Info on Aluminum foundry starup.

[bob1111]

Not sure if I have the right area or not. Looking for information about Al casting of intricate parts like 2-stroke engine cylinders. We have zero experience on the subject but are a multi axis CNC machine shop with 3D digitizing capability. We had thought that possible we could use a 3D printer to take our parts from CAD model to proto type and possibly cast from that. Not sure though. Machining of some of the parts we are looking at are nearly impossible thus our reason to look at casting.

How the heck do you get to final casted product from a CAD model where machining may not be an option? Does this have to be machined in sections?

Also, referring back to 2-stroke cylinders, what alloy options would one have for that application? Intake manifolds, heads, etc

 

[Timelord]

The mold is made in sections allowing you to do things that machining the whole part precludes. A lot of people have a plastic rapid prototype made of the part and the foundry can make the mold pieces from the rapid prototype. Talk to your chosen foundry about their prefered method.

Timelord

 

[bob1111]

We may be considered nuts but we are looking to do this work in house because of the small quantities and sizes. Do the final mold components need to be machined? From what? We can certainly design and machine a sectional mold if that is what it takes. Sounds like we need to visit a foundry or two.

 

[drawoh]

viper6383,

Some investment casting foundries cast multiple patterns and then glue them together. This explains a number of apparently impossible castings.

You could CNC machine pieces out of investment casting wax.

Rapid prototypers can RP out of wax as well.

Definitely, talk to a foundry. I am not an expert on this.

JHG

 

[bob1111]

Yeah, I just learned about that process. I guess they 3D print from wax, pour a ceramic product around the wax in a mold, burn the wax out, pour in Al. Sounds easy but you have to print a wax model for every part. He said after 25 parts or so, the cost gets high enough to look at better tooling. At that point, I get a bit lost. Still studying. He did say they would want to use A356 Al. I am not sure what that is yet and would have to see what high quality engine castings are using now.

 

[ajack1]

Viper 6383 that is pretty much how lost wax / investment casting works and as drawoh says wax parts can be glued / melted together.

The problem with most moulds or castings is you need to be able to part things, namely not have undercut conditions and often you need draft on the parts, this is not a problem with lost wax, it is however a potential problem in producing the wax part.

You can directly 3D print wax models and as with most 3D printing seemingly impossible details are possible as you are adding material not removing it, but you have to print a model for every part you want, so this is costly if any large numbers are required.

We are currently experimenting with a foundry to try and 3D print a series of moulds that they can produce wax models from and then “glue” the wax parts together, hopefully this will be a cost effective option for between 10 -50 parts, we are still having teething problems but it does at least seem a feasible option.

 

[ornerynorsk]

You can do investment casting with styrofoam cores, also. You're a bit more limited in detail and precision, when compared to wax, though. For styrofoam you can machine your own aluminum molds, buy expandable PS beads, make the parts, glue them together, then . . . . if you can sweet talk your foundry into working with the styrofoam, or you could get the ceramic slurry primary coat from them and spray up the shell so they could do the reinforcement coats without having too fragile of a pattern.

What kind of quantities are you talking? You could also machine your own wax cores like drawoh stated. This is a process that cannot readily be done "on the cheap" anyway you look at it.

 

[unclesyd]

Freeman Supply is a source of several videos and the materials to use for the different approaches to pattern making and molding as posted above.

http://www.freemansupply.com/video.htm

One approach to pattern making and replication.

http://www.dynamold.com/dmr.htm

 

[sbi]

I have been in the Aluminum & brass foundry business for over 35 years, before you think you want to start one, you need to check with your states dept.(version of the EPA), you will need a permit to operate a foundry, partly due to the fact we vent smoke!, When we set up our current foundry here in Nebr. we did it by California rules, since we also had a shop out there at the time. now a days we are glad for the pollution stuff we bought then, cost to day make it prohibitive. You may also check into have a lab or hobby foundry, in your state, which is regulated by how much you melt per year, but give you the advantage of minimal regs to deal with, # also need to check with your workman’s com insurance, there increase in premium to run a small foundry may make you lose all your breath for a spell!
But I have to admit, making a part for the first time and it comes out is a thrill, oh yea, you also need to learn how to gate the metal in to the casting as to assure you will get a good casting, with no shrink, or gas bubble just for a few of the fun things we deal with every day. Have fun.


SBI
Central Ne.,USA

 

[bob1111]

OK, I have done some studying the past day or so. I looked hard at the investment or loss wax processes and it seems that process may be a bit of an over kill and would seem that we would still have to make Al patterns in several pieces for the wax and then stick them together. Also looks like there are several machines needed to properly extract the wax before the Al pour.

I saw a Ferrari video where the parts of an engine block were just sand (I think they call these cores??) and they were piecing them together like a puzzle. I am not sure if that is just compacted sand, a special media or what. I am also unsure how they are bonded. Looked like they just placed them together.

I guess the largest decision we have to make is "is it worth us pursuing ourselves?". If so, which process is best suited for intricate engine parts with water jackets like a 2-stroke cylinder?

Would anyone know of a video that goes through the finer points of sand cast?


I did see somewhere that non-ferrous metals should be poured in a vacuum to reduce the chance of air pockets, is this a reality?

Also, one had also mentioned that with loss wax processes, the Al may cool much too slow and may weaken the tensile strength of the metal vs sand casting. Is this accurate?

 

[sbi]

two places you can look for your help are
afsinc.org = american foundry society inc, in Chicago
nffs.org/main = non-ferius foundry sociaty

and for the closest foundry to you try this neat website from the afs =

http://www.toolingnet.org/AFS/

this is a casting source directory.

There aer several ways to make a core, no-bake, is a cold process that uses a urithane binder, CO2 uses sodium silicate to wet the samd and CO2 to set it, and desoves in water( also very soft in humid climates, and shellcore, which has a fenolic risin, 1 to 3% mixed in and is blown in to a hot box to melt the plastic to hold the sand, these core are hollow, and that is just a sample of the fun we do

SBI
Central Ne.,USA

 

[Compositepro]

Go to YouTube and search for investment casting videos. There are plenty.

 

[KENAT]

viper6383 I'm 99% sure you don't want to be doing the casting yourself.

Look around find one or more good foundaries to work with and let them do the casting. For many you'll only need to supply the CAD model with associated material, tolerancing, surface finish etc and they'll do the rest.

I shouldn't say you'll only need to supply the CAD model as you'll need to work with them to make sure it suits casting such as having draft, avoiding features near gates & risers etc. Many of them have fairly extensive design guides to assist in designing the parts to be cast. In fact some foundaries will even do some of the design for you if you can give your requirements.

My previous employer was a virtual one stop shop, machine shop, treatment plant, paint, fabrication, test house, NDT even very basic heat treatment just about every major metal working technique/process known to man except Casting & Forging.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[bob1111]

Thanks for the post. You are right, I have shopped around and found that the price some of these guys will cast our parts for is nearly what I can buy material for. I am all for sending my parts out.


One of the LARGEST problems we face is these parts are engine cylinders and require "Nikasil" plating on the bore or comparable for an anti-wear coating. This is an electroplate process but we are open to other technologies for bore coating. Because one of the foundries we found is out of the country, we really need to determine how to handle that and who to go to. The cylinders must be machined before plating. Therefor we are trying to find a foundry that understands engine cylinder and has connections for bore plating. What fun.

We are also trying to determine if the cylinders should be T6 HT or remain 0 condition. I cannot see no drawback to treating them and should help machining them a lot.