Smooth Surface Finish Research Articles

Design and Depolymerization of Bis(2‐hydroxyethyl) Terephthalate‐Containing Polyurethanes for Vat Photopolymerization

AbstractVat photopolymerization (VPP) of highly aromatic polyurethanes (PUs) expands the library of additive manufacturing (AM) materials and enables a vast array of ductile thermoplastics, rigid and flexible thermosets, and elastomers. Aromatic diisocyanates and various diols enable printing of rigid, highly aromatic cross‐linked parts, which offer high glass transition temperatures and tunable thermomechanical performance. The judicious control of molecular weight of the photo‐reactive telechelic oligomers allows for a fundamental study of the influence of cross‐link density in highly aromatic 3D PU printed objects. VPP AM produces objects with high resolution, smooth surface finish, and isotropic mechanical properties. Thermal post‐processing is critical in maintaining excellent thermomechanical properties with semi‐crystallinity as a function of cross‐link density. Due to the presence of two ester carbonyls in the bis(2‐hydroxyethyl) terephthalate chain extender, the printed parts are readily amenable to depolymerization with methanolysis to produce difunctional dimethyl dicarbamates under modest reaction conditions. Dimethyl dicarbamates serve as suitable monomers for subsequent polycondensation.

Machining-Induced Damage and Corrosion Behavior of Monel-400 Alloy Under Cryogenic Cooling Conditions: A Sustainable Initiative

AbstractMonel-400 is a nickel-based heat-resistant superalloy (HRSA) that is primarily used in oil and marine applications. Machining Monel-400 alloy for marine applications usually involves drilling and milling operations for assembly purposes, which should meet the requirements to withstand use in salt-water environments (i.e. lower surface finish to reduce corrosion and lack of burrs for tight sealing between mating parts). However, drilling of Monel-400 alloy can be challenging due to its high strength and density, which induces thermal effects that can influence the surface and geometrical integrity of the holes. Consequently, the use of environmentally friendly cooling technologies, such as cryogenics, is an excellent alternative to mitigate these effects, something which has not been widely investigated in the open literature when drilling Monel-400 alloy. Therefore, the current study aims to investigate the machinability of Monel-400 alloy under dry and cryogenic cooling conditions. The effects of cutting parameters and the use of a cryogenic liquid nitrogen bath on the surface integrity and corrosion resistance of holes were evaluated. Additionally, cutting forces, chip formation, and corrosion performance were analyzed. The results showed that the cutting forces increased by up to 8% under cryogenic cooling. Under cryogenic conditions, reduced elastic deformation resulted in a smaller chip size. Both cutting conditions produced a smooth surface finish with a roughness value of less than 0.2 µm. Corrosion resistance was reduced under cryogenic conditions at spindle speed of 5000 rpm. The current work showcases that cryogenic cooling is recommended for drilling Monel-400 alloy used in marine applications, but care should be taken in employing optimal cutting parameters to mitigate any effects on corrosion resistance.

The science of printing and polishing 3D-printed dentures

Objective To analyze the effectiveness of various techniques available for printing, finishing and polishing of 3D printed prosthesis. Methods The articles were selected from electronic databases including PubMed and Scopus. Recently, lot of advancements have been observed in the field of 3D printing in dentistry. Results Numerous studies were found explaining the factors affecting the surface roughness such as printing speed, direction, layer thickness, post curing, etc., and the significance in achieving a smooth surface finish of a 3D printed prosthesis. The methods employed to achieve this range, similar to conventional and chairside polishing, are to use advanced coating materials such as light cured glazes to nanoparticles. Conclusion 3D printing is being used in day-to-day practice and the prosthesis must be aesthetic looking to satisfy the patients’ expectations. There is a lack of data supporting any one polishing method for the prosthesis. There is a need for further research on the existing techniques and newer advancements yielding aesthetic prostheses with an optimal surface finish.

Comparative assessment of Ti‐6Al‐4 V titanium alloy fatigue life improvement by vibratory peening, shot peening, and vibratory finishing

AbstractThe effects of vibratory peening (VP), shot peening (SP), and SP followed by vibratory finishing (SPVF) on the surface and fatigue properties of Ti‐6Al‐4 V were compared to conventional low‐stress grinding (LSG). VP processing produced seven times smoother surface finish than SP and 66% deeper compressive residual stresses (CRS) but with 12% lower magnitudes. SPVF produced optimal surface properties with a perfectly flat surface and CRS‐like SP. All three mechanical surface treatments generated similar fatigue life improvements (108–122%) over LSG when the cyclic stress was below the yield stress. Above the yield stress, most of the CRS relaxed during the first cycle in VP specimens, resulting in up to 97% fatigue life improvement over LSG. The CRS relaxed more gradually in SP specimens leading to larger (up to 239%) fatigue life improvement. This shows the need to amplify CRS magnitudes produced in VP to maximize fatigue life improvement.

Role of gravity magnitude on flowability and powder spreading in the powder bed fusion additive manufacturing process: Towards additive manufacturing in space

Understanding powder spreading under low gravity conditions is essential for optimizing final products using additive manufacturing in space. In this study, we investigated the role of gravity on flowability and spreading mechanisms through combined experimental and discrete element method (DEM) studies. Three powders with different theoretical densities were used to reenact low compressive conditions resembling those in a low-gravity environment. The influence of low compressive conditions on flowability and spreading behavior was examined using the Hall flowmeter, rotating drum, and spreading experiments. In the experimental result, the static flowability was primarily affected by the presence of elongated particles rather than the compressive conditions. The dynamic AoR of TD_4 powder increased compared to that of TD_8 powder, despite the presence of spherical particles with a smooth surface finish. A DEM simulation study was conducted using TD_8 powder to investigate the impact of different gravity levels on dynamic flowability. The DEM studies revealed that the dynamic flowability under rotation was decreased under low gravity owing to the promoted cohesive interactions. The powder spreading experiment was performed using the three powders with different theoretical densities. The in-situ observation with particle image velocimetry analysis revealed that kinetic energy dissipation in the spreading process was accelerated in the TD_8 powder pile, despite its high interparticle friction and cohesive force. The powder spreading simulation was conducted using TD_8 powder to clarify the effect of low gravity on the powder spreading process. In TD_8 powder under 1 G, particle supply was facilitated by a synergistic effect of free-falling and deposited particles. However, increased cohesive interactions under 0.5 G and 0.16 G restricted particle supply via free-falling, consequently reducing the powder bed density by about 2 % and 6.2 %, respectively. These findings prove that the cohesive force predominantly controls dynamic flowability and powder bed quality in the spreading process under low gravity conditions.

Influence of titanium surface roughness on a nanoscale on the zeta potential and platelet adhesion.

Thromboembolic complications still arise on blood contacting surfaces. Surface charge and topography influence the subsequent deposition of proteins and platelets, potentially leading to thrombi. Research showed a correlation of surface charge and nanoscale roughness, and a negative surface charge as well as a smooth surface finish are associated with lower thrombogenicity. The aim of this study was to compare the platelet adhesion on titanium with different nanoscale roughnesses and to examine if those roughness variations caused a change in surface charge. Titanium samples were polished and roughened to four different nanoscale roughness levels. Platelet adhesion (covered surface area (CSA), N = 8) was tested in flow chambers with human whole blood using fluorescence imaging. ζ-potential was measured over a broad range of pH-values and interpolated to obtain the ζ-potential for pHBlood (7.4). Platelet adhesion tests were evaluated in terms of p-values and the Wilcoxon test effect size and the trend of the ζ-potential at pHBlood and the CSA was compared. Ra-values ranged between 35 (polished) and 156 nm. Regarding platelet adhesion, the polished sample showed the lowest mean CSA with a medium or strong effect size compared to the roughened samples. The interpolated ζ-potentials for pHBlood follow a similar trend as the CSA, with the lowest ζ-potential measured for the polished surface. These findings suggest that the decreasing ζ-potential due to lower nanoscale roughness might be an additional explanation for the improved hemocompatibility besides the smoother topography.

Vat photopolymerization of poly(styrene-b-isoprene-b-styrene) triblock copolymers

Vat photopolymerization (VPP) additive manufacturing (AM) produces complex geometries with micron-scale resolution and smooth surface finish from a wide range of photocrosslinkable polymeric precursors. However, mass transport limitations typically constrain VPP amenable precursors to viscosities less than 10 Pa·s. Reactive oligomers and monomers comprise the majority of VPP polymeric precursors, which result in highly crosslinked and brittle 3D objects upon printing. This work describes colloidal high molecular weight ABA triblock copolymers, or latex, as a feedstock for aqueous photoreactive compositions to enable AM of thermoplastic elastomers (TPE). Photorheological analysis determined 15 wt% aqueous reactive monomers and oligomers generated a structural scaffold that achieved sufficiently high modulus to maintain feature fidelity for iterative layer formation. Subsequent thermal post-processing removed water and promoted polymeric particle coalescence throughout the scaffold resulting in an interpenetrating network (IPN) that exhibited an isotropic dimensional shrinkage of 25 %. Small-angle X-ray scattering (SAXS) confirmed microphase-separated morphologies typical of triblock copolymers, revealing a characteristic length scale of 30 nm. Using commercially available VPP printers, ABA triblock copolymer poly(styrene-b-isoprene-b-styrene) latex yielded printed elastomers with precise feature fidelity and tensile extensibility exceeding 800 %.

Experimental study on the ultrasonic assisted face turning residual stress

ABSTRACT The Experimental study investigates the impact of ultrasonic-assisted face turning (UAFT) on cutting forces, tensile residual stress, and surface topography. The primary objective is to identify optimal cutting parameters that yield a smoother surface finish while concurrently reducing cutting forces and tensile residual stress. The tests were conducted on a lathe machine equipped with ultrasonic assistance, using 1.7225 steel as the workpiece material. Various cutting parameters, including feed rate, spindle speed, and turning state, were varied. The results illuminate the significant efficacy of ultrasonic assisted face turn (UAFT) in improving surface topography, compared to conventional turning (CT). The optimal turning parameters for achieving the smoothest surface finish were determined to be a higher spindle speed and lower feed rate. Moreover, the introduction of ultrasonic vibration led to a substantial reduction in cutting forces, primarily attributable to the diminished attrition between the cutting tool insert and the work part. Overall, the experimental study demonstrates the effectiveness of ultrasonic-assisted face turning in enhancing surface topography, with an improvement of approximately 39%. Additionally, the study demonstrated a reduction in cutting forces by approximately 50% and a decrease in tensile residual stress by approximately 33.8%. These findings underscore the potential of ultrasonic vibration as a tool for optimizing cutting parameters to achieve desired surface finishes in machining applications.

Small-quantity cooling lubrication in creep-feed grinding: Surface quality and residual stress analysis

Small-quantity cooling lubrication (SQCL) has emerged as a promising eco-friendly alternative to conventional flood cooling in creep-feed grinding processes. This study delves into the influence of various cooling conditions (dry, SQCL, and flood cooling) on the creep-feed grinding dynamics of 420 stainless steel specimens. Key parameters, including friction coefficient, surface texture, and through-thickness residual stresses, are investigated. Both SQCL and flood cooling exhibit marginal reductions in the friction coefficient compared to dry conditions, owing to their lubricating properties. With a smoother surface finish, SQCL grinding exhibits an average roughness of 42 % lower than that of dry grinding. Furthermore, increasing cutting depth and feed rates lead to elevated residual stresses on the specimen's surface, with SQCL cooling demonstrating substantial reductions compared to dry conditions. The SQCL cooling condition yields surface residual stresses 46–48.28 % lower than those observed in the dry condition. This study sheds light on the efficacy of SQCL as an alternative cooling method in enhancing surface quality and mitigating residual stresses in creep-feed grinding processes.

Experimental investigation on Stereolithography process parameter optimization and its influence on smooth surface finish for ABS Accura-60 material

Rapid Prototyping Technique (RPT) is a method that involves directly translating CAD models into physical parts, making it easier to produce prototypes. These 3D prototype printers have found applications in various fields, where there's a demand for prototypes with higher strength, smoother surface finishes, and overall quality. One of the newer techniques, SLA (Stereolithography), has significantly impacted part manufacturing, as well as research and development processes. To meet the growing demands for improved surface properties, especially in polymers and plastics, standardized specimen profiles like ASTM D638 Type I are utilized for surface finishing testing. This study is focused on optimizing SLA parameters specifically for Accura-60 prototypes, with a particular emphasis on enhancing surface finish for ASTM D638 Type I specimens. The experiments conducted in this research delve into variations in parameters such as hatch angle, layer thickness, and hatch spacing to better understand their impact on surface properties. The ultimate goal is to effectively control and optimize SLA parameters to enhance surface finish, thereby improving the overall quality of the prototypes.

High Temperature Oxidation of Additively and Traditionally Manufactured Inconel 718

Abstract Additively manufactured nickel-based superalloys are now being considered as a replacement for traditionally manufactured components on commercial and military aircraft. While the potential of additive manufacturing for gas turbine engines is promising, the quality and performance of additive manufactured components still need extensive study. Coupon-sized test specimens comprised of as-printed additively and traditionally manufactured Inconel 718 with and without yttria-stabilized zirconia thermal barrier coating were tested under simulated isothermal and thermal cycling combustion conditions that were representative of gas turbine environments. Pre-test scanning electron microscopy indicated that traditionally manufactured coupons had a smooth surface finish with minor imperfections while additive manufactured coupons had a rough surface finish. Post-test scanning electron microscopy exhibited differences in oxide scale between the isothermal and thermal cycling conditions. The thermal cycling condition increased the amount of oxide scale for both additively manufactured and traditionally manufactured Inconel 718. The size of the oxide islands on traditionally manufactured coupons was significantly larger than the additively manufactured coupons. The results indicated that differences in surface roughness may affect the growth of the oxidation scale in a high-temperature combustion environment. The benefits of yttria-stabilized zirconia thermal barrier coating were characterized. The substrate of the coupons experienced little to no formation of oxide scales compared to the uncoated additive and traditionally manufactured coupons. The results further suggested that yttria-stabilized zirconia thermal barrier coating can be utilized to provide both insulation and oxidation protection when desired. Post-test energy-dispersive X-ray spectrometry results corresponded well with known elemental compositions and oxidation mechanisms.

Experimental analysis for optimization of process parameters in machining using coated tools

Manufacturers are facing challenges in achieving high productivity and quality in manufacturing through machining. PVD-coated tools can control several machining challenges by enhancing hardness and abrasion resistance of the cutting tool. These tools facilitate turning operations in terms of efficiency, accuracy, and productivity by extending cutting performance and tool life. Aluminum bronze, a copper alloy valued for its mechanical, thermal, corrosion, and wear-resistant properties, finds application in diverse industries such as aerospace, automobile, marine, and electrical engineering, as well as in the creation of sculptures, decorative elements, and thermal devices. However, machining aluminum bronze presents common challenges, including achieving a smooth surface finish and minimizing high cutting force due to its inherent strength and abrasiveness. This research aims at identifying the optimal levels of cutting velocity, feed, and depth of cut to minimize surface roughness and cutting force during dry turning of wear-resistant high-strength CuAl10Fe5Ni5-C. PVD AlTiN-coated tools were utilized, which offer many advantages over others. Experiments were conducted through Taguchi’s L27 OA (orthogonal array) of factors. The results indicate that coated tools have superior performance in reducing surface roughness and cutting force. When it comes to designing and optimizing experiments, integrating PCA with Taguchi method is a potent strategy. Again, it was observed that feed is the most influential factor affecting responses.

Surface quality enhancement by constant scallop-height in three-axis milling operations

The quality of machined part surfaces are under the impact of scallop height which should be analyzed and minimized. Achieving a uniform scallop-height is important for ensuring a smooth surface finish and maintaining consistent material removal across the machined surfaces during CNC machining operations. This approach helps to reduce material waste, tool wear and part production errors while ensuring consistent and high-quality of machined parts. Maintaining a constant scallop height can also help to reduce chatter and vibration during milling operations. The research work develops a virtual machining methodology to produce constant scallops through three-axis milling operations. The proposed approach examines free-form surfaces of workpiece in order to obtain free form surfaces curvatures. Then, free-form surfaces are separated into flat, convex and concave surfaces to provide optimized cutting tool variables in order to provide constant scallop height during CNC cutting tool paths. Achieving a constant scallop height involves optimizing cutting parameters such as feed rate, spindle speed, and step over. To calculate the optimized machining parameters of feed rate, speed of spindle and step over, the Taguchi optimization methodology is utilized in the study. Then, the machining variables of feed rate, speed of spindle and step over are optimized to achieve the uniform scallop height during milling potations of free-form surfaces. As a result, using optimized machining parameters during machining operations, the surface roughness of machined components are reduced by 23.8%. So, the proposed virtual machining method can enhance surface quality of machined parts during CNC milling operations of free-from-surfaces.

Thermal analysis of in-situ laser assisted diamond cutting of fused silica and process optimization

Fused silica is typically a difficult material to machine using conventional methods due to its high brittleness and hardness, despite its significance in optical systems such as high-power lasers and astronomical telescopes. Laser assisted diamond cutting has emerged as a promising and cost-effective alternative for machining fused silica. This study investigated the machinability and thermal response of fused silica during in-situ laser assisted diamond cutting through finite element analysis and cutting experiments. The temperature dependence of thermal parameters, identified by Beetle Antennae Search, was taken into consideration in the thermal model. To minimize surface roughness and determine the optimal machining parameters, various methods were employed, including analysis of variance, signal-to-noise ratio, and Particle Swarm Optimization coupled with Artificial Neural Network. The results indicated that various factors involved in in-situ laser assisted diamond cutting had a significant impact on the thermal response of fused silica, resulting in different surface roughness. Among these factors, spindle speed, feed speed, cutting depth, and laser power contributed to surface roughness by 17.34 %, 12.28 %, 12.03 %, and 48.31 %, respectively. By utilizing the optimal combination of parameters, which comprised a spindle speed of 2700 rpm, feed speed of 1.7 mm/min, cutting depth of 2.7 μm, and laser power of 12.5 W, a smooth surface finish of Sa 12.9 nm could be obtained.

Influences of tool tip geometry on surface/subsurface damage formation in nanoscratching of single-crystal 4H-SiC

Creating a smooth surface finish with nanometer-scale roughness on SiC is extremely difficult due to its hard, brittle properties and crystal anisotropy. In this study, nanoscratching tests were performed on single-crystal 4H-SiC along various crystal directions by using a sharp Berkovich tip (radius ~150 nm) and a blunt spherical tip (radius ~1 μm), respectively, to reveal the effects of tool geometry on its surface integrity. Results indicate that, under the same load conditions, the Berkovich face-forward tip produced the greatest penetration depth, followed by the Berkovich edge-forward tip and the spherical tip. The extent of surface and subsurface damage caused by the three tips follows the same trend as the penetration depth. Phase transformation did not occur in the scratched surface with the three tips, while it was occurred in the chips generated with Berkovich face-forward tip. The critical load for surface crack formation was larger when scratching along <01−10> directions compared to scratching along <11−20> directions, independent of tool geometry. Microcrack-like defects may form in the subsurface even the surface is free of damage. The microcracks were caused by {01−11} pyramidal <a> and <a+c> slip and by {11−22} pyramidal <c+a> slip when scratching along <11−20> and <01−10> directions, respectively.

Investigation of surface topography in ultrasonic-assisted turning of C45 carbon steel

This study compares ultrasonic-assisted turning to conventional turning in terms of their effects on surface texture and cutting forces during the machining of C45 carbon steel. Experiments were conducted on a lathe equipped with a 1000 W ultrasonic generator running at 20 kHz. Ultrasonic-assisted turning results in small, evenly distributed spherical scratches on the workpiece, while conventional turning leads to long, uneven cutting marks. Significantly, ultrasonic-assisted turning achieves a notably smoother surface finish than conventional turning. As the depth of cut increases, conventional turning causes increasingly uneven surface topography, whereas ultrasonic-assisted turning maintains surface stability and uniformity. Moreover, cutting forces see a substantial rise of approximately 40% with conventional turning as the depth of cut increases. In contrast, ultrasonic-assisted turning witnesses a marginal force increase of about 15.84%.

Evaluation on the performance of sustainable wire arc additive manufacturing using micro plasma arc welding

Metal additive manufacturing has gained popularity due to its significant advancement in minimising waste. The product design using additive manufacturing (AM) does not require mould and less material required, which is less waste. In this way, AM has the potential to transform the manufacturing industries towards greater sustainability. Besides, AM allow more complex designs and shape than conventional manufacturing. Wire arc additive manufacturing (WAAM) is one of the most popular metal AM that has received significant attention due to its usefulness for localising, repairing, and modifying instead of discarding and replacing entire components. However, conventional welding technology faced the issue of significant heat input, low surface quality, and low dimensional accuracy of WAAM components. Micro-plasma arc welding (MPAW) is a new alternative to the WAAM process. The speciality of MPAW is low current provided of 1A to 25A current range, leading to low heat input and energy-efficient manufacturing. The present study shows various metallic structures developed using an MPAW-based WAAM system, and the relative error between the CAD model and four different structures was determined. Overall, the study outcome shows the geometric uniformity of parts produced with an MPAW-based WAAM system and demonstrates smooth surface finish can be obtained.

Understanding the Effects of Surface Finish on Diffusion Bonding of AZ31 Alloys

Methods to optimize the diffusion bonding (DB) process while also creating lap joints were investigated using AZ31, the commercial Mg alloy, focusing primarily on studying the effects of varying conventional process parameters and more importantly, exploring the influence of surface roughness on creating an acceptable strong bond. The results indicate that when contact is made between surface areas of roughness (Ra &gt; 0.2 ㎛) diffusion is facilitated at reduced process parameters of time and temperature. Furthermore, this early bond initiation combined with the optimized DB process parameters results in a stronger bond with strengths increasing by ~ 150% in comparison to the DB samples created with a smooth surface finish. Additionally, less than 20% total overall distortion is observed while preserving a uniform microstructure of consistent grain sizes in the material over the entire joining region compared with the parent material.

Alumina-based ceramic cores prepared by vat photopolymerization and buried combustion method

Alumina (Al2O3)-based ceramic cores are extensively employed to form cavities within complex or difficult-to-form casting parts. As a conventional manufacturing process, investment casting requires molds and is labor-intensive. Therefore, it is crucial to develop a direct method for preparing Al2O3-based ceramic cores at a low cost. As an AM process, vat photopolymerization (VPP) can produce high-quality parts with smooth surface finish and fine details. Therefore, extensive attentions have been attracted to processing ceramic materials by VPP. Despite these benefits, the layer-by-layer accumulation strategy of VPP inevitably induces low bonding strength between adjacent layers, and induces cracks in the sintered parts. To mitigate these problems, burying VPP-printed Al2O3 green bodies into silica has been proposed in this investigation. Results show that cracks and deformation problems have been reduced when the buried combustion method is adopted. To create Al2O3-based ceramic cores with desired porosity and flexural strength properties, process parameters have been optimized. A systematic study on how the inclusion of SiO2 particles and variations in sintering temperature impact the microstructure and mechanical properties of Al2O3-based ceramic cores fabricated through VPP printing is presented. Based on experimental results, a 1300 ℃ sintering temperature is selected to produce appropriate shrinkages (4%∼8%), open porosity of over 20%, and flexural strength ranging from 20 to 50 MPa of ceramic cores.

Wear analysis on difficult to cut metals on Titanium and Inconel 718

An Inconel 718, Titanium and stainless are classified high strength and classified as difficult to cut metal. The machining of these metals requires tough cutting tools like CBN and PCBN. The research paper deals with flank wear on the above said metals by turning process. It was decided to turn up to length of 500 for both metals. The flank wear and crater wear are two dominant factors in any machining process which will affect the smooth surface finish and in turn affect the performance of the component. The surface finish affected by tool wear and increase down time which need frequent tool change. The aim of this research was to investigate flank wear using cutting speed of 30, 40 and 50 m min−1, feed rate of 0.05, 0.10 and 0.15 mm rev-1 with depth of cut 0.50, 0.75 and 1.00 mm. The investigation showed that flank increased at cutting speed of 50 m min−1, feed rate of 0.15 mm rev-1 and depth of cut 1.00 mm.