FprCEN ISO/ASTM TR 52952

Additive Manufacturing of metals - Feedstock materials - Correlating of rotating drum measurement with powder spreadability in PBF-LB machines (ISO/ASTM DTR 52952:2023)

Granular materials and fine powders are widely used in industrial applications. To control and optimize processing methods, these materials have to be precisely characterized. The characterization methods are related either to the properties of the grains (granulometry, morphology, chemical composition, ...) and to the behaviour of the bulk powder (flowability, density, blend stability, electrostatic properties, ...). The complex behaviours of granular and powder material has motivated the development of additional techniques to obtain reproducible and interpretable results. Many industries are concerned in different fields: additive manufacturing, food processing, pharmaceuticals, bulk material handling. The present technical report is focused on additive manufacturing. Metallic powders are widely used in Additive Manufacturing (AM) processes involving powder bed likepowder bed fusion (LBM, EBM, ...) or binder jetting. During such operations, successive thin layers of powderare created with a ruler or with a rotating cylinder. Each layer is then partially sintered or melted with an energy beam or glue with binder to build the parts. The layer thickness defines the vertical resolution of the printer; a thin layer leads to a better resolution. In order to obtain a thin layer, the powder is as fine as possible. However, as the grain size decreases, cohesiveness typically increases and spreadability, as defined within ASTM F42 / ISO/TC 261, is likely to decrease. The quality of the parts build with AM is thus directly influenced by powder flow properties.
Visual observation of layer homogeneity is usually the only way for operators to quantify the spreadability of powders  during  recoating. However, relating the powder characteristics to its spreadability during there coating process before hand should provide a more cost-effective way to classify and select the optimal powder and recoating speed combinations.
The aim of this technical report is to present an example of how the characterization of the macroscopic properties of metallic powders can be related to their spreadability inside LBM printers. A new technique combining measurements inside a LBM printer and image processing have been developed to quantify the homogeneity of the powder bed layers during recoating. Moreover, the flowability of four metal powders has been investigated with an automated rotating drum method, whose dynamic cohesive index measurement has been shown to correlate with the spreadability of the powder during the recoating  process.Furthemore, the PSD and morphology of each powder was characterized for each batch before testing bystatic image analysis method (ISO_13322-1_2014). The general principle of the study is presented on Figure 1

Additive Fertigung von Metallen - Ausgangsmaterialien - Korrelation zwischen der Messung der rotierenden Trommel und der Pulververteilbarkeit in PBF-LB-Maschinen (ISO/ASTM DTR 52952:2023)

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 (ISO/ASTM DTR 52952:2023)

Aditivna proizvodnja kovin - Surovine - Korelacija med meritvami rotirajočega bobna in raztresljivostjo prahu v strojih za lasersko spajanje prahu v postelji (PBF-LB) (ISO/ASTM DTR 52952:2023)

General Information

• Status: Not Published
• Technical Committee: CEN/TC 438 - Additive Manufacturing
• Drafting Committee: CEN/TC 438 - Additive Manufacturing
• Current Stage: 6055 - CEN Ratification completed (DOR) - Publishing
• Start Date: 13-Jun-2023
• Due Date: 05-Aug-2023
• Completion Date: 13-Jun-2023
• Ref Project: kSIST-TP FprCEN ISO/ASTM TR 52952:2023 - Additive Manufacturing of metals - Feedstock materials - Correlating of rotating drum measurement with powder spreadability in PBF-LB machines (ISO/ASTM DTR 52952:2023)

Standards Content (Sample)

SLOVENSKI STANDARD
kSIST-TP FprCEN ISO/ASTM TR 52952:2023
01-april-2023
Aditivna proizvodnja kovin - Surovine - Korelacija med meritvami rotirajočega
bobna in raztresljivostjo prahu v strojih za PBF-LB (ISO/ASTM DTR 52952:2023)

Additive Manufacturing of metals - Feedstock materials - Correlating of rotating drum

measurement with powder spreadability in PBF-LB machines (ISO/ASTM DTR
52952:2023)
Additive Fertigung von Metallen - Ausgangsmaterialien - Korrelation zwischen der
Messung der rotierenden Trommel und der Pulververteilbarkeit in PBF-LB-Maschinen
(ISO/ASTM DTR 52952:2023)

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

(ISO/ASTM DTR 52952:2023)
Ta slovenski standard je istoveten z: FprCEN ISO/ASTM TR 52952
ICS:
25.030 3D-tiskanje Additive manufacturing
kSIST-TP FprCEN ISO/ASTM TR en,fr,de
52952:2023

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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kSIST-TP FprCEN ISO/ASTM TR 52952:2023
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kSIST-TP FprCEN ISO/ASTM TR 52952:2023
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
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kSIST-TP FprCEN ISO/ASTM TR 52952:2023
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
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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
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kSIST-TP FprCEN ISO/ASTM TR 52952:2023
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
© ISO/ASTM International 2023 – All rights reserved
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kSIST-TP FprCEN ISO/ASTM TR 52952:2023
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.
© ISO/ASTM International 2023 – All rights reserved
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kSIST-TP FprCEN ISO/ASTM TR 52952:2023
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.
© ISO/ASTM International 2023 – All rights reserved
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kSIST-TP FprCEN ISO/ASTM TR 52952:2023
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kSIST-TP FprCEN ISO/ASTM TR 52952:2023
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.
© ISO/ASTM International 2023 – All rights reserved
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kSIST-TP FprCEN ISO/ASTM TR 52952:2023
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
© ISO/ASTM International 2023 – All rights reserved
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kSIST-TP FprCEN ISO/ASTM TR 52952:2023
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.
© ISO/ASTM International 2023 – All rights reserved
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kSIST-TP FprCEN ISO/ASTM TR 52952:2023
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.
...