5 th International & 26 th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12 th –14 th , 2014, IIT Guwahati, Assam, India 536-1 APPLICATIONOFPUREWATER JET MACHINING FOR IMPROVING SURFACE FINISH OF PARTS FABRICATED BY ABRASIVE WATER JET MACHINING Vijay Kumar Pal 1* , S.K. Choudhury 2 1* Ph.D. Scholar, Indian Institute of Technology Kanpur, Kanpur, 208016, Email: [email protected]2 Professor, Indian Institute of Technology Kanpur, Kanpur, 208016, Email: [email protected]Abstract Fabrication of 3-D features is a major research interest in Abrasive Water Jet (AWJ) process, but the poor surface quality of machined components restricts the process for being widely used. Present work initially focuses on fabrication of micro channels by AWJ and analyses the effect of process parameters namely pressure, traverse speed and stand-off distance on depth and surface finish of samples machined. Experiments were performed on Ti-6Al-4V alloy of 1 mm thickness sheet and Central rotatable Composite Design (CCD) test matrix with an alpha value of 1.68 was used for design of experiment. The correlations between the process parameters and responses like depth and surface roughness were established by multiple linear regression models. Experimental observations show that the depth is affected most by pressure, followed by traverse speed. The combination of high pressure and fast traverse speed results in a quite smooth surface because high pressure provides sufficient jet energy for smooth fracture. Second part of this paper presents an innovative path strategy to improve surface quality of machined samples. Here, AWJ was used for rough/stock removal of material followed by pure water jet (PWJ) along the same path (movement of the nozzle) as a final cut to improve surface quality of machined samples. 3-D optical profilometer with objective lens (5x) and field of view (FOV 2x) along with the SPIP software was used to measure geometry and profile of slots. Digital microscope of 230x and a scanning electron microscope (SEM) were used to observe and analyse the micro structure of the machined pockets. The SEM investigation demonstrated that for all the samples machined by PWJ (as finishing pass), the material removal mechanism is uniform and surface was found smoother than in case of AWJ and embedded particles were also removed to a certain extent. Keywords: Abrasive water jet (AWJ), pure water jet (PWJ), Traverse speed, 3-D optical profilometer, SEM 1 Introduction Pure water jet machining (PWJ) was traditionally used for cutting soft materials, cleaning and removal of coating in early 70s. Abrasive particles were mixed with high velocity water jet to improve the efficiency of the process in terms of material removal rate and making it possible to cut a wide variety of materials ranging from soft to hard. Now, Abrasive water jet machining (AWJM) has become a significantly emerging manufacturing process with its enormous capabilities of machining different materials and high speed of cutting. Initially AWJM technique was used only for shape cutting (through cuts) of different materials. It is a non-conventional machining process in which a mixture of abrasive particles with high pressure water was converted to a high velocity jet for cutting. The high speed abrasive water jet machining employed the erosion phenomenon for material removal when the abrasive particles along with high velocity water hit the target surface as explained by Finnie, (1960). Less fixture requirements and almost no heat affected zones due to non-contact between the cutting tool and work piece are some of the major advantages of this technique. Process primarily depends on the following input parameters – abrasive flow rate, traverse speed, standoff distance (SOD), water jet pressure, shape and size of abrasive particles. This process is well established for through cutting and most of the works reported was based on through cutting by AWJM. Nowadays, researchers have also started experimenting on generating blind features using AWJM. For generating blind features like pockets and channels, several authors used the multiple passes linear traverse cutting as milling strategy. This principle is based on the superposition of several passes to obtain a cavity of defined geometry. The
6
Embed
APPLICATIONOFPUREWATER JET MACHINING FOR … · 2014-12-14 · Fabrication of 3-D features is a major research interest in Abrasive Water Jet ... abrasive water jet machine (OMAX
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
5th International & 26th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12th–14th, 2014,
IIT Guwahati, Assam, India
536-1
APPLICATIONOFPUREWATER JET MACHINING FOR IMPROVING
SURFACE FINISH OF PARTS FABRICATED BY ABRASIVE WATER
JET MACHINING
Vijay Kumar Pal1*, S.K. Choudhury2
1*Ph.D. Scholar, Indian Institute of Technology Kanpur, Kanpur, 208016, Email: [email protected]
2Professor, Indian Institute of Technology Kanpur, Kanpur, 208016, Email: [email protected]
Abstract
Fabrication of 3-D features is a major research interest in Abrasive Water Jet (AWJ) process, but the poor
surface quality of machined components restricts the process for being widely used. Present work initially
focuses on fabrication of micro channels by AWJ and analyses the effect of process parameters namely pressure,
traverse speed and stand-off distance on depth and surface finish of samples machined. Experiments were
performed on Ti-6Al-4V alloy of 1 mm thickness sheet and Central rotatable Composite Design (CCD) test
matrix with an alpha value of 1.68 was used for design of experiment. The correlations between the process
parameters and responses like depth and surface roughness were established by multiple linear regression
models. Experimental observations show that the depth is affected most by pressure, followed by traverse speed.
The combination of high pressure and fast traverse speed results in a quite smooth surface because high pressure
provides sufficient jet energy for smooth fracture. Second part of this paper presents an innovative path strategy
to improve surface quality of machined samples. Here, AWJ was used for rough/stock removal of material
followed by pure water jet (PWJ) along the same path (movement of the nozzle) as a final cut to improve
surface quality of machined samples. 3-D optical profilometer with objective lens (5x) and field of view (FOV
2x) along with the SPIP software was used to measure geometry and profile of slots. Digital microscope of 230x
and a scanning electron microscope (SEM) were used to observe and analyse the micro structure of the
machined pockets. The SEM investigation demonstrated that for all the samples machined by PWJ (as finishing
pass), the material removal mechanism is uniform and surface was found smoother than in case of AWJ and
embedded particles were also removed to a certain extent. Keywords: Abrasive water jet (AWJ), pure water jet (PWJ), Traverse speed, 3-D optical profilometer, SEM
1 Introduction
Pure water jet machining (PWJ) was traditionally
used for cutting soft materials, cleaning and removal
of coating in early 70s. Abrasive particles were mixed
with high velocity water jet to improve the efficiency
of the process in terms of material removal rate and
making it possible to cut a wide variety of materials
ranging from soft to hard. Now, Abrasive water jet
machining (AWJM) has become a significantly
emerging manufacturing process with its enormous
capabilities of machining different materials and high
speed of cutting. Initially AWJM technique was used
only for shape cutting (through cuts) of different
materials. It is a non-conventional machining process
in which a mixture of abrasive particles with high
pressure water was converted to a high velocity jet for
cutting. The high speed abrasive water jet machining
employed the erosion phenomenon for material
removal when the abrasive particles along with high
velocity water hit the target surface as explained by
Finnie, (1960). Less fixture requirements and almost
no heat affected zones due to non-contact between the
cutting tool and work piece are some of the major
advantages of this technique. Process primarily
depends on the following input parameters – abrasive