Subtractive Manufacturing Methods Research Articles

Large-scale production of ultrathin carbon nitride-based photocatalysts for high-yield hydrogen evolution

Although two-dimensional graphitic carbon nitride (2D g-C3N4) and corresponding heterostructures have been widely synthesized for photocatalysis, it is still challenging to obtain 2D g-C3N4 at large-scale and also achieve high quantum efficiency. Here we report a subtractive manufacturing method mediated by Nb2O5 to mass-produce high quality Nb2O5/2D g-C3N4 and pure 2D g-C3N4. Nb2O5/2D g-C3N4 and 2D g-C3N4 both show efficient photocatalytic hydrogen evolution performance, in which the optimal Nb2O5/2D g-C3N4 exhibits high external quantum efficiency (50.65 % and 14.75 % at 405 nm and 420 nm). The origin of the high efficiency can be ascribed to two aspects: (i) nanostructure engineering forming 2D structure can shorten the charge migration distance; (ii) Nb2O5/2D g-C3N4 with strong electric coupling can further accelerate the charge transfer driven by the built-in electric field formed in Type II heterostructure. This work presents a case study to realize high-yield synthesis and high catalytic performance simultaneously over g-C3N4.

Analysis of the mechanical and physicochemical properties of Ti-6Al-4 V discs obtained by selective laser melting and subtractive manufacturing method.

The surface properties of titanium and its alloys are commonly modified by different techniques, including additive manufacturing (AM), to improve the osseointegration of dental implants. The aim of this study was to evaluate and compare the wettability, topography, chemistry, and structure of titanium-aluminum-vanadium (Ti-6Al-4 V) discs fabricated by selective laser melting (SLM) and subtractive manufacturing (conventional machining). Three different groups were evaluated: selective laser melting (SLM); conventional machining with H3 PO4 + NaOH surface treatment (CM + ST); and conventional machining without surface treatment (CM), including analysis of wettability and roughness, morphological and chemical analyses by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), and structural characterization analysis by computed tomography (micro-CT), and X-ray diffraction (XRD). The results showed that SLM surface had higher roughness (9.09 ± 1.94 Ra; 51.93 ± 11.59 Rz; 11.03 ± 1.95 Sa) and lower wettability (103.23° ± 13) than CM (0.06 ± 0.01 Ra; 0.42 ± 0.078 Rz; 0.07 ± 0.01 Sa) (76.95° ± 4.18) and CM + ST (0.17 ± 0.38 Ra; 0.88 ± 0.15 Rz; 0.18 ± 0.04 Sa) (18.55° ± 6.47) (p < 0.05). SEM images also proved the higher roughness of SLM surface, and CM + ST discs showed a topography resembling a sponge, characteristic of the nanometric treatment applied. EDX and XRD found no differences between the different surfaces, and micro-CT demonstrated the solid characteristic of the SLM disc. Compared with conventional machining, the SLM technique resulted in higher roughness and lower wettability. Meanwhile, the chemical properties and structure of the titanium alloy was not altered by the technique.

Design optimization of a business aircraft seat considering static and dynamic certification loading and manufacturability

A conceptual design for a lightweight business aircraft seat was developed using topology optimization in a 2-stage approach to consider both the static and dynamic certification test requirements of the Canadian Aviation Regulations (CARs) Section 525.561 and 525.562, respectively. Preliminary optimization was performed using static load requirements, and the interpretation of the optimization results was done considering key manufacturability metrics to reduce the cost of manufacturing components when using traditional subtractive manufacturing methods. A series of explicit dynamic models was run to predict the behavior of the seat during 14g and 16g certification tests and to estimate the maximum loads which the anthropomorphic test device (ATD) applies to the seat structure. Peak seatbelt loads were estimated at 9060 N and 8955 N for the left and right sides, respectively, and the asymmetry of the loads can be attributed to the 10° yaw of the aircraft required by the 16g certification test. Topology optimization was used to refine the design at the component level and further reduce weight using the loads determined in the dynamic modeling. The final conceptual design was 32% lighter when compared with the baseline structural components, and key manufacturability cost metrics were reduced by 24%.

Effect of porcelain firing and cementation on the marginal fit of implant-supported metal-ceramic restorations fabricated by additive or subtractive manufacturing methods

Statement of problemAdaptation between abutment and suprastructure plays a crucial role in the long-term success of implant-supported metal-ceramic crowns. Fabrication methods, the porcelain firing stage, and cementation techniques may affect the marginal adaptation between the crown and abutment. However, the information regarding this issue is sparse. PurposeThe purpose of this in vitro study was to compare marginal fit after the fabrication of cobalt-chromium alloy copings, porcelain firing, and cementation of metal-ceramic restorations that were fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM) milling and direct metal laser sintering techniques. Material and methodsThirty straight tissue-level titanium abutments were screwed onto implant analogs. All specimens were embedded in acrylic resin and divided into 2 groups according to CAD-CAM milling and direct metal laser sintering fabrication of the metal coping. Fifteen cobalt-chromium implant-supported metal copings were fabricated by using the CAD-CAM milling technique and 15 by using the direct metal laser sintering technique. In both groups, marginal gap measurements between the cobalt-chromium copings and abutments were obtained before (T0) and after the placement of the ceramic veneer (T1) and after cementation (T2) by using a stereomicroscope with a magnification of ×40. The data were statistically evaluated by using 2-way ANOVA and the Tukey post hoc test (α=.05). A t test was used to determine whether there were significant differences between the fabrication techniques (α=.05). ResultsA significant difference in the fabrication stages was found in the direct metal laser sintering group. The direct metal laser sintering coping group and porcelain applied direct metal laser sintering group had a statistically lower marginal gap value than the cemented direct metal laser sintering group (P=.021, P=.038). The direct metal laser sintering coping group had a lower marginal gap value than the CAD-CAM milling coping group, although the difference was not statistically significant (P=.216). ConclusionsPorcelain firing and cementation increased the marginal gap between the crown and abutment. No statistically significant differences were found between the direct metal laser sintering and CAD-CAM milling techniques in terms of marginal fit.

Information integrated glass module fabricated by integrated additive and subtractive manufacturing.

In this Letter, we report a novel integrated additive and subtractive manufacturing (IASM) method to fabricate an information integrated glass module. After a certain number of glass layers are 3D printed and sintered by direct ${{\rm CO}_2}$CO2 laser irradiation, a microchannel will be fabricated on top of the printed glass by integrated picosecond laser, for intrinsic Fabry-Perot interferometer (IFPI) optical fiber sensor embedment. Then, the glass 3D printing process continues for the realization of bonding between optical fiber and printed glass. Temperature sensing up to 1000°C was demonstrated using the fabricated information integrated module. In addition, the long-term stability of the glass module at 1000°C was conducted. Enhanced sensor structure robustness and harsh temperature sensing capability make this glass module attractive for harsh environment structural health monitoring.

Glass 3D printing of microfluidic pressure sensor interrogated by fiber-optic refractometry.

This letter reports a novel fused silica microfluidic device with pressure sensing capability that is fabricated by integrated additive and subtractive manufacturing (IASM) method. The sensor consists of a capillary and a 3D printed glass reservoir, where the reservoir volume change under pressure manifests liquid level deviation inside the capillary, thus realizing the conversion between small pressure change into large liquid level variation. Thanks to the design flexibility of this unique IASM method, the proposed microfluidic device is fabricated with liquid-in-glass thermometer configuration, where the reservoir is sealed following a novel 3D printing assisted glass bonding process. And liquid level is interrogated by a fiber-optic sensor based on multimode interference (MMI) effect. This proposed microfluidic device is attractive for chemical and biomedical sensing because it is flexible in design, and maintains good chemical and mechanical stability, and adjustable sensitivity and range.

Multiaxial fatigue of additive manufactured metals: Performance, analysis, and applications

Additive manufacturing (AM) has recently gained much interest from researchers and practitioners in a wide range of industries due to the many advantages it offers, as compared to the traditional subtractive manufacturing methods. Some of distinguishing features of AM, as compared to traditional subtractive manufacturing methods, include surface roughness, porosity and lack of fusion defects, residual stresses due to the thermal history of the part during the fabrication process, and anisotropy of the properties. Considering the fact that the state of stress at fatigue critical locations is often multiaxial and many of the distinguishing features of AM metals are directional, the subject of multiaxial fatigue presents an important study area for a better understanding of their fatigue performance. This paper presents an overview of the aforementioned issues using recent data generated with AM Ti-6Al-4V and 17–4 PH specimens made by two different laser-beam powder bed fusion (LB-PBF) machines and subjected to axial, torsion, and combined in-phase as well as out-of-phase axial-torsion loadings. The role of fabrication induced defects, surface roughness, and residual stresses, in addition to post fabrication heat treatment processes are discussed with implications on multiaxial fatigue performance. Important topics to multiaxial fatigue are considered. These include cyclic deformation, damage mechanism and cracking behavior, as well as damage quantification and representation for data correlations and life estimation under different stress states. The effects of some other important issues to multiaxial fatigue performance of AM metals at the component or structure level, such as mechanical notches and variable amplitude loading, are also briefly discussed.

Stereolithography-fabricated zirconia dental prostheses: concerns based on clinical requirements

ABSTRACT With the recent rapid development of the additive manufacturing family of technologies, the interest in application potential of stereolithography on producing ceramic dental prostheses has aroused and been widely discussed. While someone claimed the birth of ‘stereolithography-fabricated ceramic dental prostheses’, an overall evaluation based on the clinical requirements is lacking, making the optimism a kind of unrealistic. In this article, the prototypes of ceramic dental prostheses and standard specimens produced by the ceramic stereolithography approach are compared with those made by the classic subtractive manufacturing method by following the critical clinical requirements. Concerns on the upcoming challenges and future improvement towards clinical applications are presented that include productivity, delivery time, dimensional tolerance, mechanical and aesthetic properties. It is concluded that it is far too early to call ‘stereolithography-fabricated ceramic dental prostheses’ as a success as usable and competitive products for clinical applications.

A review on weldability of additive manufactured titanium alloys

The Additive manufacturing technologies familiarize many innovative and monetary gains when compared to conservative subtractive manufacturing methods in rapid prototyping (RP) and small production capacity. In other exceedingly industrialized fields including aerospace, automobile, and bio-medical industries, additive manufacturing has turned out to be a subject of high interest. Nowadays, Additive manufacturing (AM) of Titanium alloys has grown into an imperative field of study. The foremost prominence of Titanium alloys is excellent strength to weight ratio, high weathering resistance, and admirable characteristics involving high tensile strength and toughness with comparatively low electrical and thermal conductivity. The manufacturing of Titanium through AM technology is marginally expensive and durable as it enables to create freedom in design community to fabricate user defined and complex structures which is hard to produce through other conventional manufacturing methods. The Ti-6Al-4V alloy is popularly known as the “work horse” of titanium is comprehensively used in aerospace and biomedical industries. At present, several studies have focused on hybrid manufacturing and enhancing the mechanical properties of Ti-6Al-4V with additive manufacturing techniques. In this research work, a short review on additive manufacturing of Ti-6Al-4V alloys has been investigated to define its mechanical and metallurgical properties in both as-built and heat treated conditions.

3D Printing of Zirconia–What is the Future?

Within this review, the current needs of the dental industry will be discussed with special focus on additive manufacturing (3D printing) of dental restorations. Up to now, subtractive manufacturing methods are state of the art for production of monolithic restorations. Here, the challenges and opportunities currently existing for 3D printing of crowns and bridges will be evaluated. Over the last 10 years, the LCM technology has evolved to the state of the art 3D printing technique for dense and precise ceramics. A case study will present here the full digital workflow from acquiring the data of the patient to manufacturing the final restoration. It can be shown that with the LCM technology, it is possible to manufacture highly accurate parts with exceptional good surface quality. Furthermore, it can be shown that established techniques for staining and glazing conventionally manufactured restorations are also perfectly suitable for parts manufactured by means of the LCM technology. Particularly attractive restorations and outstanding reproduction of the sharp-edged crown margins are possible, together with the exact reproduction of the occlusal surfaces with sharp and natural replication of the fissures.

Superficial properties of Ti6Al4V discs obtained by the additive and subtractive manufacturing method

Superficial properties of Ti6Al4V discs obtained by the additive and subtractive manufacturing method

Fabrication and measurement of 3D printed retroreflective fibers

Additive manufacturing enables new fiber preform geometries to be built that were either impossible or extremely difficult with traditional subtractive manufacturing methods. Additionally fiber thermal drawing is undergoing an explosion of interest due to new materials and fiber functions. We fabricate a retroreflective fiber that possesses a complex cross-section and material combination not achievable with other textile fiber fabrication methods such melt extrusion. This is the first such 3D-printing-derived fiber to demonstrate optical scattering properties with a non-circular, non-convex cross-section.

Process-Structure-Property Relationships of AISI H13 Tool Steel Processed with Selective Laser Melting.

Due to a good combination of high hardness, wear resistance, toughness, resistance to high operating temperatures, and fairly low material cost, AISI H13 tool steel is commonly used in the manufacture of injection molds. Additive manufacturing (AM) such as selective laser melting (SLM), due to the layer-wise nature of the process, offers substantial geometric design freedom in comparison with conventional subtractive manufacturing methods, thereby enabling a construction of complex near-net shape parts with internal cavities like conformal cooling channels. The quality of SLM-manufactured parts mainly depends on the part geometry, build orientation and scanning strategy, and processing parameters. In this study, samples of H13 tool steel with a size of 10 × 10 × 15 mm3 were SLM-manufactured using a laser power of 100, 200, and 300 W; scanning speed of 200, 400, 600, 800, 1000, and 1200 mm/s; and hatch spacing of 80 and 120 µm. A constant layer thickness of 40 µm, 67° scanning rotation between subsequent layers, and a stripe scanning strategy were maintained during the process. The samples were built considering a preheating of 200 °C. The relative density, surface roughness, crack formation, microstructure, and hardness were evaluated. The relative density is shown to increase with increasing the volumetric energy density up to a value of about 60 J/mm3 and then no significant increase can be pointed out; the maximum relative density of 99.7% was obtained. A preheating of 200 °C generally aids to increase the relative density and eliminate the crack formation. The microstructure of built samples shows fine equiaxed cellular-dendritic structure with martensite and some retained austenite. The microhardness of the as-built samples was found to vary from 650 to 689 HV 0.2, which is comparable to a conventionally produced H13 tool steel.

Characterization of effective Young’s modulus for Fused Deposition Modeling manufactured topology optimization designs

Topology optimization method allows finding optimized designs in a efficient way; however, it generally leads to complex geometries difficult to manufacture by traditional methods. Additive manufacturing is one of the techniques used to build this kind of structures due to its ability to achieve complex geometries faster and at lower costs than traditional subtractive manufacturing methods. However, 3D manufacture effects such as interlayer porosity or weak interlayer bonding generate changes in the mechanical properties of the material used for printing, which lead to losses in the performance of the optimized structure if the manufacture process does not take them into account. Therefore, this article proposes a methodology using the impulse excitation technique, which is a non-destructive characterization method of materials that uses a test piece with a fixed geometry, its mass, and its natural frequencies to determine Young’s modulus, Shear modulus, Poisson’s ratio, and Damping coefficient; to obtain an effective isotropic Young’s modulus of Fused Deposition Modeling–printed thermoplastic materials to be used in topology optimization design.

Progress in femtosecond laser fabrication of artificial compound eye

Compound eyes of arthropods are widespread and fascinating visual systems created by natural evolution. Compound eyes consist of many identical small eye units called ommatidia, each of which is an individual imaging system composed of cornea lens, crystalline cone and rhabdome. Compared with single eyes, compound eyes have distinct advantages in small volumes, large field of view, large depth of field, and high temporal resolution. Therefore, it has sparked considerable research interests in developing various manufacturing technologies towards the fabrication of artificial compound eyes that can be applied in robot vision, three-dimension imaging, motion detection and medical examination. To date, various methods have been proposed for fabricating artificial compound eyes, such as hot embossing method, thermal reflow method, microdroplet jetting method, and ultraprecision machining method. However, these methods inherently suffer from low accuracy and multi-step processing. In particular, it is extremely difficult for these methods to acquire curved artificial compound eye lens, which is quite important for promoting the optical performance and practical applications of artificial compound eyes. In recent years, femtosecond laser direct-writing (FsLDW) has emerged as a practical and promising technique for fabricating artificial compound eyes owing to its capability of three-dimensional (3D) processing and high fabrication precision. First of all, FsLDW is performed by point by point scanning process layer by layer, making it capable of realizing various 3D structures as designed. Second, the extremely high transient intensity of femtosecond laser pulses leads to a non-linear absorption effect (two-photon absorption or multi-photon absorption) with materials in a much smaller volume than the cubic size of wavelength, which endows it with a high resolution (tens of nanometers) beyond the optical diffraction limit. Moreover, the high power of femtosecond laser pulses also provides the ability to process various materials, from soft photopolymer materials to rigid substrates as hard as diamonds. For soft materials, the fabrication mechanism is two- or multi-photon polymerization of photosensitive polymers triggered by the high energy at the localized laser focus region. Through point by point process, two-photon polymerization technology by FsLDW becomes a powerful tool for fabricating complex 3D structures. In spite of this, its shortcoming is obvious as well. The single point scanning procedure causes a relatively low efficiency, which needs further improvement. For hard materials, femtosecond laser serves as an ablation source to form micro-hole, where the local material is removed or chemically modified. Femtosecond laser ablation can be combined with a subsequent etching treatment for improving efficiency, including wet etching and dry etching. The drawback of etching assisted femtosecond laser ablation technology lies in that usually only concave structures can be obtained, further soft embossing treatment is needed in order to acquire convex compound eye lens. In this review, the latest progress in femtosecond laser fabrication of artificial compound eyes is summarized. Manufacturing of artificial compound eyes by FsLDW is introduced according to the two methods mentioned above: femtosecond laser two-photon polymerization that belongs to additive manufacturing and femtosecond laser ablation that is regarded as a subtractive manufacturing method. Then, the diverse applications of artificial compound eyes produced by FsLDW are described. At last, current challenges and future perspectives in this field are discussed.

A comparison of traditional manufacturing vs additive manufacturing, the best method for the job

Abstract Manufacturing industries and investors are always seeking to improve techniques to lower cost, energy and expand their capability. Additive manufacturing, started in the 1960s, has since had a rapid and continuous growth, bringing to light novel techniques to expand manufacturing capability and reinvent the wheel. At this stage, research and industry interest lie in determining where AM can replace or create new manufacturing systems. Traditional manufacturing refers to subtractive and long-established manufacturing methods, quality assured and implemented in the commercial space. This paper reviews the capability of AM and its current development to compete or add to established traditional manufacturing regions. Literature reveals the capability of AM to fit into established manufacturing regions for low and high production volume products. The paper comparison focuses on the similarities, differences, advantages and disadvantages found in AM vs SM studying the economic and quality management status of the industry today.

Pressure Sensor Based on Polyvinylidene Fluoride Nanofibers Directly Written upon Silicon Substrate

A novel integration of silicon substrate and near-field electrospun polyvinylidene fluoride (PVDF) nanofibers is applied to pressure sensor for dynamic pressure measurement. PVDF is the widely known polymer with outstanding piezoelectric property, and has a wide range of applications in energy, biology, and sensors. Near field electrospinning (NFES) has obvious advantages in the preparation of direct written PVDF nanofibers with high piezoelectric performance. This paper mainly presents the preparation of pressure sensor of PVDF nanofibers on silicon substrate with integrated subtractive and additive manufacturing methods. First, a silicon substrate with diaphragm was fabricated with MEMS techniques. Then, aligned parallel PVDF nanofibers were deposited on the diaphragm with NFES as sensing element. Last, a home-made dynamic pressure testing device was used for testing the properties, and its results showed that: with the increase of pressure, the output signal was gradually enhanced, and the sensitivity of the prototype sensor was finally obtained, which is 2214.4mV/MPa (the circuit amplification factor of 20,000 times), and the optimal linearity is 2.8%.

Multiaxial Fatigue of Additive Manufactured Metals

Additive manufacturing (AM) has recently gained much interest from researchers and industry practitioners due to the many advantages it offers as compared to the traditional subtractive manufacturing methods. These include the ability to fabricate net shaped complex geometries, integration of multiple parts, on-demand fabrication, and efficient raw material usage, among other benefits. Some of distinguishing features of AM metals, as compared to traditional subtractive manufacturing methods, include surface roughness, porosity and lack of fusion defects, residual stresses due to the thermal history of the part during the fabrication process, and anisotropy of the properties. Most components made of AM processes are subjected to cyclic loads, therefore, fatigue performance is an important consideration in their usage for safety critical applications. In addition, the state of stress at fatigue critical locations are often multiaxial. Considering the fact that many of the distinguishing features of AM metals are directional, the subject of multiaxial fatigue presents an important study area for a better understanding of their fatigue performance. This paper presents an overview of the aforementioned issues using recent data generated using AM Ti-6Al-4V and 17-4 PH stainless steel. Specimens were made by laser-based powder bed fusion and subjected to axial, torsion, and in-phase as well as out-of-phase loadings. A variety of conditions such as surface roughness, thermo-mechanical treatment, and notch effects are included. Many aspects are considered including damage mechanisms and crack paths, cyclic deformation, fatigue crack nucleation and growth, and stress concentration effects.

Process planning for hybrid additive and subtractive manufacturing to integrate machining and directed energy deposition

Abstract This paper presents a hybrid additive and subtractive manufacturing method to integrate process planning considerations. This method could offer a new solution to deliver parts in a timely manner, minimizing inventory and material waste. The method essentially incorporates the base plate of additive manufacture into a final additive/subtractive manufactured product. Manufacturing begins with a base plate, where a set of subtractive steps will first create a portion of the design geometry. Next, the additive manufacturing process will be planned to create geometry on the machined base plate in two opposite directions, to minimize support structure and build height. Finally, a secondary machining process is planned to produce finished surfaces on the additively manufactured near net shape geometry. The work is implemented in the form of planning algorithms that integrate the aforementioned subtractive and additive process planning stages.

Influence of laser parameters and complex structural features on the bio-inspired complex thin-wall structures fabricated by selective laser melting

The lobster-eye structure exhibits unique optical performance and finds its application in aerospace. However, the lobster-eye structure is highly complex and hard to process using traditional subtractive manufacturing methods. In this work, complex thin-wall structures, inspired by the lobster eye, were fabricated by selective laser melting (SLM) with AlSi10Mg powder. The influence of key laser parameter, namely laser power, on the densification behavior, dimensional accuracy, surface roughness and forming defect of SLM-processed lobster-parts was systematically investigated. Particular emphasis was placed on the impact of laser power and structural features on the inner surface roughness. Results revealed that the relative density of SLM-processed lobster-eye parts exhibited a similar trend with bulk parts against the laser power. The small dimension feature of thin-wall structures contributed to the higher relative density of lobster-eye parts comparing with that of bulk parts. The roughness of inner surfaces and outside surfaces showed completely different responds to the laser power, and the inner surface morphology behaved differently among positions. All these special surface phenomena were contributed to the combined impact of the laser parameter and the particular geometry of the lobster-eye structure. Finally, considering the optical function and post-processing, an optimal laser power was determined for the SLM-processing of lobster-eye components.