microsoft powerpoint - lecture8

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MANUFACTURINGMANUFACTURING

PROCESSESPROCESSES

-- AMEM 201 AMEM 201 ––

Lecture 8Lecture 8:: Machining ProcessesMachining Processes

DR. SOTIRIS L. OMIROU

MillingMilling

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Milling Machining Milling Machining Milling Machining Milling Machining Milling Machining Milling Machining Milling Machining Milling Machining -------- DefinitionDefinitionDefinitionDefinitionDefinitionDefinitionDefinitionDefinition

Milling is one of the basic machining processes that allows large amounts of material to be removed quickly.

Milling is a very versatile process capable of producing simple two dimensional flat shapes to complex three dimensional interlaced surface configurations.

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•At all types of milling machines, the cutting toolperforms a rotational motion, that is the cuttingmotion. The rotation axis of the tool could behorizontal or vertical, depending on machine-tool version.

• The feeding motion is achieved either by partor tool, or both, usually on three perpendiculardirections.

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The Milling process

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Milling Machining Milling Machining Milling Machining Milling Machining Milling Machining Milling Machining Milling Machining Milling Machining video 1video 1video 1video 1video 1video 1video 1video 1

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Main cutting motion

Feeding motion

MachinedSurface

Milling Tool

Part

Swarfs

In order to perform a flat surface by milling operation, a relativemotion has to be between the milling

tool and part. In this respect the milling tool will have a rotation motion, that is the main cutting motion, and either the tool or part has to perform a translation motion, that is the feeding motion.

In order to perform a flat surface by milling operation, a relativemotion has to be between the milling

tool and part. In this respect the milling tool will have a rotation motion, that is the main cutting motion, and either the tool or part has to perform a translation motion, that is the feeding motion.

Click herefor

animation

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Milling Machine Tools Milling Machine Tools Milling Machine Tools Milling Machine Tools Milling Machine Tools Milling Machine Tools Milling Machine Tools Milling Machine Tools -------- TypesTypesTypesTypesTypesTypesTypesTypes

Horizontal Milling Machine

Horizontal spindle - Designed for peripheral milling operations

X axis motion

Z axis motionY axis motion

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Vertical Milling Machine

Vertical spindle - Designed for face milling operations

X axis motion

Y axis motionZ axis motion

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Vertical Milling Machining center

Tool Post

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Automatic Tool Change on a Vertical Milling Machining center

Up milling

Also called Also called conventional millingconventional milling,,

-- Wheel rotation opposite of the feedWheel rotation opposite of the feed

-- The chip formed by each cutter toothThe chip formed by each cutter tooth

starts out very thin and increases itsstarts out very thin and increases its

thicknessthickness

-- The length of the chip is relativelyThe length of the chip is relatively

longerlonger

-- Tool life is relatively shorterTool life is relatively shorter

-- Need more clamping force to holdNeed more clamping force to hold

the work part still.the work part still.

Up Milling & Down MillingUp Milling & Down MillingUp Milling & Down MillingUp Milling & Down MillingUp Milling & Down MillingUp Milling & Down MillingUp Milling & Down MillingUp Milling & Down Milling

Down milling

Also called Also called climb millingclimb milling,,

-- Wheel rotation is parallel to the feedWheel rotation is parallel to the feed

-- The chip formed by each cutter toothThe chip formed by each cutter tooth

starts out thick and leaves out thinstarts out thick and leaves out thin

-- The length of the chip is relativelyThe length of the chip is relatively

shortshort

-- Tool life is relatively longerTool life is relatively longer

-- Need less clamping force to hold the Need less clamping force to hold the

work part still.work part still.

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Milling Operations on a Milling Operations on a Milling Operations on a Milling Operations on a Milling Operations on a Milling Operations on a Milling Operations on a Milling Operations on a HorizontalHorizontalHorizontalHorizontalHorizontalHorizontalHorizontalHorizontal Milling MachineMilling MachineMilling MachineMilling MachineMilling MachineMilling MachineMilling MachineMilling Machine

��Slab milling:Slab milling:

Cutter width extends beyond the work piece on both sidesCutter width extends beyond the work piece on both sides

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Slotting (Slot milling):Slotting (Slot milling):Cutter width is less than the work piece width, creating a slot.Cutter width is less than the work piece width, creating a slot. If If the cutter is very thin, it can be used to cut a work part into the cutter is very thin, it can be used to cut a work part into two, two, called called saw millingsaw milling..

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Side milling:Side milling:Cutter, machines the side of the work piece.Cutter, machines the side of the work piece.

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Straddle milling:Straddle milling:Similar to side milling, but cutting takes on both sides of the Similar to side milling, but cutting takes on both sides of the work part simultaneously.work part simultaneously.

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FormForm milling:milling:The cutter has the desired form of the partThe cutter has the desired form of the part

Milling of a concave half circleMilling of a concave half circle Milling of a gearMilling of a gear

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Milling Operations on a Milling Operations on a Milling Operations on a Milling Operations on a Milling Operations on a Milling Operations on a Milling Operations on a Milling Operations on a VerticalVerticalVerticalVerticalVerticalVerticalVerticalVertical Milling MachineMilling MachineMilling MachineMilling MachineMilling MachineMilling MachineMilling MachineMilling Machine

FaceFace milling:milling:The cutter with a relatively large diameter removes a layer froThe cutter with a relatively large diameter removes a layer frommthe upper side of the partthe upper side of the part

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EndEnd milling:milling:Cutters diameter is less than the work part’s widthCutters diameter is less than the work part’s width

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ProfileProfile millingmilling (also contouring or shaping)(also contouring or shaping)::Outside periphery of flat part is cutOutside periphery of flat part is cut

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PocketPocket milling:milling:The cutter removes material creating a cavity (rectangular, The cutter removes material creating a cavity (rectangular, circular etc.)circular etc.)

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33--DimensinalDimensinal surface surface milling:milling:

The cutter (ball end mill) removes material, moving in 3 The cutter (ball end mill) removes material, moving in 3

directions simultaneously.)directions simultaneously.)

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33--DimensinalDimensinal surface surface milling:milling:

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SlotSlot millingmilling TT--SlotSlot millingmilling

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Horizontalflat surface

Verticalflat surface

Profilesurface

Surface Machining on a Surface Machining on a Surface Machining on a Surface Machining on a Surface Machining on a Surface Machining on a Surface Machining on a Surface Machining on a VerticalVerticalVerticalVerticalVerticalVerticalVerticalVertical Milling MachineMilling MachineMilling MachineMilling MachineMilling MachineMilling MachineMilling MachineMilling Machine

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Milling Tools Milling Tools Milling Tools Milling Tools Milling Tools Milling Tools Milling Tools Milling Tools -------- End MillsEnd MillsEnd MillsEnd MillsEnd MillsEnd MillsEnd MillsEnd Mills

The most common cutting tool used with a vertical mill is an end-mill, which looks like a stubby twist drill with a flattened end.

An end mill can cut into a workpiece either vertically, like a drill, or horizontally using the side of the end mill to do the cutting. This horizontal cutting operation imposes heavy lateral forces on thetool and the mill, so both must be rigidly constructed

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Ball-end mills make rounded pocketsor spherical pockets; also fillets

Corner-rounders form rounded corners!

Conical end-mill for chamfers

Milling Tools Milling Tools Milling Tools Milling Tools Milling Tools Milling Tools Milling Tools Milling Tools -------- End MillsEnd MillsEnd MillsEnd MillsEnd MillsEnd MillsEnd MillsEnd Mills

Flat end-mills for::• pockets• slots• edge trim• facing

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standard drill: will flex/walk, follow pilot

stub drill for less walk/greater rigidity

reamers (straight or spiral)finish off hole (last several thousandths)precise hole diameterfor insertion of dowel pins, bearings, etc.plunge while spinning, extract still

countersink: for screw heads & deburring hole

center drill establishes hole position with no walk

Milling Tools Milling Tools Milling Tools Milling Tools Milling Tools Milling Tools Milling Tools Milling Tools -------- Drills and ReamersDrills and ReamersDrills and ReamersDrills and ReamersDrills and ReamersDrills and ReamersDrills and ReamersDrills and Reamers

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WorkWorkWorkWorkWorkWorkWorkWork--------holdingholdingholdingholdingholdingholdingholdingholding for milling operationsfor milling operationsfor milling operationsfor milling operationsfor milling operationsfor milling operationsfor milling operationsfor milling operations

Several types of fixtures are commonly used to hold partsSeveral types of fixtures are commonly used to hold parts

while milling them. The most common is a while milling them. The most common is a visevise. .

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Another common alternative is to clamp the part directly toAnother common alternative is to clamp the part directly to

the machine table using clamps. Therefore all milling the machine table using clamps. Therefore all milling

machine tables have machine tables have TT--slotsslots along the length to allow along the length to allow

placement ofplacement of the clampsthe clamps..

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Another common workAnother common work--holding method is an holding method is an indexed indexed visevise, ,

which allows the part to be rotated so as to expose a which allows the part to be rotated so as to expose a

different surface to the milling tool quickly. different surface to the milling tool quickly.

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IIf the machine tool needs to access different facets of thef the machine tool needs to access different facets of the

part to cut some shapes, then the part may need to be part to cut some shapes, then the part may need to be

released and rereleased and re--fixturedfixtured. . Each fixed position is called a Each fixed position is called a

setupsetup. In one . In one setupsetup, multiple tools can be used to cut , multiple tools can be used to cut

different shapes, or features on the part. When the different shapes, or features on the part. When the setupsetup

or tool is changed, the machinist must “locate” the part or tool is changed, the machinist must “locate” the part ––

thatthat is, the coordinates of the part with respect to the tool is, the coordinates of the part with respect to the tool

mustmust be determined. Each machine table gives feedback be determined. Each machine table gives feedback

about the relative motion of the table along each axis (X, about the relative motion of the table along each axis (X,

Y, and Z). Y, and Z). A primary goal in every machining process is to A primary goal in every machining process is to

limit to minimum the number of required part setups.limit to minimum the number of required part setups.


Definition of part SetupDefinition of part Setup

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