e ts - dressing

… things which can go wrong: here dressing

dressing

speed ratio qd dressing overlap Ud

dressing infeed aed touch dressing strategy side face dressing t.b.c. ...

dressing


dressing speed ratio qd dressing overlap Ud dressing infeed aed touch dressing strategy side face dressing t.b.c. ...

qd = vR / vSd

- 1 0 + 1

Rts

qd = vR / vSd

crus

hing

vS

vR

stat

iona

ry d

ress

ing

tool

s

vR

vS

98-021b-e Speed ratio qd influences effective wheel roughness Rts

uni directional dressing

" + "

counter directional dressing

" - "

grinding wheel grinding wheel

Effects of uni and counter directional dressing

vSd

vR vR

vSd

uni directional dressing

qd > 0

counter directional dressing

qd < 0

qd = vR / vc Highest priority should be to keep the speed of the wheel during dressing as well as grinding constant. Otherwise

disturbances in run out, balancing etc. may come up.

Advices regarding the dressing quotient qd

do not use these factors:

qd = 0 stationary dressers qd = +/- 0,1 ... 0,25 wheel will grind roller qd = + 1,0 crushing qd > + 1,0 high no. of re. from dresser

„best“ qd factors are

roughing unique direction 0,5 ... 0,85 finishing counter direction - 0,5 ... 0,85

but: test it !!!

f ad

f ad

b d

b d

a pd

a pd

Dressing overlap Ud - Animation

a ed

a ed small feedrate large Ud smooth wheel

large feedrate small Ud rough wheel

grinding wheel

grinding wheel

aed nsd

apd fad

vfad

dk

nR

The dressing overlap Ud is defined as the number of revolutions a grinding wheel moves

until the actual width apd (≈ dk) of the dressing tool is shifted exactly once in the direction of feed.

Ud = apd / fad

≈ dk / [ vfad / nsd ]

≈ dk / [ vfad *ds*π /(vcd*60.000)]

Ud [ - ] : dressing overlap apd [mm] : actual contact width dk [mm] : axial infeed per wheel revolution ds [mm] : diameter of the grinding wheel fad [mm] : axial infeed per wheel revolution nsd [1/min] : axial infeed per wheel revolution vcd [m/s] : grinding wheel speed whilst dressing vfad [mm/min] : axial dressing feed rate

Dressing overlap Ud

01-054-e Udo Mertens

paper clip 0,8 mm

human hair 0,05 mm

needle 0,6 mm

cigarette paper 0,03 mm

pork hair 0,1 mm

newspaper 0,08 mm

spider web 0.006 mm

micrometer 0.001 mm

The size of a micrometer

Setting parameters for diamond CNC dressers

diamond CNC dresser

CBN or diamond - dressing infeed - per stroke aed = 1 ... 3 µm / stroke - per cyclus aed total = 10 % of wheel grit size - dressing overlap - for roughing Ud = 2 … 4 - for finishing Ud = 8 … 12

in general dress the wheel in to a sharpe and aggressive state, it will get dull “as time goes by”

Udo Mertens

04-034-e Setting parameters for diamond CNC dressers

Setting parameters for diamond profile dressers

04-029-e Setting parameters for diamond profile dressers

Al2O3 or SiC aed = 0,10 ... 0,50 µm / wheel revolution CBN or diamond

- after setup of the wheel aed = 0,01 ... 0,05 µm / wheel revolution - for trueing in process aed = 0,10 ... 0,20 µm / wheel revolution

speed ratio qd = 0,60 … 0,85 uni directional in general as bigger aed as higher the active roughness Rts

grinding wheel

diamond profile dresser

aed

l best ≈ 35 .. 45 % d grit

Dressing – how to do it correct

best grinding wheel

tolerance limit

mac

ro g

eom

etry

m

icro

geo

met

ry

no. of components

aed ges *)

*) : radiale Abrichtzustellung . aed ges > Profilfehler

conventional dressing method

no. of components

aed *)

*): radial dressing amount aed tot > permissable deviation m

acro

geo

met

ry

mic

ro g

eom

etry

tolerance limit


l worst case ≈ 0 % d grit

best grinding wheel

tolerance limit

mac

ro g

eom

etry

m

icro

geo

met

ry

no. of components

aed ges *)



no. of components

aed *)


acro

geo

met

ry

mic

ro g

eom

etry

tolerance limit

l best ≈ 35 .. 45 % d grit


best grinding wheel

tolerance limit

mac

ro g

eom

etry

m

icro

geo

met

ry

no. of components

aed ges *)



no. of components

aed *)


acro

geo

met

ry

mic

ro g

eom

etry

tolerance limit


l best ≈ 35 .. 45 % d grit aed tot < 10 % d grit

aed ges *)


best grinding wheel

tolerance limit

mac

ro g

eom

etry

m

icro

geo

met

ry

no. of components

aed ges *)



no. of components

aed *)


acro

geo

met

ry

mic

ro g

eom

etry

tolerance limit

dressing strategy TDC

no. of components

*) : radial dressing amount aed tot ≤ 10 % d grit

aed tot *)

mac

ro g

eom

etry

m

icro

geo

met

ry

tolerance limit

Grit protrusion at vitrified CBN and diamond tools

B 151 ≅ 150 µm

l best ≅ 35 .. 45 % d grit ≅ 60 +/- 7,5 µm

aed tot < 10 % d grit < 15 µm

l best ≈ 35 .. 45 % d grit aed tot < 10 % d grit

depth of dressing infeed: 3 µm

Microstructures of CBN I after dressing



a – Dressing – how to do it correct - dressing radii

b - Dressing – how to do it correct - dressing radii

rmax

rmin

aed tot > maximum profile deviation (partly several grit levels)

c - Dressing – how to do it correct - dressing radii

rmax

rmin

Dressing parameters versus grinding results

tempe-rature δ

roughness R

G ratio grinding forces F

dimensional and shape accuracy

surface quality

F dressing overlap factor Ud

G R δ

dressing speed ratio qd

F G R δ

0 1 0 1 0 1 0 1

F dressing infeed aed

G R δ

e ts - dressing

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