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.

Production & Special Purpose Lathes

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