Microsoft PowerPoint - lecture 20 machining 2_students.ppt

MACHINING OPERATIONS

Turning and Related OperationsOutline

Turning a machining process in which a single- point tool remove material from the surface of a

vDo Df Turning and Related Operations

rotating work piece. (Lathe) df Drilling and Related Operations Milling Machining & Turning Centers Other Machining Operations Shaping and Planing Broaching Sawing Machinability

N = vDoDo D ff r = NfT = Lm fr

LRotational Speed= 2dFeed rateTime of machiningMRR = vfd

Material Removal RateDr. M. Medraj Mech. Eng. Dept. - Concordia University Mech 421/6511 lecture 20/1

Dr. M. Medraj Mech. Eng. Dept. - Concordia University Mech 421/6511 lecture 20/2Operations Related to Turning

Work HoldingContour turning

ChamferingFacing Taper turning

Form turning

mounting the work between centers using a "dog

three-jaw chuck

Cutoff

Threading

Boring

Drilling

Knurling

collet face plate for non-cylindrical workpartsEngine Lathe

Other Lathes & Turning Machine Toolroom Lathe and Speed Lathe Turret Lathe The tailstock is replaced with a turret Chucking Machines No tailstock Automatic Bar Machine Similar to chuck machine but with a collet A single- and multiple-spindle bar machines NC Lathe Boring Machines the stiffness of a boring bar Horizontal and VerticalDr. M. Medraj Mech. Eng. Dept. - Concordia University Mech 421/6511 lecture 20/5

Dr. M. Medraj Mech. Eng. Dept. - Concordia University Mech 421/6511 lecture 20/6Drilling and Related Operations Geometry of Twist drill

Shank, Neck and Drill body Helix angle, Point angle, Flute, cutting edge, Chisel edge, Margin Cutting conditions

Operation Related to DrillingSpindle rpm:

N = vDFeed rate:

f r = Nf

f(in/rev)

Reaming Tapping CounterboringMRR = D f rMetal Removal Rate: 4

For a through hole

For a blind hole

Countersinking Center drillingMachining time:

T = t + A d

Spot facingm T =r f r Drill press

Machine Tool for drilling

MillingA machine operation in which a workpart is fed past a rotating cylindrical tool with multiple edges. (milling machine) Upright drill Bench drill Radial drill Gang drill 2-6 drills together NC drill Vice, Jig and fixture

Upright drill press

Types:9 Peripheral milling

Slab, slotting, side and straddle milling Up Milling (Conventional) & down milling (Climb)9 Facing milling

Conventional, Partial face, end, profile, pocket & contour

Up MillingDown MillingRadial drill press

Large drill press designed for large partsDr. M. Medraj Mech. Eng. Dept. - Concordia University Mech 421/6511 lecture 20/9

(a) peripheral milling (b) face millingDr. M. Medraj Mech. Eng. Dept. - Concordia University Mech 421/6511 lecture 20/10Milling

Cutting Conditions

Slab slotting sidestraddle

Milling cutters Plain milling cutters Form milling cutters Face milling cutters End milling cutters Cutting conditions

Radial RakeAngle

ReliefAngleconventional face milling

Partial face milling

end milling

Spindle rotation speed:

N = vDpocket milling

Surface contouring

profile milling

Feed rate:

MRR:

f r = Nnt fMRR = wdf rMilling Machines

Machining Centers Machining center highly automated machine tool capable of performing multiple machining operations under CNC control. Automatic tool changer Pallet shuttles Automatic workpart positioninghorizontal knee-and-column

vertical knee-and-columnram type knee-and-column milling machine; ram can be adjusted in and out, and toolhead can be swiveled

CNC turning centerDr. M. Medraj Mech. Eng. Dept. - Concordia University Mech 421/6511 lecture 20/13

Dr. M. Medraj Mech. Eng. Dept. - Concordia University Mech 421/6511 lecture 20/14Mill-Turn Centers Highly automated machine tool that can perform turning, milling, anddrilling operations on a workpart General configuration of a turning center Can position a cylindrical workpart at a specified angle so a rotating cutting tool (e.g., milling cutter) can machine features into outside surface of part A conventional turning center cannot stop workpart at a defined angular position and does not possess rotating tool spindlesA part

Other Machining Operations: Shaping and Planing A single-point tool moves linearly relative to the work partShaping - A tool moves Planing A workpart moves

Stock Turning Milling DrillingOther Machining Operations: Broaching Moves a multiple tooth cutting tool linearly relative to work in direction of tool axisAdvantages:- Good surface finish- Close tolerances- Variety of work shapes possible Cutting tool called a broach- Owing to complicated and often custom-shaped geometry, tooling is expensiveInternal Broaching: Performed on internal surface of a hole A starting hole must be present in the part to insert broach at beginning of stroke

Other Machining Operations: Sawingpower hacksaw linear reciprocating motion of hacksaw blade against workbandsaw (vertical) linear continuous motion of bandsaw bladeDr. M. Medraj Mech. Eng. Dept. - Concordia University Mech 421/6511 lecture 20/17

circular sawDr. M. Medraj Mech. Eng. Dept. - Concordia University Mech 421/6511 lecture 20/18Machinability Machinability A measure of the success of a machining operation usually on a workmaterial. Tool life Force and Power Surface finish Easy of chip disposal Material Removal rate

Next Time:Cutting Tool TechnologyDr. M. Medraj Mech. Eng. Dept. - Concordia University Mech 421/6511 lecture 20/19

Dr. M. Medraj Mech. Eng. Dept. - Concordia University Mech 421/6511 lecture 20/20

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