@Janger his cross slide drill reminds me of your set up. His spindle indexing is ingenious.
Spin casting aluminum
- Thread starter DavidR8
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@Janger his cross slide drill reminds me of your set up. His spindle indexing is ingenious.
The spin casting to remove or prevent air bubbles is interesting. Looked quite dangerous though. But really shows how much you can do with only a lathe.
I actually leaned away from the chuck when he poured in the aluminum!
Former Member
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Spin casting if I remember my history correctly was the precursor for injection casting which is most common now.
It allows forced injection of molten metals into molds to allow fine details to be formed.
It allows forced injection of molten metals into molds to allow fine details to be formed.
We built a ‘Lost Wax’ vacuum moulding line for an Ontario company.
They were producing complex alloy ‘impellers’ for high RPM centrifugal pumps.
The investment casting shells were filled with molten metal under a vacuum to reduce gas entrapment and endure the parts were quickly filled to improve detail integrity.
As a test product to prove the tolerances achievable, we were producing ‘slip fit’ Woodruff keys for assembly into pump shafts.
It was the first time that I saw a ‘cast part’ with .0002” precision.
They were producing complex alloy ‘impellers’ for high RPM centrifugal pumps.
The investment casting shells were filled with molten metal under a vacuum to reduce gas entrapment and endure the parts were quickly filled to improve detail integrity.
As a test product to prove the tolerances achievable, we were producing ‘slip fit’ Woodruff keys for assembly into pump shafts.
It was the first time that I saw a ‘cast part’ with .0002” precision.
Former Member
Guest
I've designed and built some molds for aluminium casting for one of my own products years ago. An approximate 5% allowance must be made to allow for shrinkage. To build the wooden plugs for sand molds the owner of the Casting shop share some of txt books and knowledge with me. After the first casting the I was offered a job building plugs as it is an art form and they always were looking for plug builders, never took up him up in it.
Why I built them, $2k plus for the plugs was well outside my budget.
Why I built them, $2k plus for the plugs was well outside my budget.
I have known a couple patternmakers, and their tooling is...specific! Shrinkage scales, either looking like a plain old ruler, or like an Architects Scale, are often used so that the dimensions can be simply read off the scale directly, rather than having to convert by the shrinkage factor each time.
The shrink rates are VERY specific, and even in a family of casting alloys, can vary enough to bite you in the butt, so it is important to know pretty much as exact as possible, what alloy will be used.
The one fella said that the way you qualified to become a sand crab at the foundry, was you had to prove you really COULD break an anvil, with a rubber mallet! This was his observation, basd on the damage they were able to do to the patterns he built, and as often, rebuilt!
The shrink rates are VERY specific, and even in a family of casting alloys, can vary enough to bite you in the butt, so it is important to know pretty much as exact as possible, what alloy will be used.
The one fella said that the way you qualified to become a sand crab at the foundry, was you had to prove you really COULD break an anvil, with a rubber mallet! This was his observation, basd on the damage they were able to do to the patterns he built, and as often, rebuilt!
Former Member
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I will admit one of the advantages I had was I had a chance to get in the big casting shops in Orillia many years ago and see all the original plugs and their plug shop and see the production methods.
Again a little insight goes a far way.
Again a little insight goes a far way.
Former Member
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I will admit one of the advantages I had was I had a chance to get in the big casting shops in Orillia many years ago and see all the original plugs archived (including a couple of ski lift bull gears) and their plug shop and see the production methods.
What exactly are 'plugs'?
I believe he is referring to "Patterns". Thus my earlier reference to Patternmakers!
It ties in with his reference to shrinkage allowances on the patterns, I think!
Much like for 3D printing where the secret is to be able to draw using CAD or be stuck downloading whatever someone else has done, for casting the secret is pattern making. Make good patterns and minimal machining is required and the castings are pretty.
I've done two sided pattern boards. This is a simpler one with just the well for the initial metal at the bottom of the sprue:
And the other side of the pattern board with the sprue set in place.
Riser is placed on top o the screw head when the green sand is packed in. They were for the JGRO CNC router to hold motors and the end of the lead screw in ball bearings.
I've done two sided pattern boards. This is a simpler one with just the well for the initial metal at the bottom of the sprue:
And the other side of the pattern board with the sprue set in place.
Riser is placed on top o the screw head when the green sand is packed in. They were for the JGRO CNC router to hold motors and the end of the lead screw in ball bearings.
Former Member
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Plugs, patterns all the same.
Cores are different as they are separate pieces inserted into the molds allowing for more complex internals in one casting.
Cores are different as they are separate pieces inserted into the molds allowing for more complex internals in one casting.
A bit of research does seem to confirm plug is used with fibreglass or carbon fibre. Sand casting still tends to use the terms pattern and core.
Yeah, about that... No.
There is a very specific set of terminology, that helps us all stay on the same general page, as far as understanding what is being spoken about.
Patterns means one thing. Cores means another. As does Riser, Cope, and Drag.
If we all start talking about casting, it's a 'Good Thing" to al understand the terminology being used!
Plugs 'Composites', are different things than casting Patterns!