Surface finish help

I'm guessing that's about 22" long....yes? Are you constrained to a vertical orientation for burn out and/or pouring?

Best,
Kelly

 

Personally I would sand cast the flange adaptor.

 

I'll preface this by saying it isn't a convenient layout for shell........but I'll get to that.

1. The slight incline allows the part to fill continuously from one end to the other with no knit lines or converging metal fronts. It will promote directional solidification and venting at a single point.
2. The horizontal orientation allows shorter sprue length. This will reduce metal jetting turbulence as it enters the part and associated defects this can cause.
3. The spin trap is a damper that reduces the jetting. Once the spin trap fills the feed pressure to the part will increase but it will already be partially full and can accept the higher feed pressure without jetting.

It's not really a shell friendly layout. The pattern will be fragile and difficult to shell as shown. You can glue supports between the features using pieces of old shell, metal, or foam with a piece of shell glued inline obstructing it's ability to flow through the support. Or alternately....

You can include all these features by standing the part on end with or without the alternate gating system. You will have a very long sprue and much higher sprue pressures. How high? For aluminum about 1 psi/10" height. Denser metals like bronze/iron would be multiples higher. Jetting and heat loss will be a bigger problem with this approach but it will be less fragile and more shell friendly. The risk of sprue pressure cracking the shell at the bottom goes up but chances are probably small. The bottom portion of the mold could be buried. You should also consider the positions of features so you can clean/wash the mold.

There's a book by Dr. John Campbell that outlines 10 Rules. There is a condensed version available online. The offset pouring cup and spin trap are features he promotes. Then there is BiFilm theory which is a whole other subject. There is a long thread here on that. It would be good read for an aluminum caster. Just because this is shell casting doesn't escape the causes of aluminum castings.

Best,
Kelly

 

I'd do that in a heart beat.

Best,
Kelly

 

Jesus Kelly!!! Lol

I'd go a simpler route...

 

Other than the spin trap and location of the sprue, what's the difference, especially compared to the alternate? I could hot wire that scheme in foam in 10 minutes. You could omit the trap, sprue and gate into the one end, and vent at the other but the (slight) incline is a far better scheme for a host of reasons and merely a matter of how you position the part when you pour it. Ever try it?

If you had a CNC why would you ever cast it?

Best,
Kelly

 

I have the flange standing on its bottom edge with a runner over top and the sprue tapped into the runner.. I added "up" in the second photo to help with orientation..

Right now he is just working on a prototype. Lost pla casting is great for rapid prototyping.
And I suspect there may be more than simple 2d machining???

In ceramic shell ?? No... would it even be necessary when pouring into a ceramic mold heated over a thousand degrees??
What's the atmosphere like at that temperature??

Dont get me wrong Kelly it's a nice gating system you laid out, but you said it yourself

 

Fixed it... that was a wtf moment for sure lol...

 

......I've gotta be more careful with administrative rights......cut me off LOL!!!!!!

Given a clean sheet it's not a part that anyone would choose to shell unless that's all you were set up to do.....which if so is understandable......boy do I understand that.

Sure it may fill (or maybe not completely) but just because it's shell doesn't make it immune from defects for reasons arising from poor gating, feed system, etc, or others more germane to shelling and investment process as Kevin has already experienced.

I honestly see very little difference in time to do either what I or you suggested in the way of feed system. Considering the time and material cost to print, shell, and cast, the time to gate it is a drop in the bucket. With all that why not literally a couple more minutes for best chance of success?........and as always, the great thing about advice is you don't have to accept it!

So Kevin, did you notice any improvement with respect to chugging/aspirating with the offset pouring basin compared to your previous pours without?

Best,
Kelly

 

NOOOO!!! You are bound here!!
( someone has to keep me in check)

 

Well David, I never tried to edit one of your posts before but now that I know I can......LOOK OUT!!!

Sorry Kevin, back to regularly scheduled programming.

Best,
Kelly

 

Awww shit.....

 

Sounds like a plan. 3yr hiatus from your CNC Mill?.....gotta be a story there.

Best,
Kelly

 

"LIFE"