ISO/ASTM DTR 52952

Additive manufacturing of metals — Feedstock materials — Correlating of rotating drum measurement with powder spreadability in PBF-LB machines

Fabrication additive de métaux — Matières premières — Corrélation de la mesure du tambour rotatif avec la capacité d'étalement de la poudre dans les machines PBF-LB

General Information

• Status: Not Published
• ICS: 25.030 - Additive manufacturing
• Technical Committee: ISO/TC 261 - Additive manufacturing
• Drafting Committee: ISO/TC 261 - Additive manufacturing
• Current Stage: 5060 - Close of voting Proof returned by Secretariat
• Start Date: 12-May-2023
• Completion Date: 13-May-2023

Relations

• Consolidates: ISO/TR 20172:2021 - Welding — Grouping systems for materials — European materials
• Effective Date: 06-Jun-2022

Standards Content (Sample)

ISO/DTR 52952:2023(E)
ISO/TC 261 & ASTM F 42
Secretariat: DIN
Date: 2023-01-18xx

Additive Manufacturingmanufacturing of metals — Feedstock materials — Correlation of

rotating drum measurement with powder spreadability in PBF-LB machines

Fabrication additive de métaux — Matières premières — Corrélation de la mesure du tambour rotatif avec

la capacité d'étalement de la poudre dans les machines PBF-LB
---------------------- Page: 1 ----------------------
ISO/DTR 52952:2023(E)
© ISO/ASTM 2023
Commented [eXtyles1]: Not found: "ISO/ASTM 2023"
Formatted: Pattern: Clear

All rights reserved. Unless otherwise specified, or required in the context of its implementation,

Formatted: Pattern: Clear

no part of this publication may be reproduced or utilized otherwise in any form or by any means,

electronic or mechanical, including photocopying, or posting on the internet or an intranet,

without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester. In the United States, such requests

should be sent to ASTM International.
ISO copyright office ASTM International
CP 401 • Ch. de Blandonnet 8 100 Barr Harbor Drive, PO Box C700
CH-1214 Vernier, Geneva West Conshohocken, PA 19428-2959, USA
Phone: [phone] Phone: [phone]
Fax: [phone] Fax: [phone]
Email: [e-mail]@iso.org Email: [e-mail]
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been redirected to https://www.astm.org/. Please verify the
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ii © ISO 2023 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/DTR 52952:2023(E)
Contents

Foreword ......................................................................................................................................................................... iv

Introduction..................................................................................................................................................................... v

1 Scope .................................................................................................................................................................... 1

2 Normative references .................................................................................................................................... 2

3 Terms and definitions .................................................................................................................................... 2

4 Designation ........................................................................................................................................................ 2

5 Methodology ...................................................................................................................................................... 3

5.1 Powder selection ............................................................................................................................................. 3

5.2 Layer homogeneity evaluation ................................................................................................................... 3

5.3 Rotating drum ................................................................................................................................................... 4

6 Results and discussion .................................................................................................................................. 5

6.1 Spreadability ..................................................................................................................................................... 5

6.2 Rotating drum analysis ................................................................................................................................. 7

6.2.1 Experimental protocol ................................................................................................................................... 7

6.2.2 Experimental results ...................................................................................................................................... 7

6.3 Discussion .......................................................................................................................................................... 9

7 Conclusions ..................................................................................................................................................... 11

8 Additional data .............................................................................................................................................. 11

9 Perspectives ................................................................................................................................................... 12

Bibliography ................................................................................................................................................................. 13

Foreword ......................................................................................................................................................................... iv

Introduction..................................................................................................................................................................... v

1 Scope .................................................................................................................................................................... 1

2 Normative references .................................................................................................................................... 2

3 Terms and definitions .................................................................................................................................... 2

© ISO 2023 – All rights reserved iii
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ISO/DTR 52952:2023(E)

4 Designation ........................................................................................................................................................ 2

5 Methodology ...................................................................................................................................................... 3

5.1 Powder selection ............................................................................................................................................. 3

5.2 Layer homogeneity evaluation ................................................................................................................... 3

5.3 Rotating drum ................................................................................................................................................... 4

6 Results and discussion .................................................................................................................................. 5

6.1 Spreadability ..................................................................................................................................................... 5

6.2 Rotating drum analysis ................................................................................................................................. 7

6.2.1 Experimental protocol ................................................................................................................................... 7

6.2.2 Experimental results ...................................................................................................................................... 7

6.3 Discussion .......................................................................................................................................................... 9

7 Conclusions ..................................................................................................................................................... 11

8 Additional data .............................................................................................................................................. 11

9 Perspectives ................................................................................................................................................... 12

Bibliography ................................................................................................................................................................. 13

iv © ISO 2023 – All rights reserved
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ISO/DTR 52952:2023(E)
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/directiveswww.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/patentswww.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.

The committee responsible for thisThis document iswas prepared by Technical Committee ISO/TC 261,

Additive manufacturing, in cooperation with ASTM Committee F42, Additive Manufacturing

Formatted: Font: Italic

Technologies, on the basis of a partnership agreement between ISO and ASTM International with the

Formatted: Font: Italic

aim to create a common set of ISO/ASTM standards on Additive Manufacturing.additive manufacturing,

and in collaboration with the European Committee for Standardization (CEN) Technical Committee

CEN/TC 438, Additive manufacturing, in accordance with the Agreement on technical cooperation

between ISO and CEN (Vienna Agreement).

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.
© ISO 2023 – All rights reserved v
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ISO/DTR 52952:2023(E)
Introduction

Granular materials and fine powders are widely used in industrial applications. To support control and

optimize processing methods, these materials have to be precisely characterized. Characterization

methods are related either to the properties of the grains (granulometry, morphology, chemical

composition, etc.) or to the behaviour of the bulk powder (flowability, density, blend stability,

electrostatic properties, etc.). The complex behaviours of granular and powder materials have

motivated the development of numerous techniques to obtain reproducible and interpretable results.

Many industries are concerned in different fields: additive manufacturing, food processing,

pharmaceuticals, bulk material handling. This document is focused on Additive Manufacturing (AM).

Metallic powders are widely used in AM processes involving powder bed fusion (PBF-LB/M PBF-EB/M

etc.) or binder jetting. During such operations, successive thin layers of powder are created with a blade

or with a rotating cylinder. Each layer is then fused (most commonly melted) by an energy beam or

joined by an adhesive binder to build the parts. The layer thickness defines the vertical resolution of the

process; a thin layer leads to a better resolution. In order to obtain a thin layer, the powder is as fine as

possible. However, if it is assumed that among the cohesive forces, the Van der Waal forces are

[[25]]

predominant, it can be stated that as the grain size decreases, cohesiveness typically increases. . This

Formatted: Pattern: Clear
increase in cohesiveness could have a impact on the spreadability of a powder.

The quality of the parts built with AM is thus directly influenced by powder flow properties.

According to ISO/ASTM 52900, spreadability is the ability of a feedstock material to be spread out in

Formatted: Pattern: Clear

layers that fulfil the requirements for the AM process; this includes the ability to form a strictly flat

Formatted: Pattern: Clear
powder-atmosphere interface without waves and irregularities.

Visual observation of layer homogeneity is usually the only way for operators to assess the

spreadability of powders during the spreading of new layers. However, linking the powder

characteristics to its spreadability during the layer deposition beforehand can provide a more cost-

effective way to classify and select the optimal powder and layer deposition speed combinations.

vi © ISO 2023 – All rights reserved
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TECHNICAL REPORT ISO/DTR 52952:2023(E)
Additive Manufacturingmanufacturing of metals — Feedstock
materials — Correlation of rotating drum measurement with
powder spreadability in PBF-LB machines
1 Scope

This document provides an example of the relation between the characterization of certain macroscopic

properties of metallic powders and their spreadability in an PBF-LB/M AM machines.

This relation is based on a new technique combining measurements inside an PBF-LB/M machine and

image processing developed to quantify the homogeneity of the powder bed layers during spreading.

In this document, the flowability of five metal powders are investigated with an automated rotating

drum method, whose dynamic cohesive index measurement is shown to establish a correlation with the

spreadability of the powder during the layer deposition operation. Furthemore, the particule size

distribution (PSD) and morphology of each powder is characterized before testing by static image

analysis method (according to ISO 13322-1:2014).
Formatted: Pattern: Clear

The general principle of the method is described in Figure 1. Formatted: Pattern: Clear

Formatted: Pattern: Clear
52952_ed1fig1.EPS
Formatted: Pattern: Clear
Key
1 AlSi Mg
2 NiCr22Mo9Nb (inconel fine)
Good.
Bad.
Rotating drum.
PBF-LM printer.
Regular layer.
Irregular layer.

Figure 1 — General principle of comparing rotating drum measurements with powder spreading

in a PBF-LB AM machine
2 Normative references
There are no normative references in this document.

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO/ASTM 52900, Additive manufacturing — General principles — Fundamentals and vocabulary

© ISO 2023 – All rights reserved 1
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ISO/DTR 52952:2023(E)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/ASTM 52900 and the

Formatted: Pattern: Clear
following apply.
Formatted: Pattern: Clear

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp

Commented [eXtyles3]: URL Validation failed:
https://www.iso.org/obp returns an unknown connection
failure. (connection error "Error 12031:

— IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/

ERROR_INTERNET_CONNECTION_RESET").
3.1 Formatted: English (United States)
cohesiveness
Formatted: Adjust space between Latin and Asian text,

physical powder behaviour relating to the degree to which the attractive forces between particles

Adjust space between Asian text and numbers, Tab
exceed the average particle mass
stops: Not at 19.85 pt + 39.7 pt + 59.55 pt + 79.4 pt
+ 99.25 pt + 119.05 pt + 138.9 pt + 158.75 pt +

Note 1 to entry: cohesive powders is qualified as systems where the attractive force between particles exceed the

178.6 pt + 198.45 pt
average particle mass
Formatted: English (United States)
3.2
Formatted: Font: Times New Roman, English (United
powder flowability States)
ability of a solid bulk material to flow

Note 1 to entry: powder flowability is a function of multiple factors, and particularly powder size and distribution,

Seesee also ISO/ASTM 52907.
Formatted: Pattern: Clear
Formatted: Pattern: Clear
4 Designation
In this document, five powders described in Table 1 are used:
Formatted: Pattern: Clear
Table 1 — Designation of powders
Denomination used in this
Common designation European spefication
document
Scalmalloy® AlMgSc AlMgSc_Std
Formatted: Centered
Inconel® NiCr22Mo9Nb NiCr22Mo9Nb_Std
Formatted: Centered
AlSi Mg AlSi Mg AlSi Mg_Std
7 7 7
Formatted: Centered
Titanium Fine Ti6Al4V Ti6Al4V_Fine
Formatted: Centered
Inconel® Fine NiCr22Mo9Nb NiCr22Mo9Nb_Fine
Formatted: Centered
5 Methodology
5.1 General principle

The general principle for comparing rotating drum measurements with powder spreading in a

PBF-LB AM machine is described in Figure 1.
2 © ISO 2023 – All rights reserved
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ISO/DTR 52952:2023(E)
Key
1 AlSi7Mg
2 NiCr Mo Nb (inconel fine)
22 9
Good.
Bad.
Rotating drum.
PBF-LM printer.
Regular layer.
Irregular layer.

Figure 1 — General principle of comparing rotating drum measurements with powder spreading

in a PBF-LB AM machine
5.15.2 Powder selection

The recoating performance of the powders inside a PBF-LB AM machine is evaluated experimentally

with in situ observation of layer homogeneity. Five metallic powders are selected for this study: two

Nickel alloys (NiCr Mo Nb_Std and NiCr Mo Nb_Fine), two Aluminium alloys (AlSi Mg_Std and

22 9 22 9 7

AlMgSc_Std) and one Titanium alloy (Ti Al V_Fine). Particle size distribution (PSD) is summarized in

6 4
Table 2 and shape and morphology in Table 3.
Formatted: Pattern: Clear
Formatted: Pattern: Clear
Table 2 — Summary of the PSD (D10 and D90) of the five powders (volume)
D10 ( D90 (
Powder
µm) µm)
Formatted: Font: Not Bold
NiCr22Mo9Nb_Fine 6 27
Formatted: Font: Not Bold
Formatted: Font: Not Bold
NiCr22Mo9Nb_Std 17 45
Formatted: Font: Not Bold
AlSi7Mg_Std 27 69
AlMgSc_Std 26 66
Ti6Al4V_Fine 7 28
Table 3 — Shape and morphology comparison
© ISO 2023 – All rights reserved 3
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ISO/DTR 52952:2023(E)
Aspect ratio comparison
Mean ( P10 ( P50 ( P90 (
Aspect ratio (number)
µm) µm) µm) µm)
Formatted: Font: Not Bold
AlMgSc_Std 79,7 62,5 81,6 93,8
Formatted: Font: Not Bold
AlSi Mg 76,6 58,4 78,7 91,8
7 Formatted: Font: Not Bold
NiCr22Mo9Nb_Std 81,9 63,5 85,3 94,6 Formatted: Font: Not Bold
NiCr22Mo9Nb_Fine 81,8 63,5 85,8 93,3
Ti Al V_Fine 79,7 60,9 82,9 92,8
6 4
Bluntness comparison
Mean ( P10 ( P50 ( P90 (
Bluntness (number)
µm) µm) µm) µm)
Formatted: Font: Not Bold
AlMgSc_Std 74,6 54,0 74,6 95,1
Formatted: Font: Not Bold
AlSi Mg 75,5 57,1 75,5 93,8
7 Formatted: Font: Not Bold
Formatted: Font: Not Bold
NiCr22Mo9Nb_Std 84,3 67,9 86,7 97,2
NiCr22Mo9Nb_Fine 88,0 76,5 89,9 97,1
Ti Al V_Fine 85,0 70,2 87,4 96,5
6 4

Successive powder layers are produced in the PBF-LB AM machine with no laser melting. Between each

layer deposition, a picture of the powder layer is taken by a camera placed inside the AM machine. The

pictures are then processed numerically to evaluate the layer homogeneity. Three powder spreading

speeds are investigated: 30, 80 and 160 mm/s to highlight their influence on the layer quality.

5.25.3 Layer homogeneity evaluation

The powder layer surface homogeneity is experimentally evaluated using a camera placed orthogonal

to the powder bed. After each powder spreading operation, a picture is taken. For this experiment, the

focus is made on metallic coater and 30 µm layer thickness only. For the same recoater speed, 15 layers

are created and therefore, 15 pictures are taken as well. This methodology provides a quantitative and

operator independent way to quantify the layer topography homogeneity.

The gathered pictures are then processed numerically to obtain "Interface Fluctuation”, a measure of

the inhomogeneity of the produced layers. The image processing analysis principle is as follow:

a) each picture is analysed separately. The picture size is 1 200 xpixels × 1 200 pixelpixels;

b) horizontal and vertical pixel intensity profiles are extracted at discrete positions of the picture ([see

Figure 2. a));)];
Formatted: Pattern: Clear
Formatted: cite_fig
c) an average “smooth” profile is computed for each position [see Figure 2. b)];
Formatted: Pattern: Clear

d) interface fluctuation is then computed based on the deviation around the averaged profile, and then

Formatted: cite_fig
averaged over all positions;

e) the process is repeated for all the images, and the interface fluctuation is average over the whole set

of pictures.
52952_ed1fig2a.EPS 52952_ed1fig2b.EPS
4 © ISO 2023 – All rights reserved
---------------------- Page: 10 ----------------------
ISO/DTR 52952:2023(E)
b) Pixel intensity profile (plain) and average
a) Horizontal and vertical lines from which
profile (dashed) used to compute the interface
pixel intensity profiles are extracted
fluctuation
Key
X position along the line
Y pixel intensity (before normalisation)
52952_e
d1fig2_k
AlSi7Mg (top)
ey1.EPS
52952_e
d1fig2_k
NiCr22Mo9Nb_Fine (bottom)
ey2.EPS
Figure 2 — In situ layer quality assessment
5.35.4 Rotating drum

Powder flowability is evaluated with a rotating drum method which allows an automated measurement.

A horizontal cylinder with transparent sidewalls called drum is filled with the sample of powder. The

filling ratio of the drum can influence the flow of the powder and thus are kept constant to allow

relevant comparison of the results.

The volume of the drum used in this study is 100 mL and the filling ratio is fixed as 50 %. Therefore, a

50 mL powder sample is used for the measurements.

The drum rotates around its axis at an angular velocity ranging from 2 rpmr/min to 60 rpmr/min. A

CCD (charge-coupled device) camera takes snapshots at a framerate of 1 image per second for each

angular velocity.

The air/powder interface is detected on each snapshot with an edge detection algorithm.

Afterwards, the average interface position and the fluctuations around this average position are

computed. The number of snapshots taken influences the statistical relevance of the averaged interface.

© ISO 2023 – All rights reserved 5
---------------------- Page: 11 ----------------------
ISO/DTR 52952:2023(E)
[[18]]

In this experiment and, based on previous studies, , a value of 40 is chosen for each rotating speeds.

Formatted: Pattern: Clear
[27]

This value is considered sufficient to guarantee accurate and reproducible measurements .

Formatted: Pattern: Clear

The number of revolutions performed during the measurement is dependant on the rotating speed.

However, the rotating drum allows a continuous flow of material regardless of the angular position of

the drum and number of revolutions, justifying the use of a fixed number of snapshots taken whatever

the speed investigated. Then, for each rotating speed, the dynamic cohesive index σf is measured from

the temporal fluctuations of the powder/air interface. The angle formed by the flow, commonly

measured with rotating drum, is influenced by a wide set of parameters: the friction between the grains,

the shape of the grains, the cohesive forces (van der Waals, electrostatic and capillary forces) between

the grains.

On the opposite, the dynamic cohesive index σf is only related to the cohesive forces between the grains

[ ]

as highlighted in. Reference [26 ]. A cohesive powder leads to an intermitted flow while a non-cohesive

Formatted: Not Superscript/ Subscript, Pattern: Clear

powder leads to a regular flow. Therefore, a dynamic cohesive index close to zero corresponds to a non-

cohesive powder. When the powder cohesiveness increases, the dynamic cohesive index increases

accordingly.
6 Results and discussion
6.1 Spreadability

The interface fluctuation, a measure of the layer homogeneity, obtained for the powders at different

recoater speeds is presented in Figure 1.
Formatted: Pattern: Clear

In addition, a qualification of the layers spreadability is made according to the observations of the

operator. These are summarized in Table 4.
Formatted: Pattern: Clear

Table 4 — Qualification of spreadability made by the operator during testing (based on visual

observation)
Powder Observation Qualification remark
AlSi7Mg_Std Good spreading Good
Formatted: Centered
NiCr Mo Nb_Std Good spreading Good
22 9
Formatted: Centered
Good spreading with rigid wriper. Seems to be speed
Formatted: Centered
AlMgSc_Std Medium
dependant in case of spreading with silicon blade.
Bad spreading / difficulties to obtain an uniform layer on
Formatted: Centered
Ti Al V_Fine Bad
6 4
the whole plate
NiCr Mo Nb_Fine Bad spreading Bad
22 9
Formatted: Centered
52952_ed1fig3.EPS
6 © ISO 2023 – All rights reserved
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ISO/DTR 52952:2023(E)
Key
X recoated speed (mm/s)
Y interface fluctuation
52952_e
d1fig3_k
NiCr Mo Nb_Std
22 9
ey1.EPS
52952_e
d1fig3_k
AlSi7Mg_Std
ey2.EPS
52952_e
d1fig3_k
AlMgSc_Std
ey3.EPS
52952_e
d1fig3_k
NiCr Mo Nb_Fine
22 9
ey4.EPS
52952_e
d1fig3_k
Ti6Al4V_Fine
ey5.EPS
© ISO 2023 – All rights reserved 7
---------------------- Page: 13 ----------------------
ISO/DTR 52952:2023(E)

Note: The speed for powder spreading effect is noticeable for NiCr22Mo9Nb_Fine and Ti6Al4V_Fine.

Figure 3 — Interface fluctuations as a function of recoater speed (in mm/s)
Table 5 — Interface fluctuations (IF) as a function of recoater speed (in mm/s)
Interval of fluctuation vs. material
Spreader NiCr22Mo9Nb_Fin
NiCr22Mo9Nb_Std AlSi7Mg_Std AlMgSc_Std Ti6Al4V_Fine
speed e
(mm/s)
Dev.
Dev. Dev Dev. Dev. Dev.
Devi
a) a) a)
IF ia IF Devia IF Devia IF Devia IF
tion tion tion tion
tion
30 0,21 0,004 0,23 0,004 0,30 0,004 0,37 0,013 0,43 0,028
80 0,20 0,004 0,24 0,003 0,32 0,004 0,38 0,024 0,46 0,072
Formatted Table
160 0,20 0,003 0,24 0,004 0,32 0,003 0,49 0,044 0,59 0,020
Deviation

NiCr Mo Nb_Std and AlSi Mg_Std show the lower interface fluctuation and, thus, are able to produce

22 9 7

more homogeneous layers during the recoating. AlMgSc_Std exhibits a higher interface fluctuation; a

consequence of the appearance of a parallel waves pattern is shown in Figure 4. The NiCr Mo Nb_Fine

22 9 Formatted: Pattern: Clear

has the highest interface fluctuation and thus produces the less homogeneous layers among the tested

powders [see Figure 4. b)]. This could be attributed to the smaller particle sizes compared to the

Formatted: Pattern: Clear
NiCr22Mo9Nb_Std.
Formatted: cite_fig

Indeed these two NiCr22Mo9Nb powders have very close morphological criteria, see Figure 4. So, the

Formatted: Pattern: Clear

difference of behaviorbehaviour between these two powders seems to be due mainly to the effect

related to the size of the grains.

Furthermore, the smaller the particles the higher the influence of the cohesive interactions lying

between the particles composing the powders.

For NiCr Mo Nb_Fine and Ti Al V_Fine, the interface fluctuation with increasing recoater speed is

22 9 6 4

observed. This indicates a degradation of the layer homogeneity when the recoating process is speed

up. However, increasing the speed for powder spreading is interesting in order to reduce the printing

duration. Therefore, this highlights the existence of an optimal speed for spreading powder, specific for

each powder, at which the time spent on spreading powder is minimized while still guaranteeing

sufficiently homogeneous layers. Moreover, the decrease of spreading performance when the powder is

submitted to a higher shear stress may indicate that the rheology of the powder is also a key parameter

for spreadability.
52952_ed1fig4a.EPS 52952_ed1fig4b.EPS
8 © ISO 2023 – All rights reserved
---------------------- Page: 14 ----------------------
ISO/DTR 52952:2023(E)
a) AlMgSc_Std b) NiCr22Mo9Nb_Fine at 30 mm/s
Key
1 parallel waves
Figure 4 — Example of in-situ photography
6.2 Rotating drum analysis
6.2.1 Experimental protocol

For an experiment with the rotating drum, powders are poured inside the measuring cell just after the

box opening. The quantity of powder u
...

FINAL
TECHNICAL ISO/ASTM
DRAFT
REPORT DTR
52952
ISO/TC 261
Additive manufacturing of metals —
Secretariat: DIN
Feedstock materials — Correlating
Voting begins on:
2023-02-17 of rotating drum measurement with
powder spreadability in PBF-LB
Voting terminates on:
2023-05-12
machines
Fabrication additive de métaux — Matières premières — Corrélation
de la mesure du tambour rotatif avec la capacité d'étalement de la
poudre dans les machines PBF-LB
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 SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/ASTM DTR 52952:2023(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO/ASTM International 2023
---------------------- Page: 1 ----------------------
ISO/ASTM DTR 52952:2023(E)
FINAL
TECHNICAL ISO/ASTM
DRAFT
REPORT DTR
52952
ISO/TC 261
Additive manufacturing of metals —
Secretariat: DIN
Feedstock materials — Correlating
Voting begins on:
of rotating drum measurement with
powder spreadability in PBF-LB
Voting terminates on:
machines
Fabrication additive de métaux — Matières premières — Corrélation
de la mesure du tambour rotatif avec la capacité d'étalement de la
poudre dans les machines PBF-LB
COPYRIGHT PROTECTED DOCUMENT
© ISO/ASTM International 2023

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester. In the United States, such requests should be sent to ASTM International.

ISO copyright office ASTM International
RECIPIENTS OF THIS DRAFT ARE INVITED TO
CP 401 • Ch. de Blandonnet 8 100 Barr Harbor Drive, PO Box C700
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
CH-1214 Vernier, Geneva West Conshohocken, PA 19428-2959, USA
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
Phone: [phone] Phone: [phone]
DOCUMENTATION.
Fax: [phone]
IN ADDITION TO THEIR EVALUATION AS
Reference number
Email: [e-mail] Email: [e-mail]
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/ASTM DTR 52952:2023(E)
Website: www.iso.org Website: www.astm.org
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
Published in Switzerland
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN­
DARDS TO WHICH REFERENCE MAY BE MADE IN
© ISO/ASTM International 2023 – All rights reserved
NATIONAL REGULATIONS. © ISO/ASTM International 2023
---------------------- Page: 2 ----------------------
ISO/ASTM DTR 52952:2023(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Designation ................................................................................................................................................................................................................ 2

5 Methodology .............................................................................................................................................................................................................2

5.1 General principle .................................................................................................................................................................................. 2

5.2 Powder selection ................................................................................................................................................................................... 3

5.3 Layer homogeneity evaluation ................................................................................................................................................. 3

5.4 Rotating drum ......................................................................................................................................................................................... 4

6 Results and discussion ..................................................................................................................................................................................5

6.1 Spreadability ............................................................................................................................................................................................ 5

6.2 Rotating drum analysis .................................................................................................................................................................. 7

6.2.1 Experimental protocol .................................................................................................................................................. 7

6.2.2 Experimental results ...................................................................................................................................................... 7

6.3 Discussion ................................................................................................................................................................................................... 9

7 Conclusions .............................................................................................................................................................................................................11

8 Additional data ...................................................................................................................................................................................................12

9 Perspectives ...........................................................................................................................................................................................................13

Bibliography .............................................................................................................................................................................................................................14

iii
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ISO/ASTM DTR 52952:2023(E)
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 non­governmental, 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).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 261, Additive manufacturing, in

cooperation with ASTM Committee F42, Additive Manufacturing Technologies, on the basis of a

partnership agreement between ISO and ASTM International with the aim to create a common set of

ISO/ASTM standards on additive manufacturing, and in collaboration with the European Committee for

Standardization (CEN) Technical Committee CEN/TC 438, Additive manufacturing, in accordance with

the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

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.
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ISO/ASTM DTR 52952:2023(E)
Introduction

Granular materials and fine powders are widely used in industrial applications. To support control and

optimize processing methods, these materials have to be precisely characterized. Characterization

methods are related either to the properties of the grains (granulometry, morphology, chemical

composition, etc.) or to the behaviour of the bulk powder (flowability, density, blend stability,

electrostatic properties, etc.). The complex behaviours of granular and powder materials have motivated

the development of numerous techniques to obtain reproducible and interpretable results. Many

industries are concerned in different fields: additive manufacturing, food processing, pharmaceuticals,

bulk material handling. This document is focused on Additive Manufacturing (AM).

Metallic powders are widely used in AM processes involving powder bed fusion (PBF-LB/M PBF-EB/M

etc.) or binder jetting. During such operations, successive thin layers of powder are created with a blade

or with a rotating cylinder. Each layer is then fused (most commonly melted) by an energy beam or

joined by an adhesive binder to build the parts. The layer thickness defines the vertical resolution of

the process; a thin layer leads to a better resolution. In order to obtain a thin layer, the powder is as

fine as possible. However, if it is assumed that among the cohesive forces, the Van der Waal forces are

[25]

predominant, it can be stated that as the grain size decreases, cohesiveness typically increases . This

increase in cohesiveness could have a impact on the spreadability of a powder.

The quality of the parts built with AM is thus directly influenced by powder flow properties.

According to ISO/ASTM 52900, spreadability is the ability of a feedstock material to be spread out in

layers that fulfil the requirements for the AM process; this includes the ability to form a strictly flat

powder­atmosphere interface without waves and irregularities.

Visual observation of layer homogeneity is usually the only way for operators to assess the spreadability

of powders during the spreading of new layers. However, linking the powder characteristics to its

spreadability during the layer deposition beforehand can provide a more cost-effective way to classify

and select the optimal powder and layer deposition speed combinations.
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TECHNICAL REPORT ISO/ASTM DTR 52952:2023(E)
Additive manufacturing of metals — Feedstock materials
— Correlating of rotating drum measurement with powder
spreadability in PBF-LB machines
1 Scope

This document provides an example of the relation between the characterization of certain macroscopic

properties of metallic powders and their spreadability in an PBF-LB/M AM machines.

This relation is based on a new technique combining measurements inside an PBF-LB/M machine and

image processing developed to quantify the homogeneity of the powder bed layers during spreading.

In this document, the flowability of five metal powders are investigated with an automated rotating

drum method, whose dynamic cohesive index measurement is shown to establish a correlation with

the spreadability of the powder during the layer deposition operation. Furthemore, the particule size

distribution (PSD) and morphology of each powder is characterized before testing by static image

analysis method (according to ISO 13322-1).
The general principle of the method is described in Figure 1.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO/ASTM 52900, Additive manufacturing — General principles — Fundamentals and vocabulary

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/ASTM 52900 and the

following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
cohesiveness

physical powder behaviour relating to the degree to which the attractive forces between particles

exceed the average particle mass

Note 1 to entry: cohesive powders is qualified as systems where the attractive force between particles exceed

the average particle mass
3.2
powder flowability
ability of a solid bulk material to flow

Note 1 to entry: powder flowability is a function of multiple factors, and particularly powder size and distribution,

see also ISO/ASTM 52907.
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ISO/ASTM DTR 52952:2023(E)
4 Designation
In this document, five powders described in Table 1 are used:
Table 1 — Designation of powders
Denomination used in this
Common designation European spefication
document
Scalmalloy® AlMgSc AlMgSc_Std
Inconel® NiCr Mo Nb NiCr Mo Nb_Std
22 9 22 9
AlSi Mg AlSi Mg AlSi Mg_Std
7 7 7
Titanium Fine Ti Al V Ti Al V_Fine
6 4 6 4
Inconel® Fine NiCr Mo Nb NiCr Mo Nb_Fine
22 9 22 9
5 Methodology
5.1 General principle

The general principle for comparing rotating drum measurements with powder spreading in a

PBF­LB AM machine is described in Figure 1.
Key
1 AlSi Mg
2 NiCr Mo Nb (inconel fine)
22 9
Good.
Bad.
Rotating drum.
PBF­LM printer.
Regular layer.
Irregular layer.
Figure 1 — General principle of comparing rotating drum measurements with powder
spreading in a PBF-LB AM machine
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ISO/ASTM DTR 52952:2023(E)
5.2 Powder selection

The recoating performance of the powders inside a PBF-LB AM machine is evaluated experimentally

with in situ observation of layer homogeneity. Five metallic powders are selected for this study: two

Nickel alloys (NiCr Mo Nb_Std and NiCr Mo Nb_Fine), two Aluminium alloys (AlSi Mg_Std and

22 9 22 9 7

AlMgSc_Std) and one Titanium alloy (Ti Al V_Fine). Particle size distribution (PSD) is summarized in

6 4
Table 2 and shape and morphology in Table 3.
Table 2 — Summary of the PSD (D10 and D90) of the five powders (volume)
D10 D90
Powder
µm µm
NiCr Mo Nb_Fine 6 27
22 9
NiCr Mo Nb_Std 17 45
22 9
AlSi Mg_Std 27 69
AlMgSc_Std 26 66
Ti Al V_Fine 7 28
6 4
Table 3 — Shape and morphology comparison
Aspect ratio comparison
Mean P10 P50 P90
Aspect ratio (number)
µm µm µm µm
AlMgSc_Std 79,7 62,5 81,6 93,8
AlSi Mg 76,6 58,4 78,7 91,8
NiCr Mo Nb_Std 81,9 63,5 85,3 94,6
22 9
NiCr Mo Nb_Fine 81,8 63,5 85,8 93,3
22 9
Ti Al V_Fine 79,7 60,9 82,9 92,8
6 4
Bluntness comparison
Mean P10 P50 P90
Bluntness (number)
µm µm µm µm
AlMgSc_Std 74,6 54,0 74,6 95,1
AlSi Mg 75,5 57,1 75,5 93,8
NiCr Mo Nb_Std 84,3 67,9 86,7 97,2
22 9
NiCr Mo Nb_Fine 88,0 76,5 89,9 97,1
22 9
Ti Al V_Fine 85,0 70,2 87,4 96,5
6 4

Successive powder layers are produced in the PBF-LB AM machine with no laser melting. Between each

layer deposition, a picture of the powder layer is taken by a camera placed inside the AM machine. The

pictures are then processed numerically to evaluate the layer homogeneity. Three powder spreading

speeds are investigated: 30, 80 and 160 mm/s to highlight their influence on the layer quality.

5.3 Layer homogeneity evaluation

The powder layer surface homogeneity is experimentally evaluated using a camera placed orthogonal

to the powder bed. After each powder spreading operation, a picture is taken. For this experiment, the

focus is made on metallic coater and 30 µm layer thickness only. For the same recoater speed, 15 layers

are created and therefore, 15 pictures are taken as well. This methodology provides a quantitative and

operator independent way to quantify the layer topography homogeneity.
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ISO/ASTM DTR 52952:2023(E)

The gathered pictures are then processed numerically to obtain "Interface Fluctuation”, a measure of

the inhomogeneity of the produced layers. The image processing analysis principle is as follow:

a) each picture is analysed separately. The picture size is 1 200 pixels × 1 200 pixels;

b) horizontal and vertical pixel intensity profiles are extracted at discrete positions of the picture [see

Figure 2 a)];
c) an average “smooth” profile is computed for each position [see Figure 2 b)];

d) interface fluctuation is then computed based on the deviation around the averaged profile, and

then averaged over all positions;

e) the process is repeated for all the images, and the interface fluctuation is average over the whole

set of pictures.
b) Pixel intensity profile (plain) and average
a) Horizontal and vertical lines from which
profile (dashed) used to compute the interface
pixel intensity profiles are extracted
fluctuation
Key
X position along the line
Y pixel intensity (before normalisation)
AlSi Mg (top)
NiCr Mo Nb_Fine (bottom)
22 9
Figure 2 — In situ layer quality assessment
5.4 Rotating drum

Powder flowability is evaluated with a rotating drum method which allows an automated measurement.

A horizontal cylinder with transparent sidewalls called drum is filled with the sample of powder.

The filling ratio of the drum can influence the flow of the powder and thus are kept constant to allow

relevant comparison of the results.

The volume of the drum used in this study is 100 mL and the filling ratio is fixed as 50 %. Therefore, a

50 mL powder sample is used for the measurements.

The drum rotates around its axis at an angular velocity ranging from 2 r/min to 60 r/min. A CCD

(charge­coupled device) camera takes snapshots at a framerate of 1 image per second for each angular

velocity.
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ISO/ASTM DTR 52952:2023(E)

The air/powder interface is detected on each snapshot with an edge detection algorithm.

Afterwards, the average interface position and the fluctuations around this average position are

comput
...