A

CNCcont ro l l ed vert i cal

m l l i ng achi ne i s used

t o

performendm l l i ng of a

si mpl e

part sho n i n

Fi gur e

13

 

Af eedr ate of 5 mn i s

r equi r ed f or machini ng

The

r api d t r averse f eedra te

i s 25 mmmn

  can

be used f or ovi ngw t hout

machi ni ng A

const ant

spi ndl e speed

of   rpm

s

r equi r ed   Onl y one

cutter

w t h

a

di amet er of 2

mm

s

used

  The cutter i s i n i t i l l y at 40

mmbove

t he t abl e at t he

start poi nt  

Fi gur e

13 shows the dot t ed l i n e as t he

tool cent er pat h and s ol i d l i nes

as t he part  

Dmensi ons ar e speci f i ed

i n mm

Cool ant

i s

used dur i ng m l l i ng

Wite a compl et e part

rogrami n t he i ncr emen al

syst em

Froms t r t

 

t o 10mm

r om

A

10mmr omA

o

t he poi nt A

XA

CONTO RT RORAM NG

 MANUAL

N200

0 Y F5 S M08

Poi nt A o poi nt B

N300X80

N100 GO X60

YOZ- 40 F25 S M03

- i mpl i es l i ne r

i nterpol ati on   GO1 , tool i s

oved

i n

Xf or a

di stance of

6 mmf t erwhi ch t he

t o o l i s

t ur ned on  M03 and i s brough t o t he

wor kpi ece w t h a spi ndl e speed

of 1000

rpm

- i mpl i es t he begi nni ng of t he  ut

w t h cool ant on

  MO8

Note t hat t he f eedr ate

i s

r educed

t o

5 n

 9

 

Poi nt B

t o

poi nt C

The c u t t e r oves i n t he  Y

di rect i on t o t he poi nt

C Use t he Fi gur e shown

bel ow

t o comput e

t he

di stance

BC

30

P

30

2

0

BC BB -CB =60 MB t n22

 5=60=10tan22

 5 14 mm

Thus

t he

bl ock BC   wr i t t en as  

N400XO

Y64

14

Poi nt C t o poi nt

D

Fomt he

above

f i g u r e

CD=NLti

 

OC=42

  43   4   14 =

46  57

Si nce CD   at

45° r esol ve   t

i n t o X

andY

as 46 . 5 7 / 2 - ) = 32  93 mm

Thus

t he bl ock

f o r CD s wr i t t en as

N500 X 32

  93 Y32   93

 

Poi nt D

poi nt E

Af te r passi ng poi nt D

and

pri or t s t a r t t he c i rcul ar

a r c

ED

 whose cent er

t he

Fi gure shown bel ow

We can

wri t e

 

Poi nt E t o poi nt F

N700 X-40 Y-40

10 J 40

Poi nt

F

t o poi nt A

N800 GO1 XOY 6 F500

Poi nt At o s t ar t poi nt

N900 X 7 YO

Z40

F5

05 09

i  

-

=100

j y=10 i x=

.707R

. 07

Sol vi ng

al l t h e s e ,

x = i

= =7 . 07

mm y

=

2 . 93 mm

N600 G03 X-7. 07 Y2. 93 17 . 07 J 7 . 07

No cutt i ng takes pl ace bet ween

poi nt s D

and

E

i s i ncr eased t o

667 due t o t he c u t t e r r adi us

as gi ven by t he equat i on

F =

[ pa r t

cont our r adi us   tool

radi us / part contour r adi us]   r equi r ed

f e e d r a t e

=

40/ 30   500 667

Thi s examl

demonst r at es t he need f or t he

assi st ance of a comut r i n

handl i ng

t he

cal cul at i ons

 

2 

 

RO

 

m l l i ng achi ne cuts a

s l o t

2 i n

l ong a t 45° i n t heXYpl ane   The

syst em resol ut i on

i s 0

. 0005 i n   I f t he r equi r ed f eed r a t e

al ong t he

s l o t i s 4 i n. / m n   Fi nd t he di st ance

t r avel ed i n BL s and t he vel oc i t y

of

each

i ndi vi dual axi s   I f t he vel oc i t y of t he

y- axi s

decreases by

0. 5 what

i s t he er r o r

i n y- di rect i on

?

2  

I n

hi ch one of

t he f ol l ow ng

c a s e , an open

l oop

control systemwould be s u i t a b l e ?

Expl a i n

  a

b

d r i l l i n g

achi ne t a b l e

whi ch al ways

oves a t t he sa e speed and has t he

a e l oad 

m l l i ng machi ne hi ch

ove a t

var i ous speeds wi t h d i f f e r e n t l oads  

3  

st eppi ng mot or wi t h  5

step angl es

i s

coupl ed

t o

a l eadscr ew t hr ough a gear

r educt i on of   The l eadscr ew

has a pi tch of 4 mmThe workt abl e, dr i ven by t he

l eadscr ew, ust ove a

di st ance 100 mmt a feedrate of 300

n Det erm ne   a

t he nu ber

of pul ses requi red t o

ove

t he t a b l e   b t he

r equi r ed otor speed and

pul se r a t e

t o achi eve t he desi r ed t a b l e speed

4

 

Ref er r i ng

t o Pr obl em 3 , t he mechani cal i naccuracy

can be descr i bed by a nor mal

di s t r i but i on

whose standard devi at i on

i s 0. 005 mmI f t he r ange

of t he wor kt abl e a x i s

i s 500 det er m ne

  a

cont r ol

resol ut i on   b

accuracy

and   c r e p e a t a b i l i t y  

1

5  

An end

m l l i ng oper at i on i s car r i ed

out al ong a

s t r a i ght l i n e pat h t h a t i s 13

i n l engt h

on

a

CNC

machi ni ng

center   The cut t i ng speed i s 100 fpmThe end

m l l i ng c u t t e r has

2

t e e t h , f eed of 0 . 0025

i n / t o o t h , and has a

di amet er

of 0

. 6325 i n   The pi t ch of

l eadscr ew i s  . 25 i n / r e v ,

and t he o pt i c a l encoder emt s 4 pul ses per

revol ut i on  

Det erm ne t he f e e d r a t e ,

RPMof t he

mot or , and pul se f r equency of t he

encoder  

6   The di mensi ons

of t he part shown i n Fi gure a r e A' B' =

50 C =4 mm and

t he angl e ABC =

135°   The r equi r ed feedrate i s 100 . W i t e a

manual

CNCprogramof t he l i n e s

corr espondi ng t o t he segment s   and BC The

r adi us of

c u t t e r

i s

t aken

as 10mmUse i ncr ement al program ng

 

 

 NN

 O

Thi s

i s

a l i s t of codes comonl y

used i n Nm chining Thi s l i s t i s not compl et e

 nd di f f er ences c noccur bet eendi f f er ent m chi nes duet o t he manuf act urer of t he

mchi ne

and

t he contr ol l er  

N

ode

- sequence

nu ber

 

The

sequence

nu ber i s used t o i dent i f y each bl ock

w t hi n  n

N program nd pr ovi des

a eans by

which

N

co and maybe rapi dl y

l ocat ed 

G

code preparatory

ord

The preparatory f uncti on i s used

as

  co mni cati on

devi ce t o prepare t heM UThe

 

ode i ndi cates that   gi ven control f unct i on

such as  O

,

l i near i nterpol ati on i s t o be r equest ed

 

X YandZcodes - coor di nates   These gi ve t he coor di nate posi t i ons of t he tool  

Fcode - f eed rate   TheFcode

speci f i es

t he f eed i n  m chi ni ng

oper at i on  

Scode   spi ndl e speed The  code speci f i es t he cutt i ng speedof a machi ni ng

process  

Tcode

-

tool sel ect i on

 

The

T

code speci f i es

hi ch

t ool i s t o

be

used

i n

  speci f i c

oper at i on

 

M   m scel l aneou f unct i ons   TheMode used t o desi gnate  

ode of oper at i on f or an

N

mchi ne

tool

  ost m scel l aneous f unct i ons

deal

wi t h

opposi ngmchi ne

condi t i ons  

f or

exampl e

cool ant

on of f  

I J and

Kcodes  

They

speci f y

t he center of

 rccoordi nat es

fromstart ing  

f

code

 

I t pauset he next oper ati on f or t housands of seconds  

D

and

Hcodes   They

speci f y

t he

of f sett i ng val ues  

. codes   I t def i nes

t he nu ber of repeti ti ons of cycl e