4200 Vortec Casting Process

[Reprise]

I saw this a couple of minutes ago, and it surprised the hell out of me...

Take a look at the interior surface of the cylinder head in this thread (page 1, post 38):

I knew previously that a 'lost foam process' was used to cast the block / head. Some time ago, I had read what that process incorporated...but....styrofoam ?!?

(the OP from the other thread is still working on his issue, and I didn't want to hijack the thread while he's still troubleshooting)

 

[mrrsm]

Yes... the process is also called the ‘Waste Foam’ casting of the main segments of the Block. The Foam Blanks are first designed and basically blow molded into a Hardened Styrofoam structure that gets packed into some very special, re-useable molding sand that gets stuffed inside of a container that has multiple spru spigots to prevent the AL-380 Aluminum from cooling prematurely at any given point. Once the Molten Pours begin... The Styrafoam structure vaporizes and because the supporting Molding Sand is so very fine grained... it leaves the little Styrofoam ‘nubbies’ impressions into the Aluminum as the Styrofoam completely burns away.

When the Block is allowed to cool slowly and separated from the casing... the sand... which ordinarily occupies literal mountains around the places where Cast Iron Engines and Parts are made... is readily reusable and therefore... a very eco-friendly means of manufacture of the All Aluminum Block and Head set up. This also allows for very minimal machining necessary to get the Block ready for assembly.

 

[mrrsm]

This is a fairly long and comprehensive "Start to Finish" look at how the FATA Aluminum Company creates components that are manufactured using mostly Automated Processes and Robotic Machines to perform the "The Lost Foam" Process. This video perfectly shows the creation of some Aluminum 4 Cylinder DOHC Engine Heads and their matching All Aluminum Engine Blocks.

There are some very interesting views here... including how they employ the White Powdered Poly-Styrene Ball materials to create the "Plastic Powder Positive" Engine Head and Engine Block Blanks in sub-segments that are eventually Hot-Glued together.After that... they enjoy a bath in a Liquid Ceramic Emulsion coating (Tope-Gray) and drained out and Baked thoroughly to guarantee all of the Poly-Styrene surfaces are replicated and hold fast as the plastic gets vaporized on contact with the Liquid Aluminum Pours.

Afterwards, these Finished Blanks are submerged inside large, sturdy cylinders and filled or surrounded completely with the Special Casting Sand. "Shaker Tables" are used during the sand filling to vibrate the contents to ensure complete coverage of their Tope-Gray Ceramic Coated White Plastic "Positives". A Fresh Kettle of Molten Aluminum is dipped into and the right amount gets poured into a Sprue Funnel while the Liquid Aluminum displaces and vaporizes the Poly-Styrene Blanks completely away.

Once cooled down and stable... The cast Aluminum Heads and Engine Blocks are extracted from the sand containers... turned over and over to get out as much sand as possible and then washed in a liquid bath that shatters the Tope-Gray thin Ceramic Shell (...think M&Ms Peanuts here) and what is left are the Raw Aluminum Engine Heads and Blocks ready for minimal machining.

They do not show this part of the process in this video... but In the case of the GM LL8 4.2L Engines and its 5 Cylinder Sister... The Cast Iron Cylinders are Chilled down Icy Cold before being slipped into the Upper Block and once returning to ambient temperature...they remain steadfastly held tight against the sides of the Aluminum casting holes molded into the engine block.

The scenes involving their actual X-Ray Analysis of the components looking for cracks, metallic bubbles and defects in the very complex shapes first created in White Plastic and resolved perfectly as Aluminum Components bears proof at just how flexible this process can be in creating something amazing and durable made of 99% Recyclable Aluminum... out of almost nothing:

 

[Reprise]

TY for posting the vid, along w/ your explanations. I found myself wishing for narration vs the looped bkgrnd music (which probably was recycled itself - most likely from an old porn flick...lol.

Then I re-read your post and realized I had the next best thing. Appreciate the info.

Still kinda amazed that they use polystyrene (silly me thought GM was receiving foam blanks...how quaint. This factory *makes* the blanks from raw material.)

 

[cornchip]

Remember in the early 90's when GM was starting out with Saturn engines, we had samples through the shop to experiment on. They had to figure an automated way to remove a black coating from the freshly casted parts. The company I worked for specialized in water jet technology and used rotary 'fan jets' with high pressure water to blast the remaining crap off the exterior surface. It was all R&D stuff at the time.