MAGNETIC ABRASIVE FINISHING

DETAILS OF maf

1. Department of Mechanical &Industrial Engineering Indian Institute of Technology Roorkee MAGNETIC ABRASIVE FINISHING OF CERAMICS Submitted to :Dr. A K Sharma Associate Professor

2. Introduction In today’s advanced industries the designer’s requirment on component are stringent. New and advanced material are developed which having good properties like- Hardness, Strength,toughness etc. Finishing and machining of these advanced material is difficult task. When finishing of these material is to be done by conventional method, it does not give good result. These material can be finished by Advanced finishing processes.

3. Classification of Micro/Nano finishing Micro/Nano finishing Traditional Advanced Grinding Lapping Honing Shape and size constraint AFM MAF MRF MFP

4. Magnetic abrasive finishing(MAF) MAF is micro/ nano finishing process in which the material removed in the form of micro chips. In this process the granular magnetic abrasive particle are used to remove the material. These magnetic abrasive particle are composed of ferromagnetic material( Iron,steel grit) and abrasive grains( Alumina, SiC , CBN, Diamond ). Magnet is used in this process which is either permanent magnet or electromagnet.

5. Continued… These magnetic abrasive particle are bind together due to magnetic dipole intraction . Magnetic abrasive particle are two types: Bonded magnetic abrasive particle Unboned magnetic abrasive particle Bonded magnetic abrasive particle are prepared by sintering process. Its give the better finishing properties. But processing cost is high. Unbonded magnetic particle are prepared by mechanical mixing of ferromagnetic and abrasive particle.

6. Schematic diagram of MAF Schematic diagram of cylindrical and flat surface finishing using MAF Source:( Shinmura et.al 1990, V.K Jain 2009)

7. Principle: When the magnetic field applied. The magnetic abrasive particle get magnetized and alinged along the magnetic lines between the S and N poles. Magnetic abrasive particle collected and forms the flexible magnetic abrasive brush(FMAB). The strength of this FMAB depends on various factor like:Working gap, Magnetic field intensity etc. FMAB behaves like a multi point cutting tool to remove the material in the form of micro chips.

8. Continued… Abrasive particle present in the MAP taken into part of cutting action. Due to magnetic field, force are acting on the magnetic abrasive particle. This force has two component. is acting along magnetic force line and it is responsible for the penetration in the workpiece and is acting along equipotential magnetic lines which is responsible for shear off (finishing) of the material.  

9. Mechanism of cutting when, Rt < Fm Rt > Fm Schematic of magnetic field distribution and magnetic force acting on a ferromagnetic particle ( Chang et.al.(2001 ))

10. Process parameter In this process quality characterstics is surface roughness and material removal, surface integrity. Which are controlled by different process parameter. Magnetic flux density Working Gap Rotational speed Size and type of the magnetic abrasive Mixing ratio Voltage Maching time

11. Different parameter which affect the process performance Fishbone diagram of parameters of MAF

12. Application: MAPs is used for finishing of ceramics component like load bearing component ,translucent aluminum discharge lamp, advanced ceramics silicon nitride bearing for high speed spindles. It is also used for internal finishing of tubes like vaccume tubes,sanitary tubes,capillary tube in medical field( Stents, Cathater shafts, Needles, Biopsy Needles),curved pipes etc.

13. Ceramics Ceramics are inherently brittle and failure of parts made from these materials are initiated by cracks formed during machining as well as by other defects. Ceramics are generally oxide,nitride,carbide material. It is harder than metal and it has high wear resistance properties. This process most suitable for finishing of ceramics because of there is no micro cracks & surface defects after finishing when using MAF.

14. PROPERTIES OF CERAMICS: Alumina Excellent dielectric properties Good thermal conductivity High strength and stiffness Hard and wear resistance Application:High temperature electrical insulators, Electronic substrates ,load-bearing components, translucent aluminum discharged lamps etc. Silicon Nitride High strength over wide range of temperature. High fracture toughness High hardness Outstanding wear resistance. Application:Rotating bearing balls and rollers, Engine wear parts(cam followers) etc.

15. Finishing of Alumina ceramics with MAF: Workpiece is alumina ceramics tube. The abrasive particle used is diamond. Iron particle is used as a ferromagnetic material. Earlier alumina ceramics is finished by chemical eatching process. It has some drawback like chemical deposition and contol on surface quality. Lubricants is used to reduce friction, improve cooling and also bind the abrasive particle with ferromagnetic material.

16. Effect of process parameter: Volume of lubrication: The increase of the lubricant must sustain the required condition for the smooth relative motion of the abrasive against the inner surface of the tube.(optimum value 0.3 ml) To much lubrication washes out the abrasive which decrease the cutting edges which results to reduction in MRR and surface finish. Effect of particle size: When abrasive particle size decrease, surface finish increases where as MRR decrease. When ferromagnetic particle size increase the MRR increase and also upto the some extent surface finish increase after that it decreases .

17. Table:Effect of parameter on roughness (Yamaguchi et al. 2004) (parameter) in ml Surface Roughness(µm) Time (min) MRR Lubrication concentration volume 0.1 0.2 0.25 0.3 0.35 0.66 0.81 0.32 0.38 0.57 5 - - - - 6.14 6.92 8.78 10.0 8.73 (parameter) Size(µm) Surface Roughness(µm) MRR Abrasive particle 0-1 2-4 4-8 8-12 0.02 0.05 0.07 0.13 Increase when particle size increase.

18. Table : Surface roughness value of different workpiece finish with MAF: Workpiece material Surface roughness(µm) Abrasive used(µm) Ferromagnetic particle(µm) Source Alumina (translucent discharge tube) 0.05 Diamond(2-4) Iron(330) Yamaguchi & shinmura (2004) Silicon nitride 0.45 to 0.04 (Diamond)2/4 Cast iron ball(100) Shinmura et.al.(1990) Silicon nitride (ceramics tube) 0.63 to 0.01 Chromium oxide Iron Wang et.al.

19. Conclusion : When using this process on ceramics,very smooth surface( upto nano level) are produced. There is no residual stresses on the surface. No micro cracks on the surface. This process is suitable for hard and brittle material.

20. Refrences : Shinmura , T., et al. "Study on magnetic abrasive finishing." CIRP Annals-Manufacturing Technology 39.1 (1990): 325-328. V. K.singh , et al. "Effect of working gap and circumferential speed on the performance of magnetic abrasive finishing process." Wear 250.1 (2001): 384-390 Chang, Geeng -Wei, Biing-Hwa Yan, and Rong-Tzong Hsu. "Study on cylindrical magnetic abrasive finishing using unbonded magnetic abrasives." International Journal of Machine Tools and Manufacture 42.5 (2002): 575-583. Yamaguchi, Hitomi , and Takeo Shinmura . "Internal finishing process for alumina ceramic components by a magnetic field assisted finishing process."Precision Engineering 28.2 (2004): 135-142. Khairy , Ahmed B. "Aspects of surface and edge finish by magneto abrasive particles." Journal of Materials Processing Technology 116.1 (2001): 77-83. Singh, Dhirendra K., et al. "Analysis of surface texture generated by a flexible magnetic abrasive brush." Wear 259.7 (2005): 1254-1261. Mori, T., K. Hirota , and Y. Kawashima. "Clarification of magnetic abrasive finishing mechanism." Journal of Materials Processing Technology 143 (2003): 682-686. Jain VK (2004 )Advanced machining process. Allied Publisher Pvt.Ltd.,New Delhi