Transcript Lathe Practice - موقع كلية الهندسة

Lathe Practice & Milling
Introduction
Lathe is a machine, which removes the metal
from a piece of work to the required shape
&size
Types of Lathe
– Engine Lathe
The most common form of lathe, motor driven and
comes in large variety of sizes and shapes.
– Bench Lathe
A bench top model usually of low power used to
make precision machine small work pieces.
– Tracer Lathe
A lathe that has the ability to follow a template to
copy a shape or contour.
– Automatic Lathe
A lathe in which the work piece is automatically fed and
removed without use of an operator. Cutting operations
are automatically controlled by a sequencer of some form.
– Turret Lathe
Lathe which have multiple tools mounted on turret either
attached to the tailstock or the cross-slide, which allows
for quick changes in tooling and cutting operations.
– Computer Controlled Lathe
A highly automated lathe, where both cutting, loading,
tool changing, and part unloading are automatically
controlled by computer coding.
Component Description
Lathe Operations
• Turning:produce straight, conical, curved, or grooved workpieces
• Facing: to produce a flat surface at the end of the part or for making
face grooves.
• Boring: to enlarge a hole or cylindrical cavity made by a previous
process or to produce circular internal grooves.
• Drilling: to produce a hole by fixing a drill in the tailstock
• Threading: to produce external or internal threads
• Knurling: to produce a regularly shaped roughness on cylindrical
surfaces
Lathe Operations
Cutting Tools
Single point cutting tool
Work Holding in Turning:
1. Three jaw chuck
- For holding
cylindrical stock
centered.
- For facing/center
drilling the end of your
aluminum stock
2. Four-Jaw Chuck
- This is independent
chuck generally has four
jaws , which are
adjusted individually on
the chuck face by
means of adjusting
screws
3. Collet Chuck
Collet chuck is used
to hold small work
pieces
Collets Types
Fig : (a) and (b) Schematic illustrations of a draw-in-type collets. The
workpiece is placed in the collet hole, and the conical surfaces of the
collet are forced inward by pulling it with a draw bar into the sleeve.
(c) A push-out type collet. (d) Workholding of a part on a face plate.
4. Magnetic Chuck
Thin jobs can be
held by means of
magnetic chucks.
Milling
•
Milling is one of the basic machining
processes.
• Milling is a very versatile process capable of
producing simple two dimensional flat shapes
to complex three dimensional interlaced
surface configurations.
The milling process:
•Typically uses a multi-tooth
cutter
•Work is fed into the rotating
cutter
•Capable of high MRR
•Well suited for mass
production applications
•Cutting tools for this process
are called milling cutters
Classifications
• Milling operations are classified into two major
categories:
– Peripheral (side)
• Generally in a plane parallel to the axis of the cutter
• Cross section of the milled surface corresponds to the
contour of the cutter
– Face
• Generally at right angles to the axis of rotation of the cutter
• Milled surface is flat and has no relationship to the contour
of the cutter
• Combined cutting action of the side and face of the milling
cutter
Straddle milling - milling two parallel surfaces
using two cutters spaced apart on an arbor.
Cutters
Operating Parameters
• Rpm
– Cutting Speed converted into Rpm based on cutter
diameter
• Feed rate
– Feed per tooth
– Table feed rate
• Feed direction -- Conventional vs. Climb
– Conventional milling
• Most common method of feed
• Feed work against the rotation of the cutter
Workholding Devices
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Vise
Chucks
Rotating tables
Angle plates
Special fixtures
Universal dividing head
Modular fixturing systems
Clamp work to table
Vices
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Simple formula
v = πNDo (v = cutting speed mm/min, N =
rotational speed rev/min, Do = original
diameter, ft or mm)
Do-Df = 2d (d = depth of cut, mm)
fr = Nxf (f = feed in mm/rev, fr = feed rate in
mm/min)
Tm = L/fr (L = length of work piece, Tm =
machining time in min or sec
MRR = Material Removal Rate = v x f x d, MRR
in mm3/min
Example 1: A cylindrical work part 125 mm in
diameter and 900 mm long is to be turned in an
engine lathe. Cutting conditions are: v = 2.5 m/s,
f = 0.3 mm/rev, and d = 2.0 mm. Determine: (a)
cutting time, and (b) metal removal rate.
Example 2: A workbar with 5.0 in diameter and 48 in length
is chucked in an engine lathe and supported at the opposite
end using a live center. A 40.0 in portion of the length is to be
turned to a diameter of 4.75 in one pass at a speed = 400
ft/min and a feed = 0.012 in/rev. Determine: (a) the required
depth of cut, (b) cutting time, and (c) metal removal rate.