Burr Formation and Minimisation in Drilling
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8/14/2019 Burr Formation and Minimisation in Drilling
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FORMATION ANDFORMATION AND
MINIMISATION OFMINIMISATION OF
BURR IN DRILLINGBURR IN DRILLING
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BhubaneswarBhubaneswar
mailto:deepaksubudhi456@gmail.commailto:deepaksubudhi456@gmail.commailto:deepaksubudhi456@gmail.com8/14/2019 Burr Formation and Minimisation in Drilling
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What is a burr?
Unwanted material
remaining after a
machining operation
Undesirable projections
of materials beyond the
edge of the work-piece
arising because of plastic
deformation during
machining.
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Why remove burr ?
Accounts for a significant portion of machining costs
Cause Of Many Industrial Problems.
Inspection
Assembly
Automated Manufacturing Of Precision Components
Reduce the quality of machined parts
Can cause interference, jamming and misalignment
A safety hazard to personnel
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Estimates of between 10% and 30% of the total costof a part
In 1977 estimated cost of deburring $100 million inCanada alone
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Classification of burr
According to height of the burr
Uniform burr
Type 1-The height of burr varies upto 0.150 mm
Type 2-The height of burr varies in between 0.150 to1.1mm .
Also reffered as transient burr
Crown burr
Height varies in between 1.1 to 1.5 mm .Burr is not uniform
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Uniform burr Type 2Uniform burr Type 1
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Crown burr
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According to location of burr,
Entrance burrProduced on the side of the work piece where the drill enters
Smaller than the exit burr
Usually of little concern
Exit burr
Is formed on the opposite side of the work piece
They are more challenging to remove
Interlayer burr
Drilling Through A Number Of Layers
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Entrance burr, Interlayer burr and Exit burr
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Mechanism of burr formation
Uniform burrSmall feed force condition this type of burr is formed.
Fracture takes place at the chisel edge
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Crown burr
Large feed condition this type of burr is formed
initial rupture will occur at the center
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Entrance burr
Material bumped up on theperimeter of the drill
engaging region
As more part of cutting edge
engages small amount of
bumps of material is always
observed on the perimeter of
the hole
When almost all cutting
edges are engaged, the
shape of bump on the
perimeter starts to change
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Interlayer burr
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Exit burr
The mechanism of formation of exit burr is same as that of
uniform burr or crown burr depending on feed condition
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MINIMIZATION OF BURR
(DBCC) can be used to predict what
type of burr will be formed given certain
drilling parameters.feed rate and thrust force with varying
drill diameters can be approximated by
applying the shear plane modelMerchant equation, = / 4 + (-) / 2
and the expression for the rake angle
varying with relative radius, R.thrust force
2-Axis Drilling Burr Control Charts
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Pre-drilling and pre-chamfering
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Burr minimization through drill tip design
Gillespie found that increasing helix angle will reduce burr
height by up to 50%, thickness by up to 20%Sofronas increase helix angle and harden the exit surfaceby changing the tip of the drill it is possible to minimize the burr
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Plastic deformation region
is formed by the stress
caused by cutting resistancein the slant section
The position at which
bending deformation starts is
determined by the rigidity of
the remained part
When the stiffness of the
part which is bent by thrustforce imposed in drill cutting
edge is large enough, no
bending occurs and cutting is
continued
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Observation of burr formation in chamfered drill
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Observation of burr formation in round drill
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Observation of burr formation in step drill
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METHODS OF DEBURRING
Ultrasonic vibration indrilling
The distribution of the ultrasonic
vibration pressure depends on
the properties of the medium,
initial speed,
density of slurry
frequency
Results of Ultrasonic vibration in drilling
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Results of Ultrasonic vibration in drilling
Before
After
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Integrated drilling and deburring tools
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Burr off tools:
One-Pass Hole-Deburring tool which can remove both Entrance
and exit burr .Simple and Rugged One-Piece Construction
Allows cutting chips to clear easily
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References
Sung-lim ko1, Jae-eun Chang1 Development of drill geometryfor burr minimization in drilling
P. Stringer, G. Byrne and E. Ahearne Tool Design For BurrRemoval In Drilling Operations.
Jinsoo Kim Development of a drilling burr control chart for
stainless steel.
H. Z. Choi, s. W. Lee, y. J. Choi, s. L. Ko Study on deburringtechnology using Ultrasonic Cavitations
Jihong Choi ,Sangkee Min, David A. Dornfeld Finite ElementModeling of Burr Formation in Drilling of a Multi-Layered Material
Choi, Sangkee Min ,David Dornfeld ,Mahboob Alam, T. Tzong Modeling of Inter-Layer Gap Formation in Drilling of a Multi-LayeredMaterialJihong
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THANK YOUTHANK YOU
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