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).
1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.9 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.