机械制造技术英文课件

Process

Route

FormulationMachanical

Manufacturing

TechnologyDivision

ofprocessing

stagesWhen

the

processing

quality

requirements

are

high,

themachining

stage

should

be

divided

into

three

stages:

roughmachining,

semi_finish

machining

and

finish

machining,usually.

And

when

the

requirements

of

processing

precisionand

surface

quality

are

particularly

high,

superfinishing

canbe

added.Process

planningCut

most

of

the

blank

allowance,

close

to

the

shape

and

size

of

the

finished

product.The

main

surface

leaves

the

finish

machiningallowance

and

reaches

a

certain

precision,

andsome

secondary

surfaces

are

finished.Ensure

the

main

surface

precision

andsurface

roughness.to

obtain

high

dimensional

precision,reduce

the

surface

roughness

orstrengthen

the

surface.Processing

method：diamondturning/boring，lapping，honing，superfinishing，

mirror

grinding，polishing，chipless

process，etc.superfinishingrough

machiningsemi_finish

machiningfinish

machiningReasons

for

dividing

processing

stages：■（1）Toensure

the

processing

qualityDuring

rough

machining,

due

to

the

large

machining

allowance

and

the

large

cutting

andclamping

force,

large

deformation

will

be

caused.

If

the

rough

and

finish

machining

iscarried

out

continuously

without

dividing

the

stages,

the

above

deformation

can

not

berecovered,

which

will

affect

the

processing

precision.The

error

and

deformation

caused

by

rough

machining

can

be

corrected

by

semi_finishmachining

and

finish

machining,

and

the

precision

and

surface

quality

of

parts

can

beimproved

gradually.（2）For

proper

use

of

equipmentrough

machining

requires

the

use

of

rigid,

high

efficiency

and

low

precisionmachine

tools,

while

finish

machining

requires

high

precision

machine

tools.After

dividing

the

machining

stage,

it

can

avoid

rough

machining

with

highprecision

equipment,

give

full

play

to

the

performance

of

the

machine

tool,

andextend

the

service

life.（3）convenient

to

arrange

the

heat

treatment

process,

sothat

the

cold

and

hot

processing

process

can

cooperatebetterAfter

rough

machining,

the

stress

relief

aging

treatment

should

be

arranged

toeliminate

the

internal

stress.The

final

heat

treatment

such

as

quenching

should

be

arranged

before

finishmachining,

and

its

deformation

can

be

eliminated

by

finish

machining.（4）helpful

to

find

the

defect

of

the

blank

as

soonas

possible（Such

as

sand

hole

and

air

hole

ofcasting）During

rough

machining,

most

of

the

allowance

of

the

machined

surface

isremoved.

If

any

defect

of

the

blank

is

found,

it

shall

be

scrapped

in

time

toavoid

the

waste

of

working

hours

caused

by

the

continuous

machining.（5）Toavoid

damage

to

machined

surfacesIf

finish

machining

is

arranged

at

the

end,

it

can

protect

the

finished

surface

fromdamage

or

damage

less.The

division

of

machining

stage

is

not

absolute,

it

must

bedetermined

according

to

the

requirements

of

processing

precisionand

the

rigidity

of

workpiece：√A.

Generally

speaking,

the

higher

the

precision

requirement

of

the

workpiece

andthe

lower

the

rigidity

of

it,

the

more

detailed

the

stages

should

be；√B.

In

small

batch,

the

precision

requirement

is

not

too

high,

and

the

rigidity

ofworkpieces

is

good,

it

can

also

be

divided

into

no

or

less

stages；√C.

Due

to

the

difficulty

of

transportation

and

clamping,

the

rough

and

finishmachining

of

heavy

parts

is

usually

completed

under

one

clamping.

And

in

orderto

make

up

for

the

disadvantages

because

of

no

processing

stage

divided,

theworkpiece

shoud

be

loosened

after

the

rough

processing

step,

then

reclampedwith

a

small

clamping

force,

and

then

the

finish

processing

step

is

continued.（1）Arrangement

of

cutting

process

sequence①Rough

before

finish

rough

machining

is

arranged

first,

semi_finish

machining

is

arrangedin

the

middle,

and

finish

machining

and

superfinishing

are

arrangedfinally.3．Arrangement

of

processing

sequence②Primary

before

secondaryThe

machining

of

primary

surfaces

such

as

assembly

base

andworking

surface

of

parts

is

arranged

first，while

the

machining

ofsecondary

surfaces

such

as

keyways,

unthreaded

or

threaded

holesfor

fastening

is

arranged

finally.Due

to

the

small

workload

of

the

machining

of

the

secondarysurfaces

and

the

requirement

of

position

accuracy

relative

to

theprimary

ones,

the

machining

of

them

is

generally

placed

after

thesemi_finish

and

before

the

finish

machining

of

the

primary

surfaces.③Planes

before

holesFor

parts

like

box,

bracket,

connecting

rod

and

base,

the

plane

usedfor

positioning

and

the

end

face

of

the

hole

are

processed

first,

andthen

the

hole

is

processed.

In

this

way,

the

positioning

andclamping

of

the

workpiece

are

stable

and

reliable,

which

isconducive

to

ensuring

the

position

accuracy

of

the

hole

and

theplane,

reducing

the

wear

of

the

tool,

and

also

bringing

convenienceto

the

hole

processing.④Reference

surface

firstThe

surface

to

be

used

as

a

fine

reference

shall

be

machined

first.Therefore,

the

first

process

is

generally

rough

machining

and

semi_finish

machining

of

the

positioning

surface

(Sometimes

the

finishmachining

is

included).

Then

the

other

surfaces

are

processedrelative

to

the

fine

positioning

surface,

for

example,

the

machiningof

the

center

hole

of

shaft

parts.Reasons

for

dividingprocessing

stagesTo

ensure

the

processing

qualityFor

proper

use

of

equipmentconvenient

to

arrange

the

heattreatment

processhelpful

to

find

the

defect

of

theblank

as

soon

as

possibleProcess

planning（2）

Arrangement

of

heat

treatment

process

sequenceEliminate

the

non-uniform

structurerefine

the

grain

and

improve

theprocessing

performance

of

metalEliminate

internalstressand

reduce

workpiecedeformationImprove

the

hardness

andwear

resistance

of

parts①Annealing

and

normalizing

purpose②Aging

treatment

purpose③Quenching

and

tempering

purpose④Quenching

\Carburizingand

quenching\NitridingpurposeEliminate

internal

stress,

improveprocessing

performance

and

obtain

bettecomprehensive

mechanical

properties1）AnnealingAnnealing：A

heat

treatment

process

in

which

the

steel

is

heated

to

a

certain

temperature,

kept

warm

for

a

period

of

time,

and

then

cooled

slowly

in

the

furnace.Effect：Eliminate

internal

stress,

improve

strength

and

toughness,reduce

hardness

and

improve

machinability.Application：High

carbon

steel

is

annealed

to

reduce

hardness;Annealing

is

arranged

before

rough

machining

and

after

the

blankis

made.2）NormalizingNormalizing：A

heat

treatment

process

in

which

the

steel

is

heatedto

a

certain

temperature,

taken

out

of

the

furnace

after

holding

fora

period

of

time,

and

cooled

in

air.

Note:

the

heating

temperature

is

related

to

the

C

content

of

steel,

which

is

generally

about

200

℃lower

than

the

solid

phase

line.Effect：Improve

the

strength

and

hardness

of

steel,

make

theworkpiece

have

proper

hardness

and

improve

the

machinability.Application：Low

carbon

steel

is

normalized

to

improve

itshardness;

Normalizing

is

arranged

before

rough

machining

andafter

the

blank

is

made.3）TemperingTempering：A

method

of

heat

treatment

in

which

the

quenchedsteel

is

heated

to

a

certain

temperature,

held

for

a

period

of

time,and

then

cooled

in

air

or

water.Effect：Stable

structure,

eliminate

internal

stress

and

reducebrittleness.4）Quenching

and

temperingQuenching

and

tempering：High

temperature

temperingafter

quenchingEffect：Obtain

fine

and

uniform

structure,

improve

thecomprehensive

mechanical

properties

of

parts.Application：Quenching

and

tempering

is

arranged

afterrough

machining

and

before

semi_finish

machining,

andcommonly

used

in

medium

carbon

steel

and

alloy

steel.5）Aging

treatmentEffect：Eliminate

the

internal

stress

produced

in

blankmanufacturing

and

machining.Application：Aging

treatment

is

arranged

after

the

blankis

made

and

rough

machining,

and

commonly

used

inLarge

and

complex

castings.For

castings

with

complex

structure

like

machine

bed

and

uprightcolumn，aging

treatment

(artificial

aging

or

natural

aging)

isarranged

both

before

and

after

rough

machining，in

order

tostabilize

the

material

structure

and

make

sure

that

there

will

be

nolarge

deformation

in

the

future.Artificial

aging：The

casting

is

heated

at

the

rate

of

50-100

℃

/

hour

to

500-550

℃,kept

warm

for

3-5h,

and

then

cooled

with

the

furnace

at

the

rate

of

20-50

℃

/

h.

Natural

aging：The

castings

are

placed

in

the

open

air

for

several

months,

so

that

the

castings

are

exposed

to

the

sun

and

rain

in

nature,

and

the

internal

stress

of

the

material

structure

is

released

and

gradually

stabilized.6）QuenchingQuenching：

A

heat

treatment

process

in

which

the

steelis

heated

to

a

certain

temperature,

kept

warm

for

aperiod

of

time,

and

then

rapidly

cooled

in

a

coolingmedium

to

obtain

a

high

hardness

structure.Effect：Improve

the

hardness

of

parts.Application：Usually,

quenching

is

arranged

beforegrinding.Carburizing

(nitriding)

treatment：It

is

arrangedbefore

and

after

finish

machining

to

improve

thehardness

and

wear

resistance

of

workpiece

surface.In

order

to

improve

the

wear

resistance

and

corrosionresistance

of

the

workpiece

surface,

the

heat

treatmentprocess

arranged

for

the

purpose

of

decoration,

such

aschrome

plating,

galvanizing,

oxidizing,

etc.,

are

generallyarranged

at

the

last

stage

of

the

process.AuxiliaryprocessSelf-inspectionBefore

and

after

important

processesBefore

being

sent

to

the

outside

workshopAll

the

processing

is

finished.Before

quenchingAll

the

processing

is

finished.InspectionDeburringChamferingCleaningrust

protectionDemagnetizationProcess

planningIn

order

to

ensure

the

manufacturing

quality

of

parts

and

prevent

wasteproducts,

inspection

shall

be

arranged

in

the

following

occasions：All

the

rough

machining

is

finished；Before

and

after

being

sent

to

the

outside

workshop；3）Before

and

after

long

working

hours

or

important

process；4）All

the

processing

is

finished.

In

addition

to

the

geometric

dimensioninspection,

some

parts

should

also

be

arranged

with

inspection

such

as

flawdetection,

sealing,

weighing

and

balancing.（3）Arrangement

of

auxiliary

processesArrangement

of

other

processesAfter

cutting,

the

deburring

process

should

be

arranged

because

that

the

burr

of

the

surface

or

inner

cavity

of

the

part

has

a

great

influence

on

the

assembly

quality

ofthe

machine.Generally,

cleaning

process

shall

be

arranged

for

parts

before

assembly.

First,

it

iseasy

to

keep

chips

in

the

inner

hole

of

the

workpiece

and

the

inner

cavity

of

the

box.Second,

after

finishing

processes

such

as

grinding

and

honing,

small

abrasivepa