ME 338: Manufacturing Processes II

Instructor: Ramesh Singh; Notes: Profs.

Singh/Melkote/Colton

1

Machining-3

Cutting Fluid and Chatter

2

Cutting Fluids - Effects

• Reduce friction and wear

– improve tool life, surface finish

• Cool cutting zone

– reduce temperature and distortion

• Wash chips away

• Prevent corrosion

• Reduces forces and energy consumption

3

Cutting Fluids - Types

• Water based

– contain salts or

soluble oils

• Mineral-oil based

• Synthetic

• Bio-degradable

• Bio-resistant

• Soaps

• Defoamers

• Sulphur

• Chlorinated

4

Cutting Fluids -

Application Methods

• Brush

– manual

• Mist

– mostly water based coolants

• Flood

5

Coolant or Lubricant?

• Temperature

• Cutting speed

• Type of machining operation

• Method of application

– brush (manual)

– mist

– flood

6

Vibration

• Forced

– periodic applied force

• from a motor or gear drive

• Self-excited

– interaction of dynamics of chip removal process

and structural dynamics of machine tool

7

Chatter

• Results from vibration

• Tool bounces in and out of the workpiece

8

Glacial Chatter

9

Chatter Types

• Regenerative (f < 1000 Hz)

– when a surface undulation

previously produced causes a

cutting force variation

• Coupling (f < 1000 Hz)

– two modes of tool or machine

vibration are coupled (x and y

directions)

10

Chatter Types

• Self-excited vibration (1000 < f < 10,000 Hz)

– negative slope of the shear-stress vs. temperature

(t vs. q) relationship

– force components provide positive instead of

negative damping

11

Vibration Elimination

• Stiffer machines

• Tuned dampers

• Active control

• Support workpiece rigidly

• Minimize cutter overhang

• Modify tool and cutter geometry

• Change process parameters

– speed, feed, depth of cut, cutting fluid

Case study of vibration control in High

Speed Micromachining

ME 338: Manufacturing Processes II

Instructor: Ramesh Singh; Notes: Profs.

Singh/Melkote/Colton

13

Best Configuration selection

components Ribs No ribs

No slot Configuration-1 Configuration-2

Slot Configuration-3 Configuration-4

Different configurations

Static deformation in machine base and machine frame

Goal: To find most stiff configuration

Approach:-

Model : Machine base with frame

BC: Bottom of base fixed

Load : Force of magnitude 60 N applied

at the middle of bridge

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

12

34

Defo

rmati

on

(m)

Configuration no.

Max def

def_x

def_y

def_z

Configuration 3&4 better

Modes of High Speed Micromachine Tool

ME 338: Manufacturing Processes II

Instructor: Ramesh Singh; Notes: Profs.

Singh/Melkote/Colton

15

e) 18th mode (2408 Hz) f) 20th mode (2662 Hz)

0

300

600

900

1200

1500

1800

2100

2400

2700

3000

3300

3600

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Fre

qu

ency

(Hz)

Mode no.

prototype-I

with ribs

no ribs

Prototype-II frequency

more than prototype-I

No ribs case higher

frequency more than

with ribs case

first 6 modes critical

With ribs case better

than others, supported by

frequency response curve

Frequency Response Analysis

ME 338: Manufacturing Processes II

Instructor: Ramesh Singh; Notes: Profs.

Singh/Melkote/Colton

Stability Lobes (Process Controlled)

Axial depth of chip width

ME 338: Manufacturing Processes II

Instructor: Ramesh Singh; Notes: Profs.

Singh/Melkote/Colton

18

Summary

• Chip formation process

• Cutting fluids

• Vibration and chatter