Production technology Ch24

7/31/2019 Production technology Ch24

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Kalpakjian SchmidManufacturing Engineering and Technology 2001 Prentice-Hall Page 24-1

CHAPTER 24

Machining and Turning Centers,Machine-Tool Structures, and Machining

Economics


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Examples of Parts Machined on MachiningCenters

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 wouldordinarily require a variety of machine tools. Source: Toyoda Machinery.


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Horizontal-Spindle Machining Center

Figure 24.2 A horizontal-spindlemachining center, equipped with anautomatic tool changes. Toolmagazines can store 200 cuttingtools. Source: Courtesy ofCincinnati Milacron, Inc.


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Five-Axis Machining Center

Figure 24.3 Schematicillustration of a five-axis

machining center. Note that inaddition to the three linearmovements, the pallet can beswiveled (rotated) along two axes,allowing the machining ofcomplex shapes such as thoseshown in Fig. 24.1. Source:

Toyoda Machinery.


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Pallets

Figure 24.4 (a) Schematic illustration of the top view of a horizontal-spindlemachining 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 in such systems. Source: Hitachi SeikiCo., Ltd.


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Swing-Around Tool Changer

Figure 24.5 Swing-around tool changer on a horizontal-spindle machiningcenter. Source: Cincinnati Milacron, Inc.


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Touch Probes

Figure 24.6 Touch probes used inmachining centers for determiningworkpiece and tool positions andsurfaces relative to the machine table orcolumn. (a) Touch probe determining

the X-Y (horizontal) position of aworkpiece, (b) determining the heightof a horizontal surface, (c) determiningthe planar position of the surface of acutter (for instance, for cutter-diametercompensation), and (d) determining thelength of a tool for tool-length offset.

Source: Hitachi Seiki Co., Ltd.


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Vertical-Spindle Machining Center

Figure 24.7 A vertical-spindlemachining center. The toolmagazine is on the left of the

machine. The control panel onthe right can be swiveled by theoperator. Source: Courtesy ofCincinnati Milacron, Inc.


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CNC Turning Center

Figure 24.8 Schematicillustration of a three-turret,two-spindle computernumerical controlled turningcenter. Source: HitachiSeiki Co., Ltd.


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Chip-Collecting System

Figure 24.9 Schematic illustration of achip-collecting system in a horizontal-spindle machining center. The chipsthat fall by gravity are collected by the

two horizontal conveyors at the bottomof the troughs. Source: OkumaMachinery Works Ltd.


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Machining Outer Bearing Races on a

Turning CenterFigure 24.10


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Machine-Tool Structure and GuidewaysFigure 24.11 Anexample of a machine-tool structure. The box-type, one-piece design

with internal diagonalribs significantlyimproves the stiffness ofthe machine. Source:Okuma MachineryWorks Ltd.

Figure 24.12 Steel guidewaysintegrally-cast on top of the cast-ironbed of a machining center. Becauseof its higher elastic modulus, the steelprovides higher stiffness than castiron. Source: Hitachi Seiki Co., Ltd.


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Chatter

Figure 24.13 Chatter marks (right ofcenter of photograph) on the surfaceof a turned part. Source: GeneralElectric Company.


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Internal Damping of Structural Materials

Figure 24.14 The relative damping capacity of (a) gray cast iron and (b) epoxy-granite composite material. The vertical scale is the amplitude of vibration and thehorizontal scale is time. Source: Cincinnati Milacron, Inc.


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Joints in Machine-Tool Structures

Figure 24.15 The damping of vibrations as a function of the number of components on alathe. Joints dissipate energy; the greater the number of joints, the higher the damping

capacity of the machine. Source: J. Peters.


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MachiningEconomics

Figure 24.16 Graphsshowing (a) cost perpiece and (b) time perpiece in machining.Note the optimum

speeds for both costand time. The rangebetween the two isknown as the high-efficiency machiningrange.

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Production technology Ch24