Burr Formation and Minimisation in Drilling

8/14/2019 Burr Formation and Minimisation in Drilling

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FORMATION ANDFORMATION AND

MINIMISATION OFMINIMISATION OF

BURR IN DRILLINGBURR IN DRILLING

[email protected]@gmail.com

BhubaneswarBhubaneswar
mailto:[email protected]:[email protected]:[email protected]


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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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Burr Formation and Minimisation in Drilling

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