grinding
DESCRIPTION
machine grindingTRANSCRIPT
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding and Finishing
Illegitimi non carborundum
ver. 1
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Overview
Processes
Analysis
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton 3
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Horizontal Grinding
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton 5
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton 6
Horizontal grinding Vertical grinding
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton 7
Centered grinding
Centerless grinding
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Creep Feed Grinding
8
Full depth and stock is removed with
one or two passes at low work speed
Very high forces are generated
High rigidity and power
Advantages Increased accuracy
Efficiency
Improved surface finish
Burr reduction
Reduced stress and fatigue
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton 9
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding Wheels
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding Wheels
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding Wheel Information
15
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton 16
Correctly Mounted Wheel
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding Wheel Surface
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grind Wheel Dressing
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding Wheel Dressing
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding Chips
20
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Chip formation geometry
21
D
v
V
d
t
q
l
w
t l
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Chip geometry
As with rolling contact length, the chip length,
l
D = wheel diameter, d = depth of cut
Material removal rate, MRR
v = workpiece velocity, d = depth of cut, b = width
of cut
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dDl
bdvMRR
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Material removal rate
The chips have a triangular cross-section,
and ratio (r) of chip thickness (t) to chip width
(w)
So, the average volume per chip
24
2010 tot
wr
wtlltwVolchip4
1
2
1
2
1
w
t l
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Chips
The number of chips removed per unit time
(n), where c = number of cutting edges
(grains) per unit area (typ. 0.1 to 10 per mm2,
and V = peripheral wheel velocity
25
cbVn
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Combining
26
trw dDl
chipVolnbdvMRR
wtlVbcbdv4
1
dDttrbcVbdv 4
1
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Chip thickness
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dDrcV
dvt
42
or
D
d
rcV
vt
4
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Specific grinding energy, u
Consist of chip formation, plowing, and sliding
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slidingplowingchip uuuu
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Total grinding force
Get force from power
29
MRRuPower
bdvuVFgrinding
V
bdvuFgrinding
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Total grinding force
From empirical results, as t decreases, the
friction component of u increases
30
tu
1
tKu
11 or
substituting
V
bdv
tKFgrinding
11
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Total grinding force
31 ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton GIT 2006
Substituting for t
V
bdv
D
d
rcV
vKFgrinding
4
11
rearranging
dDV
vrcdbKFgrinding
41
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Force on a grain
The force per grain can be calculated
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AreauFgrain
wtuFgrain2
1
rtw and
tKu
11
ttrt
KFgrain 2
111
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Force on a grain
33 ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton GIT 2006
substituting for t, and rearranging
D
d
rcV
vr
KFgrain
4
21
D
d
cV
rvKFgrain
1
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding temperature
Temperature rise goes with energy delivered
per unit area
34
area
inputEnergyKT 2
dt
KKlb
dlbuKT
1122
D
d
Vcr
v
dKKT
4
121
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding temperature
Rearranging
= 1234
4
Temperatures can be up to 1600oC, but for a
short time.
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding Ex. 1-1
You are grinding a steel, which has a specific
grinding energy (u) of 35 W-s/mm3.
The grinding wheel rotates at 3600 rpm, has a
diameter (D) of 150 mm, thickness (b) of 25 mm, and
(c) 5 grains per mm2. The motor has a power of 2
kW.
The work piece moves (v) at 1.5 m/min. The chip
thickness ratio (r) is 10.
Determine the grinding force and force per grain.
Determine the temperature (K2 is 0.2oK-mm/N).
Room temperature is 20oC.
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding Ex. 1-2
First we need to calculate the depth of cut.
We can do this from the power.
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bdvuMRRuPower
sec60
min1025
min5.1352000
2
26
3
m
mmmmd
m
mm
sWW
md 6104.91
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding Ex. 1-3
Now for the total grinding force
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V
bdvuFgrinding
mm
m
rev
mmrev
mmmmmm
mm
sWFgrinding
1000150
min3600
25104.91min
150035
3
3
NFgrinding 7.70
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding Ex. 1-4
Next, the force per grain
39
wtuFgrain2
1 rtw
ttruFgrain 2
1
and
we need t
mm
mm
mm
grainsmm
mm
D
d
rcV
vt
150
104.91
105min
1503600
min15004
4 3
2
mmt 31032.1
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding Ex. 1-5
Substituting
40
231032.1102
135
2
1 ttruFgrain
mmJFgrain /1005.34
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding Ex. 1-6
For the temperature, we need K1 and K2. K2 is
given, so we need to calculate K1.
41
trKttrt
KttruFgrain 2
1
2
11
2
111
mKN 611 1032.110
2
11005.3
m
NK 31 102.46
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Grinding Ex. 1-7
substituting
42
Kmmm
N
N
mKT
640104.91
1032.1
12.462.0 6
6
CTTT initial 66064020
dt
KKT 1
12
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Honing and Superfinishing
Honing tool used to improve
the surface finish of bored or
ground holes.
Schematic
illustrations of the
superfinishing
process for a
cylindrical part.
(a) Cylindrical
mircohoning, (b)
Centerless
microhoning.
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Lapping
(a) Schematic illustration of the lapping process. (b)
Production lapping on flat surfaces. (c) Production lapping
on cylindrical surfaces.
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Polishing Using Magnetic
Fields
Schematic illustration of polishing of balls and rollers
using magnetic fields. (a) Magnetic float polishing of
ceramic balls. (b) Magnetic-field-assisted polishing of
rollers. Source: R. Komanduri, M. Doc, and M. Fox.
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Abrasive-Flow Machining
Schematic illustration of
abrasive flow machining to
deburr a turbine impeller.
The arrows indicate
movement of the abrasive
media. Note the special
fixture, which is usually
different for each part
design. Source: Extrude
Hone Corp.
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Robotic Deburring
A deburring operation on a robot-held die-cast
part for an outboard motor housing, using a
grinding wheel. Abrasive belts or flexible
abrasive radial-wheel brushes can also be used
for such operations. Source: Courtesy of
Acme Manufacturing Company and
Manufacturing Engineering Magazine,
Society of Manufacturing Engineers.
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Conformal Hydrodynamic Nanopolishing:
Case-study
Applications
Optics
Defence & Nuclear
Electronics
Industrial
Existing Methods
Diamond Turning
Precision Grinding
Lapping
Ion Beam Polishing
Spot Hydrodynamic Polishing
Challenges
Most processes can polish only flat
surfaces; concave/profiled surfaces
are difficult to superfinish
Concave surface on hard brittle
materials, such as single crystal
sapphire can not be finished via form
grinding due to process-induced
cracks
Diamond turning center can be used
for non ferrous materials but it is a
super-precision machine-tool (The
equipment cost is ~ 20 crores besides
the expensive operational cost)
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Conformal Hydrodynamic
Nanopolishing Process and Machine
Process Description
Improvement over existing spot hydrodynamic polishing methods
Superfinish hard and brittle concave surfaces, specially, sapphire and hardened steels
Mitigates existing surface microcracks
Polishing action due to elastohydrodynamic film in the slurry submerged rotating conformal contact (silicone ball in the cavity being polished) 1st Generation
2nd Generation Conformal Hydrodynamic Nanopolishing Machine
Delivered to Precison Engineering Division BARC
(designed and fabricated in the Machine Tools Lab
at IIT Bombay)
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Novelty and Technology Breakthrough
Existing hydrodynamic polishing employs spot polishing unable to
polish small cavities (< 6mm in dia)
More than 3 degrees of freedom required to polish the entire cavity
effectively
Small actuation system and polishing tool is required
Conformal contact has a rotating soft tool which conforms to the shape
of the cavity
Axis of this tool is inclined at 45 and the workpiece is rotated inside a
slurry filled tank which ensures non-zero relative motion between tool
and workpiece at every location in the cavity
The entire cavity can be polished at once which will be much cheaper
and faster than programming the tool path
Alternative to expensive Diamond Turning
Can finish wide range of materials ceramics (sapphire, glass) and
hardened steels
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Technology Outcomes Superfinished surfaces in
steels (< 3nm 3D surface roughness)
Crack-free surface of < 100 nm 3D surface roughness in single crystal sapphire cavity
Process knowhow and machine transferred to Precision Engineering Division, BARC for strategic applications in a nuclear device
The superfinished obtained at a fraction of cost of Diamond turning
It can also be used by gem polishers which could reduce the health hazard by reducing the dust inhalation and automation is possible
Nanometric finish on hardened steel
Crack-free superfinished surface on single
crystal sapphire cavity
4
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Economics of Grinding and Finishing
Operations
Increase in the cost of
machining and finishing a
part as a function of the
surface finish required.
This is the main reason
that the surface finish
specified on parts should
not be any finer than
necessary for the part to
function properly.
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ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs.
Singh/Melkote/Colton
Summary
Overview of processes
Analysis of process
Example problem
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