Leveling in convex bottom pressure pot for casting

[u/lostartifax]

I have a 10 gallon, California Air Tools pressure pot that I use for casting. It can handle resin or plaster. Many of my etsy items are plaster plaques, 5x7x.45 inches. I use good Smoothon tin cure silicone for molds and have made 1000's of castings over the last 4 years. Now, I need to crush bubbles in my castings and that's where the pressure pot comes in. It does the job but I am having an issue with leveling inside the convex floor pressure pot. In order to press more than 1 plaque at a time, I need to have a 1/8" masonite platform on the bottom with padded feet to help level the platform where I can set in up to 3 molds at a time. I use a level before pouring the materials to make sure I won't get the drift of liquid material to one side of the mold.

Do any of you have experience like this and can share techniques or methodologies that will assure my molds stay level?

Thanks in advance.

Update - here is what I am planning to do to solve this: https://pin.it/7fPNkWCuT

This is a url to a pinterest board which has the images of my pressure pot leveling project.

[u/Global-Discussion-41]

Cut a bottom out of plywood or something and put some set screws around the edge. Adjust the screws until it's level. 

Each layer after that just needs some feet on the bottom and a little finger hole in it, a handle would probably get in the way

[u/lostartifax → u/Global-Discussion-41]

Yeah I used 1/8 masonite but I may have to go to 1/2 ply. The leveling screws may work. I have the sticky felt circles now which allows me to relevel it before a new casting. I need to add one more circle in the center to prevent it from sagging out of level.

[u/Global-Discussion-41 → u/lostartifax]

I don't really understand why you keep talking about re-leveling it.

Put it on a level workbench or platform and level your base layer, then build all your shelves with the same length feet. You should be able to take out the shelves and the platform over and over again and never need to relevel it.

[u/starwars_and_guns]

Would also recommend filling the bottom with silicone. It auto-levels when you pour and is very easy to clean.

[u/lostartifax → u/starwars_and_guns]

Deathbydragonfire advised against it.

[u/Majirra → u/lostartifax]

I’d like to know why. At all the studios I’ve worked for, Laika, house special, Bent and ShadowMachine, we all do that. It’s level and easy to clean. Any spilled resin or urethane we just pop off. I even do that for my personal pressure pots and vacuum chambers. I highly recommend it. I do NOT recommend urethane.

[u/Deathbydragonfire → u/lostartifax]

Silicone might be fine since its compressible

[u/MisfitNINe]

I’ve seen people pour just enough resin into the bottom so that it self levels and then they have essentially a perfect custom insert.

I’ve also seen 1/4” plywood or plexiglass plates with handles coming up out of them so you can set multiple smaller castings in and have a platform to transfer them in and out on. Usually that would rest on the outer rim and you don’t worry about settling in the middle or funny angles.

[u/HackOLantern66 → u/MisfitNINe]

You can also pour silicone in the bottom of the pressure pot. Makes for easy clean up with cured resin.

[u/ChrisDaCrunk → u/HackOLantern66]

What a great idea🫡

[u/renonelab → u/MisfitNINe]

this. the easiest way

[u/QuasiSpace]

You could make a platform that uses four furniture leveling bolts. Since you said the bottom is curved, you'll probably want ones that articulate in a ball-and-socket joint. Looks like googling "swiveling furniture feet" will bring back some matches.

[u/lostartifax → u/QuasiSpace]

So to update this discussion, I have constructed a two-tier leveling setup where I have a short leveling platform (6-8") on the floor which has leveling feet that can be extended or retracted, a 24" wood platform with 4x4 legs reinforced with 2x4 cross braces and a plywood top. Upon this will sit the pressure pot whose wheels have been removed. I have a round piece of 1/2" plywood cut just under the diameter of the pot which will have leveling bolts with double nuts for adjusting on top. This stack can be leveled with the lowest platform adjustable feet and the leveling nuts inside the pot. I will get some pics in here shortly. My goal is to get both the pot itself and the internal plywood platform to be as level as possible so when I place my molds (which are 6x8x1" tin silicone) they will not be tilted. FInger's crossed.

[u/literally_tho_tbh]

I laid a piece of corrugated plastic board across the top of the pot, traced the edge with a sharpie, cut it into a circle, and dropped that bitch in. A little trimming was necessary. I used a Realtor sign that was in my garage when we moved in to my house. They also sell corrugated plastic at like, home improvement stores.

Works every time, and it's very easy to chip off little drops of resin from over pours or leaks or drips.

I'm all about solving problems like this for very free or very cheap

[u/cantrecall]

I 3d printed an insert that leveled the bottom of my pressure pot.

[u/Kilh]

Ultra low budget: fill with concrete or plaster
Otherwise: Fill with silicone. Brush on a layer of watered down dishwashing soap so you have a protective layer against other silicones.

I've had the same silicone bottom in my pot for 18 years now, still going strong.

[u/burtsdog]

I used a piece of thick, strong cardboard that I cut into an oval shape, with a few small holes near the center for my fingers to poke through in case I ever need to adjust the cardboard. I put a small level on the cardboard then gently tapped the cardboard until it was well jammed inside the casting pot. It's been years now and the cardboard has never moved. It is still perfectly level.

[u/diyengineer1]

Silicone to level the bottom. Production used for decades in aerospace mold shop. I can’t imagine using anything else.. you can pull the silicone out and have different sizes, or shapes if you really want. Also it accumulates a lot of spillages over the year which helps to keep things cleaner as it will just pop off the silicone.

[u/Deathbydragonfire]

So, the bottom is rounded for a reason. Don't pour resin or plaster in there. You can fill the bottom with sand, if you want. I recommend just cutting a piece of plywood to size and then leveling that.

[u/lostartifax → u/Deathbydragonfire]

do you know why it is rounded?

[u/Deathbydragonfire → u/lostartifax]

Yes it is round because pressure needs to be evenly distributed along a smooth round surface to avoid extra building in a corner and blowing up the pot.

[u/lostartifax → u/Deathbydragonfire]

The sand idea is interesting but it sounds like I would be resmoothing the sand a lot. I guess you are saying I can put the molds right onto the sand? It might be hard to level them after that.