SIST EN ISO/ASTM 52911-2:2020

SLOVENSKI STANDARD
01-januar-2020
Dodajalna izdelava polimernih izdelkov - Konstruiranje - 2. del: Spajanje prahu na
podlagi z laserskim žarkom (ISO/ASTM 52911-2:2019)
Additive manufacturing - Design - Part 2: Laser-based powder bed fusion of polymers
(ISO/ASTM 52911-2:2019)
Additive Fertigung - Technische Konstruktionsrichtlinie für Pulverbettfusion - Teil 2:
Laserbasierte Pulverbettfusion von Polymeren (ISO/ASTM 52911-2:2019)
Fabrication additive - Conception - Partie 2: Fusion laser sur lit de poudre polymère
(ISO/ASTM 52911-2:2019)
Ta slovenski standard je istoveten z: EN ISO/ASTM 52911-2:2019
ICS:
25.030 3D-tiskanje Additive manufacturing
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO/ASTM 52911-2
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2019
EUROPÄISCHE NORM
ICS 25.030
English Version
Additive manufacturing - Design - Part 2: Laser-based
powder bed fusion of polymers (ISO/ASTM 52911-2:2019)
Fabrication additive - Conception - Partie 2: Fusion Additive Fertigung - Konstruktion - Teil 2:
laser sur lit de poudre polymère (ISO/ASTM 52911- Laserbasierte Pulverbettfusion von Polymeren
2:2019) (ISO/ASTM 52911-2:2019)
This European Standard was approved by CEN on 8 September 2019.

This European Standard was corrected and reissued by the CEN-CENELEC Management Centre on 6 November 2019.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATIO N

EUROPÄISCHES KOMITEE FÜR NORMUN G

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO/ASTM 52911-2:2019 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO/ASTM 52911-2:2019) has been prepared by Technical Committee ISO/TC 261
"Additive manufacturing" in collaboration with Technical Committee CEN/TC 438 “Additive
Manufacturing” the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2020, and conflicting national standards shall be
withdrawn at the latest by April 2020.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO/ASTM 52911-2:2019 has been approved by CEN as EN ISO/ASTM 52911-2:2019
without any modification.
INTERNATIONAL ISO/ASTM
STANDARD 52911-2
First edition
2019-09
Additive manufacturing — Design —
Part 2:
Laser-based powder bed fusion of
polymers
Fabrication additive — Conception —
Partie 2: Fusion laser sur lit de poudre polymère
Reference number
ISO/ASTM 52911-2:2019(E)
©
ISO/ASTM International 2019
ISO/ASTM 52911-2:2019(E)
© ISO/ASTM International 2019
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
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Published in Switzerland
ii © ISO/ASTM International 2019 – All rights reserved

ISO/ASTM 52911-2:2019(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
4.1 Symbols . 2
4.2 Abbreviated terms . 3
5 Characteristics of powder bed fusion (PBF) processes . 3
5.1 General . 3
5.2 Size of the parts . 3
5.3 Benefits to be considered in regard to the PBF process . 4
5.4 Limitations to be considered in regard to the PBF process . 4
5.5 Economic and time efficiency . 5
5.6 Feature constraints (islands, overhang, stair-step effect) . 5
5.6.1 General. 5
5.6.2 Islands . 5
5.6.3 Overhang . 6
5.6.4 Stair-step effect . 6
5.7 Dimensional, form and positional accuracy . 6
5.8 Data quality, resolution, representation . 6
6 Design guidelines for laser-based powder bed fusion of polymers (LB-PBF/P) .7
6.1 General . 7
6.2 Material and structural characteristics . 7
6.3 Anisotropy of the material characteristics. 8
6.4 Build orientation, positioning and arrangement . 9
6.4.1 General. 9
6.4.2 Powder coating . 9
6.4.3 Part location in the build chamber . 9
6.4.4 Oversintering . 9
6.4.5 Packing parts efficiently in the build chamber . 9
6.5 Surface roughness .10
6.6 Post-production finishing .10
6.7 Design considerations.11
6.7.1 Allowing for powder removal .11
6.7.2 Reducing warpage .11
6.7.3 Wall thickness .11
6.7.4 Gaps, cylinders and holes .11
6.7.5 Lattice structures .12
6.7.6 Fluid channels .12
6.7.7 Springs and elastic elements .13
6.7.8 Connecting elements and fasteners.13
6.7.9 Static assemblies .14
6.7.10 Movable assemblies .15
6.7.11 Bearings .15
6.7.12 Joints .15
6.7.13 Integrated markings .16
6.7.14 Cutting and joining .16
6.8 Example applications .17
6.8.1 Functional toy car with integrated spring .17
6.8.2 Robot gripper .18
7 General design consideration .19
© ISO/ASTM International 2019 – All rights reserved iii

ISO/ASTM 52911-2:2019(E)
Bibliography .20
iv © ISO/ASTM International 2019 – All rights reserved

ISO/ASTM 52911-2:2019(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/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 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.
A list of all parts in the ISO 52911 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.
© ISO/ASTM International 2019 – All rights reserved v

ISO/ASTM 52911-2:2019(E)
Introduction
Laser-based powder bed fusion of polymers (LB-PBF/P) describes an additive manufacturing (AM)
process and offers an additional manufacturing option alongside established processes. LB-PBF/P has
the potential to reduce manufacturing time and costs, and increase part functionality. Practitioners
are aware of the strengths and weaknesses of conventional, long-established manufacturing processes,
such as cutting, joining and shaping processes (e.g. by machining, welding or injection moulding) and
of giving them appropriate consideration at the design stage and when selecting the manufacturing
process. In the case of LB-PBF/P and AM in general, design and manufacturing engineers only have
a limited pool of experience. Without the limitations associated with conventional processes, the
use of LB-PBF/P offers designers and manufacturers a high degree of freedom and this requires an
understanding about the possibilities and limitations of the process.
The ISO 52911 series provides guidance for different powder bed fusion (PBF) technologies. It is
intended that the series will include ISO 52911-1 on laser-based powder bed fusion of metals (LB-
1)
PBF/M), this document on LB-PBF/P, and ISO 52911-3 on electron beam powder bed fusion of metals
(EB-PBF/M). Clauses 1 to 5, where general information including terminology and the PBF process is
provided, are similar throughout the series. The subsequent clauses focus on the specific technology.
[8]
This document is based on VDI 3405-3:2015 . It provides support to technology users, such as design
and production engineers, when designing parts that need to be manufactured by means of LB-PBF/P.
It will help practitioners to explore the benefits of LB-PBF/P and to recognize the process-related
[4]
limitations when designing parts. It also builds on ISO/ASTM 52910 to extend the requirements,
guidelines and recommendations for AM design to include the PBF process.
1) Under preparation.
vi © ISO/ASTM International 2019 – All rights reserved

INTERNATIONAL STANDARD ISO/ASTM 52911-2:2019(E)
Additive manufacturing — Design —
Part 2:
Laser-based powder bed fusion of polymers
1 Scope
This document specifies the features of laser-based powder bed fusion of polymers (LB-PBF/P) and
provides detailed design recommendations.
Some of the fundamental principles are also applicable to other additive manufacturing (AM) processes,
provided that due consideration is given to process-specific features.
This document also provides a state-of-the-art review of design guidelines associated with the use of
powder bed fusion (PBF) by bringing together relevant knowledge about this process and by extending
the scope of ISO/ASTM 52910.
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 http: //www .electropedia .org/
3.1
downskin area
D

(sub-)area where the normal vector n projection on the z-axis is negative
Note 1 to entry: See Figure 1.
3.2
downskin angle
δ
angle between the plane of the build platform and the downskin area (3.1)
Note 1 to entry: The angle lies between 0° (parallel to the build platform) and 90° (perpendicular to the build
platform).
Note 2 to entry: See Figure 1.
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ISO/ASTM 52911-2:2019(E)
3.3
upskin area
U

(sub-)area where the normal vector n projection on the z-axis is positive
Note 1 to entry: See Figure 1.
3.4
upskin angle
υ
angle between the build platform plane and the upskin area (3.3)
Note 1 to entry: The angle lies between 0° (parallel to the build platform) and 90° (perpendicular to the build
platform).
Note 2 to entry: See Figure 1.
Key
z build direction
SOURCE VDI 3405-3:2015.
Figure 1 — Upskin and downskin areas U and D, upskin and downskin angles υ and δ, normal

vector n
4 Symbols and abbreviated terms
4.1 Symbols
The symbols given in Table 1 are used in this document.
Table 1 — Symbols
Symbol Designation Unit
a overhang mm
D downskin area mm
I island mm

normal vector —
n
P part mm
2 © ISO/ASTM International 2019 – All rights reserved

ISO/ASTM 52911-2:2019(E)
Table 1 (continued)
Symbol Designation Unit
Ra mean roughness µm
Rz average surface roughness µm
U upskin area mm
δ downskin angle °
υ upskin angle °
4.2 Abbreviated terms
The following abbreviated terms are used in this document.
AM additive manufacturing
AMF additive manufacturing file format
CT computed tomography
DICOM digital imaging and communications in medicine
CAD computer aided design
EB-PBF/M electron beam powder bed fusion of metals
LB-PBF laser-based powder bed fusion
LB-PBF/M laser-based powder bed fusion of metals (also known as e.g. laser beam melting, selective
laser melting)
LB-PBF/P laser-based powder bed fusion of polymers (also known as e.g. laser beam melting,
selective laser melting)
MRI magnetic resonance imaging
PBF powder bed fusion
STL stereolithography format or surface tessellation language
3MF 3D manufacturing format
5 Characteristics of powder bed fusion (PBF) processes
5.1 General
Consideration shall be given to the specific characteristics of the manufacturing process used in order
to optimize the design of a part. Examples of the features of AM processes which need to be taken into
consideration during the design and process planning stages are listed in 5.2 to 5.8.
5.2 Size of the parts
The size of the parts is limited by the working area/working volume of the PBF-machine. Also, the
occurrence of cracks and deformation due to residual stresses limits the maximum part size. Another
important practical factor that limits the maximum part size is the cost of production having a direct
relation to the size and volume of the part. Cost of production can be minimized by choosing part
location and build orientation in a way that allows nesting of as many parts as possible. Also, the cost
of powder needed to fill the bed to the required volume (part depth × bed area) may be a consideration.
© ISO/ASTM International 2019 – All rights reserved 3

ISO/ASTM 52911-2:2019(E)
Powder reuse rules impact this cost significantly. If no reuse is allowed, then all powder is scrapped
regardless of solidified volume.
5.3 Benefits to be considered in regard to the PBF process
PBF processes can be advantageous for manufacturing parts where the following points are relevant:
— Parts can be manufactured to near-net shape (i.e. close to the finished shape and size), without
further post processing tools, in a single process step.
— Degrees of design freedom for parts are typically high. Limitations of conventional manufacturing
processes do not usually exist, e.g. for:
— tool accessibility, and
— undercuts.
— A wide range of complex geometries can be produced, such as:
[17]
— free-form geometries, e.g. organic structures ,
— topologically optimized structures,
— infill structures, e.g. honeycomb, sandwich and mesh structures.
— The degree of part complexity is largely unrelated to production costs.
— Assembly and joining processes can be reduced through single-body construction.
— Overall part characteristics can be selectively configured by adjusting process parameters locally.
— Reduction in lead times until part production.
5.4 Limitations to be considered in regard to the PBF process
Certain disadvantages typically associated with AM processes shall be taken into consideration during
product design.
— Shrinkage, residual stress and deformation can occur due to local temperature differences.
— The surface quality of AM parts is typically influenced by the layer-wise build-up technique (stair-
step effect). Post-processing can be required, depending on the application.
— Consideration shall be given to deviations from form, dimensional and positional tolerances of
parts. A machining allowance shall therefore be provided for post-production finishing. Specified
geometric tolerances can be achieved by precision post-processing.
— Anisotropic characteristics typically arise due to the layer-wise build-up and shall be taken into
account during process planning.
— Not all materials available for conventional processes are currently suitable for PBF processes.
— Material properties can differ from expected values known from other technologies like injection
moulding and casting. Material properties can be influenced significantly by process settings and
control.
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ISO/ASTM 52911-2:2019(E)
5.5 Economic and time efficiency
Provided that the geometry permits a part to be placed in the build space in such a way that it can be
manufactured as cost-effectively as possible, various different criteria for optimization are available
depending on the number of units planned.
— In the case of a one-off production, height is the factor that has the greatest impact on build costs.
Parts shall be oriented in such a way that the build height is kept to a minimum, provided that the
geometry permits such an orientation.
— If the intention is to manufacture a larger number of units, then the build space shall be used as
efficiently as possible. Provided that the part geometry permits such orientation, strategies for
reorientation and nesting shall be utilized to maximize the available build space.
— The powder that remains in the system after a build can be reused in some cases. Reuse depends
on the application, material, and specific requirements. Powder changes can be inefficient and
time consuming. Although they are necessary when changing material type, powders from same-
material builds can be reused. It is important to note, however, that recycling of powder can affect
the powder size distribution, which in turn affects final part characteristics. The number of times a
powder can be recycled is dependent on the machine manufacturer and the material.
5.6 Feature constraints (islands, overhang, stair-step effect)
5.6.1 General
Since AM parts are built up in successive layers, separation of features can occur at some stage of the
build. This depends on the part geometry. The situations in 5.6.2 to 5.6.4 shall be regarded as critical
(the level of criticality depends on the PBF technology in focus) in this respect.
5.6.2 Islands
Islands (I) are features that connect to form a part (P) only at a later stage of the build process. How
this connection will occur shall be taken into consideration at the design stage. Parts that are stable in
terms of their overall design can be unstable at some stage of the build process (see Figure 2, left and
centre).
NOTE In some circumstances, islands are not protected against mechanical damage during the powder
application process. This can lead to deformation of the islands.
SOURCE VDI 3405-3:2015.
Figure 2 — Islands I (left) and overhang a (right) during the construction of part P in z-axis
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ISO/ASTM 52911-2:2019(E)
5.6.3 Overhang
Areas with an overhang angle of 0° produce an overhang with length a (see Figure 2, right). Small
overhangs do not need any additional geometry in the form of support structures. In such cases, the
projecting area is self-supporting during manufacturing. The permissible values for a depend on the
specific PBF process, the material and the process parameters used.
5.6.4 Stair-step effect
Due to the layer-wise build-up, the 3D geometry of the part is converted into a 2,5D image before
production, with discrete steps in the build direction. The resulting error caused by deviation of this
2,5D image from the original geometry is described as the stair-step effect. The extent of this is largely
dependent on the layer thickness (see Figure 3).
SOURCE VDI 3405-3:2015.
Figure 3 — Impact of different layer thicknesses on the stair-step effect
5.7 Dimensional, form and positional accuracy
Typically, it is not possible to produce the tolerances that can be achieved with conventional tool-
based manufacturing processes. For this reason, post-processing can be necessary to meet (customer)
requirements. Post-processing may include subtractive manufacturing, surface finishing, thermal
processing, or other operations according to ISO/ASTM 52910.
In this respect, it is particularly important to be aware of and consider process parameters that
influence characteristics of the final part. For example, build orientation to some extent determines the
level of accuracy that can be achieved. Directionally dependent (anisotropic) shrinkage of the part can
occur due to the layer-wise build-up. As another example, layer-wise consistency can be affected by the
location of the part on the build platform.
5.8 Data quality, resolution, representation
The use of AM requires 3D geometric data that is typically represented as a tessellated model, but other
representations that can also be used include voxels or sliced layer representations. For tessellated
data, files describe the surface geometry of a part as a series of triangular meshes. The vertices of the
triangles are defined using the right-hand rule and the normal vector. The STL file format is recognized
6 © ISO/ASTM International 2019 – All rights reserved

ISO/ASTM 52911-2:2019(E)
as the quasi-industry data exchange format. Additional formats include AMF, which is described in
[5]
ISO/ASTM 52915 .
In a tessellation, curved surfaces are approximated with triangles, and the chosen resolution of the
tessellation determines the geometric quality of the part to be fabricated. If the resolution is too low,
the sides of the triangles defined in the STL file will be visible on the finished surface (i.e. it will appear
faceted). However, a tessellation with a resolution that is too high requires significant storage space and
is slow to transfer and handle using processing software. The resolution of a tessellation is generally
influenced by a tolerance measure, often called “chord height”, which describes the maximum deviation
of a point on the surface of the part from the triangle face. Therefore, smaller tolerance values lead
to lower deviations from the actual part surface. A typical rule of thumb is to set the tolerance to be
at least 5 times smaller than the resolution of the AM process. As a result, a chord height setting of
0,01 mm to 0,02 mm is recommended for most PBF processes. Other parameters can be used to set
mesh accuracy, depending on the system.
AMF supports the representation of information beyond just geometry. For example, part units
(millimetres, metres, inches), colours, materials and lattice structures are supported. STL files only
contain the tessellated geometry, while 3MF files have some of the metadata representation capabilities of
AMF. Having units incorporated into the data exchange file is very important in communicating part size.
If part geometry is imported from a 3D imaging modality, such as CT or MRI, then the data are
composed of voxels. The DICOM format is the standard used in the medical imaging industry and some
AM software tools read these files directly. Geometric resolution is controlled by the imager resolution.
6 Design guidelines for laser-based powder bed fusion of polymers (LB-PBF/P)
6.1 General
The design guidelines in this clause take into account the specific characteristics of LB-PBF/P. In
general, the PBF process for polymers is similar to that for metals as it includes a thermal source for
inducing fusion between the powder particles, a method for limiting powder fusion to a zonal region
per layer, as well as mechanisms to add the powder layers. Materials typically used are polyamides
(PA 11, PA 12 and their derivatives), although other materials can be processed as well. Some unfused
powders can be recycled in subsequent builds, usually by mixing the recycled powder with virgin
powder. In addition, materials can be filled or mixed with other materials, such as glass and carbon
fibres, to improve strength and thermal, electrical and fire-retardant properties. This clause describes
the implications of
— build orientation, positioning and arrangement,
— material properties of fused polymers,
— surface characteristics of fused polymers,
— aspects of post-production finishing and
[8]
— other design considerations .
6.2 Material and structural characteristics
Different powdered thermoplastics are available for LB-PBF/P, of which semi-crystalline materials are
the most widely used. In polymer PBF, the powder bed is pre-heated and the temperature is maintained
a few degrees below the melting temperature of the polymer. The elevated powder bed temperature not
only reduces the required energy input from the laser for melting but also prevents the molten polymer
from recrystallizing during the build process. Recrystallization during the build process contributes
to part shrinkage and warpage, which can lead to a failed build. PBF polymers typically exhibit a
melt temperature that is higher than the recrystallization temperature, and the difference defines a
[8]
processing window that can be exploited by the PBF process . The typically broad softening range of
amorphous thermoplastics, on the other hand, impedes this type of process control. Areas exposed to
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ISO/ASTM 52911-2:2019(E)
the laser beam solidify rapidly. As a result, the viscous flow associated with fusion and stress relaxation
[9][10][11]
are impeded, and the parts are characterized by high porosity and low mechanical strength .
Due to their desirable characteristics for polymer PBF, the most common polymers are semi-crystalline
polyamides, including PA 12, PA 11 and their derivatives, such as glass-filled PA 12 and flame-retardant
PA 11. In special cases, amorphous, debindable, elastomeric, polymer-polymer blends and thermoset
materials can also be processed with PBF. A selection of available materials is shown in Table 2.
NOTE Material data sheets are available from material suppliers and service bureaux.
[12]
Table 2 — Overview on available materials for LB-PBF/P
Polymer powder material Application field Main properties
Semi-crystalline polymers
(Semi-)rigid polymer parts Long-term usability
e.g. PA 12
High-temperature semi-crystalline polymers
High temperature polymer parts Long-term usability
e.g. PEEK
Amorphous polymer
Investment casting and lost Accurate and partially
patterns porous
e.g. PS
Sacrificial polymers used as binder
Thermally degradable and
Metal or ceramic parts
amorphous polymers
e.g. PMMA
Filled semi-crystalline polymers
Long-term usability and can
Parts with special properties
withstand high loading
e.g. PA-GF, PA-Al, PA-Cu
Elastomeric polymers
Elastic parts Long term usability
e.g. TPU
Polymer-polymer blends Emerging applications Specialized applications
Thermo-setting polymers
Emerging applications Uses chemical binding
e.g. epoxy resin
Material properties depend on a variety of factors, including the type of polymer, particle size, degree
of powder recycling and processing conditions. In particular, the temperature distribution during the
build process has a significant effect on material properties. Temperature distribution in the build
platform is affected by the extent and uniformity of preheating, part density in the build platform, laser
energy density, and the rate of post-build cool down. For these reasons, it is difficult to make blanket
[10]
statements about the achievable material structure and properties . However, large scale studies of
polyamides have indicated that strengths comparable to injection moulded parts can be achieved with
minor variability (approximately 10 %), even for parts oriented orthogonal to the build plane, whereas
[8]
elongation at break is typically much lower than that for injection moulded parts .
6.3 Anisotropy of the material characteristics
LB-PBF/P parts generally have considerable anisotropy between orientations. Typical ranges for
the mechanical characteristic values of PA 12 derived from an interlaboratory test are indicated in
[7]
VDI 3405-1 . Anisotropy within the build plane, i.e. between x- and y- directions, is very low when
[13]
alternatingly intersecting scan directions are used . In contrast, a particularly high anisotropy occurs
between the build plane and the z-axis (z-direction). Strength and elongation at break in particular
show greater differences between orientations, while the modulus of elasticity differs by no more
than 6 %. Tensile strength between orientations can vary by up to 25 %, whereas ideally the deviation
[11]
should be significantly below 25 % . In the case of elongation at break, the difference can range from
20 % to 70 % depending on the machine and the parameters. Elongation at break therefore exhibits the
strongest anisotropic behaviour, whereby a transition can occur in some cases from a ductile fracture
behaviour with yield strength within the build plane to a brittle fracture in the build direction. The
highest strength and elongation at break are achieved within the build plane, whereas the modulus
of elasticity is often higher in the build direction. The characteristic values for the remaining build
8 © ISO/ASTM International 2019 – All rights reserved

ISO/ASTM 52911-2:2019(E)
orientations lie between these extremes, whereby elongation at break and strength in particular
decrease as the angle to the horizontal increases. Furthermore, anisotropy of the part’s mechanical
properties in the margins and corners of the build space is generally more pronounced than in the
centre due to lower preheating temperatures caused by variations in the powder bed temperature. This
effect occurs in particular when alternative materials to PA 12 are used.
6.4 Build orientation, positioning and arrangement
6.4.1 General
The orientation, positioning and arrangement of parts have a significant effect on part characteristics
in LB-PBF/P. The build orientation of the part shall be agreed upon between the customer and the
part provider and shall be documented so it can be used for inspection, finishing, or rework. The build
[6]
orientation should follow the rules given in ISO/ASTM 52921 . Therefore, it shall be taken into account
that considerations from the point of view of manufacturing can differ from considerations to achieve
optimal performance of the part. The effects of build orientation on mechanical characteristics and
surface reproduction accuracy are described in later clauses. Other aspects are briefly discussed in
6.4.2 to 6.4.5.
6.4.2 Powder coating
During LB-PBF/P, contact forces can be transferred from the recoater to the parts as the layers are
deposited. In a well set-up machine, these forces can be very low, but shall nevertheless be taken into
account when orientating filigree structures.
Whenever possible, very thin vertical walls shall not be aligned parallel to the coater.
6.4.3 Part location in the build chamber
LB-PBF/P is a thermal process. The build chamber is preheated to only a few degrees Kelvin below the
melting temperature of the material. Support structures are not normally needed during LB-PBF/P on
account of this preheating. However, temperature distribution is often inhomogeneous. It is generally
colder in the corners and around the edges. Furthermore, the surrounding volume has an impact on
heat distribution. Cooler temperatures at the edges of the build chamber can lead to diminished part
accuracy and material properties. If a particularly high level of accuracy or material properties is
required for a part, it is best to position it near the centre of the build chamber. Zonal heaters and other
technologies can help compensate for temperature differences between the inside and outside regions
of the build chamber, but obviously the most external regions of the build chamber are at greater risk of
uncontrolled temperature deviations.
6.4.4 Oversintering
As the laser scans the powder bed to fuse powders into a fabricated part, it creates heat affected zones
within and around the intended part. At the edges of the scanned regions, some of the surrounding
powder can be hea
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