Denni Kurniawan

Hard Machining of Stainless Steel Using Wiper Coated Carbide: Tool Life and Surface Integrity

Carbide cutting tools, which are inexpensive and widely used by machine shops, are alternatives for performing hard machining, yet limitations due to their low strength requires performance evaluation as well as appropriate selection of cutting parameters. In this study, a carbide tool with TiAlN coating with wiper geometry at the cutting edge is proposed for performing mild range of hard machining of martensitic stainless steel (48 HRC). The tools performance was evaluated based on its tool life and the resulting surface finish when hard machining at various cutting speeds and feeds and at constant depth of cut without using cutting fluid (dry machining). Response surface methodology was used to quantify the effect of cutting speed and feed to the tool life and proposing the optimum cutting parameters. Further observation was made on the worn tool, the machined surface, and the generated chip to observe the process. Results showed that the wiper coated carbide tool are capable of performing particular hard machining.

Cutting force and surface roughness characterization in cryogenic high-speed end milling of Ti-6Al-4V ELI

This study investigates the cutting forces induced during high-speed end milling of titanium alloy (Ti–6Al-4V ELI) as well as the surface quality of the milled surfaces. The high-speed machining was performed using carbide tool of coated and uncoated types at three cutting speeds of 200, 250, and 300 mm/min and two feed rates of 0.03 and 0.06 mm/tooth. Surface integrity was characterized in terms of surface roughness (Ra) and morphology. Cutting speed was found to be inversely proportional to the resultant cutting force at any cutting conditions. Cutting force in the X direction displayed higher sensitivity against cutting conditions. The results showed that feed rate is proportional to cutting force in X and Y directions regardless of tool type. Under the fixed feed rate condition, cutting force decreased at higher cutting speed for both tools. It was also found that uncoated tool induces less cutting force compared to coated one. High-speed end milling using uncoated tool provided better surface finish than using a coated carbide tool, especially at lower cutting conditions. However when coated carbide tool was used, surface roughness improved significantly with the increase in cutting speed. In contrast, almost opposite phenomenon was observed when uncoated tool was used.

γ-Fe2O3 nanoparticles filled polyvinyl alcohol as potential biomaterial for tissue engineering scaffold

Maghemite (γ-Fe2O3) nanoparticle with its unique magnetic properties is recently known to enhance the cell growth rate. In this study, γ-Fe2O3 is mixed into polyvinyl alcohol (PVA) matrix and then electrospun to form nanofibers. Design of experiments was used to determine the optimum parameter settings for the electrospinning process so as to produce elctrospun mats with the preferred characteristics such as good morphology, Youngs modulus and porosity. The input factors of the electrospinnning process were nanoparticles content (1-5%), voltage (25-35 kV), and flow rate (1-3 ml/h) while the responses considered were Youngs modulus and porosity. Empirical models for both responses as a function of the input factors were developed and the optimum input factors setting were determined, and found to be at 5% nanoparticle content, 35 kV voltage, and 1 ml/h volume flow rate. The characteristics and performance of the optimum PVA/γ-Fe2O3 nanofiber mats were compared with those of neat PVA nanofiber mats in terms of morphology, thermal properties, and hydrophilicity. The PVA/γ-Fe2O3 nanofiber mats exhibited higher fiber diameter and surface roughness yet similar thermal properties and hydrophilicity compared to neat PVA PVA/γ-Fe2O3 nanofiber mats. Biocompatibility test by exposing the nanofiber mats with human blood cells was performed. In terms of clotting time, the PVA/γ-Fe2O3 nanofibers exhibited similar behavior with neat PVA. The PVA/γ-Fe2O3 nanofibers also showed higher cells proliferation rate when MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was done using human skin fibroblast cells. Thus, the PVA/γ-Fe2O3 electrospun nanofibers can be a promising biomaterial for tissue engineering scaffolds.

Hard turning of stainless steel using wiper coated carbide tool

In recent years, tool manufacturers provide wiper geometry on cutting tools for turning applications with the purpose of increasing productivity and improving surface finish. Despite the potential added values, the use and study on wiper inserts are still lacking in quantity. This current study focuses on the performance of wiper coated carbide insert in hard turning with respect to tool life and surface finish. AISI 420 stainless steel hardened to 47?48 HRC was hard turned at various speeds and feeds ranging in finish turning parameters. Results showed that the maximum tool life of 18 min was achieved and the tool life decreased at higher cutting speeds and feeds. Wear occurred at both the rake and flank faces with crater formation exposing the carbide substrate indicating more severe wear on the rake face. The wiper coated carbide tool resulted in very fine surface finish, much better than the theoretical values.

Effect of Silane Treatment on Mechanical Properties of Basalt Fiber/Polylactic Acid Ecofriendly Composites

Ecofriendly thermoplastic composites combining basalt fiber and polylactic acid were prepared and analyzed, considering effects when the fiber is silane treated. Intended to improve mechanical properties of the composites, the silane treatment varied the types of silane solution (water- and methanol-based solvents) and immersion time (15 and 60 min). Optimum mechanical properties were exhibited by composite whose basalt fiber constituent was treated by silane dissolved in water-based solvent, for a short period of time.

Machining parameters effect in dry turning of AISI 316L stainless steel using coated carbide tools

Austenitic stainless steel AISI 316L is used in many applications, including chemical industry, nuclear power plants, and medical devices, because of its high mechanical properties and corrosion resistance. Machinability study on the stainless steel is of interest. Toward sustainable manufacturing, this study also includes the power consumption during machining along with other machining responses of cutting force, surface roughness, and tool life. Turning on the stainless steel was performed using coated carbide tool without using cutting fluid. The turning was performed at various cutting speeds (90, 150, and 210 m/min) and feeds (0.10, 0.16, and 0.22 mm/rev). Response surface methodology was adopted in designing the experiments to quantify the effect of cutting speed and feed on the machining responses. It was found that cutting speed was proportional to power consumption and was inversely proportional to tool life, and showed no significant effect on the cutting force and the surface roughness. Feed was proportional to cutting force, power consumption, and surface roughness and was inversely proportional to tool life. Empirical equations developed from the results for all machining responses were shown to be useful in determining the optimum cutting parameters range.

A review of evolution of electrospun tissue engineering scaffold: From two dimensions to three dimensions:

The potential of electrospinning process to fabricate ultrafine fibers as building blocks for tissue engineering scaffolds is well recognized. The scaffold construct produced by electrospinning process depends on the quality of the fibers. In electrospinning, material selection and parameter setting are among many factors that contribute to the quality of the ultrafine fibers, which eventually determine the performance of the tissue engineering scaffolds. The major challenge of conventional electrospun scaffolds is the nature of electrospinning process which can only produce two-dimensional electrospun mats, hence limiting their applications. Researchers have started to focus on overcoming this limitation by combining electrospinning with other techniques to fabricate three-dimensional scaffold constructs. This article reviews various polymeric materials and their composites/blends that have been successfully electrospun for tissue engineering scaffolds, their mechanical properties, and the various parameters settings that influence the fiber morphology. This review also highlights the secondary processes to electrospinning that have been used to develop three-dimensional tissue engineering scaffolds as well as the steps undertaken to overcome electrospinning limitations.

Development of highly porous biodegradable γ-Fe2O3/polyvinyl alcohol nanofiber mats using electrospinning process for biomedical application

The use of electrospinning process in fabricating tissue engineering scaffolds has received great attention in recent years due to its simplicity. The nanofibers produced via electrospinning possessed morphological characteristics similar to extracellular matrix of most tissue components. Porosity plays a vital role in developing tissue engineering scaffolds because it influences the biocompatibility performance of the scaffolds. In this study, maghemite (γ-Fe2O3) was mixed with polyvinyl alcohol (PVA) and subsequently electrospun to produce nanofibers. Five factors; nanoparticles content, voltage, flow rate, spinning distance, and rotating speed were varied to produce the electrospun nanofibrous mats with high porosity value. Empirical model was developed using response surface methodology to analyze the effect of these factors to the porosity. The results revealed that the optimum porosity (90.85%) was obtained using 5% w/v nanoparticle content, 35kV of voltage, 1.1ml/h volume flow rate of solution, 8cm spinning distance and 2455rpm of rotating speed. The empirical model was verified successfully by performing confirmation experiments. The properties of optimum PVA/γ-Fe2O3 nanofiber mats such as fiber diameter, mechanical properties, and contact angle were investigated. In addition, cytocompatibility test, in vitro degradation rate, and MTT assay were also performed. Results revealed that high porosity biodegradable γ-Fe2O3/polyvinyl alcohol nanofiber mats have low mechanical properties but good degradation rates and cytocompatibility properties. Thus, they are suitable for low load bearing biomedical application or soft tissue engineering scaffold.

The Effect of Cutting Parameters on Power Consumption during Turning Nickel Based Alloy

Machining process should also consider environmental aspect, with power consumption as one of the criteria. Cutting parameters can be optimized to minimize power consumption. This paper takes a study on turning of nickel-based hastelloy under dry condition (no cutting fluid) which varies cutting speed (150, 200, and 250 m/min) and depth of cut (0.5, 1.0, and 1.5 mm). Power consumption of particular machining process at various cutting parameters was derived and calculated. It was found that minimum power consumption was shown when the turning process was performed at the lowest cutting speed and depth of cut.

Effect of Electrospinning Parameters Setting towards Fiber Diameter

Fabrication of nanofibers using electrospinning has recently attracted much attention for various applications due to its simplicity. Electrospinning has the ability to produce nanofibers within 100-500 nm. Some applications require certain fiber diameter. As a relatively new process, there are many electrospinning parameters that are believed to influence the nanofibers diameter. The purpose of this review is to identify and discuss the effect of some of those parameters, i.e. concentration, spinning distance, and applied voltage, and volume flow rate, to the nanofiber diameter during electrospinning process. It was concluded that fiber volume flow rate is proportional to fiber diameter while there is no agreement in reports on other parameters.