Download - Machines & Machining Issues
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Machines & Machining Issues
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Material Removal Process
Mechanical Machining
Milling
Grinding
Turning
Drilling
All hard materials
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Machining DOF (Degrees of Freedom)DOF- # of independently controllable axes of motion-- excluding spindle rotation or tool translation responsible for cutting.
1 DOF- Drill Press
2 DOF- Lathe
3 DOF- 3 independent axis motions between tool & table Can use a ball end mill w/ 3 axis machine- for smoothest
contour Following a true 3-D contour requires a minimum of 3 DOF
2 1/2 DOF- 3 independent axes, but can only move 2 at a time
> 3 DOF- Generally allows rotation of spindle wrist or table Helps keep tool normal to workpiece/ fewer separate
fixtures 5 DOF- Minimum to follow any normal at any point
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Turning Operations
Turning (Performed on lathe) Part is moving and tool is stationary.
Used to make parts of round cross section Screws, shafts, pistons....
Number of various lathe operations Turning, facing, boring, drilling, parting, threading
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Lathe Components
Machine Components (Main items)Bed: Supports all other machine parts
Carriage: Slides along the machine ways Head stock: Power train of system (spindle included) Tail Stock: Fixes piece at end opposite to the head
stock Swing: Maximum diameter of the machinable piece Lead screw: controls the feed per revolution with a
great deal of precision
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Ref: Fig. 8.52, Kalpakjian. Manufacturing Processes for Engineering Materials 2nd Ed, Addison-Wesley 1991.
LatheSpindleSpeed
Selector
Headstock
SpindleWays
Tool PostCross Slide
Carriage (saddle)Center Tailstock quill
Tailstock
FeedRod
LeadScrew
BedApronCompoundRest &
Slide (swivels)
Feed changegear box
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Lathe Tools
Lathe toolsLeft handed
Right handed
Threading
Boring
Groove
Parting (Cut-Off )
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Lathe Operations
Ref: Fig. 8.51, Kalpakjian. Manufacturing Processes for Engineering Materials 2nd Ed, Addison-Wesley 1991.
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Cutting Speeds
Typical Lathe Cutting Speeds• Nominally 30 - 800 ft./min.
• Roughing cuts
- Depth of cut greater then .02 in
- Feed speed of .008 - .08 in/rev.
• Finishing Cuts
- Lower than roughing cuts.
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Milling
Types of Milling Machines Horizontal Milling Machine Vertical Milling Machine
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Mill Cutting DirectionCutting direction- Depending on the orientation of the workpiece
feed w.r.t. the rotation of the cutting tool.
• Climb (Down) Milling- Maximum thickness of chip at start of cut.
• Conventional (Up) Milling- Maximum thickness of chip at end of cut
Ref: Figure J-48, Kibbe ,et al. Machine Tool Practices 5th Ed, Prentice Hall,1995.
Ref: Figure J-48, Kibbe ,et al. Machine Tool Practices 5th Ed, Prentice Hall,1995.
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Vertical Knee Milling MachineBase and Column- support structure
Knee- Connected to slide on column- can move up and down
Saddle- Engages slide on top of knee- can be moved in and out.
Table- Engages slide atop of saddle- moved lengthwise. Holds workpiece.
Ram- Engages swiveling slide atop column.
Toolhead- Attached to end of ram, contains motor and quill.
Quill- Non rotating, but contains rotating spindle. Can be moved up and down.
Ref: Kibbe ,et al. Machine Tool Practices 5th Ed, Prentice Hall,1995, p 550-551
Ref: Figure 8.69, Kalpakjian. Manufacturing Processes for Engineering Materials 2nd Ed, Addison-Wesley 1991.
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Vertical Milling Machine
• Flexible• Versatile• Newer machines –
more DOF
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Bed Mill
Similar to vertical knee milling machines
Less versatile than knee mill
No knee - Bed does not move up and down
Vertical motion possible in head only
Controllable range of motion of head larger than in knee mill (total range of motion less)
Bed mill stiffer than knee mill
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Vertical Milling Applications
Collet
Ref: Process Selection, KG Swift and JD Booker, p.98.
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Scallop Height w/ Ball Nosed End Mill
R
hs x
y d
Basic Equation for a circle- x2+R−y( )2=R2
Solving for y.... y=R− R2−x2 Max height for x= s
2( )
Thus h=R− R2− s2
⎛ ⎝ ⎜
⎞ ⎠ ⎟ 2⎡
⎣
⎢ ⎢ ⎢
⎤
⎦
⎥ ⎥ ⎥ (if h≤d)
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Scallop Height- Ball Nose on an Incline
hdR
s
xy
α
Edge of cutter described byx1
2 +y12 =R2
On previous pass it was
x2 +s
cos(α )⎛ ⎝ ⎜
⎞ ⎠ ⎟
2+y2
2 =R2
Set x1 =x2 =x andy1=y2 =y
x=− s2⋅cos(α )
⎛ ⎝ ⎜
⎞ ⎠ ⎟ y=− R2 − s
2⋅cos(α )⎛ ⎝ ⎜
⎞ ⎠ ⎟
2
h=R− R2 − s2⋅cos(α )
⎛ ⎝ ⎜
⎞ ⎠ ⎟
2 (if h≤d)
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Horizontal Milling Machine
COMPONENTS Base & Column Knee Saddle Table Spindle Overarm & Arbor Support
Ref: Figure 8.68, Kalpakjian. Manufacturing Processes for Engineering Materials 2nd Ed, Addison-Wesley 1991.
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Types Horizontal Milling OperationsSlab- Axis of cutter //
to workpiece surface
Face- Axis of rotation |
to workpiece surface
Side- Axis of cutter //
to workpiece surface
Figure 8.63b, Kalpakjian. Manufacturing Processes for Engineering Materials 2nd Ed, Addison-Wesley 1991.
Figure 8.67c, Kalpakjian. Manufacturing Processes for Engineering Materials 2nd Ed, Addison-Wesley 1991.
Figure 8.63a, Kalpakjian. Manufacturing Processes for Engineering Materials 2nd Ed, Addison-Wesley 1991.
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Drilling
Any component requiring cylindrical holes.
Engine Blocks, Machine Components
Ref: Process Selection, KG Swift and JD Booker, p.104.
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Grinding and Abrasive Processes
Abrasive Processes- Generally slower (more expensive) than other traditional machining processes. Used on very hard materials, and can achieve HIGH (virtually unmatched) levels of precision and finish.
• Grinding• Deburring• Honing• Polishing• Lapping• Superfinishing
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Grinding MachinesPedestal Grinder
Surface Grinder Type I- Horizontal spindle w/ reciprocating table Type II- Horizontal spindle w/ rotary table Type III- Vertical spindle, table either reciprocates or rotates (blanchard)
Cylindrical Grinder Center-type Roll-type- workpiece in bearings rather than on centers Centerless Grinder- workpiece supported on rest blade, grinding wheel on one side, regulating wheel on the other Internal Cylindrical Grinder Tool Cutting Grinders
Specialty Grinders Form Grinders and Generating Types
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Surface GrindersType I Type II
Type IIIReciprocatingTable
RotatingTable
Ref: Figures N-1, N-3,N-4, & N-5, Kibbe ,et al. Machine Tool Practices 5th Ed, Prentice Hall,1995.
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Cylindrical Grinders
Center/Roll Type
Centerless Type
Ref: Figures N-8, N-17, N-18, Kibbe ,et al. Machine Tool Practices 5th Ed, Prentice Hall,1995.
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Surface RoughnessSurface roughness is generally described with 1 of 2 methods Ra- Arithmetic Mean Value- the average of the absolute values of the deviations from the center line of the surface
Rq (formerly RMS)- Root Mean Squared-
Rq = a2 +b2 +c2 +d2 +...n
Ra= |a| + |b| + |c| + |d| + … n( )
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Roughness Units
1 Micrometer = 1m = 1 micron = 10-6 meters 1 Microinch = 1in= 10-6 inches 1in = 0.025 m 1m = 40 in Human hair ~ 40 m
Both generally given in micrometers (microns) or microinches
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Typical Arithmetic Average Roughness
Ref: Fig. 8.35, Kalpakjian. Manufacturing Processes for Engineering Materials 2nd Ed, Addison-Wesley 1991.
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Summary
Four types of mechanical removal processes Turning Milling Drilling Grinding
Finish of workpiece
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Credits This module is intended as a supplement to design classes in mechanical
engineering. It was developed at The Ohio State University under the NSF sponsored Gateway Coalition (grant EEC-9109794). Contributing members include:
Gary Kinzel …………………………………….. Project supervisor Chris Hubert and Alan Bonifas ..……………... Primary authors Phuong Pham and Matt Detrick ……….…….. Module revisions L. Pham ……………………………………..….. Audio voice
References:Kalpakjian, Manufacturing Processes for Engineering Materials 2nd Ed,
Addison-Wesley 1991Kibbe ,et al. Machine Tool Practices 5th Ed, Prentice Hall,1995 Swift, KG and JD Booker, Process Selection, Arnold/John Wiley& Sons Inc.,
New York, 1997
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Disclaimer
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