The more a technology develops and is established in the market, the greater the need becomes for a common understanding of technical terms and process details. Metal Additive Manufacturing has today reached a status where it is stepping towards industrialisation. The dental and aerospace industries in particular have already moved to commercial scale production and they are asking for standards for material properties, testing procedures and more besides.
Standardisation is a time consuming task undertaken by major stakeholders through participation in various standardisation committees worldwide. In the end, all parties, from AM machine and powder manufacturers to parts producers and end-users, will profit from these standards as they support reliability and confidence in the technology. This article presents an overview of the AM standards published by different organisations to-date (Fig. 1). It also offers some answers as to why standardisation is so important for AM, whilst highlighting the necessity for internationally concerted action.
The present situation
Additive Manufacturing is transforming industries across the globe and a diverse range of companies are seeing the multitude of ground-breaking opportunities that the technology offers. There are, of course, still many challenges ahead in order to make this technology a sustained success. In particular, the strong links between manufacturing process parameters and material properties require special attention compared to conventional metal shaping processes. The influence of different machine systems and production conditions, resulting in differing properties, also has to be taken into account.
Additionally, material properties are strongly related to the starting material (such as metal powder), combined with a reliable set of parameters within a process window. Knowing this, it is crucial to verify properties and create robust production processes for Additive Manufacturing. Quality management systems also require attention in terms of inspection and verification rules.
Most major companies using AM for end-use part production currently create their own internal set of materials and processing guidelines because of a lack of standards. It is therefore of extreme importance to improve process knowledge and create common technical standards. Additionally, design standards will help support the further acceptance of AM as most of the today’s CAD tools do not make use of the full potential of Additive Manufacturing.
Standards help to build a level of trust in the achievability of properties, particularly in new manufacturing processes such as metal AM. Additive Manufacturing is a global business which requires international standards. Standardisation facilitates technical and economic co-operation at national, regional and international levels. Several countries and regions have already taken action to set up standardisation activities.
Two main international institutions, ISO (International Standardisation Organisation) and ASTM International, globally prepare, develop and publish standards relating to AM (see inset box for further information). The European Committee for Standardisation (CEN) has also formed standardisation committees for AM on a regional level. Additionally there are a number of national activities related to standardisation and guidelines. These include BSI (British Standards Institution) and France’s AFNOR/UN (Union de Normalisation de la Mécanique). In Germany, the national standards body DIN (Deutsches Institut für Normung) publishes standards relating to AM in cooperation with VDMA (Verband deutscher Maschinen- und Anlagenbauer) and VDI (Verein Deutscher Ingenieure).
In 2009, ASTM International established Committee F42 on Additive Manufacturing Technologies. In the same year, national activities in Germany and UK commenced. ISO started its TC261 activities in 2011 and in July 2013 both organisations, ASTM and ISO, set-up a joint standards development plan.
The first European initiatives were started in 2012. As an example, SASAM (Support Action for standardisation of Additive Manufacturing) was a project funded by the EU under the Framework Program 7. The mission of this project was to drive the growth of AM through activities that supported the integration and coordination of standardisation simultaneously whilst addressing production issues. The result of the project, which was completed in April 2014, was a roadmap for the standardisation of AM covering the stakeholders’ requirements.
In March 2013 the STAIR-AM (STAndardisation, Innovation and Research) platform on AM within CEN-CENELEC, the European Committee for Standardisation (CEN) and the European Committee for Electrotechnical Standardisation (CENELEC), was created. This serves as a meeting point for stakeholders from the AM research, service provider and global standardisation community to discuss standardisation issues. There is a continuous dialogue with the so-called AM Platform, which is a European network working on the research agenda for Additive Manufacturing.
In July 2015 the CEN/TC 438 committee was formed. Its main objectives and priorities are to standardise the processes of AM, their process chains (including both hardware and software), test procedures, environmental issues, quality parameters, supply agreements, fundamentals and vocabularies. In order to ensure consistency and harmonisation with international standards, the priority is to publish the ISO standards as EN ISO.
Intensive work is also underway within many different working groups. It is a huge challenge to harmonise all these different approaches to achieve a common set of accepted standards globally. To-date, standards have been published covering the following areas of Additive Manufacturing:
- Terminology and data formats
Table 1 gives an overview of already published standards for Additive Manufacturing. The purpose of this article is to give a condensed overview of the main content of the already available standards and over the following pages short summaries of each standard are presented.
Terminology was the first item to be standardised due to the fact that there were so many different terms and abbreviations for AM technology, as well as about aspects of the process (Fig. 2). A more general term for the whole field of Additive Manufacturing is 3D-printing, which is mainly due to the hype surrounding low cost home printers. Additive Manufacturing implies more accurately the production of an end-use part and the more complex processes to manufacture metallic components.
This establishes and defines terms used in Additive Manufacturing technology, which applies the additive shaping principle and thereby builds physical 3D geometries by successive addition of material. The terms have been classified into specific fields of application. New terms emerging from the future work within ISO/TC 261 and ASTM F42 will be included in upcoming amendments and overviews of this international standard.
This standard includes terms, definitions of terms, descriptions of terms, nomenclature and acronyms associated with coordinate systems and testing methodologies for Additive Manufacturing technologies in an effort to standardise terminology used by AM users, producers, researchers, educators, press/media and others, particularly when reporting results from the testing of parts made on AM systems. Terms included cover definitions for machines/systems and their coordinate systems plus the location and orientation of parts. It is intended, where possible, to be compliant with ISO 841 and to clarify the specific adaptation of those principles to Additive Manufacturing.
This standard describes the process fundamentals of Additive Manufacturing. It also gives an overview of existing process categories, which are not and cannot be exhaustive due to the development of new technologies. ISO 17296-2:2015 explains how different process categories make use of different types of materials to shape a product’s geometry. It also describes which type of material is used in different process categories. Specification of feedstock material and requirements for the parts produced by combinations of different processes and feedstock material will be given in subsequent separate standards and are therefore not covered by ISO 17296-2:2015. It describes the overreaching principles of these subsequent standards.
This is aimed at users and producers of Additive Manufacturing processes. It covers the principal considerations which apply to the design, fabrication and assessment of parts produced by Additive Manufacturing and defines the scope of applications. It specifies terms and definitions and deals with the fundamentals of the processes involved. This standard contains relevant quality parameters and explains in detail component testing and the drawing up of supply agreements. It also covers safety-related and environmental aspects.
This guideline assumes that the reader has a basic understanding of the process flow of various different additive processes. It explains the processes used in practice in only as much detail as is necessary to understand the statements.
The standardisation of data formats is aimed at users and producers of Additive Manufacturing processes and associated software systems. It applies wherever additive processes are used and to the following fields in particular:
- The production of Additive Manufacturing systems and equipment including software
- Software engineers involved in CAD/CAE systems
- Reverse engineering systems developers
- Test bodies wishing to compare requested and actual geometries.
The standard ISO 17296-4:2014 covers the principal considerations which apply to data exchange for Additive Manufacturing. It specifies terms and definitions which enable information to be exchanged describing geometries or parts such that they can be additively manufactured. The data exchange method outlines file type, data enclosed formatting of such data and what this can be used for. ISO 17296-4:2014 enables a suitable format for data exchange to be specified, describes the existing developments for Additive Manufacturing of 3D geometries, outlines existing file formats used as part of the existing developments, and enables understanding of necessary features for data exchange for adopters of the international standard.
This provides the specification for the Additive Manufacturing File Format (AMF), an interchange format to address the current and future needs of Additive Manufacturing technology. The AMF may be prepared, displayed and transmitted provided the requirements of this specification are met. When prepared in a structured electronic format, strict adherence to an extensible markup language (XML) schema is required to support standards-compliant interoperability. It is recognised that there is additional information relevant to the final part that is not covered by the current version of this international standard. ISO/ASTM 52915:2016 does not specify any explicit mechanisms for ensuring data integrity, electronic signatures and encryptions.
Materials and their standardisation are important in achieving robust processes and reliable component properties produced using AM. Metal powders as raw materials require specialist handling and processing and the smallest deviations in powder properties can have an enormous influence on processability and component properties. Fig. 3 shows two powders behaving differently concerning flowability.
This standard covers additively manufactured titanium-6aluminum-4vanadium (Ti-6Al-4V) components using full-melt powder bed fusion such as electron beam melting and laser melting. It indicates the classifications of the components, the feedstock used to manufacture Class 1, 2 and 3 components, as well as the microstructure of the components. This specification also identifies the mechanical properties, chemical composition and minimum tensile properties of the components.
This establishes the requirements for additively manufactured titanium-6aluminum-4vanadium with extra low interstitials (Ti-6Al-4V ELI) components using full-melt powder bed fusion such as electron beam melting and laser melting. The standard covers the classification of materials, ordering information, manufacturing plan, feedstock, process, chemical composition, microstructure, mechanical properties, thermal processing, Hot Isostatic Pressing, dimensions and mass, permissible variations, retests, inspection, rejection, certification, product marking and packaging and quality program requirements.
ASTM F3055 – 14a
This covers additively manufactured UNS N07718 (2.4668 – NiCr19NbMo) components using full-melt powder bed fusion such as electron beam melting and laser melting. The components produced by these processes are used typically in applications that require mechanical properties similar to machined forgings and wrought products. Components manufactured to this specification are often, but not necessarily, post-processed via machining, grinding, electrical discharge machining (EDM), polishing and so forth to achieve desired surface finish and critical dimensions.
This specification is intended for the use of purchasers or producers, or both, of additively manufactured UNS N07718 components for defining the requirements and ensuring component properties.
ASTM F3056 – 14e1
Standard ASTM F3056 – 14e1 covers additively manufactured UNS N06625 (2.4856 – NiCr22Mo9Nb) components using full-melt powder bed fusion such as electron beam melting and laser melting. The components produced by these processes are used typically in applications that require mechanical properties similar to machined forgings and wrought products. Components manufactured to this specification are often, but not necessarily, post-processed via machining, grinding, electrical discharge machining (EDM), polishing, and so forth to achieve desired surface finish and critical dimensions.
It is intended for the use of purchasers or producers, or both, of additively manufactured UNS N06625 components for defining the requirements and ensuring component properties.
VDI 3405 Part 2.1:2015-07
This standard has been compiled on the basis of standard VDI 3405 Part 2, which is concerned with the beam melting of metallic parts as an Additive Manufacturing process and includes material data for grade 1.2709 tool steel (maraging steel).
This standard (VDI 3405 Part 2.1) contains material characteristic data for additively manufactured parts made from the aluminium alloy AlSi10Mg obtained in a round robin test. The test procedures and methods described in VDI 3405 Part 2 were used. Since all these procedures and methods correspond to recognised industry standards, it is possible to compare the characteristic values with those of conventional manufacturing processes.
Concerning testing procedures, several standards have already been published. Here it is vital to have a basis for comparing components coming from different sources of AM. Fig. 4 shows the set-up of specimen for further testing, produced by laser beam melting. The standard ISO/ASTM 52921:2013 has already been covered in the section of this report on terminology.
ASTM F2971 – 13
This describes a standard procedure for reporting results by testing or evaluation of specimens produced by Additive Manufacturing. This practice provides a common format for presenting data for AM specimens, for two purposes; to establish further data reporting requirements and to provide information for the design of material property databases.
The standard was established because, due to variables unique to each AM process and piece of equipment, it is critical to standardise descriptions used to report the preparation, processing and post processing of specimens produced for tests or evaluation. The intent of this standard is to ensure the consistent documentation of the materials and processing history associated with each specimen undergoing test or evaluation. The level of detail for the documentation will match the application.
This practice establishes minimum data element requirements for reporting of material and process data for the purpose of:
- Standardising test specimen descriptions and test reports
- Assisting designers by standardising AM materials databases
- Aiding material traceability through testing and evaluation
- Capturing property-parameter-performance relationships of AM specimens to enable predictive modelling and other computational approaches.
ASTM F3049 – 14
This standard introduces the reader to techniques for metal powder characterisation that may be useful for powder-based Additive Manufacturing processes including binder jetting, directed energy deposition and powder bed fusion. It refers the reader to other, existing standards that may be applicable for the characterisation of virgin and used metal powders processed in Additive Manufacturing systems.
The intention of this article is to provide purchasers, vendors, or producers of metal powder to be used in Additive Manufacturing processes with a reference for existing standards or variations of existing standards that may be used to characterise properties of metal powders used for Additive Manufacturing processes.
It will serve as a starting point for the future development of a suite of specific standard test methods that will address each individual property or property type that is important to the performance of metal-based Additive Manufacturing systems and the components produced by them. While the focus of this standard is on metal powder, some of the referenced methods may also be appropriate for non-metal powders.
ASTM F3122 – 14
This standard serves as a guide to existing standards or variations of existing standards that may be applicable to determine specific mechanical properties of materials made with an Additive Manufacturing process.
As noted in many of these referenced standards, there are several factors that may influence the reported properties, including material, material anisotropy, method of material preparation, porosity, method of specimen preparation, testing environment, specimen alignment and gripping, testing speed and testing temperature. These factors should be recorded, to the extent that they are known, according to Practice F2971 and the guidelines of the referenced standards.
ISO standard 17296-3:2014 covers the principal requirements applied to testing of parts manufactured by Additive Manufacturing processes. It specifies main quality characteristics of parts, specifies appropriate test procedures, and recommends the scope and content of test and supply agreements.
It is aimed at machine manufacturers, feedstock suppliers, machine users, part providers and customers to facilitate the communication on main quality characteristics. It applies wherever Additive Manufacturing processes are used.
VDI 3405 Part 2
This is designed to complement the standard VDI 3405, which describes different Additive Manufacturing processes using a variety of materials. This standard covers the testing of components manufactured from metallic materials using additive technologies.
As with conventional manufacturing processes such as casting and milling, metallic parts produced by Additive Manufacturing technologies have critical-to-quality characteristics. In particular these include density, strength, hardness, surface quality, dimensional accuracy, residual stress properties, absence of cracks and structural homogeneity, which are typically tested in additively manufactured components. The quality of additively manufactured components is essential if functional components are produced on an industrial scale. Thus, it is necessary to qualify Additive Manufacturing processes according to uniform criteria and to apply standardised in-process testing.
VDI 3405 Part 3:2015-12
Apart from those already mentioned, there is the area of design for AM where there is also some activity concerning standardisation. One standard already published is VDI 3405 Part 3:2015-12 describing design rules for part production using laser sintering and laser beam melting. At ISO there is an activity for a standard named “Guide for Design for Additive Manufacturing” which today is still only a draft.
Additive Manufacturing is a technology that enables and stimulates innovation. AM is growing fast, with enormous investments being made worldwide. Nevertheless we are just beginning to explore the many possibilities of AM technology. To exploit the full potential it is necessary to collect available knowledge and benefit from collaboration. New business models, advances in production technology and new services are constantly arising. Almost every sector of industry will be impacted in one or another way by AM. On the other hand AM is not going to replace all other manufacturing methods in the near future.
Additionally, new product designs are feasible. Product designers are defining the specific requirements of products based on specified manufacturing processes. To fulfill requirements like material properties and quality control issues it is necessary to have appropriate standards integrated in the product development process. Standards are a vital part of the evolution of technology. Several AM standards developed by different national and international organisations have been published and more are on their way.
International collaboration is definitely beneficial for everybody as nobody would benefit from competing standards. Therefore one set of standards used all over the world should be the common goal. A global roadmap for AM standards could be an orientation. To speed up this process, existing standards could for example be modified for AM. A good example of joint efforts is the collaboration between ASTM International and ISO which is formally established and has successfully published a first set of standards. A next step could be to transform ISO/ASTM standards to CEN standards.
More experts supporting ongoing efforts through ASTM, ISO or national standardisation organisations are needed.
The basic information for this article was taken from published standards. More information is available from the websites listed below.
Prof. Dr.-Ing. Frank Petzoldt,
Deputy Director, and Dipl. Ing. Claus Aumund-Kopp, Project Leader & Senior Scientist