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Fundamental Measurement Science for Additive Processes Project

Summary:

Additive manufacturing (AM) processes have great potential for making high-value, complex, individually-customized parts, but several technical barriers must be overcome to achieve widespread use of additive processes for direct part production. Measurement science is lacking to evaluate fundamental AM process characteristics, improve the performance of AM equipment, and improve the accuracy of AM parts. This project will establish new standardized test methods to overcome key barriers for metal-additive processes.

Description:

Objective:

Develop first-ever standard test methods and validated models by 2014 that allow industry to evaluate and improve the performance of AM systems to make better parts more quickly and more economically.

What is the new technical idea?

The new technical idea is to improve the performance of AM systems and facilitate innovations throughout the AM community by establishing new standardized test methods and validated models for evaluating and controlling fundamental process characteristics for metal-based AM processes.

What is the research plan?

The research plan covers four related areas: 1) implementation of the NIST metal-additive system as a research and testing platform, 2) development of standard methods to evaluate and improve AM system performance, 3) development and validation of physics-based models of AM processes to enable process control for improved product quality assurance, and 4) outreach with AM stakeholders to understand their needs and priorities and to transfer NIST results.

The existing NIST metal-additive system (EOS M270), its auxiliary equipment (including shot peen station, heat treat oven, cleaning system), and the corresponding commercial software systems for the 3D product data interface, support structure generation, and system monitoring and control will be implemented and brought online for use by project staff. A key requirement is completion of the required hazard reviews, development of safety procedures, and implementation of safety controls, including for personal protective equipment, laser system, compressed gas, powder management, part handling, build platform preparation, and system and facility maintenance. Extensive training will be required, primarily through onsite vendor training. Under the trainer’s supervision, a variety of test parts will be built to gain hands-on experience. The research and testing platform will be implemented in two phases: first with the nitrogen environment in the build chamber for building parts using the less reactive powder materials (e.g., stainless steel), then with the argon environment in the build chamber for building parts using the more reactive powder materials (e.g., titanium, aluminum). A standard guide will be developed that documents the process and recommended best practices for implementing an AM system, from receiving the equipment to its operational state.

Test methods will be developed to evaluate and improve the performance of AM equipment and to evaluate fundamental process characteristics within the build chamber. Specific system characteristics of interest include the geometric and thermal errors of the machine, the positioning accuracy of the build platform, the accuracy of the laser motion, the repeatability of the build platform set-up, and the repeatability of the powder delivery for varying the layer thickness. Key process characteristics include powder distribution, powder melting and solidification, melt pool geometry and temperatures, laser power, and gas flow. A candidate test artifact for evaluating AM systems will be developed with customers and stakeholders and proposed for standardization. The investigation of the potential for process-intermittent, in-situ measurement of AM parts based on initial use of the NIST 3D printer will be completed.

The project will conduct collaborative research with industry and academia to design and develop a physics-based model of the overall metal additive process, including key process characteristics, to enable process control for improved product quality assurance. The initial focus of the modeling will be the direct metal laser sintering (DMLS) AM process. The process model will be evaluated and improved in an iterative manner through process measurements. Ultimately, we seek to demonstrate a predictive capability to establish optimal AM process parameters for improving part quality.

Interactions with collaborators and stakeholders throughout the AM community are necessary for NIST to understand industry needs and priorities and to transfer NIST results for widespread use. NIST will organize and conduct a roadmapping workshop with industry to further define measurement science needs and priorities. Active collaborations with the Additive Manufacturing Consortium (AMC) will continue as a primary mechanism to engage manufacturing industry users and stakeholders in the planning, execution, and delivery of project results. The project will interact with representatives from other federal agencies (e.g., NASA, Army, Navy, Air Force, NSF, FBI, DARPA) to determine their AM measurement science needs and priorities. Technical results will be published and contributed to key industry events, including the Society of Manufacturing Engineers (SME) RAPID Conference and the Solid Freeform Fabrication (SFF) Symposium hosted by the University of Texas at Austin.

Major Accomplishments:

Recent Results:

1. Output: Completed the installation, safety assessment, and development of safety procedures to bring the NIST metal-based AM system online as a research and testing platform for experimental work using stainless steel powder material.

2. Output: Completed the operator training for use of the NIST metal-based AM system and built several test parts based on an experimental plan to evaluate the system capabilities.

3. Output: Published NISTIR 7858 that documents a review of the state-of-the-art of test artifacts for evaluating AM systems.

4. Output: Designed a candidate test artifact to be considered for standardization and tested the artifact by building it in multiple AM systems.

5. Outcome: Developed AM standards through ASTM F42 on Additive Manufacturing Technologies, with contributions to AM terminology standards and the F2924-12 standard for manufacturing of titanium components using powder bed fusion processes.

6. Outcome: Proposed a future vision, strategic approach, and candidate organizational structure to the ASTM F42 Executive Committee for development of AM standards, resulting in NIST membership in the Executive Committee and leadership in ongoing strategic planning.

7. Outcome: Initiated collaborative research with industry and academia partners on AM process modeling.

8. Output: Defined the process parameter space and boundary conditions for modeling the direct metal laser sintering (DMLS) of stainless steel powder based on experiments with the NIST EOS M270 system.

9. Outcome: Served as member of the organizing committee for the National Additive Manufacturing Symposium held on August 20, 2012.

10. Output: Published a conference paper on the candidate design of a standard test artifact for evaluating AM processes and presented this design at the 2012 Solid Freeform Fabrication Symposium.

11. Output: Established baseline designs for the proposed vision system, thermal measurement system, and ultrasonic porosity sensor for in-situ measurements.

12. Output: Completed initial preparations and announced the NIST Roadmapping Workshop on Measurements and Standards for Additive Manufacturing to be held at NIST on December 4-5, 2012.

13. Output: Contributed to development of the DoD Roadmap for Metal-Based Additive Manufacturing through participation in the Joint Defense Manufacturing Technology Panel (JDMTP) workshop on June 28-29.

14. Output: Conducted baseline laboratory tests of the vision system, thermal measurement system, and ultrasonic porosity sensor for in-situ measurements.

15. Output: Demonstrated a preliminary physics-based model of the fundamental material transformation within the direct metal laser sintering (DMLS) AM process for parts fabricated with stainless steel powder.

In addition, the following activities will be completed by the end of FY2012:

1. Outcome: Proposal submitted to ASTM F42 for the content of a Standard Guide that defines best practices for implementing a metal-based AM system.

2. Output: Publication on lessons learned and best practices for implementing a metal-based AM system.

Standards and Codes:

Project staff are members of the ASTM F42 committee on Additive Manufacturing Technologies, and provide technical contributions to standards developed by the F42 subcommittees. The ASTM F42 subcommittees include: 

  • F42.01, Test Methods – focused on test specimen design, test parameters, test reporting, etc.

  • F42.04, Design – focused on file formats and data interfaces, design process guidelines, etc.

  • F42.05, Processes and Materials – focused on metrics for initial conditioning of machines, machine performance metrics, comparison standards, material traceability, material qualification, etc.

  • F42.91, Terminology – focused on definition of terms for the AM industry

NIST technical results are submitted to the respective ASTM F42 subcommittee to improve existing draft standards or as proposals for new standards. In addition, NIST experience with existing manufacturing standards accelerates progress in development of new AM standards. For example, NIST project results will impact new ASTM standard test methods to evaluate fundamental AM process characteristics, standard test methods to evaluate AM system performance, standard AM test artifacts, as well as other ASTM F42 standards.

In addition, NIST is a member of the ASTM F42 Executive Committee (F42.90) that establishes guidance and direction for F42 subcommittees. NIST serves a leadership role in the ongoing strategic planning for AM standards within the F42 Executive Committee.

Project staff also interact with the corresponding ISO TC261 standards committee on Additive Manufacturing through membership in the U.S. Technical Advisory Group (TAG). The U.S. TAG for ISO TC261 is a special subcommittee within ASTM F42 (F42.95). The ISO TC261 and ASTM F42 committees have established liaison and collaboration to ensure consistent standards.

A NIST researcher measures the geometry of metal test parts to support the development of standards for additive manufacturing processes.
A NIST researcher measures the geometry of metal test parts to support the development of standards for additive manufacturing processes.

Start Date:

October 1, 2011

Lead Organizational Unit:

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Contact

General Information:

Shawn Moylan
301 975 4352 Telephone

100 Bureau Drive, M/S 8230
Gaithersburg, MD 20899-8230