Modeling and Numerical Analysis of Advanced Machining for Orthotic Components

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.

Major Machining Characteristics of ECMM
Voltage	< 10
Current	< 1 A
Current Density	75-100 A/
Power supply -DC	Pulsed
Frequency	KHz-MHz range
Electrolyte flow	< 3 m/s
Electrolyte temperature	37-
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