Casting at home with electric mini foundry "jewelers foundry"

[nesan]

Hi I am new to the casting; could you please tell me if I can cast with good integrity of this engine cylinder case and crank case. I plane to do investment plaster plus green sand method. from 3D printed core.
total height of the engine is 100mm.
thanks
nesan

 

[GreenTwin]

Your 3D print looks pretty good.
I have not done investment castings yet, but have studied the method, and I think I understand it (maybe).

You probably already know, but there is an "as machined" set of drawings, which shows the final machined dimensions of the engine parts, and then are are "pattern" drawings", which include such things as draft angle, coreprints, machining allowances, shrinkage, etc.

For me in 3D modeling, I create the base model in the "as-machined" state, and then add machining allowances, coreprints, etc., which can be toggled on and off, so that one 3D model can generate either "as-machined" 2D drawings, or patern drawings, just by toggling features.
I include draft angle in the base model.

So you have to make sure there is enough extra material remaining after the part is cast, on the surfaces to be machined (flanges, bore, valve seats, etc.).

If the 3D print is not made large enough (ie: if a shrinkage factor is not added), then the part may not mate to the other pieces that it needs to attach to.

My understanding is that burnout is critical for intricate pieces like your cylinder, and "Polycast" filament burns out more cleanly than standard PLA.
Polycast filament is designed to be used with investment castings.
I have seen some nice parts made with PLA too, but they were not too complex of a shape.

I have seen one motorcycle cylinder cast using bound sand, and this can work if the fins have draft angle on them, and if the approriate cores are used.

Good luck.

Edit:
This is one product that seems to be popular for investment castings.


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[GreenTwin]

I have not used the investment casting method because I use the bound sand method.
With the bound sand method, you can create some intricate molds repetitively and relativey quickly, without the multiple steps required with investment casting.

With bound sand, I mix the sand with the resin, pack the mold, let the sand set, and then pull the pattern, at which point I am ready to make another mold (perhaps 30 minutes total time, or a little less depending on pattern size).

With investment casting, there is the dipping (multiple coats), I think drying between coats, burnout with a kiln, which can be a messy affair, preheating of the shell I think, and then pouring the mold.
Total time to make a shell may be days?
The good thing about the investment method is that you can make "trees" of parts, and gang them together, so that multiple parts can be cast at the same time.

The biggest problem I have heard about with investment casting is shell cracking during the burnout phase.
If the shell cracks, you can try to patch it, or you can start over again.
If the shell cracks, and you patch it, you may get some distortion in the casting, which may or may not be critical.

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[nesan]

Hi Green Twin! Thank you very much
I am appreciate the long informative post that you spare your knowledge for help me. I will take every direction you noted.
I am using AutoCad I heard Solid work is a great program so I may use "as machined" and other build in tools. the 3d print is the real size of the model, I will 3d print again with added allowances for casting shrinkage and tooling as well. my doubt is the fin gap is just 1.5 to 2 mm do you thing it will give enough to flow the molten into?
the "Polycast" is the great thing you mentioned I will switch into that for my core.
and really interested to learn "bound sand method" do you say it can hold the valve cup and spindle hole detail with out collapsing in process ? I hope Resin will do the trick if I am right.!

I expect for me it may take minimum of 10 casting for my first time before get the good one lol..

and what you think if using centrifugal force to push the molten to cast? I may build a simple machine I hope and run it into the drum for safety. is it worth anyway to spend time to build one?
when I am waiting for the foundry , I just design another one. after the first one I am proceed this one. Just attach the pictures for your review.
thanks
nesan