America Makes and the American National Standards Institute (ANSI) has announced the availability of a Gaps Progress Report tracking efforts by standards developing organizations (SDOs) and others to address the gaps identified in the Standardization Roadmap for Additive Manufacturing (version 2.0, June 2018), published by the America Makes and ANSI Additive Manufacturing Standardization Collaborative (AMSC).
The AMSC is a cross-sector coordinating body established in 2016 whose objective is to accelerate the development of industry-wide additive manufacturing standards and specifications consistent with stakeholder needs. The Standardization Roadmap for Additive Manufacturing, developed with contributions from more than 300 individuals from 175 public- and private-sector organizations, lists published standards, those being developed, and others that are needed to help grow the additive manufacturing industry. It identifies 93 gaps where no published standard or specification currently exists to respond to a particular industry need. The roadmap also flags 65 of these gaps as requiring pre-standardization research and development (R&D).
The gaps progress report was compiled by ANSI staff based on inputs from SDOs, subject matter experts, alert mechanisms, and independent research. It lists newly published standards and new standards projects, alongside suggestions for future roadmap modifications. The report is not a consensus document but rather is intended to serve as an interim “living document” that will be maintained and periodically re-published until such time as the AMSC develops a next version of the standardization roadmap. The report is provided in PDF and replaces an earlier HTML gaps tracker portal that was onerous to maintain given the volume and pace of additive manufacturing standardization work.
Specific identified measurement and metrology gaps in the report are highlighted below:
Gap D18: New Dimensioning and Tolerancing Requirements. Although ASME Y14.41, Digital Product Definition Data Practices and other standards provide some capability in addressing some of the challenges in documenting AM designs, significant gaps still remain. ASME Y14.46 will address these gaps.
Recommendation: Complete work on ASME
Gap D22: In-Process Monitoring. There is a lack of standards for validated physics- and properties-based predictive models for AM that incorporate geometric accuracy, material properties, defects, surface characteristics, residual stress, microstructure properties, and other characteristics (NIST, 2013). No standardized data models or documentation have been identified for in-process monitoring and analytics. Given the current state of the technology, this is not surprising.
R&D Needed: Yes. R&D is needed to understand what in-process monitoring data is needed for verification and validation of the part. Research efforts have been undertaken that are devoted to the development of predictive computational models and simulations to understand the dynamics and complexity of heat and phase transformations. Although computational models and simulations are promising tools to understand the physics of the process, lack of quantitative representation of their prediction accuracy hinders further application in process control and optimization. Due to this reason, it is very challenging to select suitable models for the intended purpose. Therefore, it is important to study and investigate the degree of accuracy and uncertainty associated with AM models.
Recommendation: Develop standards for predictive computational modeling and simulation tools that link measured in-process monitoring data with product properties, quality, and consistency, as an important aspect of innovative structural design (NIST, 2013). See also Gap PC16 on in-process monitoring to obtain a layer-by-layer (3D) file or quality record showing the as-built part is defect-free or contains no critical flaws, or exhibits an in-family (nominal) response when interrogated during the build.
Gap D26: Design for Measurement of AM Features/Verifying the Designs of Features such as Lattices, etc. As noted in Gap D18, working groups are currently developing methods to standardize the geometric dimensioning and tolerancing (GD&T) of AM parts. As these mature, existing V&V methods of checking part conformance to GD&T specifications must be investigated for their compatibility with AM. As part of the design process for AM, the availability of methods to measure and verify AM-unique features must be considered, especially to meet critical performance requirements. This may result in adapting existing NDE methods or creating new methods. This will likely be relevant when measuring AM features such as helixes or other complex shapes, or internal features that are not compatible with common methods such as Go/NoGo gauges or coordinate measuring machines (CMM). Especially in the case of internal features, assessing the ability of ultrasonic or radiographic methods to validate high tolerances will be required.
R&D Needed: Yes, investigation of high resolution radiographic and ultrasonic methods and the maximum achievable resolution and accuracy for GD&T of complex AM designs.
Recommendation: As GD&T standards continue to develop, perform parallel investigations of validation methods to ensure V&V is possible.
Gap NDE4: Dimensional Metrology of Internal Features. The utility of existing and draft CT standards are needed for the dimensional measurement of AM internal features.
R&D Needed: Yes.
Recommendation: ASTM E07 should address the applicability of current and draft CT standards (E1570, E1695, WK61161, and WK61974) for measurement of internal features in additively manufactured parts, especially parts with complex geometry, internal features, and/or embedded features. Current CT metrology state-of-the-art needs to be tailored to evolving AM part inspection requirements. See also Gap D26, Measurement of AM Features/Verifying the designs of features such as lattices, etc.
For more information: https://www.ansi.org