Noob question about Vacuum pumps

[Arden]

Hi All,

I'm planning on doing some resin casting. I want to know if the - Robinair 15500 Vacumaster 5 CFM 2 Stage Vacuum Pump (35 micron rating) - will work well with a 10 gallon vacuum chamber. From the research I did I think it will but as a Noob I'm not positive.

http://www.centurytool.net/15500_Robina ... o15500.htm

I appreciate your assistance.
Best,
Arden

[mangozac]

Hi Arden, welcome to RA!

You'll find some comprehensive discussion of vacuum pump selection in , but I'll run the numbers for you here

10 Gallons is quite a massive vacuum chamber. You sure you don't mean 10L? 10 Gallons is 38L or 1.3 cubic feet. The calculator says that this would take 144 seconds to evacuate with a 5CFM pump (and in reality it will be slower). Too slow for working with resin.

I recommend a 5CFM pump as the minimum for a 10L pressure pot.

[Arden]

Hi mangozac,
Thank you for your reply. 10 gallons is correct, it's the only chamber I found that is wide enough for the things I intend on making. I did see one suggestion to put filler in the chamber to reduce the volume but I doubt I can get it down 75%. Even with a 8 cfm pump the pot might be too big.

Where is a good place to get a vacuum chamber? I need somethng that is atleast 14L x 6D x 4w, I might have to build one.

[Fleafa]

Really depends on the resin. At that size, the slower the cure, the better as you'll never evacuate 10 gallons quick enough for most fast cast PUs.

[Arden]

Hi Fleafa,
Thank you for your reply.

I think I'll be ok, the resin I plan on working with has an "open time" of 15 min, is this considered slow? The molding silicone has an open time of 1 hour. There is another resin I might use, it has a "open time" of 9 minutes.

I appears that the "open times" will allow me plenty of time to do do what I need to do.
Please correct me if I'm wrong

Thanks again for your assistance

[mangozac]

Many people build vacuum chambers using a piece of steel pipe with a cap welded on one end and a piece of perspex with a seal on the other. The lid does not need to be clamped at all because it is help in place by the vacuum. I use my 10L pressure pot as my vacuum chamber.

15 minutes "open time"/"pot life" is quite long and may be long enough to degas in the large 10gal chamber with a 5CFM pump. Ideally though you should go for as high a flow rate pump as you can afford.

Can we ask what you are planning to cast?

[Arden]

Hi Mangozac,
Thanks for your reply.
The only way I can tell you what we are making is if you promise not to tell anyone.

We are making parts for model cars and planes.
Later we will make parts for surfboards.

Best,
A

[mangozac]

So what parts require such a large area? If you could make the maximum length under 12" then you could fit it into a 10L pressure pot on its side...

[Arden]

Great idea mangozac,
I'll give it a try.
The big stuff are the car bodies everything else is pretty small.

Thanks.

[Lane]

With such a large vacuum chamber you probably want a vacuum reservoir as well. This can bee something as simple as a pipe with the ends capped and a pipe nipple to get air in/ out. My chamber is a 1/4" steel pipe 10" dia and 20" tall. It has a divider at the mid point, a cap on one end and a piece of plexiglass for a lid, making the chamber and reservoir a single unit. Plumb the system with one 4 way manifold, one T fitting, a pressure gauge and three valves. The T goes to vacuum pump/ inlet valve and the 4 way. The 4 way goes to the gauge, the valves on the chamber and reservoir. To use ( assumes chamber is loaded and lid is on) close the chamber valve and inlet valve, open reservoir valve, start pump and draw vacuum in reservoir, open chamber valve, air will rapidly be drawn from chamber into reservoir and pump, When the rate of change drops (about half the gauge reading) close the reservoir valve so you are not pumping from a large volume, run pump to desired vacuum level and close chamber valve, turn off pump. To release vacuum open the inlet and chamber valves then reservoir valve until gauge reads zero, remove chamber lid.

[AdamMarosi]

10 Gallons is quite a massive . 10 Gallons is 38L or 1.3 cubic feet. Too slow for working with resin.