ASTM F3335-20

Standard Guide for Assessing the Removal of Additive Manufacturing Residues in Medical Devices Fabricated by Powder Bed Fusion

SIGNIFICANCE AND USE
5.1 Materials used in medical devices are selected in part for their biocompatibility, meaning that they have been demonstrated to have an acceptable biological response for the intended application. During manufacturing, most devices are exposed to a variety of processing steps and materials that have the potential to adversely affect the inherent biocompatibility of the device if they are not adequately removed prior to use.  
Note 1: For a fine powder, depending upon application, a new biological risk assessment may be required.  
5.2 In additive manufacturing, components are in most cases built layer-by-layer, allowing unprecedented freedom to design complex devices. This makes it possible to build devices that are very difficult to clean, such as topological optimized parts, small internal channels, lattice structures, and especially reticulated porous structures for bone ingrowth and fixation.  
5.3 Powdered fusion AM presents additional challenges. Components come out of the build volume with residual powder filling all open spaces within the device. The majority of the excess powder is typically removed by a combination of vibratory shaking, blowing with compressed gas, vacuuming, and ultrasonic cleaning in a solvent. However, the particles are typically very small and can become lodged in internal features such as pores, making removal difficult. Furthermore, particles that were immediately adjacent to the component during manufacturing can be partially sintered to the surface. Those particles can be extremely difficult to remove, are indistinguishable from loose particles when observed by most techniques, and may be at risk of detaching during the intended use of the device.  
5.4 This guide provides specific evaluation techniques for measuring the effectiveness of residue removal processes, as they should be able to yield consistent results that meet the respective performance and cleanliness criteria for the intended use.
SCOPE
1.1 This standard provides guidance for assessing the manufacturing material residues in medical devices fabricated using additive manufacturing (AM) techniques, specifically, from powder bed fusion AM technologies.  
1.1.1 Some of the techniques discussed in this guide may be applicable to devices fabricated by other types of AM equipment (e.g., stereolithography). Given each AM technique’s characteristics and post-processing challenges, there could be additional risks or considerations associated with some AM techniques or materials that are not addressed by this guide.  
1.2 This guide covers several qualitative and quantitative assessments of the presence and amount of residue remaining in or obtained by extraction in aqueous or organic solvents from powder bed fusion AM medical components.  
1.2.1 This guide identifies techniques to qualitatively determine the presence of residue and a technique to quantitatively assess it. It does not set acceptance criteria or acceptable limits for residues remaining in built parts. These methods are not the only methods to determine the presence or quantity of residual material in additive manufactured medical components.  
1.3 This guide pertains to devices in their finished state (after post-processing and subsequent manufacturing processes), as applicable. This guide may also be used to evaluate the effectiveness of cleaning processes between critical steps in the manufacturing process, to ensure minimal AM residue remains for cleaning processes downstream.  
1.4 This guide is not intended to evaluate the residue level in medical components that have been cleaned for reuse.  
1.5 Different cleaning methods, including high energy processes, can potentially damage small structures in AM parts. This guide does not address measurement or mitigation of this risk.  
1.6 This guide does not address the manufacturing occupational health issues of working with small particles (e.g., breathing hazards).  
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General Information

• Status: Published
• Publication Date: 31-Jan-2020
• ICS: 11.020.01 - Quality and environmental management in health care
• ICS: 11.040.01 - Medical equipment in general
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.15 - Material Test Methods

Relations

• Refers: ASTM F311-08(2020) - Standard Practice for Processing Aerospace Liquid Samples for Particulate Contamination Analysis Using Membrane Filters
• Effective Date: 01-Apr-2020
• Refers: ASTM F1903-18 - Standard Practice for Testing for Cellular Responses to Particles <emph type="bdit" >in vitro</emph>
• Effective Date: 01-Oct-2018
• Refers: ASTM F2459-18 - Standard Test Method for Extracting Residue from Metallic Medical Components and Quantifying via Gravimetric Analysis
• Effective Date: 01-Feb-2018
• Refers: ASTM F2847-17 - Standard Practice for Reporting and Assessment of Residues on Single-Use Implants and Single-Use Sterile Instruments
• Effective Date: 15-Sep-2017
• Refers: ASTM F1877-16 - Standard Practice for Characterization of Particles
• Effective Date: 01-Oct-2016
• Refers: ASTM G131-96(2016) - Standard Practice for Cleaning of Materials and Components by Ultrasonic Techniques
• Effective Date: 01-May-2016
• Refers: ASTM F311-08(2013) - Standard Practice for Processing Aerospace Liquid Samples for Particulate Contamination Analysis Using Membrane Filters
• Effective Date: 01-Nov-2013
• Refers: ASTM F2459-12 - Standard Test Method for Extracting Residue from Metallic Medical Components and Quantifying via Gravimetric Analysis
• Effective Date: 01-Mar-2012
• Refers: ASTM F2847-10 - Standard Practice for Reporting and Assessment of Residues on Single Use Implants
• Effective Date: 01-Dec-2010
• Refers: ASTM F1877-05(2010) - Standard Practice for Characterization of Particles
• Effective Date: 01-Jun-2010
• Refers: ASTM F1903-10 - Standard Practice for Testing For Biological Responses to Particles <i>In Vitro</i>
• Effective Date: 01-Jun-2010
• Refers: ASTM G131-96(2008) - Standard Practice for Cleaning of Materials and Components by Ultrasonic Techniques
• Effective Date: 01-Sep-2008
• Refers: ASTM F1904-98(2008) - Standard Practice for Testing the Biological Responses to Particles <i>in vivo</i>
• Effective Date: 01-Aug-2008
• Refers: ASTM F311-08 - Standard Practice for Processing Aerospace Liquid Samples for Particulate Contamination Analysis Using Membrane Filters
• Effective Date: 01-May-2008
• Refers: ASTM F1877-05e1 - Standard Practice for Characterization of Particles
• Effective Date: 01-Nov-2005

Overview

ASTM F3335-20 is a comprehensive standard guide developed by ASTM International for assessing the removal of additive manufacturing (AM) residues in medical devices fabricated by powder bed fusion technologies. Ensuring the cleanliness of medical devices is critical, as any residual manufacturing material-particularly fine powders and particulates-can compromise device biocompatibility, patient safety, and product performance. This guide provides methodologies to evaluate the effectiveness of cleaning processes, supporting quality assurance for manufacturers and compliance with global regulatory requirements.

Key Topics

• Assessment of Residual Materials:

  • Focuses on particulate residues-especially unmelted or partially sintered powders-remaining in medical devices after powder bed fusion additive manufacturing.
  • Addresses both qualitative (visual or microscopic inspection) and quantitative (particle sizing/counting, gravimetric analysis) methods of evaluating residue presence.

• Biocompatibility and Risk Management:

  • Emphasizes the need to control and minimize contaminants that could impact the biological response of implantable devices.

• Complex Geometries:

  • Discusses challenges in cleaning and residue validation posed by intricate internal channels, lattice structures, and porous regions common in AM medical devices.

• Cleaning Process Validation:

  • Outlines the importance of robust cleaning protocols and recommends use of test pieces and standardized procedures to validate the removal of unwanted powder residues.

• Limitations and Safety:

  • Clarifies that the guide does not specify allowable residue limits, nor does it address occupational safety or cleaning for reusable medical devices.

Applications

ASTM F3335-20 is primarily applied in the medical device manufacturing sector, especially for devices produced using powder bed fusion additive manufacturing techniques such as selective laser sintering or electron beam melting. Key application areas include:

• Manufacturers of Orthopedic, Dental, and Customized Implants:

  • Critical for ensuring that complex, patient-specific devices are free from hazardous powder residues.
  • Supports validation of cleaning protocols for implants with porous surfaces intended for bone ingrowth or other tissue integrations.

• Quality Assurance and Regulatory Compliance:

  • Used by quality engineers and regulatory professionals to align manufacturing practices with global standards and best practices, as required by regulatory agencies in major markets.

• Process Developers and R&D Teams:

  • Offers a framework for the selection and validation of cleaning methods as part of process development, helping to address emerging challenges with innovative device geometries.

• Testing and Inspection Laboratories:

  • Informs the adoption of appropriate analytical techniques for routine monitoring and verification of residue removal in finished devices.

Related Standards

To ensure broad applicability and integration within the industry, ASTM F3335-20 references and complements several related standards:

• ASTM F311: Practice for Processing Aerospace Liquid Samples for Particulate Contamination Analysis Using Membrane Filters
• ASTM F2847: Practice for Reporting and Assessment of Residues on Single-Use Implants and Single-Use Sterile Instruments
• ASTM F1877: Practice for Characterization of Particles
• ASTM F2459: Test Method for Extracting Residue from Metallic Medical Components and Quantifying via Gravimetric Analysis
• ASTM F3127: Guide for Validating Cleaning Processes Used During the Manufacture of Medical Devices
• ASTM F1903 / F1904: Practices for Testing Biological Responses to Particles in vitro and in vivo
• ISO 19227:2018: Implants for surgery – Cleanliness of orthopedic implants – General requirements
• USP <788>: Particulate Matter in Injections

Conclusion

ASTM F3335-20 enables the additive manufacturing industry to ensure medical device cleanliness, support patient safety, and meet regulatory expectations. By outlining systematic approaches for residue assessment, cleaning validation, and process design, the standard helps manufacturers address unique challenges of AM technologies and produce reliable, high-quality medical devices.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F3335 − 20
Standard Guide for
Assessing the Removal of Additive Manufacturing Residues
in Medical Devices Fabricated by Powder Bed Fusion
This standard is issued under the fixed designation F3335; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.7 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
1.1 Thisstandardprovidesguidanceforassessingthemanu-
standard.
facturing material residues in medical devices fabricated using
additive manufacturing (AM) techniques, specifically, from
1.8 This standard does not purport to address all of the
powder bed fusion AM technologies.
safety concerns, if any, associated with its use. It is the
1.1.1 Some of the techniques discussed in this guide may be
responsibility of the user of this standard to establish appro-
applicable to devices fabricated by other types of AM equip-
priate safety, health, and environmental practices and deter-
ment (e.g., stereolithography). Given each AM technique’s
mine the applicability of regulatory limitations prior to use.
characteristics and post-processing challenges, there could be
1.9 This international standard was developed in accor-
additional risks or considerations associated with some AM
dance with internationally recognized principles on standard-
techniques or materials that are not addressed by this guide.
ization established in the Decision on Principles for the
1.2 This guide covers several qualitative and quantitative
Development of International Standards, Guides and Recom-
assessments of the presence and amount of residue remaining
mendations issued by the World Trade Organization Technical
in or obtained by extraction in aqueous or organic solvents
Barriers to Trade (TBT) Committee.
from powder bed fusion AM medical components.
1.2.1 This guide identifies techniques to qualitatively deter-
2. Referenced Documents
mine the presence of residue and a technique to quantitatively
assess it. It does not set acceptance criteria or acceptable limits
2.1 ASTM Standards:
for residues remaining in built parts.These methods are not the
F311 Practice for Processing Aerospace Liquid Samples for
only methods to determine the presence or quantity of residual
Particulate ContaminationAnalysis Using Membrane Fil-
material in additive manufactured medical components.
ters
F1877 Practice for Characterization of Particles
1.3 This guide pertains to devices in their finished state
F1903 Practice for Testing for Cellular Responses to Par-
(after post-processing and subsequent manufacturing
processes), as applicable. This guide may also be used to ticles in vitro
evaluate the effectiveness of cleaning processes between criti- F1904 Practice for Testing the Biological Responses to
cal steps in the manufacturing process, to ensure minimal AM
Particles in vivo
residue remains for cleaning processes downstream. F2459 Test Method for Extracting Residue from Metallic
Medical Components and Quantifying via Gravimetric
1.4 This guide is not intended to evaluate the residue level
Analysis
in medical components that have been cleaned for reuse.
F2847 Practice for Reporting and Assessment of Residues
1.5 Different cleaning methods, including high energy
on Single-Use Implants and Single-Use Sterile Instru-
processes,canpotentiallydamagesmallstructuresinAMparts.
ments
This guide does not address measurement or mitigation of this
F3127 GuideforValidatingCleaningProcessesUsedDuring
risk.
the Manufacture of Medical Devices
1.6 This guide does not address the manufacturing occupa-
G131 PracticeforCleaningofMaterialsandComponentsby
tional health issues of working with small particles (e.g.,
Ultrasonic Techniques
breathing hazards).
This test method is under the jurisdiction ofASTM Committee F04 on Medical
and Surgical Materials and Devices and is the direct responsibility of Subcommittee For referenced ASTM standards, visit the ASTM website, www.astm.org, or
F04.15 on Material Test Methods. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Current edition approved Feb. 1, 2020. Published February 2020. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
F3335-20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3335 − 20
2.2 ISO Standard: of the excess powder is typically removed by a combination of
ISO 19227:2018 Implants for surgery – Cleanliness of or- vibratory shaking, blowing with compressed gas, vacuuming,
thopedic implants – General requirements and ultrasonic cleaning in a solvent. However, the particles are
2.3 Other Reference: typicallyverysmallandcanbecomelodgedininternalfeatures
such as pores, making removal difficult. Furthermore, particles
United States Pharmacopeia General Chapter 788: Particu-
late Matter in Injections that were immediately adjacent to the component during
manufacturing can be partially sintered to the surface. Those
3. Terminology
particles can be extremely difficult to remove, are indistin-
guishable from loose particles when observed by most
3.1 Definitions:
techniques,andmaybeatriskofdetachingduringtheintended
3.1.1 additive manufacturing, n—process of joining materi-
use of the device.
alstomakepartsfrom3Dmodeldata,usuallylayeruponlayer,
as opposed to subtractive manufacturing and formative manu-
5.4 This guide provides specific evaluation techniques for
facturing methodologies.
measuring the effectiveness of residue removal processes, as
they should be able to yield consistent results that meet the
3.1.2 powder bed, n—part bed build area in an additive
respectiveperformanceandcleanlinesscriteriafortheintended
manufacturing system in which feedstock is deposited and
use.
selectively fused by means of a heat source or bonded by
means of an adhesive to build up parts.
6. Cleaning Validation Approach
3.1.3 powder-bed fusion, n—in additive manufacturing,pro-
6.1 A typical approach to a cleaning validation should be
cess by which thermal energy selectively fuses regions of a
followed. This guide only applies to the removal of residual
powder bed (commonly between 10 and 200 µm of thickness).
unmelted and unsintered powder left during AM processes.
3.1.4 non-soluble manufacturing residue, n—particulates
Other residues from subsequent manufacturing processes are
remaining in the manufactured components after manufactur-
out of the scope of this guide and are covered by Guide F3127
ing and post-processing, including starting material, blast
and ISO 19227. However, these standards still detail steps to
media, and other debris.
take for validation of cleaning processes used during the
manufacture of medical devices that can be applied to powder
4. Summary of Guide
bed fusion AM. Additionally, ISO 19227 presents key risk
4.1 This guide provides an approach for assessing the
assessments to aid in cleaning process design.
presence and quantity of residual powder bed fusion material
6.2 One approach to validating the removal of residual
remaining in fabricated parts to help ensure that post-
powderistousemodularchallengetestcomponentsthatcanbe
processing protocols yield consistent and verifiable levels of
disassembled following the cleaning procedure(s) to allow
particulate residue in medical devices.
access to locations that would otherwise be difficult to assess.
5. Significance and Use
Annex A1 provides an example challenge test piece.
5.1 Materialsusedinmedicaldevicesareselectedinpartfor
7. Powder Bed Fusion Cleanliness Considerations
their biocompatibility, meaning that they have been demon-
strated to have an acceptable biological response for the 7.1 All parts fabricated with powder bed fusion AM will
intended application. During manufacturing, most devices are
contain residual powder on every surface and in intentional
exposedtoavarietyofprocessingstepsandmaterialsthathave voidspacesinthedesign.Ifnotremoved,thepowdermayhave
the potential to adversely affect the inherent biocompatibility
the potential to come loose during implantation or other
of the device if they are not adequately removed prior to use. intended use conditions, thereby potentially affecting patient
outcomes.
NOTE 1—For a fine powder, depending upon application, a new
biological risk assessment may be required.
7.2 Furthermore, it is often difficult to distinguish residual
powder material from particulates generated by post-
5.2 In additive manufacturing, components are in most
processing and subsequent manufacturing operations. Raw
cases built layer-by-layer, allowing unprecedented freedom to
powder material is carefully controlled, often spherical, with a
design complex devices. This makes it possible to build
narrow size distribution. However, sintering, melting, and
devices that are very difficult to clean, such as topological
post-processing may change the apparent shape and size of
optimized parts, small internal channels, lattice structures, and
material particles. Therefore, all particulates should be treated
especially reticulated porous structures for bone ingrowth and
as debris and accounted for in the risk analysis during device
fixation.
design and cleaning process development.
5.3 Powdered fusion AM presents additional challenges.
7.3 Assessment of the presence of residual powder can be
Components come out of the build volume with residual
performed by various quantitative or qualitative methods. The
powder filling all open spaces within the device. The majority
appropriate assessment tool will vary with part geometry, AM
process, and post-processing steps. Assessment strategies and
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
acceptance criteria should be determined during the cleaning
4th Floor, New York, NY 10036, http://www.ansi.org.
process development, used for process validation, and per-
Available from U.S. Pharmacopeial Convention (USP), 12601 Twinbrook
Pkwy., Rockville, MD 20852-1790, http://www.usp.org. formed as part of routine monitoring.
F3335 − 20
8. Residual Powder Assessments 8.5 Micro- or Nano-Computed Tomography (micro-CT,
nano-CT)—The presence of residual powder in highly intricate
8.1 Many assessment techniques exist and are being con-
devices, either polymeric or metallic in nature, can often be
tinually developed for non- destructive evaluation of parts.
assessed with micro-CT or nano-CT.
These techniques have been selected for their particular rel-
8.5.1 The scan resolution should be adequately high to
evance to particulate residue removal in complex geometries,
permit visualization of particles in the 50th percentile of the
but are not exhaustive. Other assessments may be more
size distribution of particulates used in the manufacturing
appropriate for certain geometries or specific powder bed
process. At least three voxels should span the length of the
fusion technologies. In any case, the evaluation method shall
smallest dimension of such particles.
be validated and the limit of detection shall be documented.
8.5.2 Scan protocol and consistency can greatly affect the
8.2 Visual Inspection—Presence of residual powder within
ability to accurately replicate imaging tests between parts or
porous structures with repeating unit cells can be determined
lots. Scanning protocols and post-processing should be kept
by inspection if the unit cells align to allow full thickness light
consistent between specimens of the same design and material.
penetration.
Standard
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