Cast an inline 4 engine block with plaster mold

[Xijian Su]

really excellent casting.
Two questions
1 did you pour liquid metal into hot mold ?
2 did you used common plaster or some kind of casting plaster.
Thank you

A1:
I have only one furnace, so that I can't put the baked plaster mold into furnace to keep it hot while melting aluminium and pouring. When I poured the metal into the mold, the mold cracked. But it doesn't matter, you can grind the casting after it cools down.
A2:
There's no casting plaster available, so I bought a bag of pottery mold plaster.

Xijian Su

 

[Xijian Su]

Looks very good to me!!! Someday I'll use my brass-bronze scrap to cast something, I have enough for sure!!

Good luck!

 

[Xijian Su]

looks good - was the pattern 3D printed from the solidworks 3d plan

The 3d plan of pattern is different from the engine plan.

 

[Willyb]

Hello Xijian

Your Casting has turned out very well. Congratulations on an excellent job, well done
I have a couple questions if you don't mined.

(1) In regards to the 3D Printed Molds, what material and Printer settings did you use?
(2) Any finishing work on the 3D Printed Molds? Like using Filler, sanding, etc to smooth out the lines?
(3) The last picture of your first Post, there looks to be a Downsprue with Runner entering at the upper rear of the Block.

Thank you for your help with my questions.

Cheers
Willy

 

[Xijian Su]

Mold making process
(With schematic diagrams)
I drew some diagrams to illustrate the mold making process.

• Core box making process

The following is a schematic diagram of the manufacturing process of the core box.

You need to prepare some sculpting clay, silicone rubber and release agent at first. A flask is also needed.

After completing these operations, you will get a core box to make the core for casting mold.

• External mold making process

First you need to prepare a 3D printed pattern for silicone rubber mold making. And then follow the steps on the diagrams.

After pouring the plaster into the mold, wait more than two hours to remove it.

Then you can put the plaster mold into the electric furnace and bake it.

 

[Xijian Su]

Hello Xijian

Your Casting has turned out very well. Congratulations on an excellent job, well done
I have a couple questions if you don't mined.

(1) In regards to the 3D Printed Molds, what material and Printer settings did you use?
(2) Any finishing work on the 3D Printed Molds? Like using Filler, sanding, etc to smooth out the lines?
(3) The last picture of your first Post, there looks to be a Downsprue with Runner entering at the upper rear of the Block.

Thank you for your help with my questions.

Cheers
Willy

Hello, Willy!
A1:
I sent the file to an online store for printing, and the machine they used was DLP. So I do n’t know the printer settings.
A2:
The model printed by DPL printer has a fine finish. So I didn't do any finishing work on it.
A3:
In order to find the right method, I experimented many times. The last picture on the first post is the mold used in previous experiments.

 

[Xijian Su]

looks good - was the pattern 3D printed from the solidworks 3d plan

You can refer to my recent post on how to make a mold.

 

[Xijian Su]

Wow, I am surprised that heating the mould to that temperature worked. I would have expected the plaster of paris to revert to gypsum at about 100°C, and even more suprised that it sat at 730°C. But a very nice casting, Su.

Bill in Cardiff, Wales

Thanks!
The chemical formula of gypsum powder is [CaSO4.½H2O]. When you mix it with water, a chemical reaction will occur.

The water combined with gypsum is not ordinary water, but crystal water. It becomes a part of Crystal structure a.
And It doesn't evaporate like ordinary water do.
When the temperature rises to 170 degrees Celsius, it starts to decompose water. Crystal water will be decomposed at about 400 degrees Celsius
If you bake it at a lower temperature, the crystal water will not be removed.
When the metal is pour into the mold, the crystal water will evaporate violently, causing the metal liquid to be sprayed out of the mold. This is very dangerous!
Just like this:

 

[Willyb]

Thank you very much for answering my questions and also for taking the time to produce the great diagrams.
Cheers
Willy

 

[OrangeAlpine]

Thank you for being honest with your experiences. Some of our most important lessons are learned from failures. You taught every reader a very important lesson that will stay with them.

Bill

 

[BWMSBLDR1]

Your documentation is outstanding! Better than some professional I have seen. On the subject of casting there was a system available called GlassCast that made molds from silica (SiO2). Used for casting gas turbine blades, NiMoNic alloy valves and the like. A slurry deposited on porous plaster was then fired to sinter the silica. Poured while red hot and they were able to eventually cast monocrystaline blades with internal cooling ducts! Bill in Boulder CO USA

 

[Willyb]

I'm curious as to were the crack developed in your final plaster mold?
Did you actually here it crack?
Interesting.
Thanks again for the great pictures.

Cheers
Willy

 

[kadora]

excellent explanation thank you

 

[kaycemb]

How did you make the patterns in order to cast the silcon. And was the silicon just to cast the cores? Your description missed out too much for me to be able to fiollow what you did.

 

[KenC]

Sorry but for some reason I missed a whole lot of this thread. Your descriptions and diagrams are excellent. I have done a fair amount of sand casting and die casting and I was very interested in your silicon technique. I might use your methods myself but using standard patterns which of course need no draught because of the silicon.

 

[Xijian Su]

How did you make the patterns in order to cast the silcon. And was the silicon just to cast the cores? Your description missed out too much for me to be able to fiollow what you did.

A1: 3D printing.
A2: All parts of the plaster mold were casted in silicone rubber patterns.

 

[Doug Cygan]

Very impressive! And thank you for sharing! Can you please clarify what you used for plaster? Is it Plaster of Paris or is it a type of Investment?

 

[Xijian Su]

Very impressive! And thank you for sharing! Can you please clarify what you used for plaster? Is it Plaster of Paris or is it a type of Investment?

Plaster of Paris.

 

[William May]

This was an absolutely AWESOME post! VERY well done!

 

[awake]

I echo the others - well done!

Out of curiosity, what is the advantage of the silicone/plaster method of casting as compared to sand casting? I have not yet done any casting, but I hope to start "one of these days," so I'm very interested in learning more.