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Normal Table Vacuum vs Perforated Vacuum?

Hey Guys…

I’ve always casted my perforated flasks in the vaccum chamber.

However since my casting machine also came with the option for normal table vacum i’ve been thinking.

Are there any situation where you would rather do one rather than the other?


Best regards

Perforated flasks work great, drawing through all the investment. A couple of drawbacks are expensive flasks and covering the holes for investing with several methods available. I worked in a large factory where we cast 30-100 flasks a day depending on the season. We used solid flasks and put plastic soda straws with the ends plugged with wax, clipped to the flask between the rows of waxes with bobby pins. Even if investment gets in the straws, just tilt the flask and the investment “rods” just slide out. Wax web from Rio is another great way to get the vacuum to pull through the investment.

Hey Phil

Wow that’s a lot of casting! Well dosent seem to be that many downsides to the perforated methog then! So you would suggest i just continue this? No really up / downside of doing either?

Best regards

Unless you need to buy a bunch of flasks and you don’t mind taping or “sleeving” the perforated flasks, they’re what’s used in all the high tech/high dollar medium frequency induction melter casting units like Nuetec so they are the best. I’m just saying that these other methods work and are available to anyone that has a standard vacuum caster.
If you need to buy a dozen flasks to increase production - big difference in price.

Ah alright I get your point! Duly noted!

Since you have such vast casting experience, do you mind me asking you two other questions that has been bugging me?

  1. Is there some way / hack to extend lifetime on the high temp silicone gaskets needed to vacuum? would say that they quite quickly gets burned and less effecient?

  2. Is there like a “lifetime” on a flask? have been casted with my perforated flask for 3 years now… Well the colour has changed over time and obviously not that pretty anymore, but is there like some warning signs or something i should know about?

Best regards!

best regards!

[If you’re talking about the stainless flasks that are standard equipment with these systems, they’re pretty immortal. The appearance changes, but at normal burnout temperatures they won’t burn up. The main hazard would be denting them from over-enthusiastic hammering in an effort to get the investment out.]

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not sure about the immortal thing… back in the day I used to cast over a 1000 claddagh rings a week. At one point I was welding the top cross back to the flasks on a regular basis. For production the 4 x 6 flasks were great.
I am currently into custom pieces, normally casting 2-6 pieces at a time. I have found the smaller 2+ x 3+ solid flasks work fine. No webs, no straws, just the solid flasks. The up side is I am using a lot less investment. Sprued correctly the castings have very few issues.
I have been buying the silicone pads on ebay (oh no!). I punch 4 more holes around the perimeter within 3 inches of the edge for the smaller flasks. It’s like buying 5 pads.

Yes, it is possible to cast with the solid flasks and with smaller flask sizes the results will be satisfactory but since you are trying to remove all gases and pull vacuum thru the flask to assist in pushing the metal to all the negative spaces in the flask you will get a better and more uniform vacuum on the flask,
As for the gasket , check nuetec website for graphite gaskets they are available for many flask sizes starting I believe form 3" flask diameter and up to 6" flask diameter

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Yes, the graphite gaskets for the flask will last a lot longer. Even with white gold. The only thing to watch for is to pick them up gentle from both edges. If you pick up from one spot they can flex and crack. They are not flexible. When I was using the solid flasks I was buying a sheet of graphite and rough cutting them to size and making a hole in the center. Now they are cut exactly to size and available for perforated flasks. Rio and the others have them as well as the four letter word auction site! They have some thicker ones there. A put a dab of Vaseline along the surface for an instant seal. It does smoke a little!

Sorry this response took a while!
I’m afraid that there not much can be done about burning up silicone pads. Part of the cost of casting - another expendable. I have a friend that vacuum casts w/solid flasks and an Electromelt.
She replaces her graphite crucibles every 5 casts. A small price to pay for essentially perfect castings. Apparently many people use them until they’re too thin to use anymore!
Just part of casting - sometimes there are no inexpensive solutions to problems in casting!