Material to bulk out the volume of a vacuum chamber - suggestions?

[TheHeroOfCanton]

Hi folks,

I have a bit of a strange dilemma, nothing a bit of good old fashioned problem solving can't fix. I have a 460mm dia x 460mm heigh vacuum chamber which I use for resin casting. I have a decent pump (8 cubic meters per hour) and I'd just like to find a way to bulk out the chamber and reduce it's volume. I don't need all that space and it would be nice if I could evacuate air quicker, meaning I could use my stronger and faster setting polyurethanes with better results. I'm trying to think of a material thats easily available, light, solid and easily removable if I need to. My first thought was wood chips, but these can get sucked into the valve and might block it, they also contain moisture which can really mess up the pump (been there done that, bloody nightmare!) Same goes for packing nuts, and they're not very solid either. So far I'm drawing a blank.

I know this is a bit of an unusual post, but it would be great if someone had a bright spark, several heads are better than one .

At the moment I'm casting some awesome modular starship corridors for a client. They really are spectacular I'll have to get some photos on here when they're done, with the guy's permission. The order is h-u-g-e so the quicker I can cast 'em the better. At the moment I'm using a PU which sets in one hour but has a nice long pot life, it would be nice if I could use my 15 minute stuff and still be able to vac all the nasty bubbles out !

Cheers,

Will.

 

[Zombie Killer]

The only thing i can think of is bricks but they are not light. Maybe cut some 2x4 blocks and glue them together into bigger blocks.

 

[cheech9898]

Never tried it, but what about medium density fiberboard (MDF).

 

[wasili]

Anything solid will work. I'm doing that all the time to fill up my vac chamber. Bricks, mdf, wooden blocks, very old and dry silicone molds, even left over PU resin from castings. Nearly always there's a wee bit of resin left over after a pour. Before it sets, i pour it into a plastic container, so over time you get a solid block. Material which you would've thrown away anyway.

Avoid sand (messy), or light (foam) loose material, for exactly the reaosn you mention. You don't want that clogging up your pump.

Cheers,

Wasili

 

[AbsoluteSciFi]

plaster is a very lightwieght alternative to bricks or cement, but I'd go with a custom made silicone insert.

 

[TheHeroOfCanton]

All good suggestions. So far I'm thinking of cutting equal lengths of 2x4 and joining them up to roughly fit the circuference of the chamber. Seems like the most hassle free solution. Good ideas though, feel free to add more .

 

[Stu Pidasso]

Build a lego shelf. when you need the space, add or subtract brinks at will. Light, solid, and level.

 

[DS Operative]

I was going to suggest the same thing Stu-- Lego's!!!

 

[TheHeroOfCanton]

Lego bricks aren't solid, the air would still be there are would not decrease the total volume of the chamber as much as a solid object . They are great for making small moulds though.

 

[DS Operative]

d'Oh!!! I didn't consider that! You are absolutely right. My only other suggestion would be tire weights, the lead weights used to balance the wheels and tires on your car. A few handfuls of those would take up space, be small, curved, and be solid all the way through. Good luck!

 

[TheHeroOfCanton]

Well worth considering. What I've been doing today is just chucking bit of old mould and the bits of casts I don't need like reservoirs and gates etc. Bit by bit that will fill it up I reckon. Might take a while as I try not to over pour moulds so theres barely anythig to snap off when they come out of the moulds .

 

[Alric]

Would not big lumps of polystrene packageing work. The kind of stiuff you gat around big electrical goods like TV's or Kitchen appliances. You could cut it to size to take up the space you want and it would still be light enough to remove.

 

[Raffles]

if your chamber is round then a good solution are weights. the sort you get with multigyms and stuff. They're solid, incompressable and, wait what's a vaccum effect?, explody? plus if there's any overspill or 'boiling' over of resin or silicone they're reasonably wipe clean.

 

[Jedi Dade]

Sand?

Pour silicon into the chamber until its the desired height? a bit expensive but a custom "plug" for all future casting... I'd use mold release

Jedi Dade

 

[TheHeroOfCanton]

Sand is a good idea, a really good idea actually. When I've moved into my new workshop with the concrete floor I may just do that. As long as is wasnt going to get sucked into the pump....ouch!!