Additive Manufacturing (AM) systems such as 3D printers use inexpensive microcontrollers that rar... more Additive Manufacturing (AM) systems such as 3D printers use inexpensive microcontrollers that rarely feature cybersecurity defenses. This is a risk, especially given the rising threat landscape within the larger digital manufacturing domain. In this work we demonstrate this risk by presenting the design and study of a malicious Trojan (the FLAW3D bootloader) for AVR-based Marlin-compatible 3D printers (>100 commercial models). We show that the Trojan can hide from programming tools, and even within tight design constraints (less than 1.7 kilobytes in size), it can compromise the quality of additively manufactured prints and reduce tensile strengths by up to 50%.
Additive manufacturing cyber-physical system is vulnerable to both cyber and physical attacks. St... more Additive manufacturing cyber-physical system is vulnerable to both cyber and physical attacks. Statistical methods can estimate the probability of breaching security but hackathons have revealed that skilled humans can launch very innovative attacks not anticipated before. Here, we summarize lessons learned from the past two offerings of HACK3D hackathon.
Interest in designing lightweight structures has resulted in the adoption of polymers and particu... more Interest in designing lightweight structures has resulted in the adoption of polymers and particulate composites in numerous structural applications. Weight saving is extremely beneficial both in terms of increased payload and reduced fuel consumption in transportation sector. Major challenges to the adoption of composite materials for such applications include unavailability of predictive models for high strain rate response and creep life. Dynamic mechanical analysis (DMA) is a widely used technique in polymer science for determining transition temperatures and activation energies. However, DMA results are not directly applicable to the design of structures because only frequencydomain properties are reported from those measurements. This work develops a transformation method for converting the DMA data from frequency to the time domain by appropriate integral relations from viscoelasticity theory. The material relaxation function can then be determined in order to predict the res...
Digital manufacturing (DM) cyber-physical system is vulnerable to both cyber and physical attacks... more Digital manufacturing (DM) cyber-physical system is vulnerable to both cyber and physical attacks. HACK3D is a series of crowdsourcing red-team-blue-team events hosted by the NYU Center for Cybersecurity to assess the strength of the security methods embedded in designs using DM. This study summarizes the lessons learned from the past three offerings of HACK3D, including ingenious ways in which skilled engineers can launch surprising attacks on DM designs not anticipated before. A key outcome is a taxonomy-guided creation of DM security benchmarks for use by the DM community.
This article presents and discusses the cybersecurity risks in the emerging digital manufacturing... more This article presents and discusses the cybersecurity risks in the emerging digital manufacturing (DM) context, assesses the impact on manufacturing, and identifies viable approaches to secure DM.
An ever-increasing number of industries are adopting additive manufacturing (AM), also known as 3... more An ever-increasing number of industries are adopting additive manufacturing (AM), also known as 3D printing, to their production lifecycles for manufacturing parts. A computer aided design (CAD) model is used to manufacture the part. The capability for efficient search and retrieval of the CAD models from the database has become an essential need for designers and users. However, traditional search techniques perform poorly in the context of searching CAD designs. In this paper, we propose Fourier Fingerprint Search (FFS), a retrieval framework for 3D models that deduces and leverages critical shape characteristics for search. FFS introduces a novel search methodology that incorporates these characteristics and uses two advanced matching techniques that operate at different granularities and take into account unique patterns associated with each design. In addition, FFS supports both exact and partial matching in order to provide helpful and robust search results for any scenario. We investigate a diverse set of features and enhancements for search that allows for high adaptability in all situations, such as dividing shapes into smaller parts, surface interpolation, and two different types of rotation. We evaluate FFS using the FabWave CAD dataset with approximately 3000 manufacturing models with different configurations. Our experimental results demonstrate the efficiency and high accuracy of our approach for both exact and partial matching, rendering FFS a powerful framework for CAD model search.
The layer-by-layer printing process of additive manufacturing methods provides new opportunities ... more The layer-by-layer printing process of additive manufacturing methods provides new opportunities to embed identification codes inside parts during manufacture. These embedded codes can be used for product authentication and identification of counterfeits. The availability of reverse engineering tools has increased the risk of counterfeit part production and new authentication technologies such as the one proposed in this paper are required for many applications including aerospace components and medical implants and devices. The embedded codes are read by imaging techniques such as micro-Computed Tomography (micro-CT) scanners or radiography. The work presented in this paper is focused on developing methods that can improve the quality of the recovered micro-CT scanned code images such that they can be interpreted by standard code reader technology. Inherent low contrast and the presence of imaging artifacts are the main challenges that need to be addressed. Image processing methods are developed to address these challenges using titanium and aluminum alloy specimens containing embedded quick response (QR) codes. The proposed techniques for recovering the embedded codes are based on a combination of Mathematical Morphology and an innovative de-noising algorithm based on optimal image filtering techniques. The results show that the proposed methods are successful in making the codes scannable using readily available smartphone apps.
Additive Manufacturing (AM) methods have become increasingly efficient and industrially viable in... more Additive Manufacturing (AM) methods have become increasingly efficient and industrially viable in the past ten years. These methods offer the freedom of complexity to the designers and choices of localized and pullbased production system to the managers. These propositions of AM have been enabling custom manufacturing and are catalysts for rapid growth of additive manufacturing (AM). This paper analyzes the general characteristics of AM supply chain and proposes three AM supply chain models based on the specific nature of the industry. Our description of the models emphasizes on adopting an holistic view of the AM supply chain and therefore includes raw material, printer hardware and the virtual supply chain. Throughout the product life cycle of additively manufactured products, the interlacing of the virtual supply chain (digital thread) with the physical supply chain and their operations fundamentally make the AM process a cyber-physical system (CPS). Therefore, the technology brings along with it benefits of a CPS as well as a new class of attack vectors. We discuss the possible attacks (printer, raw material and design level), risks (reverse engineering, counterfeiting and theft) and provide an enhanced risk classification scheme. We contend that the traditional cybersecurity methods need to evolve to address the new class of attack vectors that threaten the AM supply chain and also discuss the nature of existing solutions that help in addressing the risks and attack threats. In providing an holistic view of the AM supply chain the interdependencies of the processes in the AM supply chain are presented and we elucidate the effects of local attack vectors on the entire supply chain. Further, we discuss the existing security measures to mitigate the risk and identify the existing gap in AM security that needs to be bridged.
Additive manufacturing (AM) process chain relies heavily on cloud resources and software programs... more Additive manufacturing (AM) process chain relies heavily on cloud resources and software programs. Cybersecurity has become a major concern for such resources. AM produces physical components, which can be compromised for quality by many other means and can be reverse engineered for unauthorized reproduction. This work is focused on taking advantage of layer‐by‐layer manufacturing process of AM to embed codes inside the components and reading them using image acquisition methods. The example of a widely used QR code format is used, but the same scheme can be used for other formats or alphanumeric strings. The code is segmented in a large number of parts for obfuscation. The results show that segmentation and embedding the code in numerous layers help in eliminating the effect of embedded features on the mechanical properties of the part. Such embedded codes can be used for parts produced by fused filament fabrication, inkjet printing, and selective laser sintering technologies for p...
As the manufacturing time, quality, and cost associated with additive manufacturing (AM) continue... more As the manufacturing time, quality, and cost associated with additive manufacturing (AM) continue to improve, more and more businesses and consumers are adopting this technology. Some of the key benefits of AM include customizing products, localizing production and reducing logistics. Due to these and numerous other benefits, AM is enabling a globally distributed manufacturing process and supply chain spanning multiple parties, and hence raises concerns about the reliability of the manufactured product. In this work, we first present a brief overview of the potential risks that exist in the cyber-physical environment of additive manufacturing. We then evaluate the risks posed by two different classes of modifications to the AM process which are representative of the challenges that are unique to AM. The risks posed are examined through mechanical testing of objects with altered printing orientation and fine internal defects. Finite element analysis and ultrasonic inspection are also used to demonstrate the potential for decreased performance and for evading detection. The results highlight several scenarios, intentional or unintentional, that can affect the product quality and pose security challenges for the additive manufacturing supply chain. *Though the term ''3D printing'' traditionally referred only to deposition methods, we are following the popular trend to equate this term with AM.
Rapid production of high quality components is the key to cost reduction industrial applications.... more Rapid production of high quality components is the key to cost reduction industrial applications. The present work is the first attempt of manufacturing syntactic foams, hollow particle filled lightweight composites, using an industrial scale injection molding machine. High density polyethylene (HDPE) is used as the matrix material and fly ash cenospheres are used as the filler. Development of syntactic foams with cenospheres serves dual purpose of beneficial utilization of industrial waste fly ash and reduction in the cost of the component. The pressure and temperature used in injection molding process are optimized to minimize fracture of cenospheres and obtain complete mixing of cenospheres with HDPE. The optimized parameters are used for manufacturing syntactic foams with 20, 40 and 60 wt.% cenospheres. With increasing cenosphere content, density and strength reduce and modulus increases. Surface modification of constituents results in rise in strength with increasing filler content. A theoretical model based on a differential scheme is used to estimate the properties of cenospheres by conducting parametric studies because of inherent difficulties in direct measurement of cenosphere properties. The potential for using the optimized injection molding process is demonstrated by casting several industrial components.
Hollow particle filled composites known as syntactic foams presently find numerous applications i... more Hollow particle filled composites known as syntactic foams presently find numerous applications in structures exposed to high moisture and high temperature environments. Carbon nanofiber (CNF) reinforcement is attractive in these composites because of the possibility of increased strength with negligible density variation. In the present study, syntactic foams containing 15-50 vol.% glass microballoons (GMB) and 1-5 wt.% CNF reinforcement as well as CNF/epoxy composites containing 1-5 wt.% CNF were exposed to accelerated weathering by immersion in 90°C water for two weeks and characterized for their residual flexural properties. In the worst performing composites, a maximum weight gain of 3.5% and 10% was observed for CNF/epoxy and CNF/syntactic foam composites, respectively. The syntactic foams tested were observed to generally decrease in strength after weathering with the exception of the composites containing 5 wt.% CNF and 15 vol.% GMB, which were observed to increase in strength by 41-51% after
Dry sliding wear behavior of epoxy matrix syntactic foams filled with 20, 40 and 60 weight% fly a... more Dry sliding wear behavior of epoxy matrix syntactic foams filled with 20, 40 and 60 weight% fly ash cenosphere is reported based on response surface methodology. Empirical models are constructed and validated based on analysis of variance. Results show that syntactic foams have
The purpose of this study is to evaluate the dynamic mechanical properties of syntactic foam core... more The purpose of this study is to evaluate the dynamic mechanical properties of syntactic foam core sandwich structures. Aluminum matrix syntactic foams with carbon fabric skins are studied. Syntactic foams incorporate porosity in their foam-like structure by means of hollow particles. The material examined here is composed of a core made of aluminum A356 matrix filled with alumina hollow particles. Two types of sandwich composites are studied containing: (a) a single layer of carbon fabric and (b) three layers of the same fabric in 0°/90° orientation. Dynamic
Microstructural observations and flexural property datasets are provided for aluminum alloy matri... more Microstructural observations and flexural property datasets are provided for aluminum alloy matrix syntactic foam core sandwich composites. The tests are conducted in three-point bending configuration. The data supplied includes methods used for conducting microscopy and mechanical testing. Raw load-displacement data, which is used to plot stress-strain graphs, obtained during the flexural test is also included. Images from a DSLR camera are stitched together to form a detailed failure sequencing video. Failure of specimens is captured in sequential images using a digital camera. These images are stitched together to develop a video for visualization of failure mechanisms. Calculations are also included for a theoretical model that is used to estimate the flexural properties of the syntactic foam core sandwich.
The present work aims at characterizing a metal matrix syntactic foam core sandwich composite und... more The present work aims at characterizing a metal matrix syntactic foam core sandwich composite under three-point bending conditions. The sandwich comprises alumina hollow particle reinforced A356 alloy syntactic foam with carbon fabric skins. Crack initiation in the tensile side of the specimen causing failure of skin, followed by rapid failure of core in the direction applied load, is observed as the failure mechanism. Crack propagation through the alumina particles is observed in the failed specimens instead of interfacial failure. The average maximum strength, flexural strain and stiffness were measured as 91.2 ± 5.6 MPa, 0.49 ± 0.06 % and 20.6 ± 0.7 GPa respectively. The collapse load is theoretically predicted using mechanics of sandwich beams. Experimental values show good agreement with theoretical predictions.
Additive Manufacturing (AM) systems such as 3D printers use inexpensive microcontrollers that rar... more Additive Manufacturing (AM) systems such as 3D printers use inexpensive microcontrollers that rarely feature cybersecurity defenses. This is a risk, especially given the rising threat landscape within the larger digital manufacturing domain. In this work we demonstrate this risk by presenting the design and study of a malicious Trojan (the FLAW3D bootloader) for AVR-based Marlin-compatible 3D printers (>100 commercial models). We show that the Trojan can hide from programming tools, and even within tight design constraints (less than 1.7 kilobytes in size), it can compromise the quality of additively manufactured prints and reduce tensile strengths by up to 50%.
Additive manufacturing cyber-physical system is vulnerable to both cyber and physical attacks. St... more Additive manufacturing cyber-physical system is vulnerable to both cyber and physical attacks. Statistical methods can estimate the probability of breaching security but hackathons have revealed that skilled humans can launch very innovative attacks not anticipated before. Here, we summarize lessons learned from the past two offerings of HACK3D hackathon.
Interest in designing lightweight structures has resulted in the adoption of polymers and particu... more Interest in designing lightweight structures has resulted in the adoption of polymers and particulate composites in numerous structural applications. Weight saving is extremely beneficial both in terms of increased payload and reduced fuel consumption in transportation sector. Major challenges to the adoption of composite materials for such applications include unavailability of predictive models for high strain rate response and creep life. Dynamic mechanical analysis (DMA) is a widely used technique in polymer science for determining transition temperatures and activation energies. However, DMA results are not directly applicable to the design of structures because only frequencydomain properties are reported from those measurements. This work develops a transformation method for converting the DMA data from frequency to the time domain by appropriate integral relations from viscoelasticity theory. The material relaxation function can then be determined in order to predict the res...
Digital manufacturing (DM) cyber-physical system is vulnerable to both cyber and physical attacks... more Digital manufacturing (DM) cyber-physical system is vulnerable to both cyber and physical attacks. HACK3D is a series of crowdsourcing red-team-blue-team events hosted by the NYU Center for Cybersecurity to assess the strength of the security methods embedded in designs using DM. This study summarizes the lessons learned from the past three offerings of HACK3D, including ingenious ways in which skilled engineers can launch surprising attacks on DM designs not anticipated before. A key outcome is a taxonomy-guided creation of DM security benchmarks for use by the DM community.
This article presents and discusses the cybersecurity risks in the emerging digital manufacturing... more This article presents and discusses the cybersecurity risks in the emerging digital manufacturing (DM) context, assesses the impact on manufacturing, and identifies viable approaches to secure DM.
An ever-increasing number of industries are adopting additive manufacturing (AM), also known as 3... more An ever-increasing number of industries are adopting additive manufacturing (AM), also known as 3D printing, to their production lifecycles for manufacturing parts. A computer aided design (CAD) model is used to manufacture the part. The capability for efficient search and retrieval of the CAD models from the database has become an essential need for designers and users. However, traditional search techniques perform poorly in the context of searching CAD designs. In this paper, we propose Fourier Fingerprint Search (FFS), a retrieval framework for 3D models that deduces and leverages critical shape characteristics for search. FFS introduces a novel search methodology that incorporates these characteristics and uses two advanced matching techniques that operate at different granularities and take into account unique patterns associated with each design. In addition, FFS supports both exact and partial matching in order to provide helpful and robust search results for any scenario. We investigate a diverse set of features and enhancements for search that allows for high adaptability in all situations, such as dividing shapes into smaller parts, surface interpolation, and two different types of rotation. We evaluate FFS using the FabWave CAD dataset with approximately 3000 manufacturing models with different configurations. Our experimental results demonstrate the efficiency and high accuracy of our approach for both exact and partial matching, rendering FFS a powerful framework for CAD model search.
The layer-by-layer printing process of additive manufacturing methods provides new opportunities ... more The layer-by-layer printing process of additive manufacturing methods provides new opportunities to embed identification codes inside parts during manufacture. These embedded codes can be used for product authentication and identification of counterfeits. The availability of reverse engineering tools has increased the risk of counterfeit part production and new authentication technologies such as the one proposed in this paper are required for many applications including aerospace components and medical implants and devices. The embedded codes are read by imaging techniques such as micro-Computed Tomography (micro-CT) scanners or radiography. The work presented in this paper is focused on developing methods that can improve the quality of the recovered micro-CT scanned code images such that they can be interpreted by standard code reader technology. Inherent low contrast and the presence of imaging artifacts are the main challenges that need to be addressed. Image processing methods are developed to address these challenges using titanium and aluminum alloy specimens containing embedded quick response (QR) codes. The proposed techniques for recovering the embedded codes are based on a combination of Mathematical Morphology and an innovative de-noising algorithm based on optimal image filtering techniques. The results show that the proposed methods are successful in making the codes scannable using readily available smartphone apps.
Additive Manufacturing (AM) methods have become increasingly efficient and industrially viable in... more Additive Manufacturing (AM) methods have become increasingly efficient and industrially viable in the past ten years. These methods offer the freedom of complexity to the designers and choices of localized and pullbased production system to the managers. These propositions of AM have been enabling custom manufacturing and are catalysts for rapid growth of additive manufacturing (AM). This paper analyzes the general characteristics of AM supply chain and proposes three AM supply chain models based on the specific nature of the industry. Our description of the models emphasizes on adopting an holistic view of the AM supply chain and therefore includes raw material, printer hardware and the virtual supply chain. Throughout the product life cycle of additively manufactured products, the interlacing of the virtual supply chain (digital thread) with the physical supply chain and their operations fundamentally make the AM process a cyber-physical system (CPS). Therefore, the technology brings along with it benefits of a CPS as well as a new class of attack vectors. We discuss the possible attacks (printer, raw material and design level), risks (reverse engineering, counterfeiting and theft) and provide an enhanced risk classification scheme. We contend that the traditional cybersecurity methods need to evolve to address the new class of attack vectors that threaten the AM supply chain and also discuss the nature of existing solutions that help in addressing the risks and attack threats. In providing an holistic view of the AM supply chain the interdependencies of the processes in the AM supply chain are presented and we elucidate the effects of local attack vectors on the entire supply chain. Further, we discuss the existing security measures to mitigate the risk and identify the existing gap in AM security that needs to be bridged.
Additive manufacturing (AM) process chain relies heavily on cloud resources and software programs... more Additive manufacturing (AM) process chain relies heavily on cloud resources and software programs. Cybersecurity has become a major concern for such resources. AM produces physical components, which can be compromised for quality by many other means and can be reverse engineered for unauthorized reproduction. This work is focused on taking advantage of layer‐by‐layer manufacturing process of AM to embed codes inside the components and reading them using image acquisition methods. The example of a widely used QR code format is used, but the same scheme can be used for other formats or alphanumeric strings. The code is segmented in a large number of parts for obfuscation. The results show that segmentation and embedding the code in numerous layers help in eliminating the effect of embedded features on the mechanical properties of the part. Such embedded codes can be used for parts produced by fused filament fabrication, inkjet printing, and selective laser sintering technologies for p...
As the manufacturing time, quality, and cost associated with additive manufacturing (AM) continue... more As the manufacturing time, quality, and cost associated with additive manufacturing (AM) continue to improve, more and more businesses and consumers are adopting this technology. Some of the key benefits of AM include customizing products, localizing production and reducing logistics. Due to these and numerous other benefits, AM is enabling a globally distributed manufacturing process and supply chain spanning multiple parties, and hence raises concerns about the reliability of the manufactured product. In this work, we first present a brief overview of the potential risks that exist in the cyber-physical environment of additive manufacturing. We then evaluate the risks posed by two different classes of modifications to the AM process which are representative of the challenges that are unique to AM. The risks posed are examined through mechanical testing of objects with altered printing orientation and fine internal defects. Finite element analysis and ultrasonic inspection are also used to demonstrate the potential for decreased performance and for evading detection. The results highlight several scenarios, intentional or unintentional, that can affect the product quality and pose security challenges for the additive manufacturing supply chain. *Though the term ''3D printing'' traditionally referred only to deposition methods, we are following the popular trend to equate this term with AM.
Rapid production of high quality components is the key to cost reduction industrial applications.... more Rapid production of high quality components is the key to cost reduction industrial applications. The present work is the first attempt of manufacturing syntactic foams, hollow particle filled lightweight composites, using an industrial scale injection molding machine. High density polyethylene (HDPE) is used as the matrix material and fly ash cenospheres are used as the filler. Development of syntactic foams with cenospheres serves dual purpose of beneficial utilization of industrial waste fly ash and reduction in the cost of the component. The pressure and temperature used in injection molding process are optimized to minimize fracture of cenospheres and obtain complete mixing of cenospheres with HDPE. The optimized parameters are used for manufacturing syntactic foams with 20, 40 and 60 wt.% cenospheres. With increasing cenosphere content, density and strength reduce and modulus increases. Surface modification of constituents results in rise in strength with increasing filler content. A theoretical model based on a differential scheme is used to estimate the properties of cenospheres by conducting parametric studies because of inherent difficulties in direct measurement of cenosphere properties. The potential for using the optimized injection molding process is demonstrated by casting several industrial components.
Hollow particle filled composites known as syntactic foams presently find numerous applications i... more Hollow particle filled composites known as syntactic foams presently find numerous applications in structures exposed to high moisture and high temperature environments. Carbon nanofiber (CNF) reinforcement is attractive in these composites because of the possibility of increased strength with negligible density variation. In the present study, syntactic foams containing 15-50 vol.% glass microballoons (GMB) and 1-5 wt.% CNF reinforcement as well as CNF/epoxy composites containing 1-5 wt.% CNF were exposed to accelerated weathering by immersion in 90°C water for two weeks and characterized for their residual flexural properties. In the worst performing composites, a maximum weight gain of 3.5% and 10% was observed for CNF/epoxy and CNF/syntactic foam composites, respectively. The syntactic foams tested were observed to generally decrease in strength after weathering with the exception of the composites containing 5 wt.% CNF and 15 vol.% GMB, which were observed to increase in strength by 41-51% after
Dry sliding wear behavior of epoxy matrix syntactic foams filled with 20, 40 and 60 weight% fly a... more Dry sliding wear behavior of epoxy matrix syntactic foams filled with 20, 40 and 60 weight% fly ash cenosphere is reported based on response surface methodology. Empirical models are constructed and validated based on analysis of variance. Results show that syntactic foams have
The purpose of this study is to evaluate the dynamic mechanical properties of syntactic foam core... more The purpose of this study is to evaluate the dynamic mechanical properties of syntactic foam core sandwich structures. Aluminum matrix syntactic foams with carbon fabric skins are studied. Syntactic foams incorporate porosity in their foam-like structure by means of hollow particles. The material examined here is composed of a core made of aluminum A356 matrix filled with alumina hollow particles. Two types of sandwich composites are studied containing: (a) a single layer of carbon fabric and (b) three layers of the same fabric in 0°/90° orientation. Dynamic
Microstructural observations and flexural property datasets are provided for aluminum alloy matri... more Microstructural observations and flexural property datasets are provided for aluminum alloy matrix syntactic foam core sandwich composites. The tests are conducted in three-point bending configuration. The data supplied includes methods used for conducting microscopy and mechanical testing. Raw load-displacement data, which is used to plot stress-strain graphs, obtained during the flexural test is also included. Images from a DSLR camera are stitched together to form a detailed failure sequencing video. Failure of specimens is captured in sequential images using a digital camera. These images are stitched together to develop a video for visualization of failure mechanisms. Calculations are also included for a theoretical model that is used to estimate the flexural properties of the syntactic foam core sandwich.
The present work aims at characterizing a metal matrix syntactic foam core sandwich composite und... more The present work aims at characterizing a metal matrix syntactic foam core sandwich composite under three-point bending conditions. The sandwich comprises alumina hollow particle reinforced A356 alloy syntactic foam with carbon fabric skins. Crack initiation in the tensile side of the specimen causing failure of skin, followed by rapid failure of core in the direction applied load, is observed as the failure mechanism. Crack propagation through the alumina particles is observed in the failed specimens instead of interfacial failure. The average maximum strength, flexural strain and stiffness were measured as 91.2 ± 5.6 MPa, 0.49 ± 0.06 % and 20.6 ± 0.7 GPa respectively. The collapse load is theoretically predicted using mechanics of sandwich beams. Experimental values show good agreement with theoretical predictions.
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Papers by Nikhil Gupta