Papers by Keyword: Electropolishing

Abstract: Surface cleanliness and smoothness are essential criteria for pharmaceutical components and they hold significant importance. Smooth surface minimizes bacterial accumulation and facilitates easier cleaning, promoting hygiene. In the pharmaceutical industry, equipment often employs electropolished tube pipes within machine components as conduits for processed medicinal solutions. Electropolishing is a widely-used electrochemical method involving a metal anode to achieve a smooth surface finish. This research is to investigate the impact of electropolishing temperature and time on the surface roughness of the inner surface of stainless steel 316L cylinders used in the pharmaceutical industry. Studying the influence of temperature and electropolishing time variations on the lowest surface roughness value inside a cylinder material, and identifying appropriate testing according to the ASME BPE surface roughness standard of less than 0.38 μm. Additionally, this study involves measuring the inner surface roughness, morphological characterization using metallurgical microscopy and SEM, as well as conducting potentiodynamic testing to assess the effectiveness of electropolishing. Based on the conducted experiments, it can be concluded that the lowest surface roughness value is found in samples subjected to a temperature variation of 60°C with a 7-minute EP duration, yielding an average surface roughness of 0.177 μm. Operational conditions that meet ASME BPE criteria (< Ra 3.8 μm) are achieved at electrolyte temperatures of 50°C and 60°C, with electropolishing process durations of 3-7 minutes. The lowest corrosion rate obtained was 0.00274 mpy with a surface roughness reduction of 70.50%, demonstrating the effectiveness of the electropolishing process.

Abstract: The manufacturing industry has experienced tremendous growth in recent years. According to the Badan Pusat Statistik (BPS), the percentage of the manufacturing industry rise from 3.89% to 5.87%. This also applies to the pharmaceutical industry, where polishing of surface material is one of main factor in pharmaceutical industry. Electropolishing is one of the finishing stages that can be done to improve polishing of material surface. Electropolishing is an electrochemical polishing technique that incorporates an electrolytic-electric solution. This process works by dissolving a controlled anodic metal surface in an appropriate electrolyte. This makes it possible to increase the evenness of the metal surface. For the pharmaceutical equipmentded industry stipulates ASME BPE and ASME B46.1 standards for surface finish materials with an electropolish surface finish value is 0.38 µm. This study aims to determine the cathode-anode distance and time to electropolishing the surface of AISI 316L stainless steel material for pharmaceutical equipment with various suggested parameters. Metallographic and SEM (Scanning Electron Microscope) tests were also carried out to see the morphological results. The experimental results show that electropolishing with H₂SO₄ 98% (40% v) and H₃PO₄ 85% (60%v) solution, the distance and duration of the electropolishing process are correlated with each other; the closer and longer the process will give lower roughness results. The lowest roughness obtained is 0.141 µm with distance 5 cm and process duration of 10 minutes. For the corrosion rate is carried out using potentiodynamic polarization with a corrosion rate value obtained 0,001 mpy.

Abstract: This research aims to study the electropolishing conducted under vacuum status. The electropolishing can be used to finishing high purity components of SUS 316L to make them shine and without leaving residual stress, micro-cracks, etc. In the research, the electropolishing process parameters are selected, such as current density, degree of vacuum and polishing time to conduct the electropolishing experiment. The experimental results show that the bubbles attached to the surface of the work-piece in the vacuum state are reduced, thereby improving the surface roughness and surface pitting. The vacuum status in the process can improve the electropolishing process.

Abstract: Electropolishing has been widely used for surface finishing of metallic products in the industry, owing to its excellent capability of producing metallic components with a homogeneously smooth surfaces. However, this treatment is often constrained by the long duration required for the processing. Therefore, an improvement in this process is needed. The aim of this research is to introduce the use of electropolishing with circulated electrolytes for improving the surface finish of brass. In this work, electropolishing was carried out by using circulated H₂SO₄ electrolyte for 10 to 30 min in a customized electropolishing chamber. The effect of this treatment on surface morphology, surface roughness, and thickness reduction of the brass specimen was determined. The results showed a better capability of electropolishing with circulated electrolyte in decreasing the brass roughness, i.e., by 84%, than that without electrolyte circulation which only reached 45% during 30 min of the treatment.

Abstract: The typical manufacturing process of tubular metallic cardiovascular stents includes laser cutting, sand blasting, acid pickling, electropolishing, surface passivation, and cleaning. The most commonly used material for cardiovascular stents is stainless steel, such as SUS 304 and SUS 316. After the laser cutting process, substantial improvement of the stent surface morphology is required to obtain acceptable surface roughness, edge roundness, and reduction of surface defects. This study focuses on a novel post-treatment method of fluid abrasive machining to replace the conventional sand blasting and acid pickling processes, resulting in the surface smoothness and edge roundness that are suitable for cardiovascular stent fabrication. The dross deposition and striations retained after laser cutting can be significantly removed with fluid abrasive machining. Both DC current and pulse current electropolishing techniques were performed to attain the final surface and structural quality after the fluid abrasive machining process. The experimental results show that an extremely fine surface roughness and a satisfactory edge roundness can be achieved for stents through both DC current and pulse current electropolishing. The pulse electropolishing process is more effective than the DC current electropolishing process to achieve edge roundness with less weight removal.

Abstract: Electropolishing is an attractive method for surface smoothing of cardiovascular stent. This study investigated the effect of times of electropolishing on the surface characteristics both are upper surface and surface of the strut of cardiovascular stent after the by die sinking electrical discharge machining (EDM). The observed surface characteristics of the strut were recast layer, surface roughness and brightness. The weight analysis, and the reduction of the width strut were conducted. The recast layer was analyzed by optical microscope qualitatively, the surface roughness was measured by surface texture measuring instrument, the weight analysis and the reduction of width strut were calculated. The stent was made from steel AISI 316 L. The times which were used in the electropolishing were 3 minutes, 7 minutes, and 11 minutes. The experimental results show that the time for smoothing and brightening of stent at room temperature and low voltage 5 V is 7 minutes. The times affect the upper and EDM surface roughness, the weight of stent and the width of strut. The results show that increasing of times, than the value of surface roughness, the weight of stent and the width of strut will decrease, and vice versa. The average surface roughness of EDM surface after electropolishing is in the range of 3.49 – 1.62 µm. The average surface roughness of upper surface after electropolishing is in the range of 0.55-0.22 µm. The weight analysis show that the loss of weight is in the range of 0.12-1.12 %, and the reduction of width strut is in the range of 11.02 – 69.3 %.

Abstract: Malocclusion or improper teeth arrangement is the most common problem in the field of orthodontics. If the malocclusion is not corrected, it will promote more serious problems, such as bleeding gums, tooth decay, cavities, difficulty breathing and other problems. Currently, the most common technique used to cure the malocclusion is using treatment of orthodontic brackets. Normally, orthodontic brackets can be produced by machining, metal injection molding and investment casting processes. In the previous research, orthodontic brackets have been successfully produced using investment casting process. The investment casting is selected, since the technology was developed well in Indonesia which is shown by existing number of investment casting industries. However, surface roughness of the bracket produced by investment casting is still high, valued at 0.91 μm. On the other hand, surface roughness of the commercial orthodontic bracket is 0.53 μm. In this current work is focused on surface modification of investment casting brackets by using electropolishing. The best result shows that the surface roughness of cast brackets achieve up to 0.44 μm. It shows that opportunity to fabricate orthodontic brackets domestically is applicable.

Abstract: In this paper, we present electropolishing method to fabricate a thin-structural layer of microfilter which is used for filtering blood in hemodialysis system. The electropolishing method removes material based on electrolysis process, in which material removal is done through electrical current which trigger material removal by chemical reactions. The preliminary experiment shows that the SS 316L structural layer was able to be fabricated in less than 7 minutes, under machining parameter of 7 V of DC voltage, 2 cm gap between tool electrode and workpiece, and utilizing 15% of NaCl in pure water. This promising result has indicated that electropolishing could further be used as a method to make thin-structural layer of microfilter for hemodialysis system.

Abstract: This study presents an integrated approach to the teaching of surface metrology and the regulation of electrochemical polishing process control parameters. The electropolishing processes permits different ranges of surface finish through different combinations of the process parameters of current density (J) and electropolishing time (t), and students must have a sound knowledge of the procedure for selecting filters (λ_s, λ_c, λ_f). Thus, experimental trials are undertaken to establish the influence of current density (J) and electropolishing time (t) on surface finish by measuring the arithmetic average roughness parameter (Ra), and setting the filters and measurement procedure for each range of surface finish. The integrated learning of both disciplines enables students to consolidate their knowledge on the methodology for measuring surface roughness (Ra), and to establish direct correlations between variation in process control parameters and the surface finish obtained by characterizing the behaviour of the process.

Abstract: For hard disk drives (HDD), loose particles that are trapped between the head and disk during HDD operations can create damages to HDD. As a result, a nickel coating is used to minimize their loose particles. However, nickel is one of many carcinogenic metals known to be an environmental and occupational pollutant. Therefore, an electropolishing technique is proposed to replace a nickel coating process. To do experiments, a stainless steel actuator arm is set as an anode, a steel plate is set as a cathode, and a sulfuric acid is used as an electrolyte. With a design of experiment (DOE) technique, four parameters of the electropolishing technique which are an electrolyte concentration, an electrolyte temperature, a polishing time, and an electric intensity, are tested. The experiment result shows that the electrolyte concentration and electric intensity are not made any change for loose particles counts with liquid particle counter (LPC) testing whereas only two parameters which are the electrolyte temperature and polishing time play significant roles for LPC values. The lower LPC shows the smaller percentage of HDD failure. From these Box-Behnken DOE experiments, the optimal solution is 90 Celsius of the electrolyte temperature and 40 minutes of the polishing time. Although, the electrolyte concentration and electric intensity are not made any impact for LPC but they are set as a standard to be 0.2 mol/l and 0.25 A/cm² consequently. With these parameters, the predicted LPC is only 442,106 counts/part. This LPC is still in an accepted level standard that will not cause failure to HDD. This means that the electropolishing technique initially can be used to replace a nickel coating process without loose particles.