Casting a cylinder head

[gonejunking]

Alan
I agree with what you say, but when I use the head gasket for layout, I'm building a mockup that will be scanned and scaled up on the computer to cut the pattern's. It's easier to have a point of reference like the head gasket, when I'm laying out the runners, and water jackets.

[acondit]

Originally Posted by gonejunking Alan I agree with what you say, but when I use the head gasket for layout, I'm building a mockup that will be scanned and scaled up on the computer to cut the pattern's. It's easier to have a point of reference like the head gasket, when I'm laying out the runners, and water jackets.

Don't forget, before actually building the pattern, to add material for a machining allowance at places that will need to be machined (like gasket surfaces, valve seats, bolt pads and bearing surfaces).

Alan

[Kipper]

Sounds like a great beginners project to me as you will learn what can and cant be done almost immediately. My tip would be to look at the original casting to see how it was made and replicate the head. I've seen Lombardini heads which are lost foam items but never considered making anything with this method as it's too slow (I have no patience lol) Best of luck with your interesting project :beer:

[hammers]

Thanks to everyone for the information. I re-watched the Britten video that I mentioned. In it he makes what appears to be a dohc 2 cylinder bike engine using sand casting with hand made patterns. The quenching in water that I mentioned was actually heat treating after heating it in his wife's pottery kiln. It is not clear whether that casting was actually used, but there is later footage of the bike wheelieing beside the race leading ducati at daytona.

But anyway.. a couple of more noob questions if you could indulge me.

- once you have a bare casting, how do you go about starting the machining? IE how do you get one or two 'true' surfaces to use as references for machining all the other surfaces.

- is there any free or edu-priced CAD software I can use for CNC designs? I have used the emachineshop.com program which has the distinct advantage of telling you when you have designed something that is impossible to make (by them). Is there something available with more flexibility?

I have hit the library but all the books I found talk about theory of different processes, without talking about the practicalities of actually manufacturing something all the way through.

Thanks

[Splint]

Originally Posted by hammers - once you have a bare casting, how do you go about starting the machining? IE how do you get one or two 'true' surfaces to use as references for machining all the other surfaces. Hammers, you will need to incorporate datum surfaces and edges into the pattern so they appear in the casting. You will need to do this with a clear idea of how you are going to mount the casting to the mill table, allowing space for the cutting tool and spindle to cut the required sections whilst keeping clear of clamps. - is there any free or edu-priced CAD software I can use for CNC designs? I have used the emachineshop.com program which has the distinct advantage of telling you when you have designed something that is impossible to make (by them). Is there something available with more flexibility? www.alibre.com I have hit the library but all the books I found talk about theory of different processes, without talking about the practicalities of actually manufacturing something all the way through. Yes there are plenty of foundry books out there but most are more geared toward engineering students, lots of formulas, minimal practicle hands on type stuff. Have a look at this site, http://www.myhomefoundry.com/ also http://www.abymc.com/tmoranwms/Metal_Casting.html also http://virtualindian.org/3techcasting.htm also http://www.angelfire.com/tx5/hite/furnace.html also search yahoo groups as there are a number of foundry groups there. Thanks

Cheers
Splint

[Kipper]

Hi Hammers, Hows the project coming? Have you moved from theory to getting your hands dirty yet.

Originally Posted by Splint Hammers, you will need to incorporate datum surfaces and edges into the pattern so they appear in the casting. You will need to do this with a clear idea of how you are going to mount the casting to the mill table, allowing space for the cutting tool and spindle to cut the required sections whilst keeping clear of clamps.

Originally Posted by Splint Yes there are plenty of foundry books out there but most are more geared toward engineering students, lots of formulas, minimal practicle hands on type stuff. Have a look at this site, http://www.myhomefoundry.com/ also http://www.abymc.com/tmoranwms/Metal_Casting.html also http://virtualindian.org/3techcasting.htm also http://www.angelfire.com/tx5/hite/furnace.html also search yahoo groups as there are a number of foundry groups there.

Splint quoted as I never realised he'd made a reply (no offence intended just it just looked like a quote and cheers) I agree with him too

[Kipper]

Any news? Given up! cmon tell us

[Warpspeed]

A very great deal depends on if you want to make just one cylinder head for yourself, or go into mass production.

If mass production, then you need to go the proper segmented master pattern, and greensand. Making the pattern will be a huge job. Internal cores will need to be made for water passages, and it would be a very complex undertaking.

For only one head casting, if you have the facilities to cnc foam, I would do it that way, but only cnc out one cylinder. You then cnc out your four identical cylinders from foam, and just glue them all together, along with suitable end structure for the water thermostat, or any other special features. This will be a lot less work, even if it takes several attempts to get a perfect casting.

With only one cylinder to cnc out of foam, you can get right inside the water passages from both ends and do a pretty good job, and judge wall thicknesses and so on fairly accurately.

Once you have a suitable cnc program written and tested, any number of foam patterns (for one cylinder) can then be produced fairly quickly.

[Big_d]

MMM nothing like having a long term goal. Had a bit of experience with aluminium and magnesium. An OHV head is probably the grail in regards to casting. Little spurs to cool valve guides, exhaust water jacket volume, shrinkage and porosity are a few of the hurdles you have ahead. Feeders, runners and risers will be the key to the success of your project. It still amazes me that to cast a decent head nearly 50% of the molten metal is used as feeders to prevent problems with the finished part.

If you are starting from scratch I would suggest you section a couple of iron heads and look around at the layout. Because you will be using a different material you should increase thicknesses in a few critical areas like combustion chamber, block face, bolt bosses and valve spring seats. You will be able to get the metal thinner around things like intake ports and spark plugs to take advantage of the new material.

The 3D printer looks like the go for the pattern in my opinion but for my money if you are going to pay for this to get done I would get a pattern milled out of wood to mould your water jacket from sand. Combustion, ports and spring side will also benefit from this. If it's a hobby project get a pattern makers rule and start carving that foam. You can use foam and parent metal posts inside the mould to support the core if it is a bit flimsy.

With a mould you will then easily be able to produce a few to sort the feed issues and make a good clean weld free part. Using sand will also help with internal mould distortion and foam is way to easily displaced to be accurate. Sand will also allow you to cast it faster guaranteeing a better fill and less leiklyhood of a reject part. It will hold the heat longer allowing the cooling to semi solid to take longer. Certain areas will need to be cooled faster to prevent shrinkage, a good rule of thumb is deep holes need chills and in a perfect world you always cast with the combustion face down as gravity will help get a solid shrink free part. Try to cool the combustion face faster to prevent it from back feeding the rest of the hot casting. A thick steel or iron plate under the box will help a lot.

Heat treatment is easy, once your casting is cool and cleaned out warm it up to 500c from memory and quench it as fast as you can. Hot water is the go as cold will get it harder but will probably have trouble getting around evenly and may leave some softer spots. A water quench will have the added advantage of filling up the micro holes in the casting that will allow it to leak. In a fresh casting without corrosion it is really surprising how porous they can be. After getting wet and left to dry for a couple of weeks the micro leaks will be greatly reduced. There are compounds used by some company's that are vacuum induced into the casting to fill up these holes but that costs money and it doesn't really do any better than letting it sit for a while.

Excuse my ramble I get a bit carried away sometimes. :
Cheers
Daza