Update on Pressure-Vacuum Chamber

[SuperDave]

After a spinal injury, I am finally getting back to where I left off.

My pressure pot is rated to 100 PSI (not that I want to go that high... just yet)

I also wanted to use it as a vacuum chamber for silicon casting and other casting materials. However, I needed to see into the pot. I solved that when a friend dropped off a 3/4" thick CNC'd Acrylic disc that just happened to be the correct diameter.

I cut the slots for the clamps, drilled the hole for the fittings to connect the vacuum gauge (Surplus Center) and the line to the vacuum pump.

Then I cut a new gasket from a 12" x 12" x .125" rubber sheet from the Borg, using the original lid for a template.

Then a quick and dirty connection to the Thomas Vacuum Pump I got off EBAY for $40. I connected the two cylinders in series to maximize the vacuum draw-down. Need to install an exhaust muffler. I will also use this for vacuum chucks on my three lathes.

Here it is connected to test the vacuum pump, gauge, gasket, etc. Pulling 27Hg... good enough for my needs. I still need some more c-clamps and plan on installing a vacuum switch that will cut the pump off at whatever level of vacuum I set and then restart the pump if the vacuum drops beyond a predetermined level.

Here is the original lid still set up for pressure. I will need to plug the original hole in the center. Will eventually test the new acrylic lid for pressure to see if I can get by without swapping lids.

Here are some test pieces of Curly and Quilted Maple to which I did a down and dirty turning, Dying and finishing job (excuse the hurry-up picture). Pretty pleased with the results, as it is my first "Dye Job" and I have several hundred blanks waiting for processing. I want to test the penetration at various settings to see if the blanks should be pre-turned and drilled prior to pressure dying...

More to follow later... once I get to the real casting[8D]

 

[johncrane]

Good job

 

[stevers]

Looks like your on your way Dave. Nice start. Be sure to keep us updated.

 

[Blind_Squirrel]

Will eventually test the new acrylic lid for pressure to see if I can get by without swapping lids.

I would be VERY CAREFUL about applying pressure to acrylic. If it fails with a vacuum things will be sucked in. If it fails with pressure things (i.e. sharp slivers and pieces) are going to be blown OUT</u> [xx(]

 

[SuperDave]

Originally posted by Blind_Squirrel

Will eventually test the new acrylic lid for pressure to see if I can get by without swapping lids.

I would be VERY CAREFUL about applying pressure to acrylic. If it fails with a vacuum things will be sucked in. If it fails with pressure things (i.e. sharp slivers and pieces) are going to be blown OUT</u> [xx(]

Understood. I plan on testing it in an enclosed area and only up to 40-60 PSI. I will be installing an adjustable pressure relief valve. This Acrylic (or whatever it actually is...) came from a manufacturer that makes all types of close tolerance CNC "plastic" components for companies like Intel (wafer manufacturing). I think I will contact the company owner (who is president of our club) and get the specifications of this plastic so I can stay within the realm of reasonable risks... After all, it only takes a minute to swap out the lids...

 

[rherrell]

Originally posted by SuperDave

Originally posted by Blind_Squirrel

Will eventually test the new acrylic lid for pressure to see if I can get by without swapping lids.

I would be VERY CAREFUL about applying pressure to acrylic. If it fails with a vacuum things will be sucked in. If it fails with pressure things (i.e. sharp slivers and pieces) are going to be blown OUT</u> [xx(]

Understood. I plan on testing it in an enclosed area and only up to 40-60 PSI. I will be installing an adjustable pressure relief valve. This Acrylic (or whatever it actually is...) came from a manufacturer that makes all types of close tolerance CNC "plastic" components for companies like Intel (wafer manufacturing). I think I will contact the company owner (who is president of our club) and get the specifications of this plastic so I can stay within the realm of reasonable risks... After all, it only takes a minute to swap out the lids...

Look at this:http://content.penturners.org/articles/2006/snakeskinblanks.pdf
Please be careful, homemade lids can be dangerous.

 

[low_48]

I would be cautious of the "acrylic" lid as well. If it is polycarbonate it may be okay. Plexiglas can be scored and snapped just like glass. If you get a nick or scratch it may just set up a stress riser and shatter like glass. Polycarbonate, on the other hand, is so soft you can raise a curl with a hand plane. Thin stuff like 1/8 or 1/4 poly can actually be cold bent in a sheet metal brake (really cool). That's why it work so good as "bullet proof glass", it just swallows up the slug. More than my $.02 worth, just some concerns.