Resin Presure Cast Pot

Sparky · Post by **Sparky** » Fri Sep 01, 2006 11:11 am

I'll have to look, but it is bigger than 1/4 inch as you have noticed. I got an adapter straight away. the problem i have is that I can find a ball valve with a male on one side, I have to have a female-female for that too. If I have a 1/2 inch ball valve its all yours, its big for the tight area I work in. I got them on slae at harborfrieght, good to have in pinch. I'll check my stack of brass and see what fits the pot.

Can you post a quick pic. of your lid set up so I can make sure i'm on the same page.

Antenociti · Post by **Antenociti** » Fri Sep 01, 2006 1:54 pm

http://www.barrule.com/temp%20bitz/CIMG1142.jpg

Sparky · Post by **Sparky** » Fri Sep 01, 2006 2:04 pm

I will check tonight, that's perfect for a female ball valve.

Antenociti · Post by **Antenociti** » Fri Sep 01, 2006 2:11 pm

Cheers - appreciate the help.

I sort of object to paying almost as much for a ball-valve in the UK as the whole pot and extras from harbour freight in the usa - really is daft.

Sparky · Post by **Sparky** » Fri Sep 01, 2006 2:29 pm

I have found that the ball valve is also the most expensive piece. I think it is tuffer for them to make a piece that is rated for water and air pressure while moving (it can't break one you're trying to turn off the water flow of a broken pipe). The pot it self is expensive but it a lot of metal and comes with a regulator. Pound for pound I'm guessing the ball valve is the most expensive piece.

That's why I bought the ones harborfreight had on sale, they are to big for me to use for anything but atleast I got 'em cheep! Ya that was me raging against the system for all the good it does. If they fit you can have it, then they don't go to waste.

Sparky · Post by **Sparky** » Fri Sep 01, 2006 8:14 pm

It's 3/8 and I have one.

Antenociti · Post by **Antenociti** » Tue Sep 12, 2006 6:08 pm

Arrived today and fits perfectly thanks!

Might need to buy a heavier duty compressor as mines a tad slow taking around 5 minutes to get to 30psi, although we're switching to a longer pot-life resin soon anyway... so its time to experiment in that area.

The other pot is currently beign re-worked for vacuum de-gassing. Off to get some thick perspex this weekend and get to work on it.

Not entirely sure what to do about the seal at the moment though: I was considering getting a thick collar of rubber and simply sitting it over the rim of the pot allowing the suction on the perspex to force it to a seal.

Wont be pretty but its cheap and should work.. question remains as to its longevity though.

Sparky · Post by **Sparky** » Tue Sep 12, 2006 6:13 pm

I used the hard rubber gasket that came in the pot's lid. I replaced the pot lids' gasket with moldmax 30. I made a <A HREF="http://www.kc6sye.com/techmages_10_30_05.html" target="_blank">moldmax 30 seal for the vacuum lid.</A> It worked great for a ling time, now it's getting loose and due to my in-ability to make a good round collar mould box, the narrow areas are a hard to keep aligned. I suppose just gluing down the outter colar would be an easy enough solution. . .

Antenociti · Post by **Antenociti** » Sun Sep 17, 2006 12:51 pm

"Cor eky thump" its like a soap opera... cant now find any local supplier who can do a piece of perspex for a lid.

Time to hit the net again.

Took me an entire day going all over town to find a hardware store (at all) and then one that had some hose for the vacuum pump to the second pot.

Getting there (very) very slowly.

Antenociti · Post by **Antenociti** » Wed Sep 27, 2006 10:01 am

Perspex saga continues..., however after copious use of ptfe tape we're up and running just fine with pressure casting.

Works a treat and no leakage at all, had it sat at 30psi for 3 hours, no (noticeable) pressure drop at all.

First "test" casting coming out of it in 15 mins or so... some small fiddly-detail pieces that i used to have to cast very carefully by hand: this time just threw in the resin and chucked it in the pot.. will see what transpires.

Antenociti · Post by **Antenociti** » Wed Sep 27, 2006 10:18 am

coo - ek - blimmey - absolutely flawless.

impressed.

now need to find a cheap bigger pot for the 12 inch moulds...

Sparky · Post by **Sparky** » Wed Sep 27, 2006 10:51 am

Wait till you try vacuum casting. . . You can get really fine castings with out a spin caster.

I've been making these cannopies and cockpit bits with this technique.

http://www.kc6sye.com/images/images_09_ ... t_guns.jpg
http://www.kc6sye.com/images/images_09_ ... nopies.jpg

The technique requires some specfic molding styles but I've seen some reall thin castings with them
http://www.kc6sye.com/images/images_04_ ... oxprts.jpg
http://www.kc6sye.com/images/images_04_ ... s_mold.jpg

Antenociti · Post by **Antenociti** » Wed Sep 27, 2006 12:37 pm

Just got to find the flipping perspex....

Actually - under what circs would you vacuum-cast over pressure-casting?

Sparky · Post by **Sparky** » Wed Sep 27, 2006 1:38 pm

In vacuum casting you do pressure cast.

First you use the vacuum to coxe out air. Then after you have worked out the air pockets you put the regular pot lid on and pressurize.

Pressure casting eliminates the micro bubbles you get when mixing the resin or if you are using fast set resin, the micro bubbles the resin makes while building up heat to cure itself, or the bubbles that form if you vacuum the resin down to low pressure.

Resin will boil just as the RTV does accept it really foams up.

The trick with vacuum casting is to keep your hand on the relief valve. As you see big bubble percolating up out of the mold's reservoir, you let out the vacuum, and let the mold draw in more resin. You work the mold in this manner. After a few casting you'll know how long you need to do this to get resin into all the parts.

But you still pressurize the pot to eliminate the micro/pin whole bubbles out of the final casting.

You can guess that a good relief and pour spout in the molding is needed; you need the mold to be able to draw in resin while the vacuum pulls out the big air pockets. If you don't have that you will need to work the air out in the aforementioned technique.

Sparky · Post by **Sparky** » Wed Sep 27, 2006 1:41 pm

BTW I'll take a pic of the mold that make sthe piolet and canopie. The parts I used for the reservoir are really big, wasiting some resin in each casting, but it's worth it to get good castings. Evntually I'll have the skillat mold making to not waste so much resin.

Antenociti · Post by **Antenociti** » Wed Sep 27, 2006 2:22 pm

ah gotcha... cheers!

Sparky · Post by **Sparky** » Thu Sep 28, 2006 11:23 am

Here they are:
http://kc6sye.no-ip.com/images/images_0 ... ockpit.jpg

With the layout the way it happend above I found that I can increase my success rate by prefilling the bottom reservoir, the piloet, the cockpit/seat, and the little block on the raidator grill.

http://kc6sye.no-ip.com/images/images_0 ... ockpit.jpg

The air pockets form on the gun, the sliver tube on the right in the above picture, and at the nose of the canopie. It'd be best to make a solid block and vacuform the canopie. but hen I need to get the vacu-former setup.

Sparky · Post by **Sparky** » Thu Sep 28, 2006 1:18 pm

BTW I couldn't get the thick plexi etiher, I got the piece I have from Neil, who savlaged it from a display they tossed out at work. I have the rest of a 1/2 inch sheet too, but it needs to be cut down. I'm not sure the rotozip can cut this and it won't be very clean. I have a pack of blades and can take a wack at it. If you want to pay postage. . .Its heavy and big. I'll see if ter_or can cut it down for me, they're all coming over Sunday to fix up the J-57.

Darkov · Post by **Darkov** » Thu Sep 28, 2006 3:49 pm

Are you looking to make a lid out of clear plexi? Why don't you just go buy a sheet of 1/4" and bond the pieces together to form a thicker lid? I used some acrylic solvent from plastruct to make a 1" thick lid. A heck of a lot cheaper than trying to buy a 1" thick piece of plexi.

Sparky · Post by **Sparky** » Wed Oct 11, 2006 6:50 pm

BTW These are one sale again for $39.xx

Antenociti · Post by **Antenociti** » Sat Oct 21, 2006 1:50 pm

Well I've added a couple of new valves so now I can run both pots at once: they have a quick-release attachment on the inlet with a ball valve, so once they hit the 30/40psi mark i just shut the valve (sealing in the pressure) and then quick-release the pipe - hitch it to the second pot and off we go.

I've also done a bit of a "Heath-Robinson" affair with the second pot so that i can swap it from either a vertical or horizontal placement without having to worry about the inside being level etc (will add piccies soon).

Oh, and I made a very rough "tripple-decker" insert for the pots so that I can cast 3 levels of moulds at a time, which makes things a lot more useful in terms of commercial casting.

And finally the second lid how gets a quick-fit attachment for the vacuum pump so that I can finally de-gas (no Perspex lid yet but Iâ€™m de-gassing fine by guesswork: not ideal but Iâ€™m only using small amounts of silicone in rather large SMA baby-milk tins, so it wont bubble over.

After a few mistakes buying (no use to me) 3-phase pumps finally managed to pick up a "proper" vacuum pump for Â£40 - goes to 29inHg in a flash.

Also got 2 5-gallogn pots off ebay for under Â£60 the pair, sadly they have "gone missing" according to the seller, so I may never see them - BIG shame as they would have been bargain of the century at that price. Good old ebay, ecstasy and agony all in the same auction.

TonyG2:

f you get one and it works, post a report.

They work an absolute charm and for he price, even after shipping and duties/VAT they are a bargain. Im absolutely delighted with them and thanks to Sparky the "extras" were also a total bargain compared to UK prices. I think I have used everything in the "extras" other than the spray-gun attachment doodad, but all the connectors and hose etc turned out to be of immense use.

Cant recommend them enough - the only negative is their size, they aren't small, but as they are just so darn good I'm desperate now to get some 5 and 10 gallon pots so that I can transfer some of my larger wargames moulds over to pressure-casting.

- -

one PS: we use a lot of BalsaFoam (phenolic foam) for carving masters - I was a bit worried they couldnt take the 30-40psi when pressure casting moulds in the pots, turned out to not be a problem at all, ditto for our dense styrofoam master even. SO as well as casting resin pieces were also now making moulds, de-gas'd silicone followed by an overnight cure at 40psi.

A test with the pot for longevity of the pressure I ended after it hadn't dropped at all over 3 days using the new valves (If I left it connected to the compressor then the back pressure always allowed a slight leak of pressure which meant the compressor kept filling it back up every 30-40 minutes which was a nuisance, expensive, hard on the compressor and, thankfully, now entirely redundant.

If these 5-gallon pots do turn up I think another small order in to HF for some more extras will be called for (I have a UK source but they are about 5 times the price than the USA prices) , but having shopped around a LOT in the UK there is nothing even approaching the prices of the HF pots listed in this thread.

Highly, highly recommended.

Sparky · Post by **Sparky** » Sun Oct 22, 2006 12:11 am

Please post pics of your shelf and mount swivel. These are the next things I need to add to my setup.

Antenociti · Post by **Antenociti** » Sun Oct 22, 2006 4:06 pm

http://www.barrule.com/temp%20bitz/workshop1.jpg
http://www.barrule.com/temp%20bitz/workshop2.jpg

As I said, a bit Heath Robinson atm but i'll fancy something up after i get some bigger pots and know exactly how much room everything will take up.

I guess theres no need for two valves on the lids either - you only really need the in-port as once its disconected it can become the "out-port" also. Haven't got anything to seal off the other pipe though so stuck with this for now - not a big issue mind you.

The pot on the right is based on some meaty MDF to give it some extra weight - when the pot lid is added (when its in the horizontal position) it tips up the pot otherwise... of course any movement when there's a mould in there kind of ruins the result - hence making sure it doesnt tip up or move about any other way.
The styrofoam insert does need to be varified that its flat in both planes before .. couple of spirit-levels for that. I'll work out something less fussy at some point down the line again... not sure the pots are staying where they are yet so no point working out anything permanent yet.

Sparky · Post by **Sparky** » Sun Oct 22, 2006 7:55 pm

Good idea with the foam for the stand. The shelves might get gummed up with time and spilliages. But they should be quick and easy to repalce or repair. thanks for the pics.

Antenociti · Post by **Antenociti** » Mon Oct 23, 2006 10:59 am

yeah the shelves are really just storage space - i cast over a non-stick floor pad underneath the spray booth - must take a snap of the workshop some day.

rocketrider · Post by **rocketrider** » Fri Nov 17, 2006 8:11 pm

noob casting question here, I understand the pressure casting method using an air compressor to force air into the cahmber, but what do you use for the vacuumm casting, what method and equipment do you use to draw the air out?

thanks
Glen

Sparky · Post by **Sparky** » Fri Nov 17, 2006 8:45 pm

Vacuum casting is a two-step process:

Prep: You put the two part model together then dump in a lot of resin into the over sized reservoir.

As you might realize, the pour spout/reservoir have to hold enough resin to completely fill the mold. Because the next step won't work well if you have to stop and refill the reservoir . . .

1) You use your vacuum pump to vacuum down the chamber. You work it several items, vacuum down to 25 or 27 inches then release, allowing the moll to draw in resin. You also need an RTV that has good strength so that it will draw the resin back in after the pockets have been collapsed (vacuumed out).

2) The last thing you do is put the regular pressure lid on and fill the pot to 40 psi.

This not to be confused with spin casting, where you fill a reservoir with casting material and spin up the mold (at the end of an arm) to let the material fling out into the mold. This works really well if you can build a jig to do it.

rocketrider · Post by **rocketrider** » Sat Nov 18, 2006 11:48 am

Cool thanks,

One more question

In pressure casting the air compressor created the pressurized air, this I understand.

But how do you get the suction to create the vaccuum? is there a special motor other than the air compressor. I just can't figure out how an air compressor can create a vaccuum?

Thanks
Glen

Sparky · Post by **Sparky** » Sat Nov 18, 2006 2:47 pm

Yes a vacuum pump is a specail item. There was a compressor I saw that stated it could be used for either or. THe inlet would give you vacuum, or you cna hook upto the outlet to get pressure.

I never found a source for them, I can't remember the name. I got afacotry refurb vacuum pump from ebay (the store is gone) it was robniar.

These are used (normally) to vacuum out the heat exchanger of airconditioners maybe refirdigerators too. It would be very hard to get all the moisture out of the many feet of coiled tubing in the exchanger, as-well-as the compressor. So they vacuum the lines down so that he water boils out (under a vacuum lots of things boil at room temperature).

So anyways they are seasonal. If you look on ebay at the wrong time you'll never find one.

Wow looks like nows the time, there is a lot of them on ebay for purchase, 179, that's really good, mine was like 250 after shipping (it came with the vacuum pump oil too).

search for robinair

OdysseySlipways · Post by **OdysseySlipways** » Wed Nov 22, 2006 10:42 pm

okay, first off, why do you need a clear lid on you tank when you vaccum?

I just put the batch of mixed rubber into th tank, set the timer for 7 - 8 minutes and walk away.

as for tanks, i have bought a few of them tanks from HF.

My first tank was a Sears painters tank and that was hard to find.

now as for a current count of my tanks, I have:

5 - 2.5 gal
1 - 5 gal (got about 2 weeks ago)
1 - 30 gal (got late june early july this year - needs some parts to make it work - paid $500 for it including shipping)

i still looking for a 10 gal and a 15 gal tank, after that, i'm done (unless the price is just too good to pass up).

I now have to get the fuse box updated so I can get 2 - 220vt lines (one is for the new 30 gal compresser that santa might bring).

i also just found out a few weeks ago that the pressure tank will just fit down the old basement steps - and i do mean just, say maybe an inch to spare total?