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