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A. Petare et al.
1 Introduction
Abrasive flow finishing (AFF) is one of advanced non-traditional finishing process
developed in 1960s by Extrude Hone Corporation (USA) for radiusing, polishing,
deburring, surface stress relieving and geometry optimization of complicated shapes
and inaccessible areas. It uses abrasive laden viscoelastic medium called putty (i.e.
mixture of abrasive particles, viscoelastic polymer, blending oil and other additives)
which extruded across or through the workpiece at high pressure. The continuous
back and forth movement of putty causes abrasion and imparts fine finishing to
the workpiece. AFF frequently used for finishing components of aerospace, automotive, diesel, and turbine engines, pump industries, medical implant, mould and
die, additively manufactured components, recast layer removal and to finish difficult
machine materials and inaccessible areas [1]. The straight bevel gear is one of the
essential components used in the automobiles, farm and agriculture machinery, railways, and cement mill, material handling equipment, rolling mills, machine tools,
wind turbines, marine applications, and various industrial machines for transmitting
motion and/or power between two perpendicular shafts with constant velocity ratio.
It frequently used in many machines due to high power and torque transmitting capability compared to another type of gears therefore demand for this type of gear is
very high. Continuous demand for small cars, wind turbine power station, and ships
increases production of gears to several billion [2]. Gears are expected to transmit
high power with good motion transmission characteristics, light in weight and smaller
size, less maintenance, high load carrying capacity with minimum noise and vibration, better surface quality and high wear resistance. These expectations achieved by
gear finishing using appropriate finishing process. Grinding and lapping are traditional finishing processes which are used frequently for finishing bevel gears. Gear
grinding is very old and established process for all type of case hard or hardened gears
having Rockwell hardness at C scale below 92. (i) generates grinding burns causes
thermal damage to the ground gears; (ii) transverse grind lines on the ground gear
flank surface causes noise and vibrations; (iii) requires frequent supply of coolant
and redressing of grinding wheels; and (iv) costly and requires skilled operators [3].
Gear lapping can correct minute errors in profile, lead, pitch, runout and minute
distortion caused by heat treatment in the gears made of hard or hardened materials
but (i) longer lapping cycles affects the form accuracy of the lapped gears adversely;
and (ii) only mating gears are lapped in a pair and they cannot be interchanged [4].
To overcome limitation of traditional gear finishing process, there is need to explore
and develop highly productive, easy operative, economic and sustainable hybrid or
advanced gear finishing process. Recently, some researcher has explored AFF for
finishing different type of gears. AFF were used by Xu et al. [5] to finish helical gear,
and they revelled reduction of average surface roughness (R a ) from 1.42; 1.10; and
2.73 µm to 0.22; 0.21; and 1.75 µm at left flank, right flank, and addendum with
improved fatigue strength and contact stiffness in a very less time. Venkatesh et al.
[6] explored US-AFF to finish straight bevel gears (SBG) made of EN 8 steel and
reported 73% reduction in average surface roughness with glazed surface texture.
A. Petare et al.
1 Introduction
Abrasive flow finishing (AFF) is one of advanced non-traditional finishing process
developed in 1960s by Extrude Hone Corporation (USA) for radiusing, polishing,
deburring, surface stress relieving and geometry optimization of complicated shapes
and inaccessible areas. It uses abrasive laden viscoelastic medium called putty (i.e.
mixture of abrasive particles, viscoelastic polymer, blending oil and other additives)
which extruded across or through the workpiece at high pressure. The continuous
back and forth movement of putty causes abrasion and imparts fine finishing to
the workpiece. AFF frequently used for finishing components of aerospace, automotive, diesel, and turbine engines, pump industries, medical implant, mould and
die, additively manufactured components, recast layer removal and to finish difficult
machine materials and inaccessible areas [1]. The straight bevel gear is one of the
essential components used in the automobiles, farm and agriculture machinery, railways, and cement mill, material handling equipment, rolling mills, machine tools,
wind turbines, marine applications, and various industrial machines for transmitting
motion and/or power between two perpendicular shafts with constant velocity ratio.
It frequently used in many machines due to high power and torque transmitting capability compared to another type of gears therefore demand for this type of gear is
very high. Continuous demand for small cars, wind turbine power station, and ships
increases production of gears to several billion [2]. Gears are expected to transmit
high power with good motion transmission characteristics, light in weight and smaller
size, less maintenance, high load carrying capacity with minimum noise and vibration, better surface quality and high wear resistance. These expectations achieved by
gear finishing using appropriate finishing process. Grinding and lapping are traditional finishing processes which are used frequently for finishing bevel gears. Gear
grinding is very old and established process for all type of case hard or hardened gears
having Rockwell hardness at C scale below 92. (i) generates grinding burns causes
thermal damage to the ground gears; (ii) transverse grind lines on the ground gear
flank surface causes noise and vibrations; (iii) requires frequent supply of coolant
and redressing of grinding wheels; and (iv) costly and requires skilled operators [3].
Gear lapping can correct minute errors in profile, lead, pitch, runout and minute
distortion caused by heat treatment in the gears made of hard or hardened materials
but (i) longer lapping cycles affects the form accuracy of the lapped gears adversely;
and (ii) only mating gears are lapped in a pair and they cannot be interchanged [4].
To overcome limitation of traditional gear finishing process, there is need to explore
and develop highly productive, easy operative, economic and sustainable hybrid or
advanced gear finishing process. Recently, some researcher has explored AFF for
finishing different type of gears. AFF were used by Xu et al. [5] to finish helical gear,
and they revelled reduction of average surface roughness (R a ) from 1.42; 1.10; and
2.73 µm to 0.22; 0.21; and 1.75 µm at left flank, right flank, and addendum with
improved fatigue strength and contact stiffness in a very less time. Venkatesh et al.
[6] explored US-AFF to finish straight bevel gears (SBG) made of EN 8 steel and
reported 73% reduction in average surface roughness with glazed surface texture.