A Series of Questions

[amphoterik]

Is this a good tank: http://www.grizzly.com/products/2-1-4-g ... Tank/H6330?

[mangozac]

[blind pig]

[blind pig]

[mangozac]

[blind pig]

[mangozac]

Wow that's fantastic. I probably shouldn't be so surprised as that's what the professional told me, but still I'll admit I was a little sceptical. Can't wait to see the final results and will def pick up some talc on the way through Brisbane next!

[blind pig]

[amphoterik]

Yes, I was curious what the difference between baby powder and "talc" were

[mangozac]

Baby powder generally has perfume added, so non-scented baby powder should be close to pure talc.

The only reason I was going to buy the talc from Barnes is that at $6.60 for a kg I expected it to be cheaper than baby powder

[amphoterik]

OK, I've got another one for ya.

I would like to mold several bases that I have made. In the past, I glued them to a surface and just made a 1 sided mold of them. If using a 1 sided mold in a pressure pot though, will the pressure force the resin to shrink and mess the bottom of my bases up?

[mangozac]

In the past did you have issues with bubbles? If you can get away without the pressure then you're better off. Otherwise I would expect the subsidence due to the compressed resin air bubbles to be fairly minimal.

[blind pig]

[mangozac]

Out of interest how many bases do you have per mould?
Having the casting going on on your kitchen benchtop sounds a great plan for maximum productivity but I certainly won't have that opportunity for a while! It would be handy though - I just received orders for 20 of one of my kits today!

If pass by a Coles over the weekend I'll take a look and see if they have the J&J still at a good price...

[paulson games]

On difficult parts I use both mold release and baby powder/talc. I always spray the mold release first and let it dry completely before adding the powder. If you add the powder too soon it'll stick and clump up in the mold release.

I haven't tested using only powder, I need my molds to last as long as possible and don't want to mess with any potential binding issues.

I've had several of my molds cranking out as many as 200 copies when the silicon is only supposed to give 30-50 copies according to the manufactuer, so the mold release and powder does work well. I primarily use this process on my wolves as the legs and saddles tend to trap air unless the powder is used, and when it's used they cast fine. When comboed together they seem to last a relaly long time, much longer than spray alone.

I have a vaccum pump but haven't touched it in months, everything I cast I do via pressure.

The tank you showed is pretty much spot on with the ones we're using. You'll need to get some fittings in order to connect it to the air compressor hoses, or vaccum hose depending on which system you go with. Don't forget to pick up some of the plumbers teflon tape to use on the fittings to help make sure you have an airtight seal otehrwise you'llhave tons of minor leaks.

I've done bases out of one sided molds which works ok, but two issues you'll need to watch for is making sure the mold is perfectly level. If the base is off level it'll have a slight tilt which will make the base thicker on one side.


The second thing (with a pressure system) is to make sure there's something to divert the air flow entering the tank from spraying directly down on the open face of the mold, otherwise you end up with resin sprayed all over the inside of your pressure pot. All you need to fix this is a piece of plastic/wood/cardboard etc placed over the molds which keeps the air from rushing directly down on teh mold.

With a vaccum syustem you may have resin boil dumping resin out of the one sided mold, I haven't cast any of my bases with vaccum.


Another possible issue with one sided molds for bases is that the resin shrinks slightly as it cures, so even if the resin is perfectly level at the time it's poured into the mold it'll shrink down slightly in the center of teh base giving you a slight depression with a slight lip around the edge of the base. Not really a problem but it can be slightly irregular or jagged thus needing some filing or sanding work. When cast in a two sided mold the shrinkage seems to be much more evenly distributed and you won't have a noticable lip on the base edge.


Personally I've switched to a two sided mold for bases as it eliminates most of the minor difficluties, I can never seem to keep the bottom of my pot completely level and with a two sided mold I don't have to worry about that. Two sided molds for bases are incredibly easy to do, I just glue the bases down to a piece of styrene and add a couple lumps of kleen clay to the open areas of the mold to serve as mold keys. Very fast compaired to building most other 2 sided molds.


Some of the larger bases, bikes and dread bases warp slightly due to the high amounts of curing heat they generate compaired to nomral parts, and as a result often have a slight bow to them. They may need to be heated in water to be flattened back out.



The pressure pot I had to remove the metal bar/tube that is used for sucking up paint, it was welded on so I had to clamp it in a vise and use a hacksaw to cut it off. Stuff was harden steel pipe so it took me forever to cut through it and it was a rather ugly cut but it finally came off. I had thought about adding a diverter but couldn't figure out a good way of mounting one as I didn't have a welder. I just make sure nothing is placed directly under the air intake hole, or I place a spare piece of board under it to divert the air. Doesn't need much, even a paper plate placed over the molds would proabably be fine.

Do make sure that if you are left with any remainging piece of the pipe that it doesn't touch the molds and be careful when you set the lid down on things. I couldn't cut the pipe flush I have about a 1 1/2 inch piece jutting down from the lid which makes the lid wobbly when I put it on a flat surface and also I've had it touch a couple molds which really made a mess when it blasted all the resin out of them.

When I remember to turn on my brain and pay attention to how I place the molds it's not a problem.

Also if you are doing only smallparts and molds to help your system do less work you can partially fill your pot with sand (placed in a plastic bag) this helps reduce the volume of air that needs to be deplaced or compressed. I put a small garbage bag in my pot and filled about half of the pot with sand then sealed up the bag. Placed a cheap 9" cooking pan in it to use as a flat& level bottom. That way my compressor doesn't need to do as much work and the pot pressurizes much faster.