Turning Process Proses Manufaktur II

Sumber: Manufacturing Engineering & Technology Oleh: Serope Kalpakjian

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Mesin Bubut (lathe)

Mesin bubut merupakan mesin serba guna (general purpose machine), karena mampu mengerjakan berbagai jenis pekerjaan.

Bagian utama mesin bubut adalah: (1) the bed, (2) the headstock, (3) the carriage, (4) the tailstock, and (5) the gearbox.

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Engine Lathe (1600x12000) American

Salah satu cara u/ melihat dimensi benda kerja yg bisa diproses di mesin bubut adalah dengan melihat swing dan distance between center dari mesin bubut.

Swing menunjukkan diameter maksimum benda kerja yang bisa diproses di mesin bubut tersebut.

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Beberapa contoh mesin bubut (1)

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Beberapa contoh mesin bubut (2)

Big engine lathe (www.osun.org)

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Beberapa contoh mesin bubut (3)

Big engine lathe, 60 ft c - c (www.osun.org)

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Bagian-bagian mesin bubut

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Lathe Construction & Description

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Engine Lathe Part Descriptions

Spindle The spindle holds and drives the workpiece.

Cross Feed

Handwheel

The cross feed handwheel is used to manually position and/or hand feed the compound rest

in the X axis.

Carriage

Handwheel

The carriage handwheel is used to manually position and/or hand feed the carriage in the

longitudinal or Z axis.

Carriage The carriage houses the saddle, the cross slide, and the apron. The main function of the

carriage is to position the tool along the lathe bed.

Spindle

Clutch Lever This lever controls the spindle’s rotation and direction.

Brake

This type of spindle brake uses the foot pedal. The foot pedal type of brake is found on

many types of lathes. When the foot pedal is actuated, the spindle will stop regardless

of the position of the spindle clutch lever.

Feed Rod The feed rod transmits power from the headstock to the carriage for feeding operations.

Lead Screw

The lead screw transmits power from the headstock to the carriage for screw thread cutting

operations. On some lesser types of lathes the feed rod and the lead screw are used for

both the feed and the screw cutting power transmission.

Rack The rack or gear rack, as it is sometimes referred to, links with the carriage handwheel to

make longitudinal movement of the carriage possible.

Bed Ways The bed ways align the components of the lathe. The bed is the back bone of the machine.

Tailstock The tailstock is used to support the right end of the work. The tailstock is also used for

tool-holding for machining operations, such as drilling, reaming, and tapping.

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Figure 2 - Lathe Parts Descriptions

Headstock

The headstock houses the

spindle and the components

which drive the spindle and the

feed gears.

Spindle Speed

Selector

The spindle speed selector

allows the operator to adjust

the spindle speed of the

machine.

Emergency Stop

Button

The emergency stop button

turns off the power to the

machine.

Motor Start

Button

The motor start button starts the electric drive motor for the machine. The

motor start button does not control the spindle; however, it does supply the

power.

Spindle Clutch

and Brake Lever

This lever controls the spindle rotation. Through the use of this lever, the

operator controls the spindle direction, spindle on, and spindle off. On some

machines, when the spindle is turned off, a magnetic spindle brake is

applied. The other type of spindle brake is the foot pedal. The foot pedal

type of brake is found on many other types of machines.

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Lathe

Cutting

Operations

Figure 23.1 Miscellaneous cutting

operations that can be performed

on a lathe. Note that all parts are

circular – a property known as axi-

symmetry. The tools used, their

shape, and the processing

parameters are described

throughout this chapter.

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Characteristics of Machining Processes and

Typical Dimensional Tolerances

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Lathe

Figure 23.2 General view of a typical lathe, showing various components.

Source: Courtesy of Heidenreich & Harbeck.

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Turning Operation

Figure 23.3 Schematic illustration of the basic turning operation, showing depth-of-

cut, d; feed, f; and spindle rotational speed, N in rev/min. Cutting speed is the surface

speed of the workpiece at the tool tip.

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Proses Turning: terminologi

Cutting speed (kecepatan potong, m/menit): kecepatan keliling di sisi potong pahat/permukaan benda kerja.

Depth of cut (kedalaman pemotongan, mm): menunjukkan kedalaman potong pahat saat proses pemotongan.

Feed (gerak makan, mm/rev): seberapa besar pahat memakan benda kerja saat benda kerja berputar 1 putaran.

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Designations for a Right-Hand

Cutting Tool

Figure 23.4 Designations for a right-hand cutting tool. Right-hand means the tool

travels form right to left, as shown in Fig. 23.3.

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General Recommendations for Tool

Angles in Turning

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Summary

of Turning

Parameters

and

Formulas

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Forces Acting on a Cutting Tool in

Turning

Figure 23.5 Forces acting on a cuttin tool in turning, Fc is the cutting force, Ft

is the thrust of feed force (in the direction of feed), and Fr is the radial force

that tends to push the tool away from the workpiece being machined.

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Range of Applicable Cutting Speeds and

Feeds for Tool Materials

Figure 23.6 The range of

applicable cutting speeds and

feeds for a variety of tool

materials.

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General Recommendations for Turning Operations

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General Recommendations for Turning Operations, con’t.

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General Recommendations for Turning Operations, con’t

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General Recommendations for Cutting Fluids for

Machining

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Typical Capacities and Maximum Workpiece

Dimensions for Machine Tools

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Collets

Figure 23.7 (a) and (b) Schematic illustrations of a draw-in type collet. The

workpiece is placed in the collet hole, and the conical surfaces of the collet are

forced inwards by pulling it with a draw bar into the sleeve. (c) A push-out type

collet. (d) Workholding of a workpiece on a face plate.

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Mandrels to Hold Work-pieces for Turning

Figure 23.8 Various types of mandrels to hold workpieces for turning. These mandrels

usually are mounted between centers on a lathe. Note that in (a), both the cylindrical

and the end faces of the workpiece can be machined, whereas in (b) and (c), only the

cylindrical surfaces can be machined.

Mandrel berfunggi u/ memegang b-kerja yang didalamnya berlubang (hollow work-piece), agar b-kerja bisa diproses (machining) di mesin bubut.

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Turret Lathe

Figure 23.9 Schematic illustration of the components of a turret lathe.

Note the two turrets: square and hexagonal (main).

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Numerical Control Lathe and Turret

Figure 23.10 (a) A computer numerical-control lathe. Note the two turrets on

this machine. These machines have higher power and spindle speed than other

lathes in order to take advantage of new cutting tools with enhanced properties.

(b) A typical turret equipped with ten tools, some of which are powered.

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Parts Made on CNC Lathes

Figure 23.11 Typical parts made on CNC lathes.

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Example 23.3: Machining of Complex

Shapes

Figure 23.12 Examples of more complex

shapes that can be produced on a CNC lathe.

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Typical

Production

Rates for

Various

Machining

Operations

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Range of Surface

Roughness in

Machining

Processes

Figure 23.13 The range of

surface roughnesses obtained

in various machining

processes. Note the wide

range within each group,

especially in turning and boring.

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Range of

Dimensional

Tolerances in

Machining as a

Function of

Work-piece Size

Figure 23.14 Range of

dimensional tolerances obtained

in various machining processes

as a function of workpiece size.

Note that there is an order os

magnitude difference between

small and large workpieces.

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Troubleshooting Guide for Turning

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Cutting

Screw

Threads

Figure 23.15 (a) Cutting screw threads on a lathe with a single-point cutting tool. (b) Cutting screw

threads with a single-point tool in several passes, normally utilized for large threads. The small arrows in

the figures show the direction of the feed, and the broken lines show the position of the cutting tool as time

progresses. Note that in radial cutting, the tool is fed directly into the workpiece. In flank cutting, the tool is

fed inot the piece along the right face of the thread. In incremental cutting, the tool is first fed directly into

the piece at the center of the thread, then at its sides, and finally into the root. (c) A typical coated-carbide

insert in the process of cutting screw threads on a round shaft. (d) Cutting internal screw threads with a

carbide insert. Source: (c): Courtesy of Iscar Metals Inc.

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Chasers and Die for Thread Cutting

Figure 23.16 (a) Straight chasers for cutting threads on a

lathe. (b) Circular chasers. (c) A solid threading die.

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Parameter Turning

Zw adalah laju penghasilan geram,

f adalah pemakanan (feed),

nw adalah putaran benda kerja (rpm),

dm diameter benda kerja setelah di machining,

ap adalah kedalaman pemakanan,

ps adalah specific cutting energy.

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Tabel Specific Cutting Energy

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Parameter dan Perhitungan Dasar Proses

Pemesinan (Turning)

Waktu permesinan

Laju pembuangan geram

Daya pemotongan

Daya motor

nl

tw

w

m f

adnaZ pmwpwf

ZpP wsm

m

m

e

PP

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Parameter dan Perhitungan Dasar Proses

Pemesinan (Turning)

Daya pemotongan

Torsi

T adalah torsi yang dibutuhkan,

ω adalah kecepatan sudut = 2N di mana N adalah putaran spindle (benda kerja),

Fc adalah gaya pemotongan (cutting force),

davg adalah diameter rata-rata b-kerja, (dw+dm)/2

TPm

)2/( avgc dFT