Sawdust

[dai sensei]

I've been playing around with sparkles and casting in clear resin for a cheap wedding/feather pen option (I'll do a WIP on them next week), so decided to give NewLondon's resin saver mould a try out with some Sierras.

One of the problems I've had when casting is that my old cast aluminium pot has a curved bottom, so instead of pouring some plaster in the bottom like I planned (I had no plaster), I got the bright :doh: idea of using sawdust to create the level bed. Placed my moulds full of resin in the pot, pressured it up and left it for a few hours. Popped the lid and realised why I shouldn't have used sawdust. Not only did it get on the moulds, but under the pressure, the sawdust got all the way into the cast :~.

First photo is from the bottom, they look good dont' they, then the second photo is from the top :C Pretty sure they are all bin material.

The only good thing was that NewLondon's mould worked a treat :2tsup: Easy to place tubes, easy to fill, no resin in the tubes even at 4 bar, and easy removal from the moulds once set (no release).

Cheers

http://www.woodworkforums.com/attachment.php?attachmentid=120376&stc=1&d=1256468822

http://www.woodworkforums.com/attachment.php?attachmentid=120377&stc=1&d=1256468822

[gawdelpus]

Neil I know you love mixing wood and acrylics, but that's just a bit too over the top :) I would try turning and see what results you get ,you may be surprised, at the worst you could show only the good sides for sample purposes hehe, cheers ~ John :oo:

[MBUMIK]

mate i would try turning one up to see what happens, looks like the wood maybe just on the top

worse case, you loose 5 minutes

i am glad to hear you like the way the moulds work

MIK

[dai sensei]

...I would try turning and see what results you get ,you may be surprised, at the worst you could show only the good sides for sample purposes hehe, cheers ~ John :oo:

Possible, but not sure it is worth the effort. I've already madesome new ones to play with :rolleyes:

http://www.woodworkforums.com/attachment.php?attachmentid=120451&stc=1&d=1256546746


.. looks like the wood maybe just on the top

Nah, it's all the way to the middle on most of them

http://www.woodworkforums.com/attachment.php?attachmentid=120452&stc=1&d=1256546746

[dj_pnevans]

Neil we all now no not to use saw dust :) I picked up a pot on the weekend. What mods did you do to yours?
David

[munruben]

instead of pouring some plaster in the bottom like I planned (I had no plaster), I got the bright :doh: idea of using sawdust to create the level bed. Placed Sand might have worked.:)

[Sawdust Maker]

I'm sure I had nothing to do with this :q I only make the stuff

seriously - what a bummer, something else on the not to do list :doh:

[dai sensei]

Neil we all now no not to use saw dust :) I picked up a pot on the weekend. What mods did you do to yours?
David

I took the old paint extractor shaft out, the one the paint is drawn up from. I added a pressure guage and water trap also.

I have just bought a venturi vacuum pump and vacuum guage. I have designed a pipe system that will allow me to vacuum initially, then swap to pressure, avoiding the trapped air problems I sometimes get (especially on banksia).


Sand might have worked.:)

Nah, probably same result, the air pressure through the small hole in the top blows it around. I will go back to plaster, mixed and poured in base over baking powder, so I can remove it if necessary.

[Big Shed]

I made up a little stand with an extra piece on the bottom that sits in the round base and keeps the whole lot steady. See my pressure pot thread. (http://www.woodworkforums.com/f204/pressure-pot-76319/)

As I now also use conduit I have also put a T piece in the inlet so that the air doesn't go straight down in to the open conduit, which sit in a block that straddles the round base.

[Skew ChiDAMN!!]

What capacity is the dip is the bottom of your pot? Couldn't you just use some excess resin after filling a turning blank?

With a bit of release agent on the bottom first, of course?

[gawdelpus]

I have yet to set up my "pot" so all these ideas are useful ,never thought about a flat bottom ,maybe a simple round cutout plywood support that just slides into the pot .with a couple of finger holes drilled for easy removal ( a false bottom) hehe.

[NewLondon88]

,maybe a simple round cutout plywood support that just slides into the pot .with a couple of finger holes drilled for easy removal ( a false bottom) hehe.

That's what I use in my pressure pot. Then I just have to remember to level my rocking
table before I pour :oo: I use a piece if 3/8" plywood (rounded on the lathe) with two
finger holes so I can remove it. Works like a charm.

A few things.. if you're going to use vacuum, please do it before you pour. When you
remove the air from the pressure pot, something will want to replace the missing air..
namely: resin. When you suck the air out of the tubes, the resin will replace it.

Best route is to open the containers, put them in the pot and then pull a vacuum for several
minutes. I do this after I warm the bottles in a pan of hot water. This thins out the resin
and then de-gassing with vacuum gets rid of suspended air. Then mix carefully.
But with warm resin, any air bubbles you introduce by mixing will easily rise to the surface
since the resin is much thinner when it is warm. (closer to water consistency)

Careful on the pressure, too.. the silicone is soft and pressure can distort it. That could
also let resin into the tubes. I've had goo luck at 20-25psi (don't know what that is in bars)

From the picture you can see the sawdust sinking in the resin, which is too bad.
Sometimes I'll accidentally drop things on the resin .. so far they've stayed on top
where they got turned off. I was lucky.

Also, Skewchi is right.. if you pour resin (after release) in the bottom, it will make a
perfect fit for your pot. Just make sure your pressure pot is perfectly level first.
And pouring resin into a round bottom doesn't seem to give you the same problem
of shrinkage that a square wall does. When it shrinks in a round bottom, it tends to
follow the shape of the bottom as it shrinks.

Glad you got to try them! Looking good so far..:2tsup:

ps .. release isn't necessary with silicone, but it will help extend the life of the molds..

[tea lady]

Ah! So the pressure pot is on the go? :2tsup: Too bad about the sawdust.:doh: I think I would have used a little round wire rack I have kicking round the kitchen. (So any chance of those bigger cast banksia blanks? :U )

[dai sensei]

I made up a little stand with an extra piece on the bottom that sits in the round base and keeps the whole lot steady. See my pressure pot thread. (http://www.woodworkforums.com/f204/pressure-pot-76319/)

As I now also use conduit I have also put a T piece in the inlet so that the air doesn't go straight down in to the open conduit, which sit in a block that straddles the round base.

I have a similar rack, but it slopes (rocks) too much on the round bottom and the resin spills if not perfectly in the middle.

Good idea with the Tee, I'll see what I can fit in. I've been using a perforated plate on timber spacers over the moulds, but forgot this time :doh:


What capacity is the dip is the bottom of your pot? Couldn't you just use some excess resin after filling a turning blank?

Tis a bit much for resin, cost wise, hence my suggested use of plaster with sloppy mix


Careful on the pressure, too.. the silicone is soft and pressure can distort it. That could
also let resin into the tubes. I've had goo luck at 20-25psi (don't know what that is in bars)


I'm running at 60psi without any trouble with the moulds leaking. I need to bump it up higher so I can use the venturi with the same pressure.


A few things.. if you're going to use vacuum, please do it before you pour. When you
remove the air from the pressure pot, something will want to replace the missing air..
namely: resin. When you suck the air out of the tubes, the resin will replace it.


My problems are not so much air bubbles in the resin, the pressure seems to force them out anyway. My problem is entrapped air as you cast, mainly on the banksia, but your point regarding extra resin required is correct.


Ah! So the pressure pot is on the go? :2tsup: Too bad about the sawdust.:doh: I think I would have used a little round wire rack I have kicking round the kitchen. (So any chance of those bigger cast banksia blanks? :U )

The pressure pot has been on the go for a while, it is the vacuum that I was waiting for. Just got my venturi vacuum and vacuum gauge, so now I can finish my set-up and try more banksias :cool:

[gawdelpus]

Bugger ! getting too high tech for me hehe, next you will want a "centrifuge" :D
Cheers John

[NewLondon88]

Bugger ! getting too high tech for me hehe, next you will want a "centrifuge" :D
Cheers John

A commercial centrifuge would be too expensive. But there is an alternative.

Here .. hold one of these in each of your hands, please.

OK .. now .. spin around really really fast.. like you're a helicopter. :2tsup:

Now .. don't throw up..

[BoomerangInfo]

I use a plywood board in the bottom of mine, i just chamferred the edges underneath to match the bottom curve, which helps hold it in. I also left the suction pipe on the lid going down from mine, and cut the hole in the wooden base to match the pipe, so it locks it all in place when I put the lid on, just need to align it right as you go. You can then use the hole when the lid comes off to lift the wooden platform out of need but, but it stays in there permanently for me. You do lose a little of the usable space though, but my moulds fit in fine.

I have not had to destroy my pot in any way to set it up, just had to buy some caps to go over the unused outlets. Of course it uses lots of thread tap and leaks a little. But if I ever did want to restore it to original condition, I just have to refit all the connectors.

Russell.

[Dorno]

I have purchased a presure pot from supercheap but as yet i have not hooked it all up due mainly to confusion. so much to work out but I am sure i will get it going soon.

Cheers Ian

[NewLondon88]

Ian .. you should be mostly ready to go right out of the box. A few things will help
you out along the way, but they're not 100% necessary right away.

I'm sure the pressure relief valve, pressure gauge and such work as-is.. so they're
ready to go. The long stem inside will probably get in the way, you may want to
remove that first. Then it's ready to use.

Later on you might find that a combination gauge works better for you .. one that will
read both pressure and vacuum. They're not expensive and they're easy to change out.
But .. not necessary.

Some like to replace the long stem with a 90 degree elbow so that the incoming air
doesn't blow your resin around. It just re-directs the airflow off to the side. Again, not
necessary.

You might find that you want to move the air shutoff to a more convenient position
or even change it out for a sturdier one (some of the factory ones have very light
handles and feel flimsy) but again .. not necessary.

For now, you've got the pot .. you've got an air line going in .. so you're ready to go!
The rest you can do (or not do) as you see fit.

[dj_pnevans]

Ian I got mine from the same place so when I find time to do it I will let you know how I go and if you get there before me please do tell.
David

[Dorno]

David
I will let you know how I get on for sure and I hope to do it soon.

Cheers Ian