chapter 23services.eng.uts.edu.au/desmanf/manfeng/ch23mill1 and ch23mill2.pdf · chapter 23...

Kalpakjian • SchmidManufacturing Engineering and Technology

© 2001 Prentice-Hall Page 23-1

CHAPTER 23

Machining Processes Used to Produce Various Shapes


© 2001 Prentice-Hall 3-2

Examples of Parts Produced Using the Machining Processes in the Chapter

Figure 23.1 Typical parts and shapes produced with the machining processes described in this chapter.



Examples of Milling Cutters and Operations

Figure 23.2 Some of the basic types of milling cutters and milling operations.



Example of Part Produced on a CNC Milling Machine

Figure 23.3 A typical part that can be produced on a milling machine equipped with computer controls. Such parts can be made efficiently and repetitively on computer numerical control (CNC) machines, without the need for refixturing or reclamping the part.



Conventional and Climb Milling

Figure 23.4 (a) Schematic illustration of 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) Schematic illustration of cutter travel distance lc to reach full depth of cut.



Summary of Milling Parameters and Formulas

TABLE 23.1N = Rotational speed of the milling cutter, rpmf = Feed, mm/tooth or in./tooth

D = Cutter diameter, mm or in.n = Number of teeth on cutterv = Linear speed of the workpiece or feed rate, mm/min or in./minV = Surface speed of cutter, m/min or ft/min

=D Nf = Feed per tooth, mm/tooth or in/tooth

=v /N nl = Length of cut, mm or in.t = Cutting time, s or min

=( l+lc ) v , where lc =extent of the cutter’s first contact with workpieceMRR = mm

3/min or in.

3/min

=w d v , where w is the width of cutTorque = N-m or lb-ft

( Fc ) (D/2)Power = kW or hp

= (Torque) (ω ), where ω = 2π N radians/minNote: The units given are those that are commonly used; however, appropriate units mustbe used in the formulas.



Face MillingFigure 23.5 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. Source: IngersollCutting Tool Company.

Figure 23.6 A face-milling cutter with indexable inserts. Source: Courtesy of Ingersoll Cutting Tool Company.



Effects of Insert Shapes

Figure 23.7 Schematic illustration of 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. Source: Kennametal Inc. (d) Feed marks due to various insert shapes.



Face-Milling Cutter

Figure 23.8 Terminology for a face-milling cutter.



Effect of Lead Angle

Figure 23.9 The effect of lead angle on the undeformed chip thickness in face milling. Note that as the lead angle increase, 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 increase.



Cutter and Insert Position in Face Milling

Figure 23.10 (a) Relative position of the cutter and insert as it first engages the workpiece in face milling, (b) insert positions towards the end of the 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 MillingFigure 23.11 Cutters for (a) straddle milling, (b) form milling, (c) slotting, and (d) slitting with a milling cutter.



Other Milling Operations and Cutters

Figure 23.12 (a) T-slot cutting with a milling cutter. (b) A shell mill.



Arbors

Figure 23.13 Mounting a milling cutter on an arbor for use on a horizontal milling machine.



Capacities and Maximum WorkpieceDimensions for Machine Tools

TABLE 23.2 Typical Capacities and Maximum Workpiece Dimensions forSome Machine Tools

Machine toolMaximum dimension

m (ft)Power(kW)

Maximumspeed

Milling machines (table travel) Knee-and-column 1.4 (4.6) 20 4000 rpm Bed 4.3 (14) Numerical control 5 (16.5)Planers (table travel) 10 (33) 100 1.7Broaching machines (length) 2 (6.5) 0.9 MNGear cutting (gear diameter) 5 (16.5)Note: Larger capacities are available for special applications.



Approximate Cost of

Selected Tools for Machining

TABLE 23.3 Approximate Cost of Selected Tools for Machining*Tools Size (in.) Cost ($)Drills, HSS, straight shank 1/4 1.00–2.00

1/2 3.00–6.00Coated (TiN) 1/4 2.60–3.00

1/2 10–15Tapered shank 1/4 2.50–7.00

1 15–452 80–853 2504 950

Reamers, HSS, hand 1/4 10–151/2 10–15

Chucking 1/2 5–101 20–251 1/2 40–55

End mills, HSS 1/2 10–151 15–30

Carbide-tipped 1/2 30–351 45–60

Solid carbide 1/2 30–701 180

Burs, carbide 1/2 10–201 50–60

Milling cutters, HSS, staggered tooth, wide 4 35–758 130–260

Collets (5 core) 1 10–20*Cost depends on the particular type of material and shape of tool, its quality,and the amount purchased.



General Recommendations

for Milling Operations

TABLE 23.4General-purpose starting

conditions Range of conditions

Workpiecematerial Cutting tool

Feedmm/tooth(in./tooth)

Speedm/min

(ft/min)

Feedmm/tooth(in./tooth)

Speedm/min

(ft/min)Low-C and free-machining steels

Uncoated carbide,coated carbide,cermets

0.13–0.20(0.005–0.008)

120–180(400–600)

0.085–0.38(0.003–0.015)

90–425(300–1400)

Alloy steels Soft Uncoated, coated,

cermets0.10–0.18

(0.004–0.007)90–170

(300–550)0.08–0.30

(0.003–0.012)60–370

(200–1200) Hard Cermets, PCBN 0.10–0.15

(0.004–0.006)180–210

(600–700)0.08–0.25

(0.003–0.010)75–460

(250–1500)Cast iron, gray Soft Uncoated, coated,

cermets, SiN0.10–10.20

(0.004–0.008)120–760

(400–2500)0.08–0.38

(0.003–0.015)90–1370

(300–4500) Hard Cermets, SiN,

PCBN0.10–0.20

(0.004–0.008)120–210

(400–700)0.08–0.38

(0.003–0.015)90–460

(300–1500)Stainless steel,austenitic

Uncoated, coated,cermets

0.13–0.18(0.005–0.007)

120–370(400–1200)

0.08–0.38(0.003–0.015)

90–500(300–1800)

High-temperaturealloys, nickel base

Uncoated, coated,cermets, SiN,PCBN

0.10–0.18(0.004–0.007)

30–370(100–1200)

0.08–0.38(0.003–0.015)

30–550(90–1800)

Titanium alloys Uncoated, coated,cermets

0.13–0.15(0.005–0.006)

50–60(175–200)

0.08–0.38(0.003–0.015)

40–140(125–450)

Aluminum alloys Free machining Uncoated, coated,

PCD0.13–0.23

(0.005–0.009)610–900

(2000–3000)0.08–0.46

(0.003–0.018)300–3000

(1000–10,000)High silicon PCD 0.13

(0.005)610

(2000)0.08–0.38

(0.003–0–015)370–910

(1200–3000)Copper alloys Uncoated, coated,

PCD0.13–0.23

(0.005–0.009)300–760

(1000–2500)0.08–0.46

(0.003–0.018)90–1070

(300–3500)Thermoplastics andthermosets

Uncoated, coated,PCD

0.13–0.23(0.005–0.009)

270–460(900–1500)

0.08–0.46(0.003–0.018)

90–1370(300–4500)

Source: Based on data from Kennametal Inc.Note: Depths of cut, d , usually are in the range of 1–8 mm (0.04–0.3 in.). PCBN: polycrystalline cubic boron nitride;PCD: polycrystalline diamond.Note: See also Table 22.2 for range of cutting speeds within tool material groups.



General Troubleshooting Guide for Milling Operations

TABLE 23.5Problem Probable causesTool breakage Tool material lacks toughness; improper tool angles; cutting

parameters too high.Tool wear excessive Cutting parameters too high; improper tool material; improper tool

angles; improper cutting fluid.Rough surface finish Feed too high; spindle speed too low; too few teeth on cutter; tool

chipped or worn; built-up edge; vibration and chatter.Tolerances too broad Lack of spindle stiffness; excessive temperature rise; dull tool; chips

clogging cutter.Workpiece surfaceburnished

Dull tool; depth of cut too low; radial relief angle too small.

Back striking Dull cutting tools; cutter spindle tilt; negative tool angles.Chatter marks Insufficient stiffness of system; external vibrations; feed, depth, and

width of cut too large.Burr formation Dull cutting edges or too much honing; incorrect angle of entry or

exit; feed and depth of cut too high; incorrect insert geometry.Breakout Lead angle too low; incorrect cutting edge geometry; incorrect angle

of entry or exit; feed and depth of cut too high.



Surface Features and Corner Defects

Figure 23.14 Surface features and corner defects in face milling operations; see also Fig. 23.7. For troubleshooting, see Table 23.5. Source: Kennametal Inc.



Horizontal- and Vertical-Spindle Column-and-Knee Type Milling Machines

Figure 23.15 Schematic illustration of a horizontal-spindle column-and-knee type milling machine. Source: G. Boothroyd.

Figure 23.16 Schematic illustration of a vertical-spindle column-and-knee type milling machine (also called a knee miller). Source: G. Boothroyd.



Bed-Type Milling Machine

Figure 23.17 Schematic illustration of a bed-type milling machine. Note the single vertical-spindle cutter and two horizontal spindle cutters. Source: ASM International.



Additional Milling Machines

Figure 23.18 A computer numerical control, vertical-spindle milling machine. This machine is one of the most versatile machine tools. Source: Courtesy of Bridgeport Machines Division, Textron Inc.

Figure 23.19 Schematic illustration of a five-axis profile milling machine. Note that there are three principal linear and two angular movements of machine components


© 2001 Prentice-Hall -23

Examples of Parts Made on a Planer and by Broaching

Figure 23.20 Typical parts that can be made on a planer.

Figure 23.21 (a) Typical parts made by internal broaching. (b) Parts made by surface broaching. Heavy lines indicate broached surfaces. Source: General Broach and Engineering Company.



Broaches

Figure 23.22 (a) Cutting action of a broach, showing various features. (b) Terminology for a broach.



Chipbreakers and a Broaching Machine

(a)

(b)

(c)

Figure 23.23 Chipbreaker features on (a) a flat broach and (b) a round broach. (c) Vertical broaching machine. Source: Ty Miles, Inc.



Internal Broach and Turn Broaching

Figure 23.24 Terminology for a pull-type internal broach used for enlarging long holes.

Figure 23.25 Turn broaching of a crankshaft. The crankshaft rotates while the broaches pass tangentially across the crankshaft’s bearing surfaces. Source: Courtesy of IngersollCutting Tool Company.



Broaching Internal Splines

Figure 23.26



Sawing Operations

Figure 23.27 Examples of various sawing operations. Source: DoALL Company.



Types of Saw Teeth

Figure 23.28 (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

Figure 23.29 (a) High-speed-steel teeth welded on steel blade. (b) Carbide inserts brazed to blade teeth.

Figure 23.30 Types of burs. Source: The Copper Group.



Spur Gear

Figure 23.31 Nomenclature for an involute spur gear.



Gear GeneratingFigure 23.32 (a) Producing gear teeth on a blank by from 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 HobFigure 23.33 Schematic illustration of three views of gear cutting with a hob. Source: After E. P. DeGarmo and Society of Manufacturing Engineers



Cutting Bevel Gears

Figure 23.34 (a) Cutting a straight bevel-gear blank with two cutters. (b) Cutting a spiral bevel gear with a single cutter. Source: ASM International.



Gear Grinding

Figure 23.25 Finishing gears by grinding: (a) form grinding with shaped grinding wheels; (b) grinding by generating with two wheels.



Economics of Gear Production

Figure 23.36 Gear manufacturing cost as a function of gear quality. The numbers along the vertical lines indicate tolerances. Source: Society of Manufacturing Engineers.

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