Cutting conditions

Feed rate Spindle Speed

Radial cutting depth Axial cutting depth

…

CUTTING CONDITIONS

BACHELOR OF ENGINEERING

MANUFACTURING TECHNOLOGIES

CUTTING CONDITIONS

by Endika Gandarias

2 by Endika Gandarias

Dr. ENDIKA GANDARIAS MINTEGI Mechanical and Manufacturing department Mondragon Unibertsitatea - www.mondragon.edu (Basque Country) www.linkedin.com/in/endika-gandarias-mintegi-91174653

http://www.mondragon.edu/eps

http://www.linkedin.com/in/endika-gandarias-mintegi-91174653







3

CONTENTS BIBLIOGRAPHY CUTTING TOOLS CUTTING PARAMETERS CUTTING FLUIDS SELECTION OF CUTTING CONDITIONS GLOSSARY

by Endika Gandarias

4

BIBLIOGRAPHY

BIBLIOGRAPHY

by Endika Gandarias

5

The author would like to thank all the bibliographic references and videos that

have contributed to the elaboration of these presentations.

For bibliographic references, please refer to:

• http://www.slideshare.net/endika55/bibliography-71763364 (PDF file)

• http://www.slideshare.net/endika55/bibliography-71763366 (PPT file)

For videos, please refer to:

• www.symbaloo.com/mix/manufacturingtechnology

BIBLIOGRAPHY

by Endika Gandarias

http://www.slideshare.net/endika55/bibliography-71763364

http://www.slideshare.net/endika55/bibliography-71763366

http://www.symbaloo.com/mix/manufacturingtechnology

6

CUTTING TOOLS

CUTTING TOOLS

by Endika Gandarias

7

CUTTING TOOLS

by Endika Gandarias

(HSS)

VIDEO VIDEO

8

CUTTING TOOLS

by Endika Gandarias

9

CUTTING TOOLS

by Endika Gandarias

Temperature [ºC]

Har

dnes

s [H

RC

]

1550

1400

1300

900

800

Ceramic

CBN

Carbide (Hard metal)

Diamond

HSS

ºC

10

Feed [mm/rev]

Cut

ting

spee

d [m

/min

]

50

CUTTING TOOLS

by Endika Gandarias

11

Solid tool Brazed insert Mechanically clamped insert

TOOL GEOMETRY

Turning

CUTTING TOOLS

by Endika Gandarias

VIDEO

12

CUTTING TOOLS

by Endika Gandarias

TOOL GEOMETRY

Turning RAKE FACE

Front Clearance (or end-relief) angle

Major (or side) cutting edge

Minor (or end) cutting edge

Front or back rake angle Nose (or corner) radius MAJOR CLEARANCE (FLANK OR RELIEF) FACE

Minor (or end) cutting edge angle

MINOR CLEARANCE (OR FLANK) FACE

Side rake angle

Major (or side or lead) cutting edge angle

Side clearance (or relief) angle

Major cutting edge angle

Minor cutting edge angle

RAKE FACE

CLEARANCEFACE Clearance angle

Rake angle

Side clearance angle

Side rake angle

VIDEO

13

CUTTING TOOLS

by Endika Gandarias

TOOL GEOMETRY

Milling

Flat End Mill

Ball nose End Mill

Corner radius End Mill

END MILLING CUTTERS PERIPHERAL AND FACE MILLING CUTTERS

Shell End Mill

Side and Face cutter

Single and double angle cutter

14

TOOL GEOMETRY

CUTTING TOOLS

by Endika Gandarias

Drilling

Solid carbide drill

Chisel edge

Main cutting edge

Rake face

Major flank face Margin

Drill diameter

Web thickness Major

flank face

Major cutting edge

Rake face

Point angle Minor cutting

edge

Helix angle

Point angle 140°

High Speed Steel (HSS)

Point angle 118°

VIDEO

15

TOOL INSERT

Main cutting edge design

Cheap-breaker macrogeometry

Geometry for small cutting depths (ap)

Rake angle 20°

Main facet 5°

Tip cutting edge design

Cheap-breaker macrogeometry

Cutting edge reinforcement of 0,25 mm

CUTTING TOOLS

by Endika Gandarias

VIDEO

Insert design

16

CUTTING TOOLS

by Endika Gandarias

TOOL INSERT

Insert material types

17

TOOL INSERT

CUTTING TOOLS

by Endika Gandarias

VIDEO

POSITIVE

Rake angle

NEGATIVE

Increased tool insert resistance. Higher cutting forces. Shorter chip length. Clearance angle = 0º. Double side inserts.

Lower cutting forces. Longer chip length. Clearance angle > 0º. Used for internal machining.

Clearance angle

Clearance angle always > 0º.

18

TOOL INSERT

CUTTING TOOLS

by Endika Gandarias

Lead angle / Entering angle

Entering angle

Lead angle

Side Rake angle

Same advantage discussed for rake angle, applies to side rake angle.

When rake angle is positive so is side rake angle, and vice versa.

19

TOOL INSERT

CUTTING TOOLS

by Endika Gandarias

Nose radius and Nose angle Chipbreaker

Each insert has an appliation area.

Groove type Obstruction type

Nose radius Nose angle

20

TOOL INSERT

CUTTING TOOLS

by Endika Gandarias

Insert grade

VIDEO VIDEO VIDEO

VIDEO

21

TOOL INSERT

CUTTING TOOLS

by Endika Gandarias

Insert fabrication

Raw material Crushed

Spray drying

Carbide powder Ready to be pressed

Cobalt Tungsten carbide

Titanium

Tantalum Niobium

Powder fabrication

VIDEO

22

TOOL INSERT

CUTTING TOOLS

by Endika Gandarias

Insert fabrication

Pressing force 20 - 50 t

Upper and lower die

Die and center pin

Pressing

23

TOOL INSERT

CUTTING TOOLS

by Endika Gandarias

Insert fabrication Sintering

Sintering duration: 8 hours Temperature between 1200 - 2200 °C Inserts trays

Insert contraction (18% in all directions,

50% in volume)

24

TOOL INSERT

CUTTING TOOLS

by Endika Gandarias

Insert fabrication Insert grinding

Higer and lower face Free profiling Profiling

Beveling, negative facet Peripheral

Bisel

Faceta neg.

25

TOOL INSERT

CUTTING TOOLS

by Endika Gandarias

Insert fabrication Insert grinding

ER Treatment (Edge Roundness)

W/H proportion depends on the application

26

TOOL INSERT

CUTTING TOOLS

by Endika Gandarias

Insert fabrication Chemical Vapor Deposition (CVD) coating

- Large coating thickness. - Mechanical wear resistance (TiCN). - Thermal & chemical resistance (Al2O3).

TiCN

Al2O3

Substrate

Inserts trays CVD oven

27

TOOL INSERT

CUTTING TOOLS

by Endika Gandarias

Insert fabrication Physical vapor deposition (PVD) coating PVD oven

TiN

Substrate

- Thin coating thickness. - Sharp cutting edge. - Good edge toughness. - Used in all monoblock rotating tools. - Can be used with soldered tips.

28

TOOL INSERT

CUTTING TOOLS

by Endika Gandarias

Insert fabrication Visual inspection, marking, packaging

Visual inspection

Marking

Distribution

Labelling

Packaging

29

CUTTING PARAMETERS

CUTTING PARAMETERS

by Endika Gandarias

30

SELECTION CRITERIA: Make the highest profit considering the technical requirements. OPERATIONS:

– ROUGHING: It aims to remove as much as possible material from the workpiece for as short as possible machining time. Quality of machining is of a minor concern.

– FINISHING: The purpose is to achieve the technical requirements (i.e., dimensional, surface and geometric tolerances). Quality is of major importance.

In order to make most profit the most relevant variables are: • Cutting time. • Cutting tool expenditure.

Machining parameters that most affect the above variables are: • Cutting speed (Vc) • Feed (fz, fn, F) • Radial and axial depth of cuts (ap, ae)

ROUGHING FINISHING

Vc

fn

fz

F

CUTTING PARAMETERS

by Endika Gandarias

31

DEFINITION: Relative linear speed at the contact point between tool and the workpiece.

Vc · 1000 N = π · Dm

CUTTING PARAMETERS: TURNING

1. Cutting Speed (Vc)

by Endika Gandarias

N

Vc: Cutting speed (m/min)

N: Spindle speed (rpm)

Dm: machined diameter (mm)

VIDEO

VIDEO

VIDEO

VIDEO

32



Given the following parameters calculate the spindle speed for each diameter:

Cutting speed Vc = 120 m/min Diameter D1 = Ø 50 mm Diameter D2 = Ø 80 mm

VC x 1000 π x d

N =

N1

N2

by Endika Gandarias

33

F [mm/min]

DEFINITION: Relative movement between the workpiece and the tool.

fn [mm/rev]

IN TURNING

FEED PER REVOLUTION

(fn) →

2. Feed

3. Cutting depth (ap)

FEED PER REVOLUTION

F = fn·N


FEED RATE or

FEED PER MINUTE

by Endika Gandarias

F

ap

ap

ap

34

MACHINE WORKPIECE MATERIAL

TOOL MATERIAL OPERATION Vc

(m/min) fn

(mm/rev) Ap

(mm)

TURNING MACHINE

STEEL

HIGH SPEED STEEL (HSS)

Turning and facing D 30 – 40 A 40 - 50

D 0.1– 0.25 A 0.02/ 0.1

D 0.75-2 A 0.2-0.8

Parting and grooving 10 – 15 0.02 – 0.1

Threading 10 Thread pitch According to formula

Drilling 18 Manual

Knurling 10

Boring D 20 – 30 A 30 - 40

D 0.1– 0.25 A 0.02/ 0.1

D 0.75-2 A 0.2-0.8

HARD METAL


D 0.1– 0.25 A 0.02/ 0.1

D 0.75-2 A 0.2-0.8


Threading 40 - 50 Thread pitch According to formula

Drilling 30 – 40 Manual

Boring D 70 – 90 A 90 - 110

D 0.1– 0.25 A 0.02/ 0.1

D 0.75-2 A 0.2-0.8

ALUMINIUM



D 0.1– 0.25 A 0.02/ 0.1

D 0.75-2 A 0.2-0.8


Threading 15 Thread pitch According to formula

Drilling 30 Manual

Knurling 20

Boring D 30 – 50 A 50 - 70

D 0.1– 0.25 A 0.02/ 0.1

D 0.75-2 A 0.2-0.8

HARD METAL

Turning and facing D 150 – 180 A 180 – 200

D 0.1– 0.25 A 0.02/ 0.1

D 0.75-2 A 0.2-0.8

Parting and grooving 80– 100 0.04 – 0.1

Threading 50 – 60 Thread pitch According to formula

Drilling 60 – 80 Manual

Boring D 140 – 170 A 170 - 190

D 0.1– 0.25 A 0.02/ 0.1

D 0.75-2 A 0.2-0.8

by Endika Gandarias

D: Roughing operation A: Finishing operation

CUTTING PARAMETERS: TURNING O

RIE

NTA

TIV

E C

UTT

ING

TA

BLE

FO

R E

XER

CIS

ES

35

SURFACE ROUGHNESS:

Surface finish depends on: • Tool nose radius • Feed per revolution (fn)

WIPER INSERTS: Advantages:

Productivity ↑


by Endika Gandarias

VIDEO

36


by Endika Gandarias

TOOL CENTRE HEIGHT

37


VIBRATION

_ + Vibration

by Endika Gandarias

Round R

90º S

80º C

80º W

60º T

55º D

35º V _

+

Vibr

atio

n

ER: Edge Rounding GC: Ground coated inserts VB: Flank wear

_

+

Stre

ngth

38


VIBRATION

They can reduce machining vibration in turning, milling or drilling.

VIDEO

– Diameters starting from Ø > 10mm. – Maximum overhang value 14 × Ø.

by Endika Gandarias

Dampened tool Undampened tool

SSV technique may reduce or eliminate chatter. VIDEO

VIDEO

Dampened tools

Spindle Speed Variation (SSV)

39


CUTTING PARAMETERS: MILLING


by Endika Gandarias

N

N

Vc · 1000 Vc: Cutting speed (m/min) N = N: Spindle speed (rpm) π · Dc Dc: Tool diameter (mm)

VIDEO

40

Feed per tooth (fz): It defines the chip thickness, and so, the load that the tool is subjected to.

Feed per revolution (fn): It defines the tool displacement per tool revolution.

Feed rate or Feed per minute (F): It defines the tool movement speed.

fn = fz·z z tooth number (flute number)

F = fn·N = fz·z·N N spindle speed


IN MILLING

FEED PER TOOTH

(fz) →

2. Feed


by Endika Gandarias

fn

F

VIDEO

41

As there are greater tooth breakage chances during tooth entry and exit, in facing operations the following tool size and positioning are recommended.

ap: axial depth of cut

ae : radial depth of cut

3. Cutting depth

Better size

Better positioning


by Endika Gandarias

VIDEO

42 by Endika Gandarias



(m/min) fz

(mm/tooth*rev) Ap

(mm) Ae

(mm)

MILLING MACHINE

STEEL


Face milling D 20 - 25 A 25 - 30

0.05 – 0.1 0.01 – 0.05

D 1-2 A 0.2-0.5

D (~2/3)Ø A (~2/3)Ø

Side milling D 20 - 25 A 25 - 30

0.05 – 0.1 0.01 – 0.05

D (50%-80%)Ø A (50%-80%)Ø

D (10%-25%)Ø A (5%-10%)Ø

Other milling D 15 - 20 A 20 - 25

0.05 – 0.1 0.01 – 0.05

HARD METAL

Face milling D 80 - 100

A 100 – 120 0.05 – 0.1

0.01 – 0.05 D 1-2

A 0.2-0.5 D (~2/3)Ø A (~2/3)Ø

Side milling D 80 - 100

A 100 – 120 0.05 – 0.1

0.01 – 0.05 D (50%-80%)Ø A (50%-80%)Ø

D (10%-25%)Ø A (5%-10%)Ø

Other milling D 70 - 90

A 90 – 100 0.05 – 0.1

0.01 – 0.05

ALUMINIUM


Face milling D 50 - 70 A 70 - 90

0.05 – 0.1 0.01 – 0.05

D 1-2 A 0.2-0.5

D (~2/3)Ø A (~2/3)Ø

Side milling D 50 - 70 A 70 - 90

0.05 – 0.1 0.01 – 0.05

D (50%-80%)Ø A (50%-80%)Ø

D (10%-25%)Ø A (5%-10%)Ø

Other milling D 40 - 60 A 60 - 70

0.05 – 0.1 0.01 – 0.05

HARD METAL

Face milling D120 - 150 A 150 – 180

0.05 – 0.1 0.01 – 0.05

D 1-2 A 0.2-0.5

D (~2/3)Ø A (~2/3)Ø

Side milling D120 - 150

A 150 – 180 0.05 – 0.1

0.01 – 0.05 D (50%-80%)Ø A (50%-80%)Ø

D (10%-25%)Ø A (5%-10%)Ø

Other milling D100 - 130

A 130 – 150 0.05 – 0.1

0.01 – 0.05

Other milling: slot milling, t-shape milling, dovetail milling, form milling. D: Roughing operation A: Finishing operation

CUTTING PARAMETERS: MILLING O

RIE

NTA

TIV

E C

UTT

ING

TA

BLE

FO

R E

XER

CIS

ES

43

DOWN MILLING or CLIMB CUTTING Same cutter rotation and feed

UP MILLING or CONVENTIONAL MILLING Opposite cutter rotation and feed

The insert starts cutting with a large chip thickness:

It is more suitable.

Backlash elimination is necessary. Vibration tendency ↑.

Fc tend to pull the workpiece into the cutter.

Not recommended when using ceramic inserts (fragile).

The insert starts cutting at zero chip thickness:

Rubbing Friction ↑, Fc ↑, Machine power ↑

Temperature ↑, work-hardened surface, Ra ↓

Fc tend to: lift the workpiece from the table, push the cutter and workpiece away from each other.

Tensile stresses ↑ when teeth exit, tool life ↓

Mc

Ma

MILLING: Discontinuous cutting process

Ma

Mc


MILLING DIRECTION

by Endika Gandarias

VIDEO VIDEO VIDEO

44


HIGH SPEED MACHINING (HSM)

by Endika Gandarias

HSM: Feed faster than heat propagation.

Traditional milling: time for heat propagation.

In comparison with traditional milling:

Spindle speed (N) ↑, feed rate (F) ↑ and axial cutting depth (ap) ↑.

Radial cutting depth (ae) ↓ and feed per tooth (fz) ↓.

F F

VIDEO

45

CHARACTERISTICS:

More productive cutting process in small sized components.

Possible to be used with high-alloy tool steels up to 60-63 HRc (EDM process can be avoided).

Excellent surface roughness can be achieved (Ra ~ 0.2 µm).

Machining of very thin walls is also possible.

Typical applications: dies and moulds, difficult to machine materials,…



by Endika Gandarias

Trochoidal milling (typical HSM technique)

Progressive cutting (constant stock)

Constant peripheral cutting speed (Vc)

46



by Endika Gandarias

DISADVANTAGES:

Higher maintenance costs: Faster wear of guide ways, ball screws and spindle bearings.

Specific process knowledge, programming equipment and interface for fast data transfer is needed.

It can be difficult to find and recruit advanced staff.

Human mistakes, hardware or software errors give big consequences. Emergency stop is practically unnecessary.

Good work and process planning necessary.

Safety precautions are necessary:

Machines with safety enclosing (bullet proof covers).

Avoid long overhangs on tools.

Do not use “heavy” tools and adapters.

Check tools, adapters and screws regularly for fatigue cracks.

Use only tools with posted maximum spindle speed.

Do not use solid tools of HSS.

47


by Endika Gandarias

MILLING STRATEGY

When using a ball nose end mill, tilting the cutter 10 to 15 degrees can improve tool life and chip formation and provide a better surface finish.

VIDEO

ROLL-IN TECHNIQUE

48


by Endika Gandarias

MILLING STRATEGY

49


by Endika Gandarias

MILLING STRATEGY

THIN WALLS

ae sould be minimized (20% Dc).

ap should not exceed 100% Dc

Big entry-exit radii should be programmed.

Sharp and positive cutting edges should be used.

WEAK FIXTURE

50

CENTER-LINE OF THE CUTTER OUTSIDE THE WORKPIECE

CENTER-LINE OF THE CUTTER IN LINE WITH THE WORKPIECE

CENTER-LINE OF THE CUTTER INSIDE THE WORKPIECE


hex = fz cutter hits, no shearing CU

TTER

EN

TRY

MILLING STRATEGY

by Endika Gandarias

ae > 70% x Dc ae < 25% x Dc hex < fz high productivity

CVD coating inserts recommended

(better thermal protection)

hex < fz F ↑ to mantain productivity

PVD coating inserts recommended (sharper cutting edge)

Carbide handles the compressive stresses at the impact of entering well.

VIDEO VIDEO VIDEO

51

CENTER-LINE OF THE CUTTER OUTSIDE THE WORKPIECE

CENTER-LINE OF THE CUTTER IN LINE WITH THE WORKPIECE

CENTER-LINE OF THE CUTTER INSIDE THE WORKPIECE

Chip thickness is at its maximum


At exit, chip bends and generates tensile forces on the carbide increasing fracture possibilities.

VIDEO by Endika Gandarias

MILLING STRATEGY

CU

TTER

EXI

T

52


• Best for shoulder face milling & where 90° form is required. • Low axial forces Thin walls, weak fixtured components,…

• Best for face milling & plunge milling. • Excellent for ramping operations. • Lower radial forces Lower vibration. • Chip thickness ↓ feed ↑ to keep productivity.

• Best for face milling & profiling operations. • Excellent ramping capabilities. • Strongest cutting edge with multiple indexes. • The chip load and entering angle vary with the depth of cut.

: Cutting edge angle affects the cutting force direction and the chip thickness. ENTERING ANGLE (Kr)

VIDEO VIDEO VIDEO VIDEO

_ + Chip thickness _ +

Length of contact

by Endika Gandarias

90º 45º 10º VIDEO

53


The pitch is the distance between the effective cutting edges. Different pitches:

Differential pitch: A very effective way to minimize vibration tendencies.

PITCH (u)

_ + Productivity

Machine power consumption

by Endika Gandarias

Vibration

VIDEO

54

TOOL HOLDER ALIGNMENT RECOMMENDATIONS:

Finishing


by Endika Gandarias

< 0.006 mm

Roughing

Tool overhang (A) and total length (B) should be minimized.

Attention to the max. allowable torque. It depends on the tool holder type and tool diameter.

55

Surface finish, i.e. Surface Roughness, is mainly determined by the distance between the contiguous toolpaths, tool radius and surface slope.

How to calculate the axial (ap) and radial (ae) cutting depths to achieve a certain theoretical roughness?

In this type of milling; Ra ≈ Rmax/4

ae = Radial depth of cut ap = Axial depth of cut Rmax = Rz = Max. roughness Rhta = Tool radius α = Surface slope

Rmax ↓ ae ↓ ap ↓

Rhta ↑


SURFACE ROUGHNESS:

by Endika Gandarias

56

In ball end mills, cutting happens at points with different diameters. Thus, as the whole tool rotates at the same spindle speed, the cutting speed varies along the ball end.

Effective radius in ascending toolpaths Effective radius in descending toolpaths

EFFECTIVE TOOL RADIUS


by Endika Gandarias

57

CUTTING PARAMETERS: DRILLING



by Endika Gandarias

vc

N

Vc · 1000 Vc: Cutting speed (m/min) N = N: Spindle speed (rpm) π · Dc Dc: Tool diameter (mm)

N

VIDEO VIDEO

58

2. Feed


IN DRILLING

FEED PER REVOLUTION

(fn) →

3. Cutting depth (ap)

F [mm/min]

FEED RATE or

FEED PER MINUTE F = fn·N


by Endika Gandarias

ap

VIDEO

59

DRILL ALIGNMENT RECOMMENDATIONS:

by Endika Gandarias


0.02 mm 0.02 mm

Rotary drill Stationary drill

B

A

Feed force

Better B than A tool position (lower torque).

Tool alignment method.

VIDEO VIDEO

60

fn ⅓ fn ⅓ fn ⅓ fn

A B C D

ENTRY AT NON-PLANAR SURFACES:

by Endika Gandarias




(m/min) fn

(mm/rev)

DRILLING MACHINE

STEEL HIGH SPEED STEEL

(HSS)

Spot drilling 18 0.04 – 0.1 Drilling 18 0.04 – 0.1 Counterboring 9 Countersinking 9

ALUMINIUM HIGH SPEED STEEL

(HSS)

Spot drilling 30 – 40 0.04 – 0.1 Drilling 30 – 40 0.04 – 0.1 Counterboring 15 – 20 Countersinking 15 – 20

OR

IEN

TATI

VE

CU

TTIN

G T

AB

LE

FOR

EXE

RC

ISE

S

61

Excellent Acceptable

Start chip

Chip jamming

The start chip from entry into the workpiece is always long and does not create any problems.

Chip jamming can cause radial movement of the drill and affect hole quality, drill life and reliability, or drill/insert breakages.

A hole affected by chip jamming. A hole with good chip evacuation.

CHIP CONTROL

The chip formation is acceptable when chips can be evacuated from the drill without disturbance. The best way to identify this is to listen during drilling: A consistent sound = chip evacuation is good. An interrupted sound indicates chip jamming.


by Endika Gandarias

VIDEO

62

PECK DRILLING


by Endika Gandarias

Peck drilling may be necessary if chip evacuation is difficult due to a deep hole or the use of external lubricant.

VIDEO

63

CUTTING PARAMETERS

VARIABLE UNIT DESCRIPTION HOW TO CALCULATE? TURNING MILLING DRILLING

Vc m/min Cutting speed TABLES

N rpm or rev/min Spindle speed N=(Vc*1000)/(π*Ø)

fz mm/tooth*rev Feed per tooth TABLES

fn mm/rev Feed per revolution

TABLES

fn = fz * z

F mm/min Feed rate or feed per minute F = fn * N

Ap mm Axial cutting depth

TABLES

Tool radius

Ae mm Radial cutting depth TABLES

Parameter introduced into the machine.

Parameter NOT introduced into the machine.

by Endika Gandarias

SUMMARY TABLE

64

CUTTING FLUIDS

CUTTING FLUIDS

by Endika Gandarias

65

Cutting fluid is any liquid or gas that is applied to the chip or cutting tool to improve cutting performance. Cutting fluids serve 4 principle functions:

1. To remove heat in cutting (=COOLING): The energy used in the cutting process is almost exclusively transformed into heat that goes to the workpiece, tool and chip. The effective cooling action depends on the method of application, type of fluid, fluid flow rate and pressure.

2. To lubricate the chip-tool interface (=LUBRICATION): It reduces friction forces and temperatures.

3. To wash away chips (=CHIP REMOVAL): This is only applicable to small and discontinuous chips.

4. To avoid part oxidation (=ANTI-CORROSION): The environment humidity in combination with the high temperatures (500-900ºC) obtained during machining may cause part oxidation. Thus, the cutting fluid must contain anti-corrosion additives.

Use of cutting fluids contributes to: Diminish tool wear (longer tool life). Produce workpieces of accurate sizes (reduce thermal expansion). Achieve proper surface quality of the workpiece. Support chip removal. Reduce thermal stress on machine tool.

CUTTING FLUIDS

by Endika Gandarias

66

CUTTING FLUIDS

- METHODS OF APPLICATION

LUBRICATION TYPE CONTENT USED

VOLUME CHARACTERISTICS

Wet machining (using coolant)

Manual application

10 to 100 l/min

Used for manual tapping. Cutting fluids are used as lubricants.

Flooding supply Lubricating system of machine tools need to be cleaned from time to time to eliminate microorganisms.

Coolant-fed tooling or internal cooling

Some tools (typically drills) are provided with axial holes so that cutting fluid can be pumped directly to the cutting edge. Coolant pressures up to 80 bars.

Coolant-fed tool holders

Special tool holders required for milling, turning or drilling operations. Coolant pressures up to 30 bars.

Reduced lubrication

Minimum quantity llubrication (MQL)

50 ml/h up to 1-2 l/h

Cutting fluid is deposited as drops or air-oil mix. Valid for not very demanding machining operations. It can be external or internal.

Without lubrication Dry machining without It shows economic and environmental benefits. Under

research.

Novel cooling methods are under research: high pressure cooling (> 70bar), criogenic cooling (N2, CO2),...

by Endika Gandarias

VIDEO

VIDEO

67

CUTTING FLUIDS

Manual application Flooding supply Coolant-fed tooling Coolant-fed tool holder

by Endika Gandarias

Titanium alloys Nickel Stainless steel Hard steel ( 0.4 to 0.7 % C ) Copper Cast-iron Steel (More carbon more difficult) Aluminum Brass Bronze Zinc alloy

Broaching Shaping Gear machining Drilling Reaming Sawing Milling Turning

http://www.suministrosmerca.com/ferreteria-general-engrase-f107.10.html

68

CUTTING FLUIDS

by Endika Gandarias

Cutting oils are based on mineral or fatty oil mixtures. Commonly used for heavy cutting operations.

Soluble oils is the most common (95% of the time), cheap and effective form of cutting fluid. Oil droplets suspended in water in a typical ratio water to oil 30:1. Emulsifying agents are also added to promote stability of emulsion, as well as anticorrosive additives.

Chemical fluids (synthetic) consists of chemical diluted in water. They may have harmful effects to the skin.

- TYPES OF CUTTING FLUID Lu

bric

atio

n

Refrigeration

Cutting oils Soluble oils Chemical fluids Water Dry machining

Low speed applications (broaching, threading,…)

↓ High friction

↓ Maximum lubrication

High speed applications (turning, milling,…)

↓ Low friction

↓ Maximum refrigeration

69

SELECTION OF

CUTTING CONDITIONS

SELECTION OF CUTTING CONDITIONS

by Endika Gandarias

70


Productivity is a combination of factors that really make a difference, such as: • Increased cutting conditions = more parts per hour • Predictable tool life = machining security • Fewer tool changes = less down time • Fewer rejects = higher quality – more valuable end product • Product availability = less inventory • Technical training of employees = better understanding and less scrap

by Endika Gandarias

Important to identify the most relevant factors that influence the FINAL COST:

≈ 31%

≈ 27%

≈ 22%

≈ 3%

≈ 17%

71

Important to identify the most relevant factors that influence MACHINE-TOOL UTILIZATION TIME:


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Machining efficiency suggests that good quality parts are produced at reasonable cost and at high production rate. Most relevant cutting parameters that affect machining costs and productivity are:

1. Depth of cut 2. Feed 3. Cutting speed


It is predetermined by workpiece geometry and final part shape.

In Roughing operations As large as possible (max. 6-10 mm). It depends on machine tool, cutting tool strength and other factors.

In Finishing operations A single pass to achieve the final dimensions.

Finishing pass in a turning operation Roughing passes in a turning operation

1. Depth of Cut (ap, ae)

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In Roughing operations As large as possible (max. 0,5mm/rev). It depends on cutting forces and setup rigidity.

In Finishing operations Small to ensure good surface finish (~ 0,05-0,15 mm/rev).

Cutting at high cutting speed involves...

Reduction of tool life Increase of production costs as more cutting tools are needed.

Increase of productivity less time consumption. Hence, optimal cutting speed range has to be calculated for:

Cutting speed for minimum cost per unit (Vmin). Cutting speed for maximum production rate (Vmax).


2. Feed (F, fn, fz)

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Production cost

Fixed costs

Economic Vc

Tooling cost

Cutting speed Vc

Cos

t per

par

t

Parts per hour

Vc for max. productivity

High efficiency range

Machinery costs


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- HOW TO CALCULATE THOSE VALUES? Several limitations need to be considered:

1. MACHINE 2. TOOL 3. GEOMETRY 4. MATERIAL

1. MACHINE: The machinery usually exists in the workshop, and it may be a limiting factor. Anyway, either an existing or a new machine is used, attention should be paid to the following machine features:

General characteristics: number of axes, machine configuration type, general dimensions and weight,…

Axes: traversing range, power, accuracy, max. workpiece weight, max. acceleration and feed.

Workholder system: Forces, vibrations,… Spindle head: power, speed range, run-out, stiffness, clamping system,

automation possibilities, internal cooling. Toolholder system: Run-out, torque,… Tool changer: chip to chip time, max. number of tools, tool length and diameter,… Cooling unit system: internal or external, MQL, HPC CNC controller: capabilities …

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2. TOOL: Tool wear will occur. There are five main wear mechanisms which dominate in metal cutting:

1. Abrasion. 2. Diffusion. 3. Oxidation (corrosion). 4. Fatigue (thermal). 5. Adhesion.

These wear mechanisms combine to attack the cutting edge in various ways depending upon the tool material, cutting geometry, workpiece material and cutting data. Flank wear is the most common type of wear (abrasion) and the preferred wear type, as it offers predictable and stable tool life.

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2. TOOL

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In the case of pasty materials, layers / new

edges are formed. Adhesive

SiC inclusions of Fe foundry materials may

create cutting edge wear. Abrasive

Chemical reaction between tool carbides and the machining part

create wear.

Chemical

Temperature variations create cracks in the

cutting edge. Thermal

Mechanical efforts on the cutting edge create tool

failures. Mechanic

Cause Wear description Symbol Load type

FA

FA = Filo de aportación

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1. Flank wear 2. Crater wear 3. Plastic deformation 4. Notch wear 5. Thermal cracks 6. Mechanical fatigue cracks 7. Chipping on edge 8. Tool breakage 9. Built-up edge (BUE)

TOOL WEAR TYPES

Inappropriate cutting conditions Inappropriate tool features Material properties Too low or high cutting temperature …

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3. GEOMETRY: Part geometry will define: Dimensional tolerances, expected surface roughness values and geometrical

tolerances to be obtained. Process limitations such as vibration, chatter,…

Tool geometry will be chosen according to the process operations to be accomplished.

4. MATERIAL: Tool-workpiece material combination is very important. According to that, tool manufacturers usually offer customers cutting condition tables for free. These tables are the result of many experiments carried out.

Usually these values correspond to a tool life of 15 minutes and should be regarded as starting values. They are obtained according to Taylor’s equation. Taylor’s Tool life formula: Vc * Tn = C Expanded Taylor`s Tool life formula: Vc * Tn * fna * ap

b = C

Vc : Cutting speed [m/min] fn : Feed per revolution [mm/rev] ap : Cutting depth [mm] T : Tool life [min] a, b, n, C: Constants

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Vc

fn

ap

Workpiece material hardness

Tool material

R: Roughing M: Medium machining

F: Finishing

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INSERT GRADE

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WORKPIECE MATERIAL

INSERT GRADES

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Select geometry and grade depending on the type of the workpiece material and type of application.


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CUTTING DATA ON DISPENSERS

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TURNING INSERTS

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When increasing the cutting speed (vc), feed rate (fn) should be decreased and vice versa.

Cutting speed and feed data compensation for turning

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GLOSSARY

GLOSSARY

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GLOSSARY

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ENGLISH SPANISH BASQUE

Alignment Alineación Alineazio Alloy Aleación Aleazio Aluminium casting Fundición de aluminio Aluminio burdinurtua Axial cutting depth Profundidad de pasada axial Sakontze sakonera Backlash Desajuste Desdoitze Ball nose end mill Fresa de punta esférica / punta de bola Boladun fresa Bend Doblar Tolestu Beveling Biselado Alakaketa Brass Latón Letoia Brazed Soldado Soldatua Breakdown Averiar Matxuratu Broaching Brochado Brotxaketa Bronze Bronce Brontzea Built-up edge Filo de aportación Aportazio ertza Carbide Metal duro Metal gogorra Carbon steel Acero al carbono Karbono altzairua Cast-iron Fundición Burdinurtu CBN (Cubic Boron Nitride) Nitruro de Boro Cúbico Boro nitruro kubikoa Cheap breaker Rompevirutas Txirbil hauslea Chip Viruta Txirbil Chip Viruta Txirbil Chipping Astillado Zati Chisel edge Filo central Erdiko sorbatz Clamp Abrazar Lotu Clearance face Cara de incidencia Eraso aurpegia Climb cutting Concordancia Konkordantzia Coarse Basto Baldar Coat Recubrimiento Estaldura

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GLOSSARY

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Contiguous Contiguo Alboko Conventional milling Contraposición Kontrajartze Coolant Lubricante Lubrifikatzaile Corner radius end mill Fresa tórica Fresa torikoa Crush Machacar Birrindu Cutting edge Arista de corte Ebaketa ertz / Sorbatz Cutting speed Velocidad de corte Ebaketa abiadura Cutting tool Herramienta de corte Ebaketa erraminta Dampened tool Herramienta antivibratoria Bibrazioen aurkako erraminta Die Molde Molde Diminish Disminuir Gutxitu Dispenser Dispensador Kaxa Dovetail Cola de milano Mirubuztan Down milling Concordancia Konkordantzia Drilling Taladrado Zulaketa Drop Gota Tanta Edge rounding Redondeo de arista Ertz biribiltze EDM Electroerosión Elektro-higadura Enclosing Cerramiento Itxitura End mill Fresa plana Fresa laua Engagement Empañe Lausotua Fatty Graso Oliotsu Feed per revolution Avance por vuelta Aitzinamendua birako Feed per tooth Avance por diente Aitzinamendua hortzeko Feed rate Avance por minuto Aitzinamendua minutuko Finish Acabado Akabera Flank Flanco / Lateral Albo Flooding Inundación Gainezkatze

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GLOSSARY

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Friction Fricción Marruskadura Gauge Calibrar Kalibratu Gear Engrane Engranai Grinding Rectificado Artezketa Hard metal Metal duro Metal gogorra Hardening Endurecimiento Gogortze Hardness Dureza Gogortasuna Harmful Dañino Kaltegarri Heat Calor Bero Height Altura Altuera High Speed Machining Mecanizado a alta velocidad Abiadura azkarreko mekanizazioa High Speed Steel (HSS) Acero rápido Altzairu lasterra Hit Golpear Kolpe Insert Plaquita intercambiable Plakatxo trukagarria Jamming Atasco Trabatze Labelling Etiquetado Etiketa jarri Load Carga Karga Major Mayor Nagusi Margin Faja guia Faxa gidaria Marking Marcado Markaketa Milling Fresado Fresaketa Minor Menor Txiki Nose radius Radio de punta Muturreko erradioa Notching Entallado Hozkaketa Oven Horno Labe Overhang Voladizo Hegalkin Overhead Gastos generales Gastu orokorrak Packaging Empaquetado Paketeak egin

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GLOSSARY

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Pecking Picada Ziztada Pin Punzón Puntzoi Pitch Paso Neurri Plunge Penetración Barneratze Powder Polvo Hauts Power Potencia Potentzia Pressing Prensado Prentsaketa Profiling Perfilado Profilaketa Radial cutting depth Profundidad de pasada radial / ancho de pasada Iraganaldi zabalera Radii Radios Erradioak Rake Desprendimiento Jaulkitze Reaming Escariado Otxabuketa Reject Rechazo Errefus Relief face Cara de desahogo Lasaitasun aurpegia Revolution Vuelta Bira Roughing Desbaste Arbastaketa Rubbing Bruñido Txartaketa Sawing Serrado Zerraketa Scrap Residuo Hondakin Seat Asiento Eserleku Shank Mango Kirten Shape Forma Forma / Itxura Shaping Limado Karrakaketa Sharp Afilado Zorrotz Shearing Cizallamiento Ebakidura / Zizailadura Shell end mill Fresa hueca Kofadun fresa Shift Relevo Txanda / Errelebu Shim Calza Altxagarri

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GLOSSARY

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Shoulder milling Escuadrado Eskuairaketa Side Lateral / Secundario Albo/Bigarren Sintering Sinterizado Sinterizazio Skin Piel Azal Slope Pendiente Malda Solid tool Herramienta enteriza Pieza bakarreko erraminta Spindle Cabezal Buru Spindle speed Velocidad de giro Biraketa abiadura Spray drying Secado por pulverización Lainoztatze bidezko lehorketa Staff Personal Langilego Stiffness Rigidez Zurruntasun Strength Resistencia Erresistentzia Stress Fatiga / Estrés Estres Substrate Sustrato Substratu Surface roughness Rugosidad superficial Gainazal zimurtasuna Tapping Roscado con macho Ardatzarekin egindako hariztaketa Thickness Espesor Lodiera Tilting Inclinación Inklinazio Tip Punta Punta Toolholder Portaherramientas Erraminta etxea Torque Par Momentu Toughness Tenacidad Zailtasun Tray Bandeja Erretilu Trochoidal Trocoidal Trokoidal Turning Torneado Torneaketa Unleaded Sin plomo Berunik gabeko Up milling Contraposición Kontrajartze Wash away Limpiar Garbitu

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GLOSSARY

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Weak Debil Ahul Wear Desgaste Higadura Web Alma Arima Wedge Cuña Kuña / Falka Weight Peso Pisua Wet Humedo Busti Workpiece Pieza Pieza Workshop Taller Tailer

Cutting conditions

Engineering

Transcript of Cutting conditions