Production & Special Purpose Lathes
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Production & Special purpose Lathes
Capstan Lathe
Turret Lathe
Automatic Lathe
Duplicating Lathe
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Engine Lathe Limitations:Higher job setting time.
Multi-machining is not possible.
Higher Tool changing time
Accuracy and precision is poor.
Improvements:
Collect chuck, pneumatic chuck
Automatic bar-feed mechanism,
Auto-feeding of cutting tool,
multi-tool arrangements,
Automatic control of operation
sequences
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Break even analysis
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Automation in Lathe
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Production Lathes Capstan and Turret lathe -- used forrepetitive
production ofduplicate parts (i.e
interchangeable products)
Tailstock is replaced by a hexagonal turret,
which is an indexable toolholder that allows
multiple cutting operations to be performed,
each with a different cutting tool.
http://en.wikipedia.org/wiki/Interchangeable_partshttp://en.wikipedia.org/wiki/Indexing_(motion)http://en.wikipedia.org/wiki/Cutting_tool_(machining)http://en.wikipedia.org/wiki/Cutting_tool_(machining)http://en.wikipedia.org/wiki/Indexing_(motion)http://en.wikipedia.org/wiki/Interchangeable_parts -
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Difference with centre Lathe
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Aspects Production lathe Centre lathe
Nature of productionwork
Applied to quantityproduction
Applied to differentjobs
Constructionaldifference Hexagonal turret, notailstock Has a tailstock
No of tools handled ata time
Multi tool holding,multi machiningpossible
No such provisionavailable
Tool set up/ changing
time
less more
Lead screw Thread cuttingperformed by dieheads, no lead screw
Has one lead screw
Degree of automation Semi or full
automation
Very normal
Rate of production high low
Labour cost low high
Overhead cost high low
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Collet chuck
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Difference between capstan & turret lathe
Aspects Turret Lathe Capstan lathe
Turret position Mounted directly on saddleMounted on an auxiliaryslide, which can move onsaddle
Feeding of tools Entire saddle is moved Auxiliary slide (ram) is
moved on saddle
Extent of rigidity Very high Lower due to overhung of the ram results tooldeflection
Capability to handle job Heavier job can be
machined
Lighter and smaller jobs
only can machine
Maximum bar size Up to 200 mm diameter Up to 60 mm diameter
Tool travel Almost full length of bed Limited tool travel
Type of carriage Over hung type Reach over type
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Turret Lathe
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Tool Layout
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Production Lathes may be Classified by: size (small, medium, or large); method of control (manual, automated mechanically, or automated via
computer (numerical control (NC) or computer numerical control (CNC));and
bed orientation (horizontal or vertical).
Semi-automatic turret lathes -- power feeds and automatic turret-indexing atthe end of the return stroke.
Automatic turret lathes (automatic screw machines) --can execute manypart-cutting cycles without human intervention and thus, productivityincreased significantly.
---use cams to automate the sliding and indexing of the turret and
the opening and closing of the chuck.
CNC turret lathes: The advent of electronics-based automation in
machine tools via numerical control (NC) and thencomputer numerical control (CNC) displaced to a large extent.
Vertical turret lathes: the headstock to sit on the floor and the faceplate tobecome a horizontal rotating table.
--useful for the handling of very large, heavy, short workpieces
http://en.wikipedia.org/wiki/Camhttp://en.wikipedia.org/wiki/Chuck_(engineering)http://en.wikipedia.org/wiki/Machine_toolshttp://en.wikipedia.org/wiki/Numerical_controlhttp://en.wikipedia.org/wiki/Computer_numerical_controlhttp://en.wikipedia.org/wiki/Lathe_faceplatehttp://en.wikipedia.org/wiki/Lathe_faceplatehttp://en.wikipedia.org/wiki/Computer_numerical_controlhttp://en.wikipedia.org/wiki/Numerical_controlhttp://en.wikipedia.org/wiki/Machine_toolshttp://en.wikipedia.org/wiki/Chuck_(engineering)http://en.wikipedia.org/wiki/Cam -
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Multispindle lathes--have more than one spindle and automatedcontrol
-- via cams orCNC).
--production machines specializing in high-volume production.--smaller types are usually called screw machines,
-- larger variants are called automatic chucking machines
Screw machines usually work from bar stock, while chuckers
automatically chuck up individual blanks from a magazine.
Typical minimum profitable production lot size on a screw machineis in the thousands of parts due to the large setup time.
Once set up, a screw machine can rapidly and efficiently producethousands of parts on a continuous basis with high accuracy, lowcycle time, and very little human intervention.
http://en.wikipedia.org/wiki/Camhttp://en.wikipedia.org/wiki/CNChttp://en.wikipedia.org/wiki/Screw_machinehttp://en.wikipedia.org/wiki/Screw_machinehttp://en.wikipedia.org/wiki/CNChttp://en.wikipedia.org/wiki/Cam -
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Automatic Lathes
Single- and multiple-spindle automatic lathes
Six or eight different operations may be performed on
many parts at the same time
Will produce parts for as long as required Tracer lathes/ duplicating Lathe
Used where a few duplicate parts required
cross-slide controlled by stylus bearing against round
or flat template
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Programmable lathe
Operated as standard lathe or programmable lathe toautomatically repeat machining operations
2-axis -- exact location of cutting tool and work-piece in
X and Z axes
Computerized numerically controlled lathes
Cutting-tool movements controlled by computer-
controlled program to perform sequence of operations
automatically
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Taper turning attachment
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Duplicating Lathe
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Transfer Machining
system of automatic machining, in which a
number of machine tools are arranged in a
series in the sequence of operations and
linked together with transfer equipments.
Application areas:
mass production of identical parts.
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Classification of TM
In-line transfer machine: 25 or more station,pallet, guide-rails, conveyor system, auto-clamping
devices at each station.
Rotary transfer machine: 6-8 stations, less floorspace required, round/ rotary table with indexing
mechanism
Drum type transfer machine: rotary drum withfixtures, front and rear slide machining head
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Specific characteristics of TM
Automatic work loading mechanisms:Electric hoist and conveyor (large work)
Hopper and chutes (small work)
Automatic transfer mechanisms: Pawl type, rotating bar and finger mechanism, walking beam
mechanism etc.
Auxiliary equipments:
Electrical control systemAutomatic work lading and unloading devices
control and disposal of unwanted chips
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Advantages and Limitations
output, accuracy and precision increases
But, high initial cost, complex controlsystem, breakdown of one machine
results complete stoppage, limited to high
volume of production.