used by agreement NOTE 2 If l 1 < 2l 5 take the measurement at l 1 /2

Measurement of redial runout, t 6.1 , of bearing seat related to AA′, per unit length l:

Diameter t 6.1a mm _ àm mm _ àm mm _ àm mm _ àm

Place the dial gauge at the distance l 6 perpendicular to the cylindrical surface

Rotate the ball screw slowly and record the dial gauge readings

Measurement of radial runout, t 6.2 , of bearing seat related to the centreline of the screw part:

Dial gauge and V-blocks (assembled nut or jig for exclusive use)

Support a screw shaft at near both ends of threaded part, using the plural number of balls of the same size as the balls used

Place the dial gauge at the outside diameter of the ball bearing seat of the screw shaft

Rotate the screw shaft one revolution and record the dial gauge readings

NOTE This test can be used on an agreement between user and manufacturer If used, it replaces test E 6.1

Measurement of radial run-out, t 7.1 , of journal diameter related to the bearing seat by determining the difference: for l 7 ul (l see table) for l 7 > l to be valid t 7.1a u t 7.1p l 7 l

Diameter t 7.1a _ mm _ àm _ mm _ àm _ mm _ àm _ mm _ àm

Place the dial gauge at the distance l 7 perpendicular to the cylindrical surface

Rotate the ball screw slowly and record the dial gauge readings

Measurement of radial run-out, t 7.2 , of the journal diameter related to the centreline of the bearing seat:

Support a screw shaft at its supporting bearing seats horizontally using V-blocks

Put the dial gauge at the outside diameter of the journals

Measurement of axial run-out, t 8.1 , of shaft (bearing) faces related to AA′:

Diagram t 8.1a u t 8.1p − |∆| where ∆ is the deviation of straightness

Diameter t 8.1a _ mm _ àm _ mm _ àm _ mm _ àm

Test instructions Reference to test code ISO 230-1:1996, 5.632

Place ball screw at points A and A′ on V-blocks

Secure the ball screw shaft in the axial direction against movement (e.g by placing a ball between the centres of the ball screw shaft and the mounting surface)

Place the dial gauge perpendicular to the end face of the journal and to the cylindrical surface of the corresponding diameter

Measurement of axial run-out, t 8.2 , of the shaft faces related to the centreline of the screw shaft:

Support a screw shaft horizontally by the V-blocks at the supporting bearing seats while butting one end of the screw shaft to the fixed face

Place the dial gauge at its supporting bearing seat end face

Measurement of axial run-out, t 9 , of ball nut location face related to AA′ (for preloaded ball nuts only):

Observations and remarks t 9a max = _ àm

System preloaded Place the ball screw on V-blocks at points A and A′

Secure the ball screw shaft in the axial direction against movement (e.g by placing a ball between the centres of the ball screw shaft and the mounting surface)

Place the dial gauge perpendicular to the flange face at the outer rim of the inspection diameter D 2

Secure the ball nut against rotation on the ball screw shaft

Rotate the ball screw shaft and record the dial gauge readings

Measurement of radial run-out, t 10 , of ball nut location diameter related to AA′(for preloaded and rotating ball nuts only):

Ball nut body outer diameter

Observations and remarks t 10a max = _ àm

System preloaded Place the ball screw on V-blocks at points A and A'

Place the dial gauge perpendicular to the cylindrical surface of ball nut location diameter D 1

Secure the ball screw shaft

Rotate the ball nut body slowly Record the dial gauge readings

Deviation of parallelism, t 11 , of rectangular ball nut related to AA′ (for preloaded ball nuts only):

0 1 3 5 7 10 t 11p , àm, for each 100 mm (cumulative)

Place ball screw on V-blocks at points A and A′

Place the dial gauge perpendicular to the inspection surface and probe along the specified inspection length l

Record the dial gauge readings

Functional tests

Measurement of dynamic preload drag torque, ∆T p :

T t = F t × lwith end seals l n = ball nut length

Test bench with recorder for force value measured

System preloaded (with or without end seals)

For the recording of the radial preload force, couple the ball nut body to a load cell at the distance l from the axis of rotation

Take recordings of the force indicator at a rotational speed 100 min -1 in both directions of rotation a

For optimal lubrication, use a lubricant with an ISO viscosity grade 100 Alternative lubricants, rotational speeds, and measuring instruments can be employed if agreed upon by the user and the manufacturer (ISO 2006 – All rights reserved)

Object: Positioning or transport ball screw E 13

Measurement of axial rigidity, R nu :

Y load, F a Fixed against rotation b Axially fixed.

Dial gauges and load cell

Fix the preloaded ball nut axially in both directions and secure the ball screw shaft against rotation

Place the dial gauge supports securely on the ball screw shaft, ensuring stability during measurement Touch the measuring stylus gently against the face of the ball nut body, positioning it as close as possible to the shaft for accurate readings Align the stylus parallel to the ball screw shaft axis to ensure precise measurement results.

Apply the axial load F 1 =0,5F pr or F 2 = 2F pr to the ball screw shaft in tension and in compression

F pr is the preload and∆l 1 or ∆l 2 are the elastic deformations (reversal range) caused by the axial test loads ± F 1 and ± F 2 respectively

Rigidity in the ranges ± F 1 : nu1 1 pr

Rigidity in the range + F 1 to + F 2 and − F 1 to − F 2 : ( 2 1 ) pr nu2 2 1 2 1

= ∆ − ∆ ∆ − ∆ Other test loads F may be used by agreement between the user and the manufacturer

Table A.1 — Tolerance values on specified travel, e p , for a band width per 300 mm ( v 300 ) and for a mean travel deviation, e , and for the standard tolerance grades according to ISO 286-2:1988

> u Tolerance on specified travel, e p àm

5 000 6 300 48 a 92 a 170 a 390 a 1 550 a a These values were calculated by linear extrapolation from the IT values in accordance with ISO 286-2 for sizes above 500 mm and less than or equal to 3 150 mm.

Table A.2 — Minimum number of measurements over 300 mm (measuring intervals)

P h mm Minimum number of measurements

Tiêu đề	Ball Screws — Part 3: Acceptance Conditions And Acceptance Tests
Trường học	International Organization for Standardization
Chuyên ngành	Standards
Thể loại	standard
Năm xuất bản	2006
Thành phố	Geneva

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