Casting different metals - same pattern 1

[gaufridus]

I am anticipating a situation that may arise.
I am designing a component that is to be sand cast in, say, Aluminium alloy but there may, in the future, be a requirement for the same component in Cast Iron(for the sake of argument lets ignore the actual grades of material).

If we ignore the relative strengths, weights, etc. of the materials viz-a-viz the actual end component what would be the problems (from a purely casting point of view)in using the same pattern? I am thinking of shrinkage rates, feeder and riser arrangements.

 

[deanc]

http://www.castsolutions.com/

Check the links inside.

 

[swall]

I assume we are talking about sand casting. I don't see any problems with your idea and you've already identified the major issues. As there is always trial and error with gating and feeding a new casting design, patterns get reworked all of the time to deal with these things. So in going to iron from aluminum, you might need to have the gating and risering on the pattern reworked again. One other factor--the volume change from liquid to solid will be different for iron compared to aluminum. So your final casting dimensions will be slightly different going from aluminum to iron,using the same patterns.

 

[EdStainless]

I have used the same patterns for casting GI, DI, Ni-Resist, Brass, and NAB. Yes, we had to make some changes. They always proved to be 'backward compatable'. That is if we had to increase a riser size for one alloy we left it that for all of the others. The patterns were not efficent.
And yes, the parts all came out slightly different sizes. It was easier to change the required dimensions or machine more as opposed to making unique patterns.

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[arunmrao]

The factors to be considered while making a pattern is being repeated once again.

> Solidification shrinkage to be added. This varies with different metals.

> Machining allowances to be provided.

> Thin sections that can be cast and thin and thick section joints.( hot tear related problems)

> The length to which a thin section casting can poured.

> Any metal padding to assist directional solidification or mold filling capability.

> In case of castirons the smallest section that can be cast without chilling effect.

> Molding draft to be provided.

> Cored holes that can be made.

> Location of risers and their sizes . Will vary with different metals.

> Provision for placing breaker cores .

> Design of gates and down sprues. Especially in aluminium bronze and light metal casting aspiration poses a serious problem.

In view of some of these issues,it is simpler to provide a different sets of patterns for different alloys and have a peaceful weekend else it will be stressful guaranteed!!

 

[metengr]

arunmrao;
Your the voice of experience on this matter.