Supporting > Casting

Casting a flywheel in ZL12 alloy.

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A7er:
I have been using aluminium from a Renault car wheel for my recent casting attempts. Today I used an aluminium/zinc alloy called ZL12, which is 88% zinc and 12% aluminium. The flywheel cast from the car wheel weighs 169g, from ZL12 it weighs 385g. The first picture shows a slight depression in the rim of the flywheel. The shrinkage is right above the ingate. I am assuming that the metal wasn't hot enough and it "froze". The dip is less than 1mm (it looks deeper because of the rim sticking out), so it would machine out. I had allowed for the removal of 2mm from the outer faces. The second picture shows the small amount of flashing on the casting. It seems I can either get a casting with virtually no flashing, or with a good surface finish, but not both! The flywheel is approx 90mm in dia by 18mm wide.

Jasonb:
Certainly a nice surface finish.

The small amount of flash looks to be where sand has come away when removing the pattern rather than poor contact between the two halves

That's a good weight increase using the heavier alloy and only about 50g less than if it were iron

A7er:
I think you are right Jason. I am still removing my patterns by inverting the flask and tapping it until the pattern falls out. I need to find a better way of extracting the pattern.
Lee

Edit. I am 100% convinced that the flashing is down to the way I have been removing the pattern. I now have something positive to work on!

Jasonb:
A common way to do it is to lightly tap the alignment studs which just loosen the pattern  and for the other half that has the mating holes use a couple of tapped ones so you can put a screw in and give then a gentle sideways tap just to loosen the pattern and then lift out by the same screws.  You might just be able to leave small holes in the prints and use self tapping screws

A7er:
Hi Jason,
I drilled two 6mm holes in the back of the hub of the pattern that has the locating stud holes, the other pattern has the locating pins. I filled the holes with car body filler and will drill two holes for small screws. I can then attach a small buldog clip to the screws, and then with the aid of a vertical puller, which I have yet to make a-la Olfoundryman, extract the pattern. I will use the same procedure on the pattern with a central locating pin. The bulldog clip is 20mm wide and will sit on the pattern without rocking. Well that's the plan anyway!
Lee

Edit. The other alternative is a match plate. I am watching videos to get some ideas.

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