Applied Mechanics and Materials Vol. 842

Abstract: This paper described a methodology to simulate production activities by using object-oriented programming language. Simulation of production to be modeled are the production activities in a workshop. The first step of modelling was defining objects that constitute the main part of a machining center. The main part of machining-center which was being modeled are column spindle, pallet fixture, pallet changer and tool magazine. From these objects can be created a new object that was an object of machining center. The next step was modeling pallet stocker and stacker crane. Pallet Stocker is a container used to store the workpiece or product on the pallet. A stocker crane is a device used to move a workpiece from the pallet stocker to a machining center or vice versa. The final step was modeling a workshop in which there are some machining centers, pallet stocker and stocker crane. Object modeled can be used to simulate a workpiece transfer activity undertaken by stacker crane from the pallet stocker to the machining center.

Abstract: Generally, a maintenance process of a machine tool is oriented to maintain its reliability and availability in a relation of its productivity. This productivity will make a direct impact on the economic aspect of its plant. Ecomaintenance is a maintenance concept which sees maintenance in a different perspective. There is another effect on a machine that is maintained well on the environmental aspect beside its benefit of technology and economic aspects. If a machine is maintained with a proper maintenance, it will have a performance suitable with its age design condition. A machine with a good maintenance generally has a minimum rate of pollutant and waste which is possible emerging from the machining process. Then, if it uses for a machining process, it will produce a good quality product on its surface roughness and dimension accuracy. The electrical energy consumption of the machine also can be saved. It means that the GHG which usually emerges from the process of electrical energy generation in the power plant can be minimized, also the coal as fuel can be saved. The result of experiment has proven that the machine with bad maintenance will consume the electrical power higher in range 10%-60.81% than the machine with a good maintenance.

Abstract: Batik is one of the Indonesian heritage culture that needs to be preserved, especially for traditional batik using wax to form batik pattern and resist dyeing color. One way to draw batik on fabric is by using a stamp. Nowadays, most of traditional batiks are still produced manually with limited capacity. On other hand, the number of batik craftsman is decreased due to lack of regeneration of young craftsman. This study aimed to develop software for designing stamped batik, along with its production steps, and information used to execute the design on batik machine with moving module. The software required a batik stamp design, size of fabric (maximum 12 m), pattern of stamping, and color. Digital image of the batik design and its colour will be generate along with the G-Code for executing the design on batik machine with moving module. Batik machine with moving module consists of 13 meters working table and a bridge runs along the table by carrying stamp and wax module. For each step of the bridge, stamp module will stamp wax on fabric along its width. These movements are controlled by programmable computer with G-Code from batik design system. Batik design system and the machine have been tested and is able to give information about size of fabric used, kind of dye used, and G-Code for controlling the machine.

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: Hydroxyapatite (Ca₁₀(PO₄)₆(OH₂), HA has similarities with human bone mineral composition and morphology, bioactive, and non-toxic. However, HA has a weakness in the decay of material, so it can inhibit the growth of new bone tissue. The other materials used as biodegradable bone substitute are Tri Calcium Phosphate (TCP). It has the reception of the body is almost as good as HA but it have fast decay time, so that the material has been discharged before the newly formed tissue. This study aimed to developed a Biphasic Calcium Phosphate (BCP) which is a combination of the properties of HA and TCP, it makes the decay time can be in accordance with the growth of new bone tissue. Calcination method was used in this study. Four groups of bovine bone samples were calcined at four different temperatures ranging from 1000^oC to 1300^oC using the electric furnace. The heating rate during calcination process was 5^oC/minute and dwell time of 2 hours. The calcined bioceramics samples are being examined to determine the characterization of materials. XRD testing to determine the chemical compounds, FTIR performed to determine the ionic bonds that exist in materials and SEM to determine the microstructure of the material calcination results. The current investigation confirms the possibility of producing porous BCP bone graft from porous bovine bone cube, without any important impurities as indicated by XRD and FT-IR techniques. The partially decomposition of HA into TCP was started when bovine bone samples were heated at 1200^oC.

Abstract: Dynamic Compression Plate (DCP) is a plate made of biomaterials like stainless steel 316L (SS-316L) or titanium, which is used for joining fractured/broken bones for fast recovery. Due to its excellent properties on corrosion, toughness, and hardness; SS-316L is widely used for medical application. Despite its excellent properties, the surface of SS-316L commonly degraded after machining. Therefore, the surface of SS-316L needs to be treated before further use. Shot peening is one of the methods to increase the surface hardness and roughness of material. This research aims to investigate the effect of shot peening to the surface of DCP made of SS-316L from its microstructures, surface roughness, and hardness. In this research, the DCP is designed for joining arms, which are upper-arm (humerus) and forearm (radius and ulna). First we machined the DCP to have holes and bend the plate to match the user bone structure. The DCP is 105 mm × 12 mm × 4 mm in dimension and has 6 holes, 5 mm diameter each, with holes aligned to the plate. After machining, the surface is modified by shot peening using following properties: steel ball (0.4 mm in diameter and hardness 250 HV), 100 mm nozzle-to-plate distance, and shot for 10 minutes. Our parameters are variations in pressure, ranging from 4 to 6 bar. The microstructure of the treated surface was analyzed after shot peening. The result shows that the shot peening treatment of SS-316L has increases its surface hardness and roughness with significant change on its microstructure, which makes a better surface characteristics for DCP.

Abstract: Exoskeleton is an external cantilever to support inner living organism organs. Some animals have the exoskeleton attached naturally on their body as those found in a million species of arthropods order. The word “Arthropods” itself are related to their body plan—their segmented body, hard exoskeleton, and jointed appendages [1]. This structure inspired us to implement the exoskeleton to help humans who are permanently or temporarily have problems with their lower limb, for example those who are recovering from stroke or road-accidents. Stroke is a condition where lower limb is partially paralyzed (Hemiplegia) and causes inability to walk normally or to do other physical activities [2].The exoskeleton consists of four main parts; frame for the leg (XOTF), frame for the thigh (XOF), the belt, and the controller stick. The frame is designed using lightweight material. Considering the material’s availability and price at the local market, we choose Aluminum Composite Panel (ACP) as frame’s material. The belt acts as the brain for the exoskeleton, where it provides electrical power and the source of motion. There are four frames on the exoskeleton which moves simultaneously while walking. In the design, we use two joy-sticks as main controller to adjust position of each exoskeleton frame. The sticks are attached to standing-canes which help the user to improve stability. The sticks have buttons and lever to control the exoskeleton and adjust thighs and legs fit for several moves; stand, sit, walk, going up and downstairs, or any other position which need balance and power.The exoskeleton design has been tested for its motion and stability. The results show that the design is suitable for those who are fully or partially paralyzed on their lower limb.

Abstract: Shot-peening is one of the surface modification methods to increase material hardness and smoothen its surface at the same time. SS-316L, one type of biocompatible material, is commonly used in medical field particularly for joining fractured bones. However, the surface-crack-prone characteristic of SS-316L has limited its application to be used for such application. In this research, steel balls with diameter 0.4 mm is subjected to the surface of SS-316L Osteosynthesis Plate with variation of time; 9, 10, 11 and 12 minutes holding at constant pressure of 6 bar. The nozzle-to-plate distance is fixed at 100 mm. The impact of the shot balls is a deformed surface and produces a flat-like structure on osteosynthesis plate shot in 12 minutes time. The result shows that shot peening of SS 316L gives its best microstructure after 12 minutes of treatment.

Abstract: An invalid is a person with physical or mental abnormalities which hinders their ability of doing normal human activities. One of the aforementioned abnormalities is the loss or malfunction of a body part or organ, such as the human leg. Problems brought about by this disability could be alleviated by the use of prosthetic limbs to restore normal bodily functions [1]. While there are many needs for leg prosthetics in Indonesia, the price of commercially available prosthetic is prohibitively high for most amputees. The current available affordable prosthetics are very basic and employ monocentric knee joints. Here an attempt is made towards acquiring an optimal design of an affordable prosthetic leg using previously developed four-bar knee joint [2,3]. The design is carried out by implementing a systematic design method to arrive at an affordable, yet ones with better performances. The procedure involves a rubric and analyzing various alternatives to arrive at an optimal design conclusion. The evaluation objective is to maximize the performance of the leg and knee prosthetics through an extensive analysis with considerations from various stakeholders, including the potential users, fabricator, and hospitals in Indonesia [4]. The final design of the leg consists of a composite socket, an aluminum pylon, and a solid-ankle cushioned-heel foot design. Its components are modular and compatible with prosthetic industry standards. The knee is made of a combination of polymers and stainless steel and employs a polycentric mechanism in order to satisfy design requirements while keeping costs low [4,5]. The leg and knee were then fabricated according to the analysis results. The total cost of fabrication is approximately 5.5 million IDR, significantly cheaper than commercial prosthetics. The prototype is then tested and examined using a gait analysis system previously developed at Institut Teknologi Bandung by the Biomechanics Research Team [6]. The results show satisfactory performance, albeit with a host of potential improvements.