Manufacturing Rounded Shapes Processes

Examples of Lathed Parts

Outline Types of Processes Turning Parameters Lathe Components Geometry Material Removal Rate Forces Lathe Components Lathe Attachments Design Considerations Types of Lathes

Types of Processes Turning Facing Form Tools Boring Drilling Parting Threading Knurling

Various Turning Operations

Turning Operation

Turning Parameters Geometry Forces in Turning Material Removal Rate side rake angle back rake angle relief angles cutting-edge angles nose radius Forces in Turning cutting force thrust force These forces cannot be calculated accurately; they are determined by experiments Material Removal Rate

Lathe Tool Parameters

Lathe Tools

Lathe Tool Inserts

Lathe Tool Holders

Lathe Feed and Speed V = πDN/12 V = cutting speed in ft/min; Velocity at which the tool head moves along the workpiece surface D = diameter of the rotating tool or rotating workpiece N = RPM of the rotating tool or rotating workpiece Feeds for a lathe are listed as in/rev or m/rev. Multiply these by the RPM to obtain the feed in in/min or m/min.

Lathe Feed and Speed Example: Work Material: Aluminum Tool Material: High Speed Steel Workpiece Diameter: 3.375 in Recommended Cutting Speed: 600 ft/min N = 12V/πD N=12*600/(π*3.375) =679.2 RPM The closest available speed on the lathe, without exceeding this value, is 630 RPM so this value should be used. Recommended Feed for HSS/aluminum = .01-.02 in/rev f = (.01-.02)*630 RPM = 6.3-12.4 in/min

Material Removal Rate Material Removal Rate (MRR) is the volume of workpiece material removed per unit time MRR = πDavgdf N Davg = average diameter =(Doriginal + Dfinal)/2 = (Doriginal - d) d = depth of cut f = feed, in/rev or mm/rev N = RPM

Material Removal Rate Example: Original Diameter = 3.375 in RPM = 630 RPM Feed = .01 in/rev Depth of cut = .02 in MRR = πDavgdfN Davg = 3.375 - .02 = 3.355 in MRR = π*3.355*.02*.01*630 = 1.33 in3/min

Lathe Components Bed Carriage Headstock Tailstock dead center live center Feed Rod and Lead Screw

Lathe Components

Example of a Lathe

Centers

Lathe Attachments Chucks Collets Face Plates Mandrels Accessories

Chucks

Lathe Attachments

Collets

Mandrels

Design Considerations Design parts so they can be fixtured or clamped easily Design the part so that tolerances of the dimensions and finishes are as large as possible Avoid tapers, sharp corners, and large variations in the dimensions of the part Produce blanks as close to the final design as possible Design the workpiece so that the cutting tools can move across it without obstructions Standard cutting tools should be able to machine the design Select materials that can be machined properly

Types of Lathes Tracer Lathes Automatic Lathes Automatic Bar Machines Turret Lathes Computerized Lathes

Turret Lathe Operations

Turret Lathes and Computerized Lathes

Example of a Turret Lathe

Vertical Turret Lathe

Summary Various processes are available to create different shapes and surface effects Several different fixtures exist to hold a workpiece in a lathe A workable design must be considered in order to allow efficient machining

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