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Transcript
Slide 1
Presented by Phil Brooks January 8, 2013 Designing Vacuum
Systems for the Lathe
Slide 2
Introduction Presentation was originally part of Leonards Need
to do two things in designing a vacuum system: Seal the vacuum
Decouple the rotation Will discuss 3 different approaches &
their advantages and disadvantages Theory of designing vacuum
systems & key parameters effecting performance 2
Slide 3
Bob Leonards Vacuum Chuck Seals and decouples at the inboard
side on the chuck using a sealed bearing. 3
Slide 4
Pros & Cons of Bobs Chuck Pro FeaturesCon Features 4
Relatively easy and inexpensive to build a single chuck. Works
great for a limited range of bowl sizes. Need scroll chuck to hold
vacuum chuck. Need a complete vacuum chuck for each size and shape.
Making multiple vacuum chucks for different sizes and shapes can
get expensive.
Slide 5
My Vacuum System 5
Slide 6
My Seal & Decoupler 6
Slide 7
Pros and Cons of My System Pro FeaturesCon Features 7 Vacuum
chucks are simpler, cheaper and attach directly to the drive
spindle. Can have many sizes and shapes Dont need a scroll chuck.
Decoupler is industrial grade decoupler which is expensive.
($70)
Slide 8
Alternate Vacuum System (Outboard End) 8 Seals and decouples at
the outboard end using closed cell foam and sealed bearing
Slide 9
Pros and Cons of Alternate System Pro FeaturesCon Features 9
Vacuum chucks are simpler, cheaper and attach directly to the drive
spindle. Can have many sizes and shapes Dont need a scroll chuck.
May be harder to get a good seal on small outboard handle.
Slide 10
Vacuum Chucks for My System 10
Slide 11
Tapping Wooden Threads (Drum) 11
Slide 12
Treaded Base w/Spacer 12
Slide 13
Base Front View 13
Slide 14
Gluing The Drum Chuck Parts 14
Slide 15
Vacuum Chuck w/Goblet Head 15
Slide 16
Origin of Measuring Pressure 16
Slide 17
Effects of Creating a Vacuum 17
Slide 18
Vacuum Holding Forces Atmospheric Pressure (Sea Level) = 29.92
in Hg, or 14.7 lbs./in 2 Good vacuum pump gives 20Hg 20 Hg produces
the following forces in lbs. 18 Dia.2345678 Force (Lbs.)
30.869.5124193278378494
Slide 19
Table For Other Vacuums Pressures Use the same table and divide
your actual vacuum pressure by 20. (20Hg was used to create the
table) Multiply this number by the force in the table. Example:
15Hg & 8 bowl: 15/20 x 494 lbs. (from table) = 370.5 lbs.
19
Slide 20
Universal Calculation of These Forces To calculate the lbs./in
2 for vacuum (in of Hg): (in of Hg) 29.92 x 14.7 =.49(in of
Hg)lbs./in 2 To calculate the area of the bowl in in 2 : Area = x
dia. 2 / 4 Force = Area( x dia. 2 / 4) x Pressure (lbs./in 2) To
calculate the force for any vacuum and bowl dia., substitute your
pressure and bowl dia. 20
Slide 21
General Information Flat-plate chucks should have taper of /ft.
on its face. Need minimum force of 50 lbs. to be safe. Use CA glue
before and after tapping wooden hubs. Use bleeder value on fragile
pieces to prevent crushing. Put tape on any small voids in piece
you want to hold to maintain vacuum. When building vacuum system.
Check maximum vacuum by taping off at compressor. Add 1 piece at a
time and check pressure for leaks after each piece is added. Dont
vacuum chuck freshly lacquered pieces or it can effect the finish.
Its a great tool if used properly and with appropriate safety
considerations. 21