Cutting Processes

Transcription

Cutting Processes

Cutting Processes
Simulation Techniques in Manufacturing Technology
Lecture 7
Laboratory for Machine Tools and Production Engineering
Chair of Manufacturing Technology
Prof. Dr.-Ing. Dr.-Ing. E.h. Dr. h.c. Dr. h.c. F. Klocke
© WZL/Fraunhofer IPT
Outline
1
Introduction
2
Cutting processes with rotary motion
3
Cutting processes with parallel translation
4
Hard machining
5
Modeling of Machining
Seite 1
Breakdown of the techniques involving a rotational main movement
Turning
– work piece
rotation
– tool translation
main movement
subsidiary
movement
Milling
Boring
– tool- rotation
– work piecetranslation
– tool rotation
main movement
main movement
sub. movement
sub. movement
Sawing
– tool rotation
main movement
sub. movement
Seite 2
Breakdown of the techniques involving a translational main
movement
broaching
–
–
–
–
–
–
planing
multi teeth tool
feed due to tool geometry
high surface quality
high accuracy
high tool costs
inflexible
– Cutting motion by work
piece
– Tool feed
– Stepwise, linear cutting
motion
– Successive feed
movement
– Machining of large, planar
areas
shaping
– Cutting motion by tool
– workpiece feed
– Stepwise, linear cutting
motion
– Successive feed
movement
– Machining of large, planar
areas
tool
work piece
track
Seite 3
Outline
1
Introduction
2
2.1 Turning
2.2 Milling
2.3 Drilling
3
4
Hard machining
5
Seite 4
Outline
1
Introduction
2
2.1 Turning
2.2 Milling
2.3 Drilling
3
4
Hard machining
5
Seite 5
Example: rough turning
Source: Widia
Seite 6
Example: finishing
Source: Widia
Seite 7
Terms at the cutting edge
tool shank
cutting direction
rake face Aγ
feed direction
major cutting edge S
minor cutting edge S‘
major flank face Aα
minor flank face Aα‘
corner radius
Seite 8
Definition of the tool cutting edge angle κr
tool orthogonal plane Po
tool reference
Plane Pr
tool cutting edge plane Ps
Seite 9
Definition tool cutting edge angle κr
trace of the tool
orthogonal plane Po
trace of the tool
cutting edge plane PS
feed direction
rε
κr
trace of the
working plane Pf
tool
tool reference plane Pr
Seite 10
Definition of the inclination angle λs
working plane Pf
tool cutting
edge plane PS
tool reference
plane Pr
Seite 11
Definition of the inclination angle λs
trace of the
working plane Pf
λs
major cutting edge S
+
-
tool
trace of the tool
reference plane Pr
cutting direction
tool cutting edge plane PS
Seite 12
Definition of the rake angle γ
Seite 13
Definition of the angles at the cutting edge
trace of the tool
reference plane Pr
trace of the rake
face plane Aγ
γo
trace of the
flank face
plane Aα
tool
expected
cutting direction
βo
αo
expected
feed direction
trace of the tool
back plane Pp
tool orthogonal plane Po
Seite 14
Tool variants in longitudinal cylindrical turning
right hand
side cutting
left hand
side cutting
neutral
Seite 15
Facing (DIN 8589-1: ON 3.2.1.1)
cross face turning
workpiece
tool
cross parting off
longitudinal face turning
workpiece
workpiece
tool
tool
Source: Sandvik Coromant
Seite 16
Facing (DIN 8589-1: ON 3.2.1.1): cross / longitudinal face turning
Seite 17
Facing (DIN 8589-1: ON 3.2.1.1): cross parting off
Seite 18
Cylindrical turning (DIN 8589-1: ON 3.2.1.2)
longitudinalcylindrical turning
workpiece
tool
centreless rough turning
workpiece
cross-cylindrical
turning
workpiece
tool
tool
Source: Iscar, Ceratizit
Seite 19
Threatening (DIN 8589-1: ON 3.2.1.3)
thread turning
workpiece
chasing
tapping
workpiece
workpiece
tool
tool
tool
thread turning (external)
thread turning (internal)
Source: Garant, Seco, Ceratizit
Seite 20
Profile turning (DIN 8589-1: ON 3.2.1.5)
trepanning
workpiece
workpiece
DIN 8589-1
cross-profile turning
grooving
tool
tool
workpiece
tool
Seite 21
Hob turning (DIN 8589-1: ON 3.2.1.4)
workpiece
tool
Seite 22
Contour turning (DIN 8589-1: ON 3.2.1.6)
NC-contour turning
workpiece
copy turning
workpiece
kinematiccontour turning
workpiece
tool
tool
NC
tool
gear
reference formed part
Source: Sandvik Coromant
Seite 23
Internal turning
skimming
undercut
cut in
workpiece
workpiece
workpiece
tool
tool
tool
DIN 8589-1
Source: Iscar
Seite 24
Internal turning tools
Source: Sandvik
Seite 25
Outline
1
Introduction
2
2.1 Turning
2.2 Milling
2.3 Drilling
3
4
Hard machining
5
Seite 26
Milling processes DIN 8589-3
3.2.3
milling
DIN8589-3
3.2.3.1
3.2.3.2
3.2.3.3
3.2.3.4
3.2.3.5
3.2.3.6
slab / face
milling
circular
milling
helical
milling
hobbing
profile
milling
form
milling
Seite 27
Face milling (DIN 8589-3: ON 3.2.3.1)
Seite 28
Face milling (DIN 8589-3: ON 3.2.3.1)
Seite 29
Slab milling (ON 3.2.3.1): face- and peripheral milling
face milling
peripheral milling
– Workpiece surface is generated by
face of the milling tool
– Workpiece surface is generated by
peripheral surface of the milling tool
vf
vf
Ps
n
fz
n workpiece
workpiece
κr
ϕ
vc
ap
ae
tool
tool
fz
Seite 30
Up- and down milling
down milling
up milling
vc
n
n
fz
fz
Ff
Ff
Fc
ae
Fc
vt
Up- and down milling
vt
up milling part
down milling part
vt
Seite 31
Tool-in-hand system: peripheral milling
vf
fz
trace of Pr
vc
tool
ae
workpiece
ω E = 0°
ωc = ω A − ω E
Pf ≡ Po
trace of Ps ≡ Pp
Seite 32
Tool-in-hand system: face milling
vf
trace of Ps
tool
trace of Po
ωA
n
ωc
ωE
κr
ap
νf
n
trace of Pf
workpiece
fz
fz
Pr
ae
trace of Pp
trace of the
entrance plane
Seite 33
Contact conditions and cutting edge geometry in face milling
fz
ae2
n
vc
C
ae
C
ϕs
ae1
vf
-εεA n
ϕA
+εεE
ϕ
entry plane
φ=0
tangential plane
view A
tool
cutting C-C
fz
ap
tool cutting edge
contact types
U
T
γp
A
B
B
b
Sb
K
S Sa V Va
plane B-B
n
b =
ap
ϕi = arccos
h
sin κ


a ei
D2
ϕ 
= f • sin ϕ • sin κ
z
r
(fz << D)
Seite 34
Contact conditions depending on the radial and axial rake angle
workpiece
γf > 0°
γp > 0°
milling
cutter
S
insert
γf > 0°
γp < 0°
γf > 0°
γp = 0°
T
T
S
datum plane
S - contact
T - contact
ST - contact
U
γf < 0°
γp < 0°
γf < 0°
γp > 0°
U - contact
V
V - contact
γf = 0°
γp > 0°
V
S
SV - contact
Seite 35
Precision milling operations
fz1
a p1
ap
fz
ap
fz
finish-milling
wide finish-milling
no. of teeth 10 to 60
ap = 0.3 bis 1 mm
fz = 0.3 bis 0.5 mm
no. of teeth 1 bis 6
ap = 0.05 to 0.2 mm
fz = 0.5 bis 6 mm
fz2
a p2
finish-milling with planing knives
and wide finishing cutting edge
no. of planing knives 20 to 30
no. of wide finishing cutting edges 1 to 2
finishing cutting ap1 = 0.5 to 2 mm
edges
fz1 = 0.1 to 0.3 mm
wide finishing
ap2 = 0.03 to 0.05 mm
cutting edges
fz2 = 2 to 5 mm
Seite 36
Circular milling (DIN 8589-3: ON 3.2.3.2)
workpiece
tool
nw
ap
nw
workpiece
tool
nF
nF
vf
vf
additional axial cutting edges
radial cutting edges
nF
Mill
nW
workpiece
chipping space
Source: Walter
Seite 37
Helical milling (DIN 8589-3: ON 3.2.3.3)
a
b
c
d
e
f
Seite 38
schub
Hobbing (DIN 8589-3: ON 3.2.3.4)
Tange
ntialvo
r
-
Fräserdrehung
rotation
of hobb
Werkraddrehung
rotation
of workpiece
Fräserdrehung
Radialvorschub
radial feed
vc
fa
fw
cutting speed
axial feed
hob feed
Seite 39
Different types of hobs
Monobloc gear hob
Roughing-finishing multi hob
Indexable insert hob
high revolutions of the mill
high cutting ability
no sharpening
short milling times
rough- and finish milling
low accuracy
short first cut length
easily to re-sharpen
only for rough milling
large gearing
large gearing
Fotos: Fette, Saazor, Saacke
Seite 40
Profile milling (DIN 8589-3: ON 3.2.3.5)
profile milling cutter
gang milling cutter
workpiece
workpiece
DIN 8589-3
workpiece
Source: Sandvik Coromant, Ingersoll, ALESA AG
Seite 41
Form milling (DIN 8589-3: ON 3.2.3.6)
tool
workpiece
form-profile milling
Source: Milltech, Dalscheid
Seite 42
Outline
1
Introduction
2
2.1 Turning
2.2 Milling
2.3 Drilling
3
4
Hard machining
5
Seite 43
Drilling processes DIN 8589-2
3.2.2
drilling
countersinking
reaming
DIN 8589-2
3.2.2.1
3.2.2.2
3.2.2.3
3.2.2.5
3.2.2.6
spot facing
centre drilling
tapping
profile drilling
form drilling
Seite 44
Example of gun drilling
Source: Widia
Seite 45
Example of gun drilling
Seite 46
Criteria for drilling
Material separation and reaming at the major
cutting edge
Plastic deformation at the chisel edge
Cutting speed drops down to zero in the centre
of the drill
n
f Bohrwerkzeug
drill
friction
Reibung
Reibung
friction
Werkstück
workpiece
Chips are difficult to remove
Unfavourable heat distribution at the interface
Increased wear at the sharp-edged corner
Reaming between leading lands and drilling wall
Plastische
plastic
Verformung
deformation
Stofftrennung
material
seperation
Seite 47
Cutting conditions dependent on drill diameter
0
mm
1
7
αfe
γfe
vc
8
9
chisel edge
6
drill radius r
5
main cutting edge
4
10
40°
30°
20
m/min
20°
10
10°
0°
-10°
0
-20°
-30°
-40°
-50°
-60°
Rake angle γ; clearance angle α
cutting speed vc
Seite 48
Fundamental kinematics: centre drilling
γf
β
γ
α
f
cutting edge 1
cutting edge 2
αxe
η
f/2
cutting direction
η
effective direction
feed direction
Seite 49
Geometry of the cutting part of a twist drill
cutting part
plunge (lettering point)
flat tang
drill diameter d
tapered shaft
plunge length
point length
cutting length
cone length
flute length
total length
nach DIN 8589-2
Seite 50
Geometry at the cutting edge of a twist drill
major
Hauptschneide
cutting edge
α
Querschneide
chisel edge
flank
Freifläche
face
construction dimensions DIN 6539, Typ N
diameter d:
1 mm
drill-point angle σ :
118°
δ
major clearance angle α:
angle of twist: δ:
cutting material:
grain size DK:
10°
35°
HW -K20
0.5 - 0.7 µm
Seite 51
Specific geometries of twist drills
cone shaped
drill (basic
polish for form
A-D)
Form A
Form B
Form C
pointed
transverse
cutting edge
pointed cutting
edge with corrected
major cutting edge
cross-wise
polish
Form D
Form E
pointed trans-verse point angle 180°
cutting edge with
with centre tip
facetted cutting edge
corners
Seite 52
Twist drill for various materials
Seite 53
Drilling processes I
drilling:
Cutting with circular primary motion. The axis of rotation of the tool and of
the produced internal area are identical. The direction of the feed has the
direction of this axis of rotation.
centre drilling
gun drilling
primary
motion
tool
tool
feed
motion
tapping
profile drilling
primary
motion
primary
motion
primary
motion
feed
motion
feed
motion
feed
motion
tool
tool
workpiece
workpiece
workpiece
tool
workpiece
source: DIN 8589-2
Seite 54
Gundrilling
drill bushing
cemented
HM-Kopf
carbide
mit
Schaft
shaft
head
with indexable
eingeschliffenen
inserts
Führungsleisten
lubrication
outlet cutting edge
crimp
Source: Sandvik
Seite 55
Drilling processes II
sinking:
Drilling for producing planes which are orthogonal to the axis of rotation or
rotationally symmetric cone and form planes.
reaming: Bore up with a low undeformed chip thickness for producing better qualities
of the surface.
countersinking
cylinder sinking
reaming
primary
motion
primary
motion
feed
motion
feed
motion
tool
tool
tool
workpiece
workpiece
workpiece
primary
motion
feed
motion
source: DIN 8589-2
Seite 56
Fundamental kinematics: centre drilling
vf
n
minor cutting edge
n
trace of Po
trace of Pr
major cutting edge
tool
web
thickness
vc
workpiece
trace of Ps
trace of Pp
κr =
εr
Pp
trace of
chisel edge
σ
ap =
2
h
fz
σ
Pr
trace of Pf
ap
1
⋅D
2
Pr
b
Seite 57
Outline
1
Introduction
2
3
3.1 Shaping/ Planing
3.2 Broaching
3.3 Sawing
4
Hard machining
5
Seite 58
Outline
1
Introduction
2
3
3.2 Broaching
3.3 Sawing
4
Hard machining
5
Seite 59
Definitions and kinematics
planing/
shaping:
Cutting with repeated parallel translation as primary motion and successive
feed motion which is orientated orthogonal to the primary motion.
The kinematics of planing and shaping are identical. When the primary motion
comes from the workpiece the process is called planing, when the primary
motion comes from the tool the process is called shaping.
planing
shaping
primary motion
at the tool
primary
motion at the
workpiece
Seite 60
Planing processes
finish planing
primary
motion
contour planing
feed motion
profile planing
feed
motion
tool
circular planing
feed
motion
tool
tool
tool
workpiece
feed
motion
workpiece
primary
motion
workpiece
primary
motion
workpiece
primary
motion
source: DIN 8589-4
Seite 61
Tool-in-hand system: planing
trace of Ps
tool
primary
motion
at the
workpiece
κr
vf
trace of Pf
workpiece
trace of Po
trace of Pp
Pr
Seite 62
Outline
1
Introduction
2
3
3.2 Broaching
3.3 Sawing
4
Hard machining
5
Seite 63
Internal broaching tools (schematic)
end piece
A
shank
way
roughing-
fz
t
finishing-
calibrating part(fz=0)
bα
α01
B
α01
α02
γ0
bα01
detail B
width of chamber
α01 chamfer inclination
t
division
γ0
fz
inclination
α02
detail A
clearance angle
rake angle
Seite 64
Broaching processes I
broaching:
Cutting with a tool with more than one flute. The flutes are orientated one after
another with the stepping of the undeformed chip thickness. The feed motion is
substituted by the stepping. The last flutes of the tool produces the desired
profile of the workpiece. After one run, the workpiece is ready and the surface
finished.
plane broaching
primary
motion
workpiece
external broaching
primary
motion
feed motion
tool
feed
motion
internal broaching
tool
feed
motion
tool
workpiece
primary
motion
workpiece
source: DIN 8589-5
Seite 65
Broaching processes II
profile broaching
feed
motion
primary
motion
helical broaching
tool
tool
cylindrical broaching
feed
motion
tool
primary
motions
primary
motions
workpiece
workpiece
initial shape of
the workpiece
workpiece
end shape of
the workpiece
workpiece
tool
source: DIN 8589-5
Seite 66
Tool-in-hand system: internal broaching
vf
feed motion is
realized with the
stepping flutes
Pf ≡ Po
tool
vc
4 ⋅ fz
ap
trace of Pr
tz
primary
motion
workpiece
trace of Ps ≡ Pp
tool and workpieces
Seite 67
Outline
1
Introduction
2
3
3.2 Broaching
3.3 Sawing
4
Hard machining
5
Seite 68
Sawing processes
sawing:
Cutting with circular motion or parallel translation as primary motion. The
Tools have more than one flute. The depth of cut is low and the primary
motion comes from the tool.
hack sawing
band sawing
tool
feed
motion
primary
motion
workpiece
feed
motion
tool
workpiece
circular sawing
tool
primary motion
primary
motion
workpiece
feed
motion
source: DIN 8589-6
Seite 69
Terms and cutting part geometry of the sawing belt
g0
R
width
b0
base of a
gear tooth
H
back of
belt
belt saw
cutting part
a0
h
t
vc
ve
tooth head
tooth gap
tip of tooth
fz
90o
working plane
workpiece
(chip space)
ae
t
tooth division
vc cutting speed
R
base radius
ve operating speed
H
tooth height
fz
tooth feed
ae width of cut
Seite 70
Tool-in-hand system: hack sawing
primary motion
feed
motion
tool
trace of Pr
vf
fz
workpiece
trace of Ps ≡ Pp
Pf ≡ Po
κr
trace of Pf ≡ Po
Pr
trace of Ps ≡ Pp
Seite 71
Outline
1
Introduction
2
3
4
Hard machining
5
Seite 72
Hard machining with geometrically defined cutting edges
Techniques
Cutting materials
turning
ultra fine grained carbides
milling
ceramics
broaching
PCBN
Technological specialties
cutting process is conducted by a single or a few cutting edges
strong relation between the condition of single cutting edges and the surface rim zone of the
workpiece, because the materials are hard and thus the tools posses a high wear risk
risk of white layers
Seite 73
Mechanically strong steel parts need to be hardened / tempered
Hardening steel leads to mechanically strong parts
Soft
Hard
Hardening /
Tempering
Micro structure:martensite
Hardness: 20 - 35 HRC
Hardness: 55 - 65 HRC
Stress s
Stress s
Micro structure: ferrite
Strain e
Material volume: 100 %
Strain e
Material volume: approx. 103 %
non-uniform strain and
distortion
=> Final cut necessary to achieve high accuracy in form and size,
small and medium parts need to be oversized by approx. 0.3 - 0.5 mm
Seite 74
Typical parts for hard machining
Cams shaft
Slipping load
(e.g. contact with bucket tappet)
Rolling load
(contact with rollers)
Bearing rings
Micro slipping
(Contact with shaft)
Rolling load
(Contact with partner gear)
Gears
Bending load
(at tooth ground)
Slipping load
(Contact with synchronising ring)
Seite 75
Hard machining, turning and grinding
Hard machining can be realised by
defined and undefined machining principles.
Hardened steel can only be cut defined if the
material in front of the cutting tip is heated
and softened by the process itself.
This leads to special requirements for the
cutting material and the press design.
Seite 76
Application for Precision Hard Turning
Machining time
Part:
Precision profile roller
O 150 mm
Material:
X210CrW12
hardened (63 HRC)
Machining:
Hard turning of the
profile
Machining Cost
100 %
100 %
90 %
90 %
80 %
80 %
70 %
70 %
60 %
60 %
50 %
50 %
40 %
40 %
30 %
30 %
20 %
20 %
10 %
10 %
Grinding
Hard Turning
Grinding
Hard Turning
Seite 77
Outline
1
Introduction
2
3
4
Hard machining
5
Seite 78
Force calculation: time function
Substitution of the empirical force equation proposed by Kienzle with the technical terms:
1− mi
Fi = ki1.1 ⋅ b ⋅ h
diameter of the tool
(1− mi )
π ⋅ D ⋅ v f

⋅
⋅ sin ω ⋅ sin κ r 
Fi ≈ ki1.1 ⋅
sin κ r  z ⋅ vc

equation proposed by
Salomon or Kienzle
ap
number of teeth
polar coordinate
source: Diss. Rehse
hmax ≈ f z ⋅ sin κ r ⋅ sin ω
b=
Question: What is the angle ω?
)
⋅
ω=2 b
D
ap
sin κ r
)
b = vc ⋅ t
discretisation of the equation:

a p π ⋅ D ⋅ v f
 2 ⋅ vc ⋅ dt 
≈
⋅
⋅
⋅
⋅
κ
 sin r 
dFi ki1.1
sin

 D 

(1− mi )
basement for modeling
Seite 79
Force calculation: technical terms
discretisation of the equation:
dFi ≈ ki1.1 ⋅
π ⋅ D ⋅ v f

 2 ⋅ vc ⋅ dt 
⋅
⋅ sin
⋅
κ
 sin r 
 D 

ap
(1− mi )
Solving the equation for
discrete times
discrete time function
discrete force components
dFi (dt )
force in x / N
calculated
measured
time / sec
addition of the force
components in x- and
y- direction separately
transformation of the
force components into
the x- and y- direction
The same procedure
for the other flutes!
Seite 80
Penetration calculation: peripheral milling
data of the machine tool
data of the tool
data of the workpiece
matrix model for the penetration calculation
feed
velocity
vector field for representation the tool
vector field for representation the workpiece
thickness of cut h
width of cut b
Seite 81
Thank you for your attention!!
Seite 82
Outline
1
Introduction
2
3
4
Hard machining
5
Seite 83
Outline
1
Introduction
2
3
4
Hard machining
5
Seite 84
Process classification
Manufacturing Processes
1
primary
shaping
2
secondary
shaping /
forming
3
4
5
cutting
joining
coating
6
changing
material
properties
3.2
cutting
3.2.1
3.2.2
drilling
turning reaming
rotary motion
3.2.3
milling
3.2.4
planing
shaping
3.2.5
3.2.6
broaching
sawing
3.2.7
filing
rasping
3.2.8
3.2.9
scraping
brushing chiselling
parallel translation
source: DIN 8589-0
Seite 85
Evaluation
Attend:
knowledge of the complete workpiece design (angel ω)
if the information is not available the modeling cannot success!
advantages
general model
possibility to use
general software
possibility to expand
with dynamic terms
mathematical formulation
disadvantage
no direct material
information
This information is contained in the
specific force parameter!
Seite 86

Cutting Processes

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