I’m going to try and print a cylinder head for casting but I’m wondering if it is necessary to use a vacuum chamber to take out all the air in the Plasticast, or can I do it differently without having to purchase a vacuum chamber? The castings cannot have any airbubbles for air leakage when the engine is running. However, it’s merely a test, so I don’t want to invest too much.
Wondering how you guys do this.
Thanks
@Alex_Vermeer, I will admit I do not have input for the casting question, but I am a huge 2 stroke fan! What’s the head for? I’m excited to see this complete. Do you plan on running an engine with it once it is post machined? It will be interesting to see how the water jacket holds up in the casting process.
-Aaron
Well, I’m glad to have found another 2-stroke fan 
. It’s a Honda NSR 125cc cylinder head which I downloaded from Grabcad (https://grabcad.com/library/honda-nsr-125-jc20-cylinder-head-sub-assembly-1)
I myself am a 2-stroke PUCH fan, and together with another Puch fan, we’re designing a race-spec liquid cooled puch cylinder. Hopefully we’ll be able to create a proper mold and cast it in aluminium with a cast-iron cylinder for the piston. And ofcourse… we’re hoping it’ll work properly 
So yes, we’re definitely planning on trying it out on an E50 motor.
We’re trying out different methods for creating molds and casting. That’s why I’d like to try without a vacuum chamber first. But if many of you say that would end up as a disaster. I might need to invest in one anyway.
I have had nearly a dozen 2 stroke motocross bikes in the last 15 years. Had a bunch of 4 strokes mixed in there, but the 2 strokes are (IMO) just way more fun to ride and far easier to maintain. Do you have an NSR 125? If so, I am quite jealous!
Have you considered using an aluminum rather than cast iron cylinder for the Puch with a hard plated bore? In the States we have a bunch of companies that can hard plate aluminum bores for a nominal fee (~$200). The would also likely be able to rough bore and hone the bore perpendicular to the base/head gasket surfaces for you. Eric Gorr works within Millenium Technologies in Wisconsin and would be a great resource for a one stop shop to finish the ports and plate an all aluminum cylinder. He has done all of my 2/4 stroke big bore work and is quite excellent.
Okay, back to the scheduled topic since I have sufficiently sidetracked this! If you do end up needing a vacuum chamber, something like this or this should work quite well and isn’t very expensive…I think it is cheap insurance to help ensure that your casting comes out flawlessly. I am not sure what Amazon offers in the Netherlands, but I am sure you can find something similar. You might also be able to vibrate the plasticast with the print inside, similar to what is done with concrete work when they want to get the bubbles to rise to the top. Maybe a palm sander on the outside of the container with the plasticast and print would be enough vibration to get most of the bubbles to rise to the surface. I’ve seen folks who make concrete countertops using palm sanders on YouTube to get bubbles out.
Look forward to seeing this project progress!
-Aaron
Thanks for the advice, @Aaron_Silidker!
I’ll be ordering a simple chamber like this one: http://www.bol.com/nl/p/unold-4801007-vacuum-doos-0-6-l/9200000019062986 to do my first tests. You gave me this idea as with your ‘concrete work’ as I can put this on top of my ultra sonic cleaner to ‘shake’ out the bubbles. Afterwards I’ll connect a pump (which I have lying around apparantly) to suck out all the air.
There are many ways to cast the cylinder, and casting it in aluminium with a hard plate alu bore was an option (as well as a nicasil plating), however, this creates the problem of manufacturing custom piston rings as well. If we choose a cast-iron bore (or nicasil bore) we can use pre-made piston rings with original (slightly modified) pistons. This would save a lot of money, not only for the build process, but also if others would like to purchase the cylinder (knowing that Puch parts in general are quite cheap).
If my ‘ultrasonic chamber’ idea doesn’t work, i’ll have a look at your vacuum chambers on Amazon.
Thanks for the advice, and i’ll update my posts once I have some news.
Ofcourse, input from other members is appreciated too!
And no, I don’t own an NSR unfortunately
I had a lot of fun on a Honda 185 (4-stroke) when I was a kid. And recently I have started melting aluminum cans to convert my 3D prints into aluminum. I tried twice and succeeded twice. The second casting was a lost-PLA casting from plaster and silica sand. I have a HVAC vacuum pump, and I degassed it by putting my casting container in this container my wife had. After, I baked it in the oven at time intervals that “felt right” haha. The final burn-out was with the oven on self-clean for 4.5 hours. She said you could see my efforts on our electricity bill haha. Anyway it worked out well. I can tell you that when I de-gassed the soup, many bubbles came out. So I don’t think that is a step you want to skip. I don’t think either that the ultrasonic cleaner has the shaking power for something with so much mass. Anyway, keep us updated, and let me know if you have a question on what worked for me.
Thanks for the tip @JoshK! Great to hear your efforts delivered goog results! So to be clear; you de-gassed the container by heating it to ensure all gasses would rise up out of the mixture? Because the containers you are showing don’t have an option to place a vacuum pump.
And you might be right; the ultrasonic shaking power will most probably not be enough to force out the bubbles. So that’ll be a no-go.
I’ll have a browse on the internet to see if I can find the right tools to get it done. I’ll keep you updated.
Hi I’ve been casting for almost 40 years, and while today I have all kinds of equipment I didn’t when I first started out. My early castings were done using soup cans for the casting flasks with no vacuum equipment at all. The vacuum is to draw the air bubbles out of the investment so that there are no bubbles sticking to the surface of your model, which when cast would show up as bubble shaped bumps on the surface of the casting. To cast without vacuum equipment, you need to find another way to remove or prevent the bubbles from being in contact with the surface of the model. One way to do this is you would first coat your model with debubblizer (you can make your own by using one part dawn dishwashing liquid and two parts rubbing alcohol. Let it dry and set up on your flask base. Next mix a small batch of investment a little runnier than normal, about like paint and paint a thin coat onto the model making sure to pop any bubbles that may form and let dry about 15 minutes. Recoat several times for larger castings (like yours) to build up about a 1/8" layer. this should be plenty thick enough to prevent any metal from getting into any bubbles that form when you pour your bulk mix. Now put the flask onto the flask base and fill with a normal batch of investment. While it is still liquid tap the flask to get large bubbles to rise to the top. Let set for at least 2 hours without moving it at all. This allows it to achieve maximum strength and toughness. Cast normally. If you have any questions just ask. ill be happy to help.
Daniel
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Here’s a picture of the vacuum setup.