# Cast an inline 4 engine block with plaster mold



## Xijian Su (Feb 24, 2020)

Hallo to all!
Recently, I started my first project. I tried to cast aluminum alloys with plaster mold. 

*Design the engine parts*
*



*
This is the engine block designed with SOLIDWORKS. It takes me a week to build the 3D model.




*Design the mold for 3D printing*
To make the plaster mold, I've got to make a Silicone rubber mold first. So I designed a mold for the silicone rubber mold making. Here's the picture.




Then I bought a can of silicone rubber from the "Taobao" for the mold making. 



There're 3 mold for the plaster core and mold making.








Plaster mold making
The mixing ratio of water and plaster powder is 1:1.5. 




This is the mold that hardened. The I put it into my electric furnace.


----------



## Xijian Su (Feb 24, 2020)

*Bake the mold*


----------



## Xijian Su (Feb 24, 2020)

To prevent the plaster mold from cracking. I slowly raised the temperature. No faster than 150 'C / h.
Here's the curve of temperature I followed.




After nearly a whole day later, the plaster mold finished. Then I poured the metal into the mold.




After a few minutes, I break the mold.




The casting has a fine surface.


----------



## Rod Cole (Feb 24, 2020)

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


----------



## retailer (Feb 24, 2020)

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


----------



## aka9950202 (Feb 25, 2020)

WOW! What an amazing result.  Are the plans for your engine your own design?

I will be watching with great interest. 

Cheers, 
Andrew in Melbourne


----------



## BillD (Feb 25, 2020)

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


----------



## kadora (Feb 25, 2020)

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


----------



## mnay (Feb 25, 2020)

very good!!!


----------



## gadabout (Feb 25, 2020)

The design appears to be of the Westbury Seal. Is it the 15cc version or the 30 cc version?


----------



## michelko (Feb 26, 2020)

Wow very nice.

Michael


----------



## peter2uat (Feb 26, 2020)

@BillD 
according to
https://en.wikipedia.org/wiki/Plaster_mold_casting
you can use special plaster molds up to 1200°C / 2200°F - Xijaan Su even gave the heating/timing curves for drying the mold AND using it immediately thereafter in post #3.
Aluminum can be cast safely with this plasters, as can be brass - the temperatures here are 900 to 940 °C / 1,650 to 1,720 °F.
Always use a well dried & preheated mold to avoid cracking.


----------



## Brian Hutchings (Feb 26, 2020)

Thank you for posting your sequence for casting a cylinder block, very interesting and very informative.
Brian


----------



## IceFyre13th (Feb 26, 2020)

What was the mold shrinkage % after curing and casting?


----------



## kadora (Feb 28, 2020)

thank you Peter2


----------



## Dubi (Feb 29, 2020)

Xijian Su said:


> To prevent the plaster mold from cracking. I slowly raised the temperature. No faster than 150 'C / h.
> Here's the curve of temperature I followed.
> View attachment 113992
> 
> ...


Very impressive, well done.


----------



## Xijian Su (Feb 29, 2020)

aka9950202 said:


> WOW! What an amazing result.  Are the plans for your engine your own design?
> 
> I will be watching with great interest.
> 
> ...


My engine  drawing is referenced to a 15cc inline 4 model engine designed in 1940s which name is "seal".


----------



## Xijian Su (Feb 29, 2020)

IceFyre13th said:


> What was the mold shrinkage % after curing and casting?


About 3%


----------



## Xijian Su (Feb 29, 2020)

peter2uat said:


> @BillD
> according to
> https://en.wikipedia.org/wiki/Plaster_mold_casting
> you can use special plaster molds up to 1200°C / 2200°F - Xijaan Su even gave the heating/timing curves for drying the mold AND using it immediately thereafter in post #3.
> ...


Thank you!

Xijian Su


----------



## Xijian Su (Feb 29, 2020)

gadabout said:


> The design appears to be of the Westbury Seal. Is it the 15cc version or the 30 cc version?


15cc version


----------



## Xijian Su (Feb 29, 2020)

kadora said:


> 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 (Feb 29, 2020)

Rod Cole said:


> 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 (Feb 29, 2020)

retailer said:


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


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


----------



## Willyb (Feb 29, 2020)

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 (Feb 29, 2020)

*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 (Feb 29, 2020)

Willyb said:


> 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.
> ...


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 (Feb 29, 2020)

retailer said:


> 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 (Feb 29, 2020)

BillD said:


> 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 (Feb 29, 2020)

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


----------



## OrangeAlpine (Mar 1, 2020)

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 (Mar 1, 2020)

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 (Mar 1, 2020)

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 (Mar 2, 2020)

excellent explanation thank you


----------



## kaycemb (Mar 5, 2020)

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 (Mar 5, 2020)

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 (Mar 6, 2020)

kaycemb said:


> 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 (Mar 8, 2020)

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 (Mar 9, 2020)

Doug Cygan said:


> 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 (Apr 18, 2020)

This was an absolutely AWESOME post! VERY well done!


----------



## awake (Apr 20, 2020)

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.


----------



## retailer (Apr 24, 2020)

There is a video on youtube by a guy who goes by "myfordboy"  amongst his videos he has a video of a similar process to cast a complex part, he 3d plastic filament prints the part, embeds it in casting plaster, melts the 3d printed plastic part out of the plaster which has now become a mold, and then casts into the mold using a regular sand casting process. It may not work for all parts as you obviously need the melted plastic to run out of the mold somewhere,


----------



## Tim Wescott (May 12, 2020)

It looks good!  Please post the rest of the build when you get to it!


----------

