Metal casting

[Swoop]

The patterns have to be exact or the casting will not be satisfactory.

The pattern has to be exactly larger, to allow for the shrinkage of the metal as it cools down.
I spent a short while working with patternmakers and we had expansion rulers for that job. Just like a "normal" ruler with the regular graduations, but these were specific for metal type. Use the "Aluminium" expansion rule for that metal and just work to the sizes stated on the plan.
From watching the guys doing the casting work, the sand was only wetted enough to allow the sand to stick together and nothing more! A real art in what they were doing.

[wbks]

Sure milling is probably better but it's not something I'd have access to and I was just wondering about casting. What would you do to learn CNC milling programs? Engineering? Software?

[jrandom]

What would you do to learn CNC milling programs? Engineering? Software?

PM Timmay, tell him I said, etc. You're in Auckland, yeah? Yous fullas should hook up.

[Madmax]

Like Jim2 sez, lots of automation out there these days. If you can make a 3D CAD model of it, someone can cut it for you on their CNC mill.

If you don't have the right 3D CAD software, uh, well, let me know. I can probably help you find someone who can help you with that. Learn to use it and you've gained an employable skill, too.

Machining one-offs with computer-controlled gear is far easier, faster and probably (time being money, etc) cheaper than attempting to cast things.

Not to mention that, assuming your design or replication is correct, you get a stronger, higher-quality part.

There are some parts you have to cast! cylinder heads are one,
you cant CnC machine the internal water passage ways,
Aircooled clyinder heads are a piece of piss to machine,
Pistons are cast or forged as this changes the property
of the alloy,
you just finish machining with CnC

[jrandom]

you cant CnC machine the internal water passage ways

Well, not if you insist on fancy curved paths, I suppose.

[gatch]

There are some parts you have to cast! cylinder heads are one,
you cant CnC machine the internal water passage ways,

Like JR says below depends how fancy you want them, you can do quite a bit with some lateral thinking and experience..

[Ocean1]

There are some parts you have to cast!

Why you no listen?

Looky here: http://www.gizmag.com/go/6657/

And: http://www.sme.org/cgi-bin/find-arti...&&SME&#article

Volvo already make most of their water pumps like this.

The ONLY production constraints to such systems currently is the limited range of metals, and the dimensional capacity.

For now.

Welcome to the future.

[Madmax]

Casting CNC they all have there place
Making one off con rods from billet is easy just CNC them
there not as strong as forged rods though
Forged ones are made in piece and you have to
cut the cap off before you do your final machine work
I had to make a crankshaft for a V12 flathead once
could not cast it, made it up from seperate bits
welded together, heat treated and machined.
It had hand machined Alloy heads!
to get round the water jacket problem
They had machined the head face plug holes water jacket and all
then made a top cover and welded it on!
It was an old race engine
when it blew up they chucked it in a chook shed (bloody Yanks)
when we got it there was about 60 years of shit on it
(looked like a giant turd)

[Madmax]

Why you no listen?

Looky here: http://www.gizmag.com/go/6657/

And: http://www.sme.org/cgi-bin/find-arti...&&SME&#article

Volvo already make most of their water pumps like this.

The ONLY production constraints to such systems currently is the limited range of metals, and the dimensional capacity.

For now.

Welcome to the future.

ss

I am Computer Engineer these days so i am already hear
Fully CNC/CAM conversant
Have seen this in stuff in use at middlemore
Not much help when you have a broken bit you can
remake like they use to in less time than it would take to program it,
I like CNC but if your CNC/CAM station is down or the milling centre is
broke
Can you make it with your hands and manual tools

I CAN

CAN YOU

I see in your profile your a engineer so mabey you can

[rocketman1]

I broke the casting that hold the throttle control in place on my old Mariner outboard, apart from the difficulty of finding a replacement the dealers wanted a fortune to replace it, so I glued it back together and took it to the local foundry in Hamilton, they cast a new one in no time. I had to drill out the holes and tidy it up. But it worked a treat. A bit of paint and you couldnt tell the diff.
All for about 20% of the price.
It would be better to take the part (or a sample, loaned part) to the local founders. they would do a better job than you can.
I have worked in a foundry for a short while and I know the problems they can encounter.

[P38]

If you wanna see what the capability of a modern 5 axsis machining center is just check out this You Tube Beauty.

[P38]

Prepareing a mould for casting including setting a core.

[P38]

Then melting and pouring the metal.... all very facinating and to think this process has been followed for thousands of years.

[wbks]

how long you recon to map that block out on CAD?

[Ocean1]

how long you recon to map that block out on CAD?

You wouldn't model the block alone. In fact the block details are sort of dictated by the crank/rod/piston and secondary assemblies. But to answer your question, (and ignoring the design work that accompanies any such task), probably about a week.