AMSC Gaps Portal

Process Control Section


Existing process control standards do not adequately address digital format and digital system control.

R&D Needed: Yes.

Recommendation: Leverage NIST research and work with SDOs to ensure that AM process control standards include digital format and digital system control.

Priority: Medium

Organization: NIST, ISO/ASTM JG 56, SAE, IEEE-ISTO PWG

Status of Progress: Green

Update: The ISO/TC 261/ASTM F42 JG 56 standard in development addresses digital data configuration control.

There are no known industry standards addressing machine calibration and preventative maintenance for additive manufacturing. Current users may not have established best practices or their own internal standards and may assume that the OEM maintenance procedures are sufficient to start/restart production. Additionally, AM machines have many mechanical components that are similar to conventional subtractive machinery. The motion control components are trusted to provide accurate positioning and it is currently unknown how errors in these systems affect the output quality. This is important during machine qualification and could be addressed in a standard.

R&D Needed: Research is required to determine how errors in machine components affect output quality so that tolerances can be developed for machine calibration and preventative maintenance checks

Recommendation: Complete work on standards in development addressing machine calibration and preventative maintenance. In addition, OEM and end user best practices should ensure adequate and recommended calibration and maintenance intervals that have been documented with data for different processes and machines. OEMs and SDOs should develop technical reports that incorporate case studies related to machine restart after maintenance. Standards should account for motion control components that guide measurement and remediation of error in positioning systems where possible in AM machines. OEMs should also take this into account when designing AM machines.

Priority: High. There is an urgent need to develop guidelines on day-to-day machine calibration checks.

Organization: AWS D20, ASTM F42/ISO TC 261, SAE AMS-AM, NIST, OEMs, end users, experts in machine metrology

Status of Progress: Green

Update: As noted in the text.

There are no known industry standards addressing AM machine health monitoring. Machine health monitoring is a process of observing the machinery to identify changes that may indicate a fault. The use of a machine health monitoring system allows maintenance to be scheduled in a timely manner so as to prevent system failure.

R&D Needed: Yes

Recommendation: Adapt existing health monitoring (diagnostics and prognosis) standards for use in the additive manufacturing industry. Examples of such standards are the semiconductor industry “Interface A” collection of standards and ISO 13379-1:2012, Condition monitoring and diagnostics of machines - Data interpretation and diagnostics techniques - Part 1: General guidelines and ISO 13381-1:2015, Condition monitoring and diagnostics of machines - Prognostics - Part 1: General guidelines. Additional information can be found in NISTIR 8012, Standards Related to Prognostics and Health Management (PHM) for Manufacturing. * Further research/guidelines/specifications may be needed. For example, NIST may be able to identify critical indicators that need to be documented or controlled to assist end users with quality assurance. See also Gap M6, Tracking Maintenance.

* http://dx.doi.org/10.6028/NIST.IR.8012

Priority: Low

Organization: NIST, ISO, ASTM, AWS, IEEE-ISTO PWG, ASME

Status of Progress: Not Started, or Unknown

Update: ASME has a non AM-specific project concerning Advanced Monitoring, Diagnostics, and Prognostics for Manufacturing Operations.

Current users may not have considered the influence of machine control on resulting product quality and material properties beyond form and fit, including machine-to-machine variation (even between machines of the same make and model). While guidelines for machine qualification can be developed, a broader view of part-specific, process-specific, material-specific, and application-specific recommended practices is needed.

R&D Needed: Yes

Recommendation: SDOs should develop qualification standards for AM machines to pass in order to provide a level of confidence that these machines can produce parts with the required material properties. In addition, SDOs should develop guidelines or technical reports that incorporate case studies of various part types and applications across materials. Additional research may be needed in relation to machine-to-machine variation and on key parameters.

Priority: Medium

Organization: NIST, AWS, SAE AMS-AM, ASTM F42, NAVSEA, NASA MFSC

Status of Progress: Green

Update: As noted in the text.

5/8/2019, LY: SAE AMS-AM plans to open a project for a machine qualification document in Q2 2019.

As a result of the many sources of variability within and among AM parts, and because a complete understanding of the specific effects of so many build process parameters on AM part performance is not currently available in the AM industry, standards are needed to identify requirements for demonstrating that a set of build process parameters produces an acceptable part, and for ensuring that those build process parameters remain consistent from build to build.

R&D Needed: Yes. Develop and establish one verifiable key process parameter that combines both material and process parameters (such as power absorption coefficient or power ratio parameter, verifiable by melt pool geometry, as shown in the research) that is independent of material and machine brand. R&D is needed to verify the concept of power ratio as the single controlling parameter and its applicability to all materials and machine brands.

Recommendation: Develop a standard that identifies key build process parameters for AM machines, taking into account the different processes, materials, industry-specific applications, and machines involved. Complete work on AWS D20.1. See also Gap QC3 on harmonizing Q&C terminology for process parameters.

Priority: Medium

Organization: AWS D20, ASTM F42, SAE AMS-AM, OEMs, IEEE-ISTO PWG

Status of Progress: Green

Update: As noted in the text, AWS D20.1 has been drafted. ASTM F42 process and materials standards cover the parameters for PBF and Inconel 625 but not the values. SAE AMS7100 is trying to address FDM process control including setting parameters for the aerospace industry. SAE AMS7003 includes an appendix on PBF-L process characteristics but contains no values.

4/4/2019, LY: The AWS recently published a new standard on AM, AWS D20.1/D20.1M:2019 Specification for Fabrication of Metal Components using Additive Manufacturing.

There is a need for more research as well as standards or specifications that address AM machines being able to work in adverse environmental conditions.

R&D Needed: Yes.

Recommendation: Develop standards and specifications to address external environmental factors that could negatively impact component quality.

Priority: Low

Organization: OEMs, DoD for military-specific operational environments, ASTM

Status of Progress: Unknown

Update: None provided

There are many practices in the materials industry of how to recycle, re-use, and revert materials in production. They are also highly material dependent. End users need to understand best practices for how to qualify their various precursor material streams.

R&D Needed: Yes. Research should be conducted to understand the effects of mixing ratios of reused to virgin material.

Recommendation: Develop guidance as to how reused materials may be quantified and how their history should be tracked (e.g., number of re-uses, number of exposure hours [for a laser system], or some other metric). Guidelines for sieving reused powder prior to mixing must be created.

Priority: High

Organization: ASTM F42/ISO TC 261, ASTM D20, MPIF, NIST, SAE, trusted end user-group

Status of Progress: Green

Update: SAE is looking at it on the aerospace side. NIST has published one study on the subject on metals but more R&D is needed before you can build parts to be qualified.

Powders used in additive manufacturing are composed of a distribution of particle sizes. Stratification may take place during container filling, transportation, or handling before and after being received by a user of powder. Users must know what conditioning is appropriate to ensure that the powder’s particle size distribution is consistent and acceptable for the specific process. There is currently a lack of guidance in this area.

R&D Needed: Yes. Research should be conducted to understand the effect of stratification on particle size distribution of as-received powder and mixed powder prior to being put into service. The results from this work can be used to guide the re-blending of powder before being put into service.

Recommendation: Develop guidelines on how to maintain OEM characteristics in new use and re-use powder scenarios. There is documented variability in the final part properties in various AM processes; the AM community must either rule out stratification of powder precursor material or provide guidelines for mixing of lots to achieve acceptable particle size distribution.

Priority: Medium

Organization: NIST, trusted end user-group, ASTM

Status of Progress: Unknown

Update: None provided

AM materials can be sensitive to changes in environmental conditions including temperature, humidity, and ultraviolet radiation. Therefore, general guidance must be provided to ensure the environmental conditions in which the material is used and stored remain within acceptable ranges for all material types. Specific material packaging requirements are addressed in Section 2.2.1.3.9. No standards or specifications have been identified regarding this topic.

R&D Needed: Yes.

Recommendation: Develop guidance on the storage of AM materials so that AM materials are stored and used in environments with acceptable conditions. Research should be conducted to identify these ranges.

Priority: High.

Organization: ASTM F42/ISO TC 261, NIST, SAE, UL, Powder Manufacturers/Suppliers

Status of Progress: Green

Update: UL 3400, Outline of Investigation for Additive Manufacturing Facility Safety Management, is a document for the evaluation and certification of any additive manufacturing facility that uses powder as the initial form of feedstock material to print parts. It identifies the potential hazards within an AM facility, which includes environmental conditions. It does not provide specific reference to acceptable ranges for material storage within a facility. The effect of environmental conditions on AM materials can be dependent on a number of factors, which can vary by facility. UL 3400 provides guidance based on the requirements and conditions of the facility being evaluated. ASTM F42.06 is looking at environmental conditions for storage via work item ASTM WK59813, New Guide for Hazard Risk Ranking and Safety Defense. SAE AMS7003, Laser Powder Bed Fusion Process, contains requirements for feedstock powder handling and storage plans.

7/18/19 JM: ASTM WK59813 was deleted due to lack of activity.

There is a lack of industry guidance on the re-use of material that has not been processed.

R&D Needed: Yes.

Recommendation: Develop a standard for the re-use of material that was not processed but is already within the system (e.g., for inkjet it can be in the plumbing, the reservoirs, the printing heads, etc.).

Priority: Medium

Organization: ISO/ASTM

Status of Progress: Unknown

Update: None provided

There is a lack of industry guidance on the re-use of material that was already processed.

R&D Needed: Yes.

Recommendation: Develop a standard for re-use of material that was already processed and cannot be reused as precursor material. For inkjet, there are two concerns: Material that was jetted but not polymerized and material that was polymerized to some extent (waste from each processed layer or the actual support material). Example: non-polymerized material that was jetted can be reused as material to fill bulky areas of the model (by filtering, re-jetting, and polymerizing).

Priority: Low

Organization: ASTM

Status of Progress: Unknown

Update: None provided

There is no known standard for defining:

  • Method of DED process powder flow monitoring
  • Location of monitoring
  • Accuracy of flow monitoring
  • Standardized calibration process of flow

R&D Needed: Yes.

Recommendation: Develop a standard for DED process powder flow monitoring so that operators/users will have a way to ensure the powder flow is coming out consistently and with minimal fluctuations so as to not alter the desired build and its properties. See also Gap PM1 on flowability.

Priority: Medium

Organization: NIST, ISO/ASTM

Status of Progress: Unknown

Update: None provided

No published standards or standards in development have been identified for monitoring and control of all flow related parameters for material jetting.

R&D Needed: Yes.

Recommendation: Develop a standard for monitoring and controlling all flow parameters for material jetting such as flow rate, temperature, viscosity, pressure level, wetting of the orifice plate, etc. This standard should include:

  • Monitoring and controlling similar flow in different material feeding channels. This is needed to allow multi-material printing while minimizing cross talk or non-uniformity between channels keeping quality of all printed materials.
  • Controlling the thickness of the printed layer. In material jetting, the material flows to the surface and controlling the thickness of each layer is clearly critical to maintain quality. The layer thickness can be controlled by controlling the material flow within the system and within the printing heads as well as by direct measurement after deposition.
  • Expanding the performance envelope to enable more degrees of freedom for the flow of material. For example, to enable a wider range of temperatures, humidity control, oxygen level control, ink recirculation in the print heads, etc. All this can allow using more viscous materials, with larger filler particles and exotic materials that might not be compatible with the print head materials in a standard environment.

Priority: Low

Organization: NIST, OEMs, ASTM, IEEE-ISTO PWG

Status of Progress: Unknown

Update: None provided

There is a need for standards to address environmental health and safety (EHS) in the AM process. Typical hazards to be addressed include: guarding from moving parts that are not protected from contact; chemical handling (liquids, powders, wires); air emissions (dusts, vapors, fumes); noise (cleaning apparatus); electrical (water wash systems, electro-static systems); flammable/combustible cleaning materials; solid waste; laser use (sintering processes); and UV light (may require eye and skin protection based on design). See Gaps P5 and P6 in section 2.2.3.6 related to health and safety, specifically to toxic gases/vapors from polymers.

R&D Needed: Yes.

Recommendation: Recommend creating a standard addressing EHS issues relative to additive machines (power, laser, handling, air quality, etc.). Physical measurement of operator exposure to AM materials is one of the most critical needs and can be leveraged from existing industry standards. As noted in the text, research is underway.

Priority: High.

Organization: ASTM F42/ISO TC 261, UL, ASSP, B11, LIA (Z136), ISO/TC 262

Status of Progress: Green

Update: UL has published UL 3400, Outline of Investigation for Additive Manufacturing Facility Safety Management, for the evaluation and certification of any additive manufacturing facility that uses powder feedstock to print parts. ASTM WK59813, New Guide for Hazard Risk Ranking and Safety Defense, is being developed to cover risks associated with different types of AM technologies and the recommended PPE and safety measures. ISO/TC 261 has a Working Group on Environment, health and safety (ISO/TC 261/WG 6), and two Joint Groups with ASTM F42 on AM: EH&S for 3D printers (ISO/TC 261/JG 68) and EH&S for use of metallic materials (ISO/TC 261/JG 69)..

7/18/19 JM: ASTM WK59813 was deleted due to lack of activity.

Best practices for maintaining and controlling the programming environment for additive processes are needed to ensure repeatable product quality.

R&D Needed: Yes.

Recommendation: Develop best practices to protect digital files used in the AM process. See also Gap M7 on cybersecurity for maintenance.

Priority: Medium

Organization: America Makes, NIST, UL, IEEE-ISTO PWG

Status of Progress: Unknown

Update: None provided

No published standards have been identified that address 1) the conversion of in-process monitoring data into an accurate 3D file representing the part manufactured, or 2) the use of in-process monitoring data to self-monitor and self-calibrate processing equipment. More than likely, there will be no “one size fits all” standard for any given additive process, piece of equipment, or material. It would be highly dependent on end user analytics of OEM or internally developed sensing systems. A standard guide is being developed in ASTM E07 (WK62181) that covers conversion of in-process monitoring data into an accurate 3D file representing the part manufactured, based on real-time measurement of part dimensions, surface finish, density, hot spots, or defect state during the build. Ideally, the information gathered during in-process monitoring is used to evaluate part acceptance, as a go/no-go before expensive post-processing operations are performed, and/or to guide NDE performed on the part after build.

R&D Needed: Yes. Seamless incorporation of sensor-based monitoring techniques into the build without interfering with the build is nontrivial. While commercial based systems have been developed (for example, visible-spectrum layer-wise imaging; co-axial melt pool monitoring (visible or near-infrared); infrared, off-axis thermography; single-point, and off-axis pyrometry and/or photodetectors), other techniques (for example, spectroscopic measurements of plume; high speed visible-spectrum imaging (stationary view); single-point surface profilometry; and in-situ laser ultrasonic or AE monitoring) are lower TRL and warrant additional R&D.

Recommendation: Issue standards on in-process monitoring of the feedstock (supply ratios and other metrics), process conditions (atmosphere, humidity), process parameters (beam diagnostics such as location, laser power, scan width, scan rate), and the part during build (dimensions, surface finish, density, hot spots, defect state). See also Gap D22 on the use of physics-based models and simulation tools (analytics).

Priority: Medium, given the relatively low TRL state of the art

Organization: ASTM E07.10

Status of Progress: Yellow

Update: ASTM E7.10 is developing a draft guide WK62181 on in-process monitoring covering commercial based systems (visible-spectrum layer-wise imaging; co-axial melt pool monitoring (visible or near-infrared); infrared, off-axis thermography; single-point, off-axis pyrometry and/or photodetectors). Potentially, other techniques that show promise will be included (spectroscopic measurements of plume; high speed visible-spectrum imaging (stationary view); single-point surface profilometry; and in-situ laser ultrasonic or AE monitoring). The goal of WK62181 is 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. WK62181 does not address control of equipment functions such as feedstock supply, process conditions, or process parameters (no known gap), or physics-based models or simulation tools used in prognostics or diagnostics (see Gap D22).