pcmhacking.net

Mentioned in Tazzi's 3d printing thread, I need a few manifolds made up for my superchared VW project. This is how I do it. This one is simple, its an adaptor plate to bolt a GB TBI to an AMR500 Charger. No Cores, just a simple two part mold.

We start by drawing up both flanges in CAD.
Then we merge them so no support bolts are interfering, no breach of any sealed surfaces, add clearance for both the bolt head and the socket to tighten them. Add a mm either side for finishing on the mill/lathe and we're almost ready.
We print a 1mm slice to confirm everything is lined up and no gross errors.
Now I fill in the through holes and add a dimple to locate the drill when drilling. I do this because every edge must have a draft angle to help removal from the sand. It is just easier not to have complete small diameter through holes and instead drill them in the finishing stage.

I'm printing the master pattern now, Should be done in an hour or so. I'll add more photo's when I'm ready to make the sand molds and pour them.

Happy Easter Holidays!

Nice work, I'm very interested to see how this progresses and the final product.

Wow im watching with great interest

Me 3

+4 Life is easy when you have access to the right equipment

OK, so a bit of a backstory:

I usually cast with what is known as 'greensand'. This is clay bonded sand with water to help bind it all together. There are limits to the detail and surface finish you can achieve with greensand due to the required porisity of the sand to aid in venting when the 900deg metal gets poured into the mold. This means course grain sand and due to the water to bind it, it evaporates and requires constant mulling (compacting and breaking). It is hard work! but it works well.

I invested the money and got 15kgs of 'Petrobond' binder (~$220 in shipping alone from the US!!!). This works in the same way as greensand but uses synthetic 2-stroke oil to bind. No evaporation, no constant mulling. No water means no steam which means extremely fine grade sand (I'm using al-ox 120grit sand blasting media) and almost mirror surface finish. You can easily cast the detail off a 10c piece. I can even see my fingerprints in the casting! Being my first time mixing this oil bonded sand I ran into a few issues. I'm still working out why there isn't much strength to my sand. Consequently, Some parts of my mold couldn't be achieved. Anyway, On with the show! So not exactly what I wanted, Now I have to drill the holes manually

I'll have to add more draft in my next print to make up for the weak sand. Also, I printed in PLA rather than ABS. The neat thing with ABS is you can acetone vapour polish it which gives it a very hard mirror shell and sand won't stick to it. You can get away with some vertical edges using that technique.

I might re-do my master and do another pour tomorrow. Then on with the more complicated manifolds!

Will you be mass producing these? May be easier with a mill and some extruded flat bar if it's just a one off.

Even plasma cutter and mill for small batch production

For something like this plate I agree, plasma, water or mill would be best. For manifolds with complex core geometry there is no better method than sand casting.

This simple adaptor was more to test the new sand before I get stuck into multi piece molds with cores.

And if I choose to do a production run, it is far more time and cost effective casting with a quick skimming on the mill/lathe.

BennVenn wrote:For something like this plate I agree, plasma, water or mill would be best. For manifolds with complex core geometry there is no better method than sand casting.

This simple adaptor was more to test the new sand before I get stuck into multi piece molds with cores.

And if I choose to do a production run, it is far more time and cost effective casting with a quick skimming on the mill/lathe.

Don't get me wrong. Awesome project. I need to look into this sort of fab myself. I just meant that there may be easier methods for the project you are working on.