Can a newbie quickly pick someones brains about pressure casting please ?

[Guest]

Hi chaps, I suppose it’s time I stopped lurking around here anonymously snooping for information and properly introduced myself.



I’m writing for the first time hoping one of you experts could help me please ? I want to start casting some parts for myself and the compressor I’ve got is as follows :





Marksman 2HP 1.5 KW motor 25 Litre Air Compressor

240V AC mains powered

Restart pressure 70 PSI

Maximum outlet pressure 115 PSI

Max air delivery 206L/Min (8.3 CFM)

Air outlet size ¼ BSP

ROHS Compliant 2002/95/EC



(This is just the information I’ve managed to get off the box and out of the instructions, I’m entirely new at all this so sorry if I’ve missed something obvious off)



I’m going to try casting under pressure and I want to get myself a pressure pot (no way I’m going to try and build one myself, sod that for a lark, I like my head where it is cheers and not bouncing off the bonnet of my neighbours Volvo). One of the ones I’ve got my eye on is below











Right, my problems are :



1)Would this pressure pot be suitable with this type of compressor ?

2)Is it as simple as just connect to 2 together and away you go ?

3)How to you get the compressor to cut out when you’ve got the pressure you want, Is there a switch you can set on compressors ?

4)I’ve just noticed that the pressure pot mentions 8.8 CFM, but my compressors only up to 8.3 CFM, is this a problem ?

5)Is this price the going rate for a pressure pot in the UK ?



I really appreciate any help anyone can give me as I’m stumped ! I don’t know anyone who does casting so I’m flying blind.



Thanks in advance

Mark J

[Guest]

Hello Mark,

Don't know anything about pressure casting, all my casting experience is with lead mixtures.

But the compressor bit I am ok with, yes you add to the compressor a pressure reducing control available from for instance screwfix, machine mart and such at a price around £25 usually with a moisture filter incorporated, and as you are reducing the pressure there-for a small reduction in CFM would be of no consequence.

hope this helps.

?expert = an ex. is something that was; a spert is a drip from the end of your ****

Experience is what really counts, me? just old and can't remember what the question was allready?

[Guest]

Hi m8

I pressure cast a lot, and have a pressure pot similar to that one you added the link for but slightly bigger. Saying that get the biggest you can afford as you will always want to cast bigger things once you see how well the casts come out.

In answer to your questions

1)Would this pressure pot be suitable with this type of compressor ?

This is not important as one needs to be filled with compressed air and one makes it. The smaller the compressor the long it runs for.

2)Is it as simple as just connect to 2 together and away you go ?

It is, but you will need to take a trip to your local plumbers to get some blanking plugs to shut off any unwanted in or outlets

3)How to you get the compressor to cut out when you’ve got the pressure you want, Is there

a switch you can set on compressors ?

Compressors cut out on their own when they reach a preset pressure, but also have a pressure gauge for varying the outlet pressure. There will also be a pressure gauge on the pot which you can adjust to the desired pressure.

4)I’ve just noticed that the pressure pot mentions 8.8 CFM, but my compressors only up to 8.3 CFM, is this a problem ?

This is not relevant for pressure casting. If you're spraying, CFM = cubic feet per minute which is how much air is consumed by your spray gun. Its kind of odd to have it on a pressure pot, as its down more to the gun you use than the pot.

5)Is this price the going rate for a pressure pot in the UK ?

These varies, but look out on ebay for seconds, as sometimes you can pick one up cheap with a damaged inlet or outlet valve (they normally have two of three, so as you will be removing all but one, it's not so important,) or broken caster foot.

Other things the pot you linked to has is wing nuts on like mine did but you can't get these done up tight enough or anything over 40psi by hand. I swapped them for nuts and super thick washers, and do them up using a torque wench so I know all four at done up the same amount. If you do them by hand with spanner and one is a fraction looser than the other it can leak.

It's also best to have an in line air drier or you can fill the pot with moist air.

As for resin use smooth-on 310. This has around a 25 minute gel time, so gives you plenty of time to fill your moulds and get them in and it all done up. then leave them for at least an hour and a half to make sure they are set properly

The other thing you need to pay careful attention to is how the items you are casting are moulded. You still need to make sure as much of the air can rise out the mould prior to putting in the pressure pot. If you have an area air can get trapped in, even under 80psi you will still have a air bubble. You have to remember even at 80psi this is way off the pressures used in proper injection moulding

I did you a short bit on my 'How To' page on my website which shows my pots and compressor.

Under Pressure

Hope this helps and any question feel free to ask.

Don

[Guest]

Ken, Don, what can I say, thanks chaps you're lifesavers ! There's light at the end of the tunnel now, aw sod it I think I'm going to take the plunge and give it a bash ! Thanks again I really appreciate it ! Mark