5.4.1.1.3 Thermoplastic Filament 

Table 11—Filament Feedstock Control 
Filament 
a Requiring filament producers and distributors to operate under a QMS conforming to 
SAE AS9100, SAE AS9120, or an equivalent approved by the CEO. 
b Specifying unambiguously the method of filament manufacture. 
c Specifying filament chemistry requirements, including acceptable methods of 
measurement and tolerance. 
d Specifying geometric constraints and length requirements, including acceptable methods 
of measurement and tolerance. 
e Specifying moisture requirements, including acceptable methods of measurement and 
tolerance. 
f Specifying permissible method of joining both ends for repair or break during filament 
processing at the production facility, if applicable. 
g Providing requirements for filament cleanliness and contamination control. 
h Providing requirements for filament winding packaging, labeling, and environmental 
controls. 
i Providing batch monitoring requirements for differential scanning calorimetry. 
j Specifying a certificate of compliance be provided for all levied requirements along with 
identifiers for each filament lot and the date and location of filament production. 


5.4.1.1.4 Photopolymeric Thermoset Resin 

Table 12—Liquid Feedstock Controls 
Liquid 
a Requiring resin producers and distributors to operate under a QMS conforming to SAE 
AS9100, SAE AS9120, or an equivalent approved by the CEO. 
b Specifying unambiguously the method of liquid manufacture. 
c Specifying liquid chemistry requirements, including acceptable methods of measurement 
and tolerance. 
d Specifying liquid viscosity, including explicit tolerance. 
e Prohibiting post-production additions to the material lot for control of chemistry 
(doping). 
f Providing requirements for liquid cleanliness and contamination control. 
g Providing requirements for liquid packaging, labeling, and environmental controls. 
h Specifying a certificate of compliance be provided for all levied requirements along with 
identifiers for each material lot and the date and location of material production. 


 Feedstock Reuse Requirements 

[AMR-39]  For a candidate QMP-A or candidate QMP-B, a feedstock reuse protocol governed by 
the following rules shall be defined and implemented: 

 Metrics are defined for tracking the progression of feedstock reuse for each unique 
machine operated per the QMP. 

 Limits on feedstock reuse are defined and implemented based on metrics. 

 The performance of AM material produced from reused feedstock up to the defined limit 
of reuse is tested and substantiated through material characterization in the MPS per the 
requirements of section 6.6 of this NASA Technical Standard. 

d. Feedstock at the defined limit of reuse cycles continues to meet all requirements of the 
original feedstock specification. 

e. For powder feedstock systems, used feedstock is sieved in accordance with the coarse 
particle limits of the particle size distribution specification and remixed and/or blended with 
additional virgin powder to eliminate particle size segregation after every cycle through the build 
process. 

f. Once a reused portion of a feedstock blend reaches the reuse limit, the feedstock blend is 
no longer used in part production under the auspices of the QMP. 

g. Feedstock blends that have reached the reuse limit may still be used in material 
characterization builds used to evaluate reuse limits on material properties. 

h. Reuse limits may be reevaluated and expanded as long as the requirements of items “c” 
and “d” of this section are met. 

i. When a reused feedstock no longer meets the virgin feedstock requirements, the addition 
of virgin feedstock or other additions to bring the feedstock back into specification is not allowed. 

[Rationale:  Feedstock can degrade through reuse due to changes in chemistry and morphology, 
each of which can affect the quality of the material process and the resulting hardware integrity. 
The acceptability of allowing feedstock reuse has been demonstrated when proper controls are 
verified and maintained.]  

Metrics for tracking feedstock reuse include machine operation hours, the number of days feedstock 
is present in the machine, the number of build operations, or likely a combination of such metrics. 
Other metrics for monitoring feedstock reuse may be proposed.  


Feedstock reuse blends exceeding the reuse limit may be used in developmental or nonproduction 
builds.  

The feedstock reuse protocol may be specified in the QMP or internal specification, or described 
more generally by the AMCP required by this NASA Technical Standard (see section 4.2). 

 Build Process 

 AM Build Process 

[AMR-40]  The AM build process shall be defined in the Candidate QMP by a comprehensive list 
of fixed, key process variables of known influence on the AM build process for any given AM 
machine. 

[Rationale:  Identifying the set of key process variables for a specific AM machine, model, and 
serial number makes the process unique to that machine. The machine configuration, parameter 
settings, and firmware and software versions are all important to the process.]  

Key process variables may include, but are not limited to, feedstock characteristics (e.g., size 
distribution, shape, chemistry, cleanliness, handling, and storage), environmental conditions in the 
AM equipment (e.g., temperature, gas flow rate, humidity, gas chemistry), process parameter 
settings (e.g., layer height, beam power, translation speed, beam spot size), tool path settings (e.g., 
hatch spacing, area fill schemes, tool path distribution across the entire build area, start/stop 
sequences), and time (e.g., dwell times, pauses between layers). 

Any factors identified with the potential to influence the AM process are intended to be included in 
the definition of the build controls. Multiple parameter sets may be defined to accommodate specific 
geometries (e.g., thin sections or overhung surfaces). Some control parameters may be defined as a 
range of allowed values to accommodate variations from preceding process steps or other 
dependencies. These parameter ranges and associated guidelines have to be documented in the 
QMP. 

Controls related to the system are typically defined by an electronic parameter file on the machine. 
This file may be developed by the AM part producer or may be supplied as a non-editable 
parameter set by the machine manufacturer. These controls are preferably defined as a set using 
this parameter file. The values of the parameters may remain undisclosed and proprietary. To 
establish the QMP using the build control parameter file, the file name and its cryptographic hash 
are referenced in the QMP record. See the discussion of the cryptographic hash and its use in 
section 4.13.1 of this NASA Technical Standard. 


 Process Restart Procedures 

[AMR-41]  If a capability to restart the AM process is intended, criteria for determining the 
suitability for process restart and the detailed procedures for restarting the AM process shall be 
defined as part of the Candidate QMP specific to the AM equipment for which the material process 
applies. 

[Rationale:  Restart of a stopped AM process represents a significant risk to part integrity. These 
risks can only be mitigated if the soundness of the restart procedure is evaluated to established 
criteria, and, if restarted, such operations are controlled by detailed, qualified procedures.] 

Examples of restart criteria include, but are not limited to, the reason for the process stop, 
maximum allowed stop time, build platform cooling limits, and the condition of the last part layer. 
The restart procedures are specific to the AM equipment for which the material process is being 
defined and exist in the form of a detailed procedure or checklist. These criteria and procedures 
may be documented directly with the QMP, or the material process may reference criteria and 
procedures established in other configuration-controlled documentation that is controlled by the 
QMS. Establishing and qualifying a process restart capability does not imply that parts built to the 
QMP will always be successfully restarted. All planned restarts are qualified in the development of 
the QPP, and all unplanned restarts are assigned nonconformance status per the QMS pending 
disposition of the part. In situ monitoring systems may inform the restart procedure. Feedback from 
in situ monitoring systems may become part of the parameters associated with restart rationale and 
guidelines. 

 Post-Processing 

[AMR-42]  All AM post-processing (e.g., thermal processing, photo processing, curing) that affects 
bulk material condition shall be defined in the Candidate QMP to manage property and 
microstructural evolution from the as-built state to the final state. 

[Rationale:  This NASA Technical Standard requires post-build thermal processes to evolve 
hardware bulk microstructure or polymerized linkages toward a uniform and orderly state to 
mitigate risks, both known and unknown, associated with material performance due to the complex 
as-built microstructure or polymerization from the AM process.] 

  Control of Thermal Post-Processing  

[AMR-43]  Control of thermal post-processing operations shall be compliant with SAE AMS2750, 
Pyrometry, or similar approved standard. 

 [Rationale:  Essential controls on the thermal process are necessary to ensure part reliability.] 


  Variations in Post-Processing 

[AMR-44]  Variations on post-processes that affect material condition (e.g., thermal or photo 
process) shall be included in the definition of the Candidate QMP and each unique variation 
qualified and documented per section 5 of this NASA Technical Standard through demonstration 
that the performance of the resulting material is equivalent to that of the baseline. 

[Rationale:  Allowing for variations in the thermal or photo-process definition of the candidate 
material process reduces the burden of developing QMPs for each variant. Allowing such variants 
is acceptable only when it can be shown that equivalent material is produced; otherwise, part 
reliability could be compromised relative to performance expectations.]  

To determine whether the variation in post-processing produces an equivalent material, an 
appropriate statistical test would be applied to demonstrate equivalence. 

An example of a thermal process variation is the addition of a second solution treatment cycle 
following welding processes prior to aging a welded assembly. In such cases, the material 
unaffected by the weld cannot be adversely affected by the second solution heat treatment. 
Variations to heat treatment that affect material properties or result in material with a different 
microstructure than the baseline are intended to be qualified separately as different AM 
metallurgical processes. 

An example of a photo process variation is the addition of a second photo treatment cycle following 
support structure removal. In such cases, the material unaffected by the removal of the support 
structure should not be adversely affected by the second photo processing treatment. Variations to 
photo treatment that affect material properties or result in material with a different polymerization 
than the baseline are intended to be qualified separately as different stereolithography (SLA) 
thermoset processes. 

  Hot Isostatic Pressing (HIP) 

[AMR-45]  MPs used for metallic Class A, B1, and B2 part production shall include HIP. 

[Rationale:  This NASA Technical Standard requires HIP for metallic Class A, B1, and B2 parts to 
mitigate risks, both known and unknown, that are associated with material performance due to the 
complex as-built microstructure and voids inherent with AM processes.] 

Depending on the alloy system being used, HIP can have a dramatic effect on the fatigue and 
fracture performance of the material. Specific exceptions to this requirement may be approved via 
the PPP:  (a) when sufficient evidence shows that HIP provides little to no performance 
improvement for that material and use case, and/or (b) when a component is too large for currently 
available HIP facilities. Omission of HIP for metallic Class A, B1, and B2 have to be documented 
as part of an integrated structural integrity rationale in a PPP to meet the requirements of section 
7.3 of this NASA Technical Standard and as part of the associated QMP.  


 Customized Material Process  

[AMR-46]  Any candidate material process using specific controls or unique witness specimen 
testing to achieve and/or demonstrate particular material performance characteristics shall be 
identified as a customized material process and include the following in the definition of the 
candidate material process: 

a. Description of the desired performance characteristics. 

b. Definition of the unique process controls used to achieve the desired material 
performance characteristics, if any. 

c. Definition of the requisite witness specimen tests and acceptance criteria used to confirm 
the desired performance characteristics of the material. 

[Rationale:  The identification and definition of customized material processes prevent the loss of 
unique process controls that may be critical to part integrity.] 

Customized material processes are those that require specific controls or unique witness specimen 
testing beyond the basic controls levied by this NASA Technical Standard to achieve a particular 
performance characteristic (e.g., cryo-fracture toughness) important to successful use in design. 
When these unique process controls and witness testing procedures are required to achieve a 
performance characteristic that is reflected in the MPS and assumed present by the structural 
design assessment, then the material process is identified as a customized material process. Once 
qualified per section 5.5 of this NASA Technical Standard, the process is considered a Customized 
QMP. 

5.5 Qualification of a Candidate Material Process 

This section defines the requirements for qualifying a candidate material process as a QMP.  There 
is an allowance for reduced qualification burden using the concept of a Sub-QMP. The builds used 
for process qualification are required to be standardized for consistency and uniformity. The 
criteria for qualification include verification of the as-built material quality, evaluation of material 
microstructure and its evolution (as applicable), evaluation of as-built surface texture and detail 
resolution, evaluation of mechanical performance, and finally, registration of the QMP to an MPS 
by verification of “engineering equivalence” of the QMP material to that of the applicable MPS. 

[AMR-47]  All candidate material processes shall be qualified as either a QMP-A, QMP-B, or 
QMP-C prior to production use, with an option to use a sub-QMP if the process commonality 
criteria of section 5.5.1 of this NASA Technical Standard are met. 


[Rationale:  The qualification process ensures the defined candidate QMP yields material of the 
intended quality and reliability. Hardware produced under the auspices of this document is to be 
produced using a QMP of equal or higher classification.] 

 Subsequent Qualified Material Process (Sub-QMP) 

[AMR-48]  A candidate material process shall share the following commonality criteria with an 
existing, approved QMP to enable the use of a Sub-QMP: 

a. Feedstock controls are identical. 

b. The AM build process definition is equivalent, meaning: 

(1) Same make of AM machine with equivalent configuration and build volume. 
(2) Same make and model of printer head hardware.  
(3) Same scheme for setting build path and assigning parameters. 
(4) Same layer thickness. 

c. Post-AM process definition is identical. 

[Rationale:  The use of a Sub-QMP provides efficiencies by leveraging existing QMPs that are 
consistent based on machine and process commonality.] 

If a candidate material process meets the commonality criteria for an existing, approved QMP, then 
that candidate material process may be qualified as a Sub-QMP. Leveraging the success of an 
existing QMP to qualify Sub-QMPs allows for reduced documentation of material evolution and 
reduced mechanical evaluation for registration to the MPS. The acceptance criteria of the “parent” 
QMP for material quality, microstructure, and reference part metrics are intended for qualifying 
candidate material processes as Sub-QMPs. 

The sub-QMP is assigned the same class (i.e., -A, -B, or -C) of the parent QMP.  

Once established, a Sub-QMP is independent of the QMP on which it was based. 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