. The sub-QMP is 
not affected if the machine associated with the “parent” QMP is removed from service, undergoes 
maintenance, is updated or moved, or undergoes another similar change that requires a 
requalification. If issues are discovered that uncover fundamental flaws with the “parent” QMP, 
then additional verification will be required for all associated Sub-QMPs to ensure those flaws do 
not invalidate the Sub-QMP’s qualification status.  


 Standardized Content for Builds Used for Qualification 

[AMR-49]  A set of builds that specifies the content, geometry, and layout of all evaluation 
specimens needed for qualification of the candidate material process as QMP-A, QMP-B, QMP-C, 
or associated Sub-QMP shall be standardized for use in the evaluations required by section 5.5.3 of 
this NASA Technical Standard. 

[Rationale:  The use of standardized content in the builds used for qualification of candidate 
material processes maintains the necessary consistency and traceability in the qualification and 
requalification methodology for AM processes and machines.] 

Each standard qualification build set should be designed to efficiently and consistently achieve the 
required qualification evaluations. These standard qualification builds are also used to maintain the 
active status of QMPs when requalifying machines. Witness specimen geometry should be consistent 
with specimens used for qualification and qualification maintenance to ensure data are as 
consistent as possible for evaluating equivalency.  

Although the intent is to maintain consistent, standardized specimen geometry and location in the 
qualification process, the content of the qualification builds may evolve to improve efficiency or 
improve upon the quality of the qualification process. 

For QMP-C qualification builds, it is acceptable to build the specimens alongside the part to 
streamline the qualification and build process. 

Mechanical property evaluations for the QMP have been defined to investigate common failure 
modes related to tensile strength, ductility, cyclic fatigue initiation, and fracture toughness per 
Table 13, Minimum Mechanical Property Tests for Metal QMP Builds, and Table 15, Minimum 
Mechanical Property Tests for Polymeric QMP Builds. Sub-QMPs are qualified with a reduced 
quantity of mechanical property evaluation requirements, as shown in Table 14, Minimum 
Mechanical Property Tests for Metal Sub-QMP and SPC Evaluation Builds, and Table 16, 
Minimum Mechanical Property Tests for Polymeric Sub-QMP and SPC Evaluation Builds. 

The specified specimen quantities in section 5.5.3 of this NASA Technical Standard are considered 
minimum quantities for QMP qualification. A higher quantity of specimens or other test articles may 
be needed to meet all the QMP qualification objectives. For example, the number of specimens 
needed to adequately represent process quality for a large-format L-PBF machine is likely to be 
greater than the quantities specified in the tables. 

For candidate material processes that allow for a process restart, the restart procedure is qualified 
using specimens whose build process includes a process restart for evaluation of microstructure and 
mechanical properties (see section 4.11 of this NASA Technical Standard). Allowance for this 
restart condition can impact the design of the standardized content in the qualification builds. For 
some metallic AM processes (e.g., laser blown powder systems), the number of possible process 


restart scenarios requires users to develop evaluation methodology and criteria specific to their 
process. 

 Qualification Criteria 

A candidate material process is qualified as a QMP-A, -B, -C, or an associated Sub-QMP upon 
successful completion of the evaluations prescribed in the following requirements and the outcome 
recorded as part of the QMP record, as specified in section 5.5.4 of this NASA Technical Standard. 

[AMR-50]  For AM machines with multiple energy sources, all evaluations and qualification criteria 
of section 5.5.3 of this NASA Technical Standard shall apply independently to each energy source. 
[Rationale:  Each energy source within an AM machine has potential independent failure modes for 
performance; thus, the standardized qualification content must provide for qualification of each 
energy source independently.] 
A candidate material process applies to the overall machine, inclusive of all energy sources; thus, 
the resulting QMP is assigned to the overall machine rather than to individual energy sources. The 
supporting data and evaluations substantiating the QMP are expected to be traceable to their 
associated energy source and location in the build, and to permit evaluations of equivalency.  

 Quality of the As-built Material, Metals 

[AMR-51]  For QMP-A and QMP-B, the as-built material shall be demonstrated free of detrimental 
defects for each of the following cases when evaluated in cross-section at a minimum magnification 
of 50x, with resolution sufficient to distinguish defects common to the process and a combined area 
of evaluation ≥6 cm2 (0.93 in2) when combined across all cases and evaluations listed here: 

a. Survey of consistency throughout the build area. 

b. Demonstration that the process window remains free of detrimental defects at the 
credible extremes of the process (i.e., at the limiting range, given allowed tolerances of key process 
variable parameter settings, or at the extremes of thermal history due to geometry and 
scan/deposition pattern). 

c. Restart-layer interfaces. 

d. Interfaces or overlaps in build path (e.g., striping, islands, multi-laser overlap zones), 
surface contours, cosmetic passes, including any interface associated with a unique build parameter 
set (e.g., down-facing, or low-angle surfaces). 

e. Typical geometry of the as-built deposition layer characterized for record using an 
unaltered final deposition layer for specimens representing nominal process conditions, to include 
metrics such as depth of the melt-pool and depth of melt-pool overlaps normalized by nominal layer 
thickness averaged over a minimum of measurements. (See commentary.) 


[Rationale:  The quality of the as-built microstructure produced by the machine, with no post-
processing, establishes the basis for AM part integrity. Therefore, the AM process is required to 
demonstrate refinement that precludes detrimental defects created by the AM process.]  

For this requirement, defects in the material’s as-built structure do not have to result in measurable 
impact on material performance to be considered detrimental. Such defects may be considered 
detrimental because they indicate a poorly tuned process or a lack of process control. 

For example, to meet the intent of this requirement for L-PBF, detrimental defects may include, but 
are not limited to, evidence of unmelted powder particles, lack-of-fusion defects, microcracking, 
organized porosity related to scan strategy, weld melt-pool keyhole defects, overall porosity fraction 
greater than 0.25% by volume, individual porosity greater than 100 µm (0.004 in), and epitaxial 
grain growth greater than five layer thicknesses. Randomly dispersed porosity representing less 
than 0.25% by volume in the as-built microstructure is not necessarily cause for rejection. 

For these evaluations, metallurgical cross sections are made parallel to the axis of the build (Z-axis 
as defined in ISO/ASTM 52921, Standard Terminology for Additive Manufacturing—Coordinate 
Systems and Test Methodologies). Depending on the AM process, additional sample directions may 
be warranted. Interface evaluations in bulk material may also benefit from evaluations in a plane 
parallel to the build platform (normal to Z). 

Evaluation and characterization of the top-layer melt-pool geometry provides a clear, quantitative 
record and strong indication of how robustly a process is operating. These characteristics are 
recorded but are not required to have accept/reject criteria, although such criteria are 
recommended. Characterizations such as melt-pool depth and overlap depth relative to layer 
thickness provide insight into the potential for defects, as well as provide a baseline for the process 
condition for comparison during requalification. See further discussion and figures for typical L-
PBF top-layer melt-pool characterization in section 4.2.3.2 and Appendix A of MSFC-STD-3717, 
Specification for Control and Qualification of Laser Powder Bed Fusion Metallurgical Processes. 


 Quality of the As-built Material, Polymer 

[AMR-52]  For QMP-B, the as-built material shall be demonstrated free of detrimental defects for 
each of the following cases when evaluated in cross section at a minimum magnification of 50x, 
with resolution sufficient to distinguish defects common to the process and a total area of evaluation 
≥6 cm2 (0.93 in2) when combined across all cases listed here: 

 Survey of consistency throughout the build area. 

 Demonstration that the process window remains free of detrimental defects at the 
credible extremes of the process (i.e., at the extremes of the parameter settings, considering 
tolerance, or at the extremes of thermal history due to geometry and scan pattern). 

 Restart layer interfaces. 

d. Interfaces or overlaps in build path (striping, islands, multi-processed zones), surface 
contours, and cosmetic passes, including any interface associated with a unique build parameter set 
(e.g., down-facing surfaces for relevant overhang angles). 

e. Typical geometry of the as-built deposition layer characterized for record using an 
unaltered final deposition layer for specimens representing nominal process conditions, to include 
measures such as the depth of the melt-pool and depth of melt-pool overlaps normalized by nominal 
layer thickness, averaged over a minimum of ten measurements. 

[Rationale:  The quality of the as-built microstructure establishes the basis for AM part integrity; 
therefore, the AM process is required to demonstrate refinement that precludes detrimental defects 
in the base process.]  

For this requirement, defects in the AM as-built structure are considered detrimental not only if they 
impact material performance, but also if they result from a process that is either inconsistent or 
operating beyond the limits of an acceptable process box. 

For these evaluations, microstructure cross sections are made parallel to the axis of build (i.e., Z-
axis as defined in ISO/ASTM 52921). Depending on the AM process, additional sample directions 
may be warranted. Interface evaluations in bulk material may also benefit from evaluations in a 
plane parallel to the build platform (normal to Z). Evaluation and characterization of the top layer 
geometry provides a strong indication of how robustly a process is operating. Characterizations 
such as melt-pool depth, overlap, and penetration into preceding layers provide insight into 
polymeric microstructure characteristics. 

The morphology of polymers can vary widely depending on their composition and material process. 
These materials may exhibit a range of microstructural features, depending on their crystallinity. 
Generally, AM thermoplastics demonstrate crystalline to semi-crystalline structures (e.g., polyether 
ether ketone (PEEK) or Nylon), while AM thermosets exhibit nearly amorphous morphology (e.g., 


photosensitive acrylates and methacrylates). The crystallinity is conventionally lower than those 
evident in metals and ceramics; consequently, the optical examination of the polymer 
microstructure is critical in developing an independent understanding of the behavior of a given 
materials system. The use of fillers, for example, requires an understanding of all processing steps 
that affect their distribution, alignment, and volume fraction, especially relative to geometric 
features in first articles. 
The examination of the microstructure, in addition to studying fillers, should look at void content 
and orientation, the distribution and relative volume fractions of multi-component systems (e.g., co-
polymers, etc.), as well as inclusions from processing or reuse of feedstock materials. For a given 
materials system, 50x represents a reasonable starting point; but the precise magnification used to 
examine effects must reflect the relative microstructural features (e.g., 50x magnification may not 
resolve agglomeration or aggregation of fillers sufficiently). Other microstructural features (e.g., 
residual stress crazing from processing) may be present in the material, although care must be 
taken to ensure that any crazing or similar strain-induced features are a result of processing and 
not the cross-sectioning and polishing processes. 

 Material Microstructural Evolution 

[AMR-53]  The candidate material process shall be evaluated for objective evidence of controlled 
evolution of the material microstructure as follows: 

a. QMP-A and QMP-B:  from the as-built to the final material structure, including all 
intermediate post-processing steps that alter the material structure. 

b. Sub-QMP-A and Sub-QMP-B:  as-built and final material structure. 

c. QMP-C:  the final material structure. 

[Rationale:  The requirements levied in this NASA Technical Standard are predicated upon material 
processes that evolve the microstructure in a consistent manner from the complex, as-built state to a 
final state more closely representing familiar structure of common product forms. This requirement 
minimizes potential failure mechanisms associated with native AM microstructures (e.g., strong 
anisotropy, complex residual stress states, and fatigue and crack growth characteristics).]  

For a QMP-A or QMP-B, the microstructure is documented at each step of post-processing, starting 
with the as-built state and continuing with each intermediate stage to reveal recrystallization and/or 
evolution through to the final microstructure. Documentation of how a material evolves during each 
stage of process evolution is important for root cause and corrective action processes following a 
process escape. 

Polymeric processes that do not evolve microstructures can indicate exceptions to this requirement 
in the QMP. 


5.5.3.3.1 Material Microstructural Evolution Acceptance Criteria 

[AMR-54]  The microstructural evolution acceptance criteria shall be documented for: 

a. QMP-A and QMP-B:  the as-built and the final material structure, at minimum. 

b. Sub-QMP-A and Sub-QMP-B:  as-built and final material structure. 

c. QMP-C:  the final material structure. 

[Rationale:  Microstructural acceptance criteria defined by the QMP are used to maintain 
consistent process control by establishing uniform standards for requalification, for qualifying Sub-
QMPs, and for parts requiring microstructural evaluation for witness test acceptance.]  

The defined acceptance criteria are intended to be appropriately adapted to the material and 
sufficiently complete to ensure that reliable material process control is maintained. 

Examples of appropriate metallic microstructural acceptance criteria in the as-built state include 
interpretation of the criteria required by sections 5.5.3.1 and 5.5.3.3 of this NASA Technical 
Standard, as rendered in the alloy and by the AM machine and post-processing. For the final state 
microstructure, acceptance criteria should be applied to the results of evaluations such as average 
grain size, grain shape, grain boundary appearance, presence or lack of certain phases (e.g., 
precipitates, carbides), or other features appropriate to the alloy. 

For process consistency, Sub-QMPs use the same acceptance criteria as the “parent” QMP. 

Polymeric processes that do not evolve microstructures can indicate exceptions to this requirement 
in the QMP. 

 Surface Texture and Detail Resolution 

[AMR-55]  For QMP-A and QMP-B, as-built surface texture and detail resolution capability of the 
AM process shall be evaluated using reference part(s) from a minimum of two locations in the build 
area: 

a. Near the center of the build area. 

b. The edge of the build area or other process-sensitive location identified with reduced 
build quality. 

[Rationale:  The rendering capability of an AM process is commonly not uniform across the build 
area due to machine influences (e.g., laser incidence angle, light-curing plane, and multiple 
parameter sets for a given process). These two evaluation locations are intended to bound the 
process capability.]  


This NASA Technical Standard does not levy specific quality criteria for surface texture and detail 
resolution for the purposes of qualifying a material process. The QMP should be refined regarding 
these qualities to meet part performance goals or to satisfy material property performance goals 
(e.g., fatigue life). 

Variations of reference parts (i.e., small complex parts that push the limits of the AM process) are 
used to understand surface texture and detail resolution of an AM system. When the AM process is 
pushed to the limits of its operational capability, it will become more sensitive to perturbations in 
operational parameters. By monitoring the reference parts for variations, an AM part producer will 
have an indication of process capability limitations, as well as early indications of process change 
during production. The reference part is intended to provide quantitative criteria to judge process 
performance and repeatability in development of QMPs, AM machine qualification, and AM part 
production. When used for such purposes, reference part metrics defined by the QMP process are 
used as acceptance criteria. 

5.5.3.4.1 Surface Texture Metrics and Acceptance Criteria 

[AMR-56]  For each QMP-A and QMP-B, consistent measures of as-built surface texture and detail 
resolution with associated acceptance criteria shall be defined. 

[Rationale:  To maintain consistency in the AM process, surface texture and detail resolution for 
process requalification or the development of Sub-QMPs are evaluated with reference parts using 
the acceptance criteria of the applicable QMP. In many cases, consistency in surface texture and 
detail are critical to part performance.] 

 Mechanical Properties 

[AMR-57]  Mechanical properties shall be evaluated for all candidate material processes with, at 
minimum, the specimen quantities according to Tables 13, 14, 15, or 16, as applicable.   

[Rationale:  Mechanical property performance is a fundamental measure of the quality of the 
candidate material process and forms the basis for evaluation of material engineering equivalence 
for the applicability of material allowables and design values.] 
Per section 5.5 of this NASA Technical Standard, minimum specimen quantities apply to each 
individual energy source in the machine.  
Table 13 is applicable to evaluate QMPs in metals of Classes A, B, or C.   
Table 14 is applicable to evaluate Sub-QMPs in metals of Classes A, B, or C, and for builds used 
for SPC supporting continuous build operations for witness sampling. 
Table 15 is applicable to evaluate QMPs in polymers of Classes B or C. 
Table 16 is applicable to evaluate Sub-QMPs in polymers of Classes B or C and for builds used for 
SPC