getting a grip under vacuum todd m. reith met 123
TRANSCRIPT
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Getting a GripGetting a GripUnder VacuumUnder Vacuum
Todd M. ReithMET 123
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Hold-down DilemmaHold-down Dilemma
Clamps
Vise
Magnetic Chuck
Bolt Directly to the Table
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Use What is Around Us!Use What is Around Us!
At Sea Level
14.7 PSI
3” X 3” ~ 132 lbs
Denver, CO
12.23 PSI
3” X 3” ~ 110 lbs
14.7PSI
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Vacuum AdvantagesVacuum Advantages
Clamping of Thin Parts
Parts that Deform under Clamping
Non-magnetic Parts
Reduce Setup and Clamping Time
Machine Contours without Interference
Hold-Down Odd-Shaped Parts
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The Real DealThe Real Deal
Altitude(feet)
Barometer(in-Hg)
% of Change of BarometricPressure
Downward Pressure perSquare Inch
(psi)
Effective VacuumPump rated
25 in-Hg83.5% Efficient
(in-Hg)
Effective PSIPump rated
25 in-Hg83.5% Efficient
(psi)
0 29.92 0.00% 14.70 24.98 12.64
2000 27.82 -7.00% 13.70 23.23 11.44
4000 25.84 -13.00% 12.79 21.58 10.68
5000 24.90 -16.80% 12.23 20.79 10.21
10000 20.58 -31.20% 10.11 17.18 8.44
Local Barometric Pressure
Vacuum Pump Effectiveness
Surface Area of Part Under Vacuum
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Forces Against the VacuumForces Against the Vacuum
Machining Forces
Rotational from Edge of Cutter
Lifting from Aggressive Depth or Rake
Vacuum Pump Power & Flow
Slow Recovery (Flow) CFM
Lack of Vacuum Draw (Power) in-Hg
Fixture Design
Vacuum Loss or Vacuum Restriction
Surface Finish Too Smooth, Twisting
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Machining AdaptationsMachining Adaptations
Reduce Aggressive Depth of Cut
Use Ideal Rake for Material
Reduce Size of Cutter Diameter
Slow the Feed Rate
Use Down-Cut Geometry if Applicable
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Choosing the Right PumpChoosing the Right Pump
Understand the Physical Properties of the Material you are Machining
Rotary Vane Pumps
<1 to 112 cfm, 20 to 29.5 in-HG
More Efficient and Quieter
Slow Recovery
Blower Pump
27 to 1350 cfm, 20 to 25 in-Hg
Loud and Inefficient
Fast Recovery
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Vacuum SystemVacuum System
Rotary VaneVacuum Pump
Vacuum Tank
Flexible Hose withShut-off Valve and
Fixture Fittings
Vacuum PressureLimit Switch
Hi/Low
Vacuum PressureGauge in-Hg
In-LineParticulate Filter
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Dedicated Vacuum FixturesDedicated Vacuum Fixtures
Single Purpose
High Initial Cost
Maximized Part Surface Area under Vacuum
Minimal Vacuum Loss
Machining Through Material or Through Pocketing
No Break-Out or Excessive Pre-Finish Prep Work
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Dedicated FixturesDedicated Fixtures
© All-Star Adhesives © All-Star Adhesives
© Custom Luthier © Custom Luthier © Custom Luthier
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Universal Vacuum FixtureUniversal Vacuum Fixture
Multi-Purpose
Low One-Time Cost
Flexible Grid System
Reduced Setup Time
Greater Loss of Vacuum
Less Surface Area
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Universal FixturesUniversal Fixtures
© Horst Witte Gerätebau
© Horst Witte Gerätebau
© Horst Witte Gerätebau
© Horst Witte Gerätebau
© Vac-U-Lok
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SummarySummary
Lower Stability Higher Stability
Universal Fixture Dedicated
Heavy Machining Aggressiveness Light
High Air Seal Loss Low
Low Pump Flow (cfm) High
Low Pump Power (in-Hg) High
Low Barometric Pressure High
Small Part Size (Surface Area) Large