Ultrasonic machining (USM) is a mechanical process that uses high frequency vibrations and an abrasive slurry to erode fine holes and cavities in hard or brittle materials. It is well-suited for machining brittle materials like glass, ceramics, and semiconductors. The material removal occurs through abrasion by the particles in the slurry, with no thermal or chemical changes to the workpiece. USM produces intricate shapes and profiles with good surface finish and integrity.

1. ULTRASONIC MACHINING PROCESS
(USM)
BY,
ARAVINDKUMAR B

2. ULTRASONIC MACHINING PROCESS (USM)
 Ultrasonic machining (USM) is a mechanical
material removal process.
 It is used to erode material in the form of fine holes
and cavities in hard or brittle workpiece through the
use of formed tools, vibrations of high frequency
along with the use of a suitable abrasive slurry-mix.
 The Ultrasonic Machining (USM) process is suitable
for machining brittle materials such as glass,
ceramics and semiconductors for increasingly
complex operations to provide intricate shapes and
workpiece profiles.

3.  The USM is a non-thermal and non-chemical process
which creates no change in the chemical, physical or
metallurgical properties of the workpiece.
 It is therefore being widely used in the manufacturing of
hard and brittle materials which are normally unfeasible to
machine by the traditional methods.
 The cutting is actually performed by the abrasive particles
which are suspended in the slurry (fluid).
 Ultrasonic machining accomplishes the material removal
through the abrading action of the grit-loaded slurry which
circulates between the tool and the workpiece.
 Small amplitudes and high frequency of vibrations are
given to the tool,typically in the range of 10–20 μm at 20–
40 kHz.

4.  The hard abrasive particles in the slurry are accelerated
towards the workpiece surface by the oscillating action of
the tool -through repeated abrasions, the tool further
machines a cavity of cross section identical to its own.
 The material removal takes place is the form of fine
grains by shear deformation.
 Different mechanisms could be attributed to this material
process such as brittle fracturing of the work material,
impact action of abrasives, cavitation and chemical
reaction due to the slurry.
 The workpiece shape and dimensional accuracy is
directly dependent on the geometry of the tool.

7. MECHANISM OF MATERIAL REMOVAL
 Mechanical abrasion: Occurs due to the
hammering effect of abrasive particles on
workpiece through the tool.
 Impact: The freely moving particles impact with a
certain velocity on the work piece resulting in micro
chipping.
 Erosion: Due to cavitation effect of the abrasive
slurry, erosion of the work surface occurs.
 Chemical: Due to fluid employed, chemical effect
can come into consideration.

8. ADVANTAGES OF USM
 In USM process, there are no physical, chemical or
thermal changes.
 There is no direct contact of the tool and workpiece
due to the slurry used, it makes it a wet cutting
process. The surfaces produced are free from
stress and damages.
 The process is free from burrs and distortions.
 The process is suitable for any materials,
irrespective of electrical conductivity
 The process is very much suitable for machining
brittle materials
 The process offers good surface finish and
structural integrity.

9. DISADVANTAGES / LIMITATIONS OF USM
 Soft materials like lead and plastics are not suitable for machining by the USM
process, since they tend to absorb the abrasive particles rather than to chip under
their impact.
 The USM process consumes higher power and has lower material-removal rates
compared to traditional fabrication processes.
 The tool wear rate in USM process is fast.
 The areas of machining and higher depths are the constraints in USM.
 As the USM process continuous, the lateral wear of the tool increases gradually
and it tends to make the holes tapered. The sharp corners of the tool get rounded
off thereby requiring tool replacement essential for producing accurate blind holes.
 The accuracy of the machined surface gets lost due to setting up of strong lateral
 vibrations. This occurs if the axis of the tool and horn, which are brazed together,
are not properly aligned with the transducer axis. In such a case, the tool needs to
be redesigned.
 The holes produced in USM have a tendency to break out at the bottom owing to
the static load and high amplitudes.
 While producing deeper holes through USM method, there is ineffective slurry
circulation leading to presence of a fewer active grains under the tool face. Due to
this, the bottom surfaces of blind holes tend to become slightly concave.

10. APPLICATIONS OF USM
 USM process is used in machining hard and brittle
metallic alloys, semiconductors, glass, ceramics,
carbides etc.
 In machining of advanced ceramics for applications
in auto-engine components.
 In machining, wire drawing, punching or blanking
of small dies
 Machining ceramic substrates for drilling holes in
borosilicate glass for the sensors used in electronic
industries
 Drilling small holes in helicopter power
transmission shafts and gears.