Selecting an Air Compressor?

[silent35]

Hello all. Looking to give a go at pressure casting, but have a question how large a compressor I need to select. It is looking to be the largest cost I'm going to have to deal with. I hear people saying they got 2.5 or 3 hp compressor, but those are looking to be several hundred dollars.

How small a compressor can I get away with and is there any real advantage of getting a larger one?

Also, will getting an oil lubricated compressor effect the silicon/resin? Will I need to make sure there is a filter in the line?

[mangozac]

Welcome aboard silent35 - those are all good questions!

I'm away from my compressor at the moment but if I remember correctly it's only about 2hp. Ultimately it's not so much the power, but rather the size of the storage tank that is important (although in practice the two work together). You see a bigger storage tank means that more air can be kept under pressure which is available for immediate transfer into your pressure pot. If the storage tank isn't big enough then the compressor needs to be powerful enough to deliver the extra air required very quickly.

I'm sure that there are some nice calculations that could be performed to work out the optimums, but sometimes plain old "this will work" is better
The compressor I'm currently using is just a cheap no-name one very similar to the following: . A full tank will easily fill my 10L pressure pot to 55PSI, although near the end the compressor will cut in again to top itself up. And that's under AU$90!

I wouldn't go under the 2hp mark, and with a price like that above there is really no need to. Actually, more of the expense is in setting up all of the fittings and hoses!

I've always used oil lubricated compressors and have never had a problem with the silicone or resin. I'm sure it can't hurt to run an oil filter and water trap, but I don't have either (it's on the list of "one day" things to do). It may in fact come down to the specific brand of silicone and resin - I know some silicones can certainly be more sensitive than others.

Hope this helps!

[silent35]

Mangozac, thanks for the response. Model I was looking at is 2HP but with a smaller 4 gal (15L) tank. Space is also an issue for me so the larger tank is out of the question.

Yea, picked up my pressure pot today and going to see where I may need to seal it better. Making it air tight will probably have a bigger impact than going with a bigger compressor.

[mangozac]

It's not so much a problem with air leaking, but with the speed at which the pot can be bought up to pressure. If the resin has a very short pot life you don't want it to start setting before it's at full pressure (and thus not all bubbles fully compressed).

15L sounds like a very small tank. I would suggest trying to use a smaller pressure pot if possible. It's not to say that it won't work though - it ultimately all depends on the moulds, resin and shapes being cast.

[silent35]

Hmmm.. will have to see if I can fit a larger compressor in the garage then. The shop I'm going to has an 8 gal (30L) for the same price and HP.

[mangozac]

Yeah I do think that would be the best way to go.

[silent35]

Hey just wanted to let everyone know that I successfully casted my first pieces last weekend

Took a bit longer to get everything up and running than planned. There were a lot more fittings needed than I realized.

But still everything is working great

[mangozac]

Awesome great to hear about your success! Can you share any pictures?