aluminum casting wall thickness

[njlee]

Hi All,

For aluminum casting part (sand cast, permanent mold or investment casting), do we need to core out the part? I have seen a lot of casted parts with very thick section. What is the recommended maxinum wall thickness for a part size of about 3" X 2" X 24"?

Thanks,
Lee

 

[swall]

It depends. I have seen brake system parts, such as master cylinders and ABS bodies cast solid as well as cored for the same configuration part in both sand and permanent mold processes. With modern machine tools, it is often cheaper to hog out the extra metal than put the extra cost into the casting. On the other hand, sometimes the use of a core can get you out of a shrinkage problem or help you get a finer dendrite size in a critical strength area.

 

[arunmrao]

All founders like to sell solid parts instead of cored ones.(The advantage being lesser work for the foundry and more yield per box.) But this is an utopian wish.

Customers demand more of cored work to reduce their operation cost and sometimes geometry and locations require these to be produced as cast. There is no reason why a foundry should not produce a cored thin walled casting.(They are meant to do this or else they would be flushed out by the primary bars, rounds flats etc producers)

 

[BillPSU]

Good casting design is the key. Consistent web thickness reduces the problem of hot spots. Offset web intersections. Have the casting go from a thin section to a thick section to have directional cooling. Where do you want the in-gate(s). Where is the parting line. How much draft do you need.

Is the part a structural component or a decorative component? Maybe total degassing is not required.

Typically when there is a thick section there are also thin sections. The thick section will be the last to solidify and will have the most shrink in the large section. To reduce shrink a riser is attached to the large section meaning more metal is poured for the casting.

If you currently buy castings talk with your supplier he can help you with casting design and lead you through some of the complexity of designing a casting with lowest cost.

 

[njlee]

Thanks for all the response. The summary is :

consistent wall thickness is good casting design practice, but sometimes "it is cheaper to hog out the extra metal than put the extra cost into the casting".

now I know I don't have to put as much effort into shelling out the casted part as plastic injection molded part.

Thanks,
Lee