3D Surface Finishing Using Magnetorheological Finishing

Under the guidance ofDr. Sunil Jha

Presented by

Amitesh kumar

(2010MEP2968)

CONTENTS

• Introduction• Literature Review • Experimental Setup• Motivation and Objective• 4th axis integration• Experimentation• Results and conclusion• Scope of future work• References

Introduction

• Huge demand of good surface finish in different industries specially automotive, aerospace, mold manufacturing etc.

• All traditional finishing processes are incapable of producing required surface finish of nanometer level for these industries.

• A number of processes like Abrasive Flow Machining (AFM), Magnetic Abrasive finishing (MAF), Magnetic Float Polishing (MFP) etc. have been developed.

• Magnetorheological (MR) finishing is one of the processes which can provide surface finish up to nano meter level

MR Fluid

Constituent % volume concentration

Carbonyl iron powder 20

Silicon carbide 20

Base fluid medium 60

Changes in rheological behaviour in presence of external magnetic field.

Iron particles acquire dipole moment in presence of magnetic field and is proportional to field strength.

(a) Abrasives & Carbonyl iron particles at zero magnetic fields

(b) Abrasive particles embedded in Carbonyl iron particle chains on application of external magnetic field [2]

No finishing action in absence of external magnetic field [2]

Finishing action on a single profile in presence of external magnetic field[2]

Literature Review• Design and development of Magnetorheological Abrasive flow

finishing process by S. Jha and V. K. Jain (2004) • It was observed that chain formation takes place in

magnetorheological fluid on application of external magnetic force.

• It was also observed that surface roughness reduces with increase in magnetic field.

Change in rheological behaviour of MR fluid during finishing [2]

• Seok et al. (2008) [3] has proposed magnetorheological finishing process for hard materials using sintered iron-CNT compound abrasives.

• It was observed that material removal rate increases with rotational speed of tool upto a certain critical value (500 rpm) and decreases for speed beyond this critical value.

• It was also observed that if the rotation speed of tool is increased to increase the material removal rate, the centrifugal force acting on CI particle plays an adverse role.

• A. Sidpara & V. K. Jain (2010) [4] investigated the role of different parameters on force.

• It was observed that the contribution of working gap on forces developed was observed maximum followed by CIP concentration while the least contribution was observed for rotating speed.

Experimental setup at IITD

Schematic of existing setup installed at IIT DELHI[1]

Electromagnetic model of MR finishing tool [1]

Shape of magnetic flux density generated at the MR finishing tool [1]

Magnetic flux density at the interface between MR fluid and work surface [1]

Motivation and Objective• For an inclined surface, the outer surface of the MR fluid

touches the work surface where the magnetic field intensity is very less as compared to centre.

% improvement in finish

No of finishing passes

Ra (nm) of flat surface

Ra(nm) of 30° surface

Ra(nm) of 45° surface

Ra(nm) of curve surface

0 1334.1 1452.3 2739.3 1754.7

15 812.3 1296.1 1949.4 1513.2

39.13 10.74 28.84 13.74

Objective

• Integration of rotary axis on to machine for tool tilting.

• Experimentation on 3D MRF Machine for verification of improvement in surface finish

4th axis integration

To give the 4th axis motion to the existing setup, these components are being used:

Rotation stage Stepper motor Stepper drive

MRS series Holmarc rotation stage Tool post to be mount on rotation stage

Stepper motorStepper drive

Rotation control of rotary stage by computer

Rotary stage with stepper motor mounted on vertical slider

Proposed setup after integration of 4th axis

Perpendicular angle between tool and workpiece after 4th axis integration

Experimentation

• Preparation of workpiece• Fluid preparation• Surface finishing with MR fluid

• Motion control with the help of software • Measurement of surface finish using Taylor Hobson Talysurf

Preparation of workpiece

Fluid preparationConstituent Density (gm/cm³)

Base fluid 0.638

CIP 7.8

SiC 3.22

Densities of MR fluid constituents

Carbonyl iron powder silicon carbide powder

• Total sample of MR fluid prepared = 500 cm³

• CIP by volume = 100 cm³ = 100×7.8gm/cm³ = 780 gm

• SiC by volume=100 cm³ = 100×3.22 gm/cm³ = 322 gm

• volume of base fluid = 300 cm³ = 300×0.638 gm/cm³ = 191.4 gm

• These three components of MR fluid in above mentioned proportion was mixed and stirred in funnel. Thus required MR fluid has been prepared for conducting experiment.

Parameters used for experimentation

Parameter Conditions

Rotational speed of tool core 500 rpm

Current 4A

Working gap 0.66mm

Workpiece material Ferromagnetic

SiC abrasive mesh number 800

Speed of stepper motor 1 rps

Experimental setup with integrated 4th axis

Motion control with the help of software

• Two software have been used:– ACR View 1505 – Pro E wildfire 4

For a particular motion, programming is done to generate the path of the tool.

To generate the path, either code generated in pro E can be used or code can be written manually in ACR View.

ACR1505 code used to control the motion of tool:

Flat surface 30º inclined surface 45º inclined surface

PROGRAM RES X Y Z A VEL 1 MOV Y/20 MOV X/2 MOV Y/-20 MOV X/2 MOV Y/20 MOV X/2 MOV Y/-20 MOV X/2 MOV Y/20 MOV x/2 MOV Y/-20

PROGRAM RES X Y Z A VEL 1MOVA/-20 MOV Y/20 MOV z/1 x/-1.732 MOV Y/-20 MOV z/1 x/-1.732 MOV Y/20 MOV z/1 x/-1.732 MOV Y/-20 MOV z/1 x/-1.732 MOV Y/20

PROGRAM RES X Y Z A VEL 1MOVA/-10 MOV Y/20 MOV z/1.414 x/-1.414 MOV Y/-20 MOV z/1.414 x/-1.414 MOV Y/20 MOV z/1.414 x/-1.414 MOV Y/-20 MOV z/1.414 x/-1.414 MOV Y/20 MOV z/1.414 x/-1.414

Important terminology used in ACR View programming:

• RES X Y Z A• VEL• MOV• ENDP

For step over along inclined plane, the two axis changes its coordinate accordingly

Manual programming

z h

x

a

b

Z= h sinαX =h cosα

Result and conclusion

• Perpendicular angle between tool tip and work surface can be achieved for any surface after integration of 4th axis

Setup for finishing flat surface Tool tilting for 30° surface

Tool tilting for 45° surface Tool tilting for curve surface

Surface roughness with 3 axis setup [1]

No. of finishing passes

Ra (nm) of flat surface

Ra (nm) of 30º surface

Ra (nm) of 45º surface

Ra (nm) of curve surface

0 1334.1 1452.3 2739.3 1754.7

15 812.3 1296.1 1949.4 1513.2

%ΔRa -39.13 -10.74 -28.84 -13.74

Surface roughness with 4 axis setup

No. of finishing passes

Ra (nm) of flat surface

Ra (nm) of 30º surface

Ra (nm) of 45º surface

Ra (nm) of curve surface

0 145.4 120.7 142.6 164.8

15 69.3 61.4 76.7 97.7

%ΔRa - 52.33 -49.13 - 46.21 -40.71

Comparison of improvement in surface finish after 15 passes

Conclusion

• With 3 axis setup, improvement in surface finish varies significantly for different surfaces.

• Much improvement has been observed in the case of flat surfaces with respect to inclined or curved surfaces.

• improvement in surface finish is almost same for flat as well as curved or inclined surface after integration of 4th axis .

• Tool tilting provides perpendicular angle between the tool tip and the work surface, so maximum magnetic field intensity can be used to get better surface finish

Scope for future work

• Surface like sphere can not be finished by existing setup. 5th and 6th axis can be integrated to finish more complex geometry.

• Requirement of a mechanism to reduce the temperature of the coil while applying high current so that continuous finishing can be done for longer period of time

References• [1] A.K.Singh, S.Jha, P.M. Pandey, Design and development of nanofinishing process for

3D surfaces using ball end MR finishing tool, International Journal of Machine Tools and Manufacture 51 (2011) 142-151.

• [2] S. Jha, V.K. Jain, Design and development of magnetorheological abrasive flow finishing (MRAFF) process, International Journal of Machine Tools and Manufacture 44/10 (2004) 1019-1029

• [3] Bongsu Jung, kyung-In-Jang, Byung-Kwon Min, Sang Jo Lee, Jongwon Seok , Magnetorheological finishing process for hard materials using sintered iron-CNT compound abrasives, International Journal of Machine Tools and Manufacture, 49 (2009) 407-418.

 • [4] A.Sidpara, V.K. Jain, Experimental investigations into forces during

magnetorheological fluid based finishing process, International Journal of Machine Tools And Manufacture 51 (2011) 358-362.

• [5] S.Jha ,V. K. Jain, Modeling and simulation of surface roughness in

Magnetorheological abrasive flow finishing (MRAFF) process, Wear 261(2006) 856-866.

Thank you