CHAPTER 23

Machining Process Used to ProduceVarious Shapes

Introduction• Addition to producing various external or internal round

profiles,cutting operations can produce many other parts with more complex shapes

Fig:Typical parts and shapes produced with the machining process

Milling Operation

• Highly versatile machining operation• Multitooth tool that produces a number of chips in one revolution

Fig:Some of the basic type milling cutters and milling operations.

Fig : A typical part that can be produced on a milling machine equipped with computer controls.Such parts can be made efficiently and respectively on computer numerical control (CNC) machines, without the need for refixturing or reclamping the part

Example of a part produces in a CNC milling machine

Slab Milling• Slab milling also called as peripheral milling• Cutters have straight or helical teeth resulting in

orthogonal or oblique cutting action

Fig : (a) Conventional milling and climb milling (b) Slab milling operation, showing depth of cut , d, feed per tooth, f, chip depth of cut, tc, and workpiece speed, v. (c) cutter travel distance lc to reach full depth of cut.

Milling parameters

Face Milling• The cutter is mounted on a spindle having an axis of rotation perpendicular

to the workpiece surface.

Fig : Face milling operation showing (a) action of an insert in face milling; (b) climb milling; (c) conventional milling d)dimensions in face milling. The width of cut, w, is not necessarily the same as the cutter radius

Fig:A face milling cutter with indexable inserts.

Effects of Inserts Shapes

Fig:The effect of insert shape on feed marks on a face-milled surface (a) small corner radius, (b) corner flat on insert, and (c) wiper consisting of a small radius followed by a large radius which leaves smoother feed marks (d) feed marks due to various insert shapes

Face milling cutter

Fig:Terminology for a face milling cutter

Effect of Lead Angle

Fig : The effect of Lead angle on the undeformed chip thickness in face milling. Note that as the lead angle increases, the chip thickness decreases, but the length of contact (i.e. chip width) increases. The insert in (a) must be sufficiently large to accommodate the contact length increases

Cutter and Insert position in Face Milling

Fig : (a) Relative position of the cutter and insert as it first engages the workpiece in face milling, (b) insert positions towards the end of cut, and (c) examples of exit angles of insert, showing desirable (positive or negative angle) and undesirable (zero angle) positions. In all figures, the cutter spindle is perpendicular to the page.

Cutters for different types of Milling

Fig : Cutters for (a) Straddle Milling, (b) form milling, (c) slotting, and (d) slitting with a milling cutter.

Other Milling Operations and Cutters

Fig : (a) T-slot cutting with a milling cutter. (b) A shell mill.

Arbors

Fig : Mounting a milling cutter on an arbor for use on a horizontal milling machine.

Surface Features and Corner defects

Fig : Surface features and corner defects in face milling operations

Horizontal and Vertical Spindle Column and Knee type Milling Machines

Fig : Schematic illustration of a vertical-spindle column-and-knee type milling machine.

Fig : Schematic illustration of a horizontal-spindle column-and-knee type milling machine.

Bed Type Milling Machine

Fig : Schematic illustration of a bed-type milling machine. Note the single vertical-spindle cutter and two horizontal-spindle cutters.

Additional Milling Machines

Fig : Schematic illustration of a five-axis profile milling machine. Note that there are three principal linear and two angular movements of machine components.

Fig : A computer numerical control, vertical-spindle milling machine. This machine is one of the most versatile machine tools.

Examples of parts made one Planer and by Broaching

Fig : Typical parts that can be made on a planer.

Fig : (a) Typical parts that can be made by internal broaching. (b) Parts made by surface broaching. Heavy lines indicate broached surfaces.

Broaches

Fig : (a) Cutting action of a broach, showing various features. (b) Terminology for a branch.

Chipbreakers and a Broaching Machine

Fig : Chipbreaker features on (a) a flat broach and (b) a round broach. (c) Vertical broaching machine.

Internal Broach and Turn Broach

Fig : Terminology for a pull-type internal broach used for enlarging long holes.

Fig : Turn broaching of a crankshaft. The crankshaft rotates while the broaches pass tangentially across the crankshaft’s bearing surfaces.

Broaching Internal Splines

Fig : Broaching in internal splines.

Sawing Operations

Fig : Examples of various sawing operations.

Types of Saw Teeth

Fig : (a) Terminology for saw teeth. (b) Types of tooth set on saw teeth, staggered to provide clearance for the saw blade to prevent binding during sawing.

Saw Teeth and Burs

Fig : High-speed steel teeth welded on steel blade. (b) Carbide inserts brazed to blade teeth.

Fig : Types of burs.

Spur Gear

Fig : Nomenclature for an involute spur gear.

Gear Generating

Fig : (a) Producing gear teeth on a blank by form cutting. (b) Schematic illustration of gear generating with a pinion-shaped gear cutter. (c) Schematic illustration of gear generating in a gear shaper using a pinion-shaped cutter. Note that the cutter reciprocates vertically. (d) Gear generating with rack-shaped cutter.

Gear Cutting with a Hob

Fig : Schematic illustration of three views of gear cutting with a hob.

Cutting Bevel Gears

Fig : (a) Cutting a straight bevel-gear blank with two cutters. (b) Cutting a spiral bevel gear with a single cutter.

Gear Grinding

Fig : Finishing gears by grinding: (a) form grinding with shaped grinding wheels; (b) grinding by generating with two wheels.

Economics of Gear Production

Fig : Gear Manufacturing cost as a function of gear quality. The numbers along the vertical lines indicate tolerances.

THE END