2. Importance of smooth surface
• Reduction in Friction and Wear – Bearings,
Bushings
• Torque and Fuel Economy - Engine
• Appearance – Body, Furniture
• Clearance – Disk head
• Sharpness – Cutting tools
• Eliminate imperfection – Dies, Medicine
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3. Abrasive Flow Machining (AFM)
AFM can
Polish and deburr parts internally
Through holes
Intersecting holes
Calibrate fuel injection nozzles to a specific flow rate.
• A method to radius difficult to reach surfaces like intricate
geometries
• Produce surface finish (Ra) as good as 0.05 µm deburr holes
as small as 0.2 mm radius edges from 0.025 mm to 1.5 mm
• Widely used finishing process to finish complicated shapes
and profiles
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4. Principle of AFM Process
• It uses two vertically opposed cylinders,
which extrude an abrasive medium back and
forth through passage formed by the
workpiece and tooling.
• Abrasion occurs wherever the medium
passes through the restrictive passages.
• The key components of AFM are the machine,
the tooling, types of abrasives, medium
composition and process settings.
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5. Three major elements of the process
(a) The Tooling, which confines and directs the abrasive
medium flow to the areas where deburring, radiusing and
surface improvements are desired.
(b) The Machine to control the process variables like
extrusion pressure, medium flow volume, and flow rate.
(c) The abrasive laden Polymeric Medium whose
rheological properties determine the pattern and
aggressiveness of the abrasive action. To formulate the
AFM medium, the abrasive particles are blended into
special viscoelastic polymer, which show change in
viscosity when forced to flow through restrictive
passages.
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7. Abrasive Media of AFM
• Abrasives, viscoelastic polymer, and additives.
• Abrasive particles - abrasive type (silicon carbide,
alumina oxide, boron carbide, diamond, etc.)
• Viscoelastic polymer –polyborosiloxane, silicone
rubber, natural rubber, silly putty, etc.,
• The additives or plasticizers-hydraulic oil, silicone
oil, etc.,
• Type and its concentration are the parameters
that affect the media viscosity and which decides
the media flowability.
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8. Properties of AFM
• Deburring, radiusing, and polishing are
performed simultaneously in a single operation
• AFM can produce true round radii even on
complex edges
• Reduces surface roughness by 75 to 90 % on cast
and machined surfaces
• AFM can process dozens of holes or multiple
passages parts simultaneously with uniform
results
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10. Working
• Abrasive action accelerates by change in the
rheological properties of the medium when it enters
and passes through the restrictive passages.
• Viscosity of polymeric medium plays an important role
in finishing operation.
• This allows it to selectively and controllably abrade
surfaces that it flows across.
• Work piece held by fixture is placed between two
medium cylinders which are clamped together to seal
so that medium does not leak during finishing process.
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11. One-Way AFM
• One-way flow AFM
processing pushes
abrasive media
through the work
piece in only one
direction, allowing the
media to exit freely
from the part.
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13. Advantages of One Way AFM
• Faster cycle processing
• Easy clean-up
• Media temperature control generally not required
• Able to process larger parts
• Simpler tooling and part change-over
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14. Two-Way AFM
The typical two-way flow AFM
process uses two vertically
opposed cylinders to extrude
an abrasive media back and
forth through or around
passages formed by the
workpiece and tooling. Abrasive
action occurs wherever the
media enters and passes
through the most restrictive
passages.
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16. Advantages of Two-Way AFM
• Excellent process control
• Can finish both ID and OD of component
• Good control of radius generation
• Fully automated system capabilities
• Faster setup and quick-change tooling
• Faster change-over of media
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17. Orbital AFM
• Surface and edge finishing are achieved by
rapid, low-amplitude, oscillations of the work
piece relative to a self-forming elastic plastic
abrasive polishing tool.
• The tool is a pad or layer of abrasive-laden
elastic plastic medium (similar to that used in
two way abrasive flow finishing), but
typically higher in viscosity and more in
elastic.
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20. Process Input Parameters of AFM
• Extrusion Pressure
• Number of cycles
• Abrasive medium composition and Type
• Tooling
• Fixture design
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