mechanisms of chip formation

8/6/2019 Mechanisms of Chip Formation

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TOPIC : CHIP BREAKER

KOSAMIYA RAJVIR

VIMAL

GUIDED BY : G.B.PATEL

N.G.PATEL POLYTECHNIC



MECHANISMS OF CHIP

FORMATION



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.



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



CLASSIFICATION OF CHIP

´ 1. discontinuous chips

´ 2. continuous chip

´ 3. continuous chip with built up edge.



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.



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.



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.



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.



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



FUNCTOIN OF CHIP BREAKER



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.



TYPES OF CHIP BREAKERS

´ 1. groove type chip breakers

´ 2. obstruction type chip breakers



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.



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.



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.



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

mechanisms of chip formation

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