Modeling and Numerical Analysis of Advanced Machining for Orthotic Components

Modeling and Numerical Analysis of Advanced Machining for Orthotic Components

Pankaj Charan Jena (Veer Surendra Sai University of Technology, India), Barsarani Pradhan (Veer Surendra Sai University of Technology, India) and D. Dhupal (Veer Surendra Sai University of Technology, India)
DOI: 10.4018/978-1-5225-8235-9.ch010

Abstract

Electrochemical micromachining plays a vital role in the advanced machining domain. Particularly, it helps the medical industry in machining micro-level devices in hardened materials. Though it is maintaining a very small inter-electrode gap during machining, it is required to understand suitable machining parameters before machining. These parameters can be achieved by proper modeling and simulation. In this chapter, a model for flow analysis of electrolytes in inter-electrode gaps is designed to obtain optimal process parameters for machining. The geometric model used in this simulation consists of cylindrical workpiece, an inlet allowing the flow of sodium nitrate solution as electrolyte to the machining zone, and a cylindrical tool with a flat end. Electrolytic flow simulation is incorporated using computational fluid dynamics by ANSYS–CFX 15.0 for finding pressure variation, streamline velocity pattern, turbulent energy, and temperature contour in IEG. According to the CFD analysis, the passivation effect, stagnation effect, pressure, and temperature zone are studied.
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Introduction

Electrochemical micro machining plays a vital role in advanced machining domain. Particularly it helps to medical industry to machining in micro level devices in harden materials. Currently Biomedical instruments are more micro in size and high accuracy. Manufacturing and selecting suitable machining process of such instruments are a challenge for present researchers. Electrochemical process is one of the advanced machining processes and can be possible to manufacture micro sized medical instruments like nozzles, tubes, etc.

Though it is maintaining a very small inter electrode gap during machining therefore it is required to understand a suitable machining parameters before to machining. These parameters can be achieved by proper modeling and simulation. In present research a model for flow analysis of electrolyte in inter electrode gap is designed to obtain optimal process parameter for machining.

Material removal of the dimension ranging between 1.0 micrometers to 999.0 micrometers comes under micromachining. Using conventional micromachining for producing these shapes has its own share of limitations, which include high tool wear rate, thermal stress, and imperfect surface finish. To overcome these limitations, researchers are exploring new non-conventional micromachining technique. One such technique is Electrochemical micromachining (ECMM) having advantages like tool having no wear, stress-free surfaces, machining electrically conductive material regardless of physical as well as chemical property, bright surface finish. ECMM is workedon anodic suspension at atomic level in electrolyte. This problem can be modeled and simulated by studying the flow pattern of electrolyte. This information in turn will help to avoid the passivation, which is one of the major problems in ECMM related to complex shape machining. Another problem, which is associated with ECMM, is generation of hydrogen gas at cathode. As electrolyte passes through cathode, it absorbs hydrogen gas generated at cathode. Due to this absorption, electrical conductivity of electrolyte decreases. As MRR and surface finish in ECMM is directly dependent on the electrical conductivity of the electrolyte, a decrease in it will hamper the machining rate and surface finish of work piece. In order to avoid all these, we need to know the source, effects, & pattern of hydrogen bubble generation. How it affect various critical parameters and overall machining performance.

Table 1.
Major machining characteristics of ECMM
          Major Machining Characteristics of ECMM
  Voltage  < 10
  Current  < 1 A
  Current Density75-100 A/
  Power supply -DC  Pulsed
  Frequency  KHz-MHz range
  Electrolyte flow  < 3 m/s
  Electrolyte temperature37-
  Electrolyte type  Natural salt or dilute acid/alkaline solution
  Electrolyte concentration  < 20 g/l
  Size of the tool  Micro
  Inter-electrode gap  5-50µm
  Operation  Mask/maskless
  Machining rate  5µm/min
  Side gap  < 10µm

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