Mechanisms of Chip Formation
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Transcript of Mechanisms of Chip Formation
8/6/2019 Mechanisms of Chip Formation
http://slidepdf.com/reader/full/mechanisms-of-chip-formation 1/17
TOPIC : CHIP BREAKER
KOSAMIYA RAJVIR
VIMAL
GUIDED BY : G.B.PATEL
N.G.PATEL POLYTECHNIC
8/6/2019 Mechanisms of Chip Formation
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MECHANISMS OF CHIP
FORMATION
8/6/2019 Mechanisms of Chip Formation
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MECHANISMS OF CHIP
FORMATION
´ when a tool cuts metal it is driven by a force to
overcome friction and the forces that hold the
metal together. the metal that the toolfirst
meets is compressed and caused to flow up
the face of the tool. the pressure against the
face of the tool and the friction force opposing
the metal flow build up to large amounts.
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THE VARIABLES WHICH INFLUENCE THE TYPE
OF CHIP PRODUCED WHEN CUTTING ARE:
´ 1. properties of the material cut, especially the
ductility
´ 2. rake angle
´ 3. cutting speed
´ 4. depth of cut
´ 5. feed rate
´ 6. type and quality of cutting fluid employed
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CLASSIFICATION OF CHIP
´ 1. discontinuous chips
´ 2. continuous chip
´ 3. continuous chip with built up edge.
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DISCONTINOUS CHIPS
´ factors for discontinous chip :
1. brittle material
2. small rake angles
3. low cutting speed
4. greater depth of cuts
5. absence of cutting fluid
´ advantages:
1. high quality surface is obtained.
2. low power consumption.
3. tool application is favourable.´ dis advantages:
1. for ductile material discontinous chips are not favourable because friction on tool is more hence
low finish is achieved.
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CONTINUOUS CHIP
´ factors for continous chip :
1. ductile material eg m.s. c.u. etc.
2. large rake angle.
3. small depth of cuts.
4. sharp cutting edge.
5. smooth tool face.
6. efficient lubrication system.
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CONTINUOUS CHIP
´ advantages:1. smooth surface can be obtained.
2. high speed and fine feed can be used.
3. large rake angle is used hence tool wear is less
4. power consumpition
´ dis advantages:1. because of high quality coollant is used, it is expensive.
2. as cutting point is kept sharp so regrinding is frequently required hence it isexpensive.
3. handling of chip is a problem.
4. hazardous to operator.
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CONTINUOUS CHIP WITH BUILT UP
EDGE.
´ factors for continuous chip with built up edge:
1. ductile material.
2. low cutting speed.
3. small rake angle.
4. high feed .
5. high depth of cut.
6. improper cutting fluid.
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CONTINUOUS CHIP WITH BUILT UP
EDGE.
´ advantages:
1. tool point is protected by b.u.e. from heat zone hence it
increases tool life.
´ dis advantages:
1. because of coarse feed, surface finish obtained is poor.
2. tool crater wear is more
3. power consumption is more
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FUNCTOIN OF CHIP BREAKER
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FUNCTOIN OF CHIP BREAKER
´ the chip obtained by machining brittle materials like cast iron and majority
of nonferrus metal are small and discontinous and tehir diposal do not pose
any problem with the operator.on the other hand while machining ductile
materials long homogenous, continuous chip are obtained. even continuous
chip with built up edge are also obtained. these chip create many difficultiesand problems.
´ the chip breakers have to perform two main function:
1. to control the sliding chips on tool face and also to direct the chip in proper
direction.
2. to break the chip.
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TYPES OF CHIP BREAKERS
´ 1. groove type chip breakers
´ 2. obstruction type chip breakers
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GROOVE TYPE CHIP BREAKERS
´ in this type of chip breakers, shallow grooves are cuts by the
slide of the cutting edge of the tool which edge of the tool wich
will defect the continuous chip obtained from the work
piece.commonly groove width is kept three to four times the
feed. the groove depth of 0.01 inch is kept. in gullet type chip
breaker the land width is equl to feed or 1.5 times feed.
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OBSTRUCTION TYPE CHIP BREAKERS
´ this type of chip breakers provide obstruction in chip flow and
force them to curl and break into pieces. the path of chip can
be estimated considering the width and thickness of the chip
breaker. on carbide tipped tools inserts are mechanically
clamped and they are adjustable according to the workpiece
tool combinations. thus are flexible in use.
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ADVANTAGES CHIP BREAKERS
1. helps in getting desired results.
2. by proper selection of speed, feed and depth of cutcombination, desired metal removal rate can be obtained.
3. helps in maintaining almost constant production rate.
4. restricts the wear rate as well as power consumption.
5. provides safety for operator and machine tool.
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DISADVANTAGES CHIP BREAKERS
1. groove type chip breaker weakens the tool.
2. to provide the groove special type of grinding wheel is necessary
3. when cutting condition alter, the groove type breaker will have to be
replaced by other chip breaker
4. it offers resistance in chip flow.
5. it increases cutting force.
6. it increases power consumption