. Takım Tezgâhları: Planya, Freze ve İşlem Merkezleri

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1 1. Takım Tezgâhları: Planya, Freze ve İşlem Merkezleri.1 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..2

2 2 Examples of Milling Cutters and Operations Figure 23.2 Some of the basic types of milling cutters and milling operations..3 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..4

3 3 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, t c, and workpiece speed, v. (c) Schematic illustration of cutter travel distance l c to reach full depth of cut..5 Summary of Milling Parameters and Formulas TABLE 23.1 N = Rotational speed of the milling cutter, rpm f = Feed, mm/tooth or in./tooth D = Cutter diameter, mm or in. n = Number of teeth on cutter v = Linear speed of the workpiece or feed rate, mm/min or in./min V = Surface speed of cutter, m/min or ft/min =D N f = Feed per tooth, mm/tooth or in/tooth =v /N n l = Length of cut, mm or in. t = Cutting time, s or min =( l+l c ) v, where l c =extent of the cutter s first contact with workpiece MRR = mm 3 /min or in. 3 /min =w d v, where w is the width of cut Torque = N-m or lb-ft ( F c ) (D/2) Power = kw or hp = (Torque) (ω ), where ω = 2π N radians/min Note: The units given are those that are commonly used; however, appropriate units must be used in the formulas..6

4 4 Face Milling Figure 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: Ingersoll Cutting Tool Company..7 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..8

5 5 Face-Milling Cutter Figure 23.8 Terminology for a face-milling cutter..9 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..10

6 6 Cutter and Insert Position in Face Milling Figure (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..11 Cutters for Different Types of Milling Figure Cutters for (a) straddle milling, (b) form milling, (c) slotting, and (d) slitting with a milling cutter..12

7 7 Other Milling Operations and Cutters Figure (a) T-slot cutting with a milling cutter. (b) A shell mill..13 Arbors Figure Mounting a milling cutter on an arbor for use on a horizontal milling machine..14

8 8 Capacities and Maximum Workpiece Dimensions for Machine Tools TABLE 23.2 Typical Capacities and Maximum Workpiece Dimensions for Some Machine Tools Machine tool Maximum dimension m (ft) Power (kw) Maximum speed Milling machines (table travel) Knee-and-column 1.4 (4.6) rpm Bed 4.3 (14) Numerical control 5 (16.5) Planers (table travel) 10 (33) Broaching machines (length) 2 (6.5) 0.9 MN Gear cutting (gear diameter) 5 (16.5) Note: Larger capacities are available for special applications..15 Approxima te 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/ / Coated (TiN) 1/ / Tapered shank 1/ Reamers, HSS, hand 1/ / Chucking 1/ / End mills, HSS 1/ Carbide-tipped 1/ Solid carbide 1/ Burs, carbide 1/ Milling cutters, HSS, staggered tooth, wide Collets (5 core) *Cost depends on the particular type of material and shape of tool, its quality, and the amount purchased..16

9 9 General Recommenda tions for Milling Operations TABLE 23.4 Workpiece material Low-C and freemachining steels Alloy steels Soft Cutting tool Uncoated carbide, coated carbide, cermets General-purpose starting conditions Feed Speed mm/tooth m/min (in./tooth) (ft/min) ( ) Uncoated, coated, cermets ( ) Hard Cermets, PCBN ( ) Cast iron, gray Soft Uncoated, coated, Hard Stainless steel, austenitic High-temperature alloys, nickel base Titanium alloys Aluminum alloys Free machining cermets, SiN Cermets, SiN, PCBN Uncoated, coated, cermets Uncoated, coated, cermets, SiN, PCBN Uncoated, coated, cermets ( ) ( ) ( ) ( ) ( ) Uncoated, coated, PCD ( ) High silicon PCD 0.13 (0.005) Copper alloys Uncoated, coated, PCD ( ) Thermoplastics and Uncoated, coated, thermosets PCD ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) 610 (2000) ( ) ( ) Range of conditions Feed mm/tooth (in./tooth) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) Speed m/min (ft/min) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ,000) ( ) ( ) ( ) Source: Based on data from Kennametal Inc. Note: Depths of cut, d, usually are in the range of 1 8 mm ( in.). PCBN: polycrystalline cubic boron nitride; PCD: polycrystalline diamond. Note: See also Table 22.2 for range of cutting speeds within tool material groups..17 General Troubleshooting Guide for Milling Operations TABLE 23.5 Problem Tool breakage Tool wear excessive Rough surface finish Tolerances too broad Workpiece surface burnished Back striking Chatter marks Burr formation Breakout Probable causes Tool material lacks toughness; improper tool angles; cutting parameters too high. Cutting parameters too high; improper tool material; improper tool angles; improper cutting fluid. Feed too high; spindle speed too low; too few teeth on cutter; tool chipped or worn; built-up edge; vibration and chatter. Lack of spindle stiffness; excessive temperature rise; dull tool; chips clogging cutter. Dull tool; depth of cut too low; radial relief angle too small. Dull cutting tools; cutter spindle tilt; negative tool angles. Insufficient stiffness of system; external vibrations; feed, depth, and width of cut too large. Dull cutting edges or too much honing; incorrect angle of entry or exit; feed and depth of cut too high; incorrect insert geometry. Lead angle too low; incorrect cutting edge geometry; incorrect angle of entry or exit; feed and depth of cut too high..18

10 10 Surface Features and Corner Defects Figure Surface features and corner defects in face milling operations; see also Fig For troubleshooting, see Table Source: Kennametal Inc..19 Horizontal- and Vertical-Spindle Column-and-Knee Type Milling Machines Figure Schematic illustration of a horizontal-spindle column-and-knee type milling machine. Source: G. Boothroyd. Figure Schematic illustration of a verticalspindle column-and-knee type milling machine (also called a knee miller). Source: G. Boothroyd..20

11 11 Bed-Type Milling Machine Figure Schematic illustration of a bed-type milling machine. Note the single vertical-spindle cutter and two horizontal spindle cutters. Source: ASM International..21 Additional Milling Machines Figure 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 Schematic illustration of a five-axis profile milling machine. Note that there are three principal linear and two angular movements of machine components.22

12 12 Examples of Parts Made on a Planer and by Broaching Figure Typical parts that can be made on a planer. Figure (a) Typical parts made by internal broaching. (b) Parts made by surface broaching. Heavy lines indicate broached surfaces. Source: General Broach and Engineering Company..23 Broaches Figure (a) Cutting action of a broach, showing various features. (b) Terminology for a broach..24

13 13 (a) Chipbreakers and a Broaching Machine Figure Chipbreaker features on (a) a flat broach and (b) a round broach. (c) Vertical broaching machine. Source: Ty Miles, Inc. (c) (b).25 Internal Broach and Turn Broaching Figure Terminology for a pull-type internal broach used for enlarging long holes. Figure Turn broaching of a crankshaft. The crankshaft rotates while the broaches pass tangentially across the crankshaft s bearing surfaces. Source: Courtesy of Ingersoll Cutting Tool Company..26

14 14 Broaching Internal Splines.27 Sawing Operations.28

15 15 Types of Saw Teeth Figure (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..29 Saw Teeth and Burs Figure (a) High-speed-steel teeth welded on steel blade. (b) Carbide inserts brazed to blade teeth. Figure Types of burs. Source: The Copper Group..30

16 16 Spur Gear Figure Nomenclature for an involute spur gear..31 Figure (a) Producing gear teeth on a blank by from cutting. (b) Schematic illustration of gear generating with a pinionshaped gear cutter. (c) Schematic illustration of gear generating in a gear shaper using a pinionshaped cutter. Note that the cutter reciprocates vertically. (d) Gear generating with rackshaped cutter. Gear Generating.32

17 17 Gear Cutting With a Hob Figure Schematic illustration of three views of gear cutting with a hob. Source: After E. P. DeGarmo and Society of Manufacturing Engineers.33 Cutting Bevel Gears Figure (a) Cutting a straight bevel-gear blank with two cutters. (b) Cutting a spiral bevel gear with a single cutter. Source: ASM International..34

18 18 Gear Grinding Figure Finishing gears by grinding: (a) form grinding with shaped grinding wheels; (b) grinding by generating with two wheels..35 Economics of Gear Production Figure Gear manufacturing cost as a function of gear quality. The numbers along the vertical lines indicate tolerances. Source: Society of Manufacturing Engineers..36

19 19 Examples of Parts Machined on Machining Centers Figure 24.1 Examples of parts that can be machined on machining centers, using various processes such as turning, facing, milling, drilling, boring, reaming, and threading. Such parts would ordinarily require a variety of machine tools. Source: Toyoda Machinery..37 Figure 24.2 A horizontal-spindle machining center, equipped with an automatic tool changes. Tool magazines can store 200 cutting tools. Source: Courtesy of Cincinnati Milacron, Inc. Horizontal-Spindle Machining Center.38

20 20 Five-Axis Machining Center Figure 24.3 Schematic illustration of a five-axis machining center. Note that in addition to the three linear movements, the pallet can be swiveled (rotated) along two axes, allowing the machining of complex shapes such as those shown in Fig Source: Toyoda Machinery..39 Pallets Figure 24.4 (a) Schematic illustration of the top view of a horizontal-spindle machining center showing the pallet pool, set-up station for a pallet, pallet carrier, and an active pallet in operation (shown directly below the spindle of the machine). (b) Schematic illustration of two machining centers with a common pallet pool. Various other arrangements are possible.40 in such İmalat systems. MakinalarıSource: Hitachi Seiki Planya, Co., Ltd. Freze vd. Eylül 2008

21 21 Swing-Around Tool Changer Figure 24.5 Swing-around tool changer on a horizontal-spindle machining center. Source: Cincinnati Milacron, Inc..41 Touch Probes Figure 24.6 Touch probes used in machining centers for determining workpiece and tool positions and surfaces relative to the machine table or column. (a) Touch probe determining the X-Y (horizontal) position of a workpiece, (b) determining the height of a horizontal surface, (c) determining the planar position of the surface of a cutter (for instance, for cutterdiameter compensation), and (d) determining the length of a tool for toollength offset. Source: Hitachi Seiki Co., Ltd..42

22 22 Vertical-Spindle Machining Center Figure 24.7 A vertical-spindle machining center. The tool magazine is on the left of the machine. The control panel on the right can be swiveled by the operator. Source: Courtesy of Cincinnati Milacron, Inc..43 Figure 24.8 Schematic illustration of a three-turret, two-spindle computer numerical controlled turning center. Source: Hitachi Seiki Co., Ltd. CNC Turning Center.44

23 23 Chip-Collecting System Figure 24.9 Schematic illustration of a chipcollecting system in a horizontal-spindle machining center. The chips that fall by gravity are collected by the two horizontal conveyors at the bottom of the troughs. Source: Okuma Machinery Works Ltd..45 Machining Outer Bearing Races on a Turning Center Figure

24 24 Machine-Tool Structure and Guideways Figure An example of a machine-tool structure. The box-type, one-piece design with internal diagonal ribs significantly improves the stiffness of the machine. Source: Okuma Machinery Works Ltd. Figure Steel guideways integrally-cast on top of the cast-iron bed of a machining center. Because of its higher elastic modulus, the steel provides higher stiffness than cast iron. Source: Hitachi Seiki Co., Ltd..47 Chatter Figure Chatter marks (right of center of photograph) on the surface of a turned part. Source: General Electric Company..48

25 Internal Damping of Structural Materials Figure The relative damping capacity of (a) gray cast iron and (b) epoxy-granite composite material. The vertical scale is the amplitude of vibration and the horizontal scale is time. Source: Cincinnati Milacron, Inc..49 Joints in Machine-Tool Structures Figure The damping of vibrations as a function of the number of components on a lathe. Joints dissipate energy; the greater the number of joints, the higher the damping capacity of the machine. Source: J. Peters

26 26 Machining Economics Figure Graphs showing (a) cost per piece and (b) time per piece in machining. Note the optimum speeds for both cost and time. The range between the two is known as the high-efficiency machining range..51