Good for Robert Maw.

this is really the only way anything like this could happen. anything else would just get bikeshedded into paralysis. if we are lucky, he will make the cad files available so some of us can make our own too.

I spent some time researching how billet aluminum is made. Most of billet is extruded at very high pressure at a temperature lower than melting point of the alloy. The pressure ensures there are no cavities in the metal. No wonder billet is costly to manufacture! The alloy is forced through a restriction in a continuous process and sections are cut away as it cools. The process is sort of like extrusion honing except its a solid material and much much higher pressure. There are other processes that make billet but all require extreme mechanical pressure. Billet will probably always be very costly.

the cost to get custom extrusion is actually very low as long as you buy a decent quantity. the cost of extruding billets is not signifigant to the cost. Aluminium is expensive because of the process to refine it. the price of aluminium is effectivley the cost of electricity. Aluminium ore is super cheap, and its everywhere, but you use a crap load of electricity to turn it into metalic aluminium. the next cost for billet machined parts is that most of the material goes back to the recycler as dirty scrap metal.

What I found interesting is the alloy is heated to 750 F to up to 950 F depending upon the composition of the material. Aluminum melts at 1,220 F, but the extrusion pressure is so great so as to squeeze it through the mandrel as it it were plastic, like one of the Play-Doh toys we had as kids! I'm looking forward to hearing of progress from Mr. Maw. I'm glad at least he can afford to do it.

I'm not exactly following all this aluminum discussion....the bottom line is he (or anyone else) will pick up the phone and order a chunk of aluminum with which to make his part. He won't have any say in how it's made or where it comes from.....not when he's buying a few hundred dollars' worth. In using a 7000 Series piece of aluminum, he's not breaking any new ground or inventing anything...it's pretty much the normal material.

While it might well involve the extrusion process, it's a generic chunk of aluminum. Typically, in aluminum production the term 'extrusion' is used to refer to shapes far more complex than the square or rectangle.

The material is the least of his concerns in making a cylinder head. His two main obstacles will be the massive amount of stock removal (in all the right places) and the effort needed to incorporate water jackets.

Here is the inside of a billet valve cover.
looks like you just let the machine follow the maze.

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Hyper_pak

If I had known it was THAT easy......

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-MattMan
LEANED & MEAN

It's not very hard, if you make someone else do it.

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Hyper_pak

My thinking was whether a block casting could be used instead of billet for the CNC work. "Probably", is the answer. The billet would be very high quality. Even a simple block cast can have porosity and castings usually don't weld as well as billet. But, if you melt scrap aluminum of a known source you have a good guess of what alloy was used. A local buyer of aluminum pays 20 cents a pound - I can't recall the exact number. But, if I pad $1.00 a pound I could get pretty much the best scrap cylinder heads. Assuming I could cast a rectangular shaped block of aluminum, then maybe 2 of 3 raw castings would be suitable for CNC work. After 25 of these castings were produced, have the CNC shop work on them. Assuming the casting was weldable, then minor defects can be corrected by welding. I'm thinking of how MacGyver might do it. Billet isn't a casting, but a casting can be decent and the finished head could be beefier than an OEM head so it might be less likely to crack and warp without the engineering costs of an OEM head.

I dont know what custom castings are worth. I have considered attempting my own cast intake, but the volume of aluminum makes it impractical for the casting equipment I have access to. If you can heat all of it, casting a solid block without porosity isnt hard, weld up an open top steel box and away you go.

with the new cnc router at my local makerspace, I would carve a 2 piece design from foam, then lost foam cast the head as one piece. the 2 factors that slow it down is that we can only melt about 1/3 of a head worth of aluminum in a go and the CNC mill isnt big enough to mill the whole head at once. i would need to move it a few times to machine the whole head, with the opportunity to wreck it each time.

An A-40 crucible can melt 40 pounds. I've read you need to plan on melting twice as much metal as you need. It would take an awful lot of heat to melt that much aluminum, but only having to pour into a metal box would be simpler, I think. There is a foundry up the road (Stevens Art Foundry) from me that could probably teach me a few things, just over the creek from here that specializes in bronze statues. I've just decided to visit and maybe learn how they do it. Many of their castings are huge.

Some parts can be made from recycled thermoplastic, if you don't care about it being in metal. Plastic melts at a much lower temperature, but as the intake/exhaust on a slant six are on the same side I think a plastic intake couldn't work, even if the base insulator were metal, as I see on new vehicles. But you could make a plastic valve cover. Nearly all automotive plastic is thermoplastic these days.

https://www.mysanantonio.com/community/ ... 385337.php

That's it..

Be different.

A bronze head......………

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I called and was invited over to observe a casting on Monday morning. He can give me some pointers on building the foundry furnace. He said its not too hard. I did a search and found that the the big 'un crucibles cost $300 or so, like everything there are different qualities and materials. Some have used a large steel pipe for the crucible. I've had troubles finding a casting buddy in the local area, but once I've done it a few times on a small scale, I think I can find another person. I now own a milling machine so I can learn to finish small castings.

I'd like to also be able to melt iron, which requires much more BTUs.

It sounds like many here think an extrusion is no big deal to jig up and CNC. That maybe true, and above my pay grade.

However, I have worked quite a bit with 6061 T-6 extrusions, and have noticed over the decades, when cutting a relatively thick section (1"?), the innermost alum material will "suck in" slightly away from the cut. If that phenomena happened to me unexpected partly thru the machining process of a huge chunk of alum, I would be very unhappy.

Maybe others have seen this, and can explain and tell how its accounted for and/or if this is normal.