Lathe Opns

8/11/2019 Lathe Opns

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Machining Operations

Generally performed after other manufacturingprocesses (casting, forging, ) Other processes create the general shape of the workpart Machining provides the final shape, dimensions, finish, and

special geometric details that other processes cannot create

9/19/2014 IENG 475: Computer-ControlledManufacturin S stems

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Most important machining operations: Turning Drilling Milling

Other machining operations: Shaping and planing Broaching Sawing


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Primary Machining Parameters

Cutting Speed (v) Primary motion Peripheral speed m/s ft/min

Feed (f)


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econ ary mo on Turning: mm/rev in/rev Milling: mm/tooth in/tooth

Depth of Cut (d) Penetration of tool below original work surface Single parameter mm in

Resulting in Material Removal Rate (MRR)MRR= v f d mm3/s in3/min

where v= cutting speed; f= feed; d= depth of cut


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Turning Parameters Illustrated


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Figure 22.5 - Turning operation [Groover (2004), p.503]


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Drilling

Creates a round hole ina workpart

Contrasts with boringwhich can only enlarge


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an existing hole Cutting tool called a drill

or drill bit

Customarily performedon a drill press

Figure 21.3 (b) drilling[Groover (2004), p.501]


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Milling Parameters Illustrated


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Figure 21.3 - Two forms of milling:

(a) peripheral milling, and (b) face milling[Groover (2004), p.516]


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Machining Operations &Parameters

Operation Type Speed Feed Depth of Cut

Turning:workpiece rotates

single point cutting

Surface speed(periphery) of

workpiece

Parallel to theworkpiece axis*

(*except parting/grooving)

Tool penetrationbelow originalwork surface


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Drilling:tool rotates

single pass cutting


tool

Parallel to thetool axis


(depth of hole)

Milling:tool rotates

multi-point cutting


tool

Perpendicular tothe tool axis



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Cut Types: Roughing &Finishing

Cut Type

Number

of

PassesSpeed Feed Depth of Cut

Roughing:

1 + Low High

High


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removes largeamounts to getclose to shape

0.4 - 1.25 mm/.015 - .050 in/

2.5 - 20 mm.100 - .750 in

Finishing:achieves final

dimensions,tolerances, andfinish

1 - 2 High Low

0.125 - 0.4 mm/

.005 - .015 in/

Low

0.75 - 2.0 mm

.030 - .075 in


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Turning

A single point cutting tool removes materialfrom a rotating workpiece to generate arotationally symmetric shape


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Types of cuts: Facing Contour turning Chamfering Parting (Cut-off) / Grooving Threading


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Turning Parameters Illustrated


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Figure 22.5 - Turning operation [Groover (2004), p.503]


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Facing

Tool is fedradially inward


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Figure 22.6 (a) facing


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Contour Turning

Instead of feeding thetool parallel to the axisof rotation, tool follows a


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necessarily straight(thus creating acontoured form).

Figure 22.6 (c) contour turning


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Right & Left Hand Tools

Right Hand Tool: Cuts from right to left


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Left Hand Tool:

Cuts from left to right


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Chamfering

Cutting edgecuts an angle onthe corner of the


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cylinder, forminga "chamfer"

Figure 22.6 (e) chamfering


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Parting (Cutoff) / Grooving

Tool is fedradially intorotatin work at


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some location tocut off end ofpart, or provide

a groove

Figure 22.6 (f) cutoff


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Threading

Pointed form toolis fed linearlyacross surface of


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parallel to axis ofrotation at a largefeed rate, thus

creating threads

Figure 22.6 (g) threading


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Figure 22.7

Engine Lathe


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an enginelathe,showing itsprincipal

components


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Chuck


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Figure 22.8 (b) three-jaw chuck


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Turret Lathe

Manual operation is replaced by aturret that holds multiple tools

Tools are rapidly brought into action by


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indexing the turret Tool post is replaced by multi-sided turretto index multiple tools

Applications: high production work thatrequires a sequence of cuts on the part


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CNC Turret Lathe

Tool Turret

Spindle Speed

+ X-axis


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SpindleCross Slide

+ Z-axis


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CNC Lathe: Air-Operated Chuck

Ri ht Hand


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Profile Tool

Chuck


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CNC Lathe: Tool Turret

Tool Turret

Left HandProfile Tool


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Right Hand

Profile Tool

Grooving /Parting Tool

Tool Holder


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Machining Calculations:Turning

Spindle Speed - N (rpm)

v = cutting speed Do = outer diameter

Feed Rate - fr (mm/min -or- in/min) f = feed er rev

oD

vN =

ff =


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Depth of Cut - d (mm/rev -or- in/rev) Do = outer diameter Df = final diameter

Machining Time - Tm (min)

L = length of cut

Matl Removal Rate - MRR (mm3/min -or- in3/min)

2

fo DD

d

=

r

mf

L

T =

dfvMRR=

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