Most of us here at Power Automedia are power enthusiasts. It doesn’t matter how that power is made, we can appreciate it. We now have 12 publications that range from hot rods to diesel trucks to import tuners to American muscle. Just about every one of our publications spends a good amount of time highlighting how to make power.
Basics on sand casting:
Basically, casting is pouring liquid metal into a mold and the liquid metal solidifies into the shape of the void within the casting. There are a couple key parts to a cast. The outermost portion of the form is called a cope and drag. The Cope is the top of the form and the bottom portion is called the drag.
If the part shape is basic like a solid block, then these are the only two parts needed to cast. Many castings aren’t basic or solid. In this case, the Cope and Drag form the outside of the part. The inner shapes are formed with Cores. Cores basically create the voids within the finished structure.
They can be made out of a number of different materials depending on the complexity of the shape and type of casting. Cores are sold and they do not have any voids for the liquid metal to flow into. An upper and lower mold collectively called core boxes are used to form a Core. When the Core boxes are connected, they are filled with the material (usually a sand and resin mixture. The sand creates the shape and the resin bonds the sand to keep its shape.) Once the mixture is formed, it can be pulled out of the Core Boxes and it is ready to be used.
The number of Cores that are used to cast a part varies by the complexity of the part. Some parts may only have one Core, while others may have many. The Cores then placed inside of the Drag.
The Cope and Drag are formed similar to the Cores. The biggest difference is that their finished shape is the void not the sand. In addition, the Cope and Drag are much thicker to prevent blow out and there are channels, cavities and vents designed into them to help the liquid metal flow, as well as deal with venting the gases and dealing with shrinkage as the metal cools.
After the Drag is formed, the cores are laid into the drag according to the design. Once everything is laid out, the Cope is added. The next step is to pour liquid metal into the Cope.
The actual manufacturing of a turbocharger is quite a long process and not something that can be condensed down into 5 minutes. So, there are obvious steps ignored. The video starts out showing how the compressor covers are made.
If it showed how the compressor wheels or turbine wheels are made, they would follow quite a different process. The compressor cover, turbine housing and bearing housings are sand cast (usually). Compressor and turbine wheels are manufactured quite differently. Most of the internal parts of a turbocharger are machined and they too, by pass this process.
One really cool aspect of building a turbocharger that they did show, was the VSR (Vibration Sort Rig), which balances the rotating assembly in the cartridge. This is a very expensive piece of equipment and something that really separates turbocharger manufacturers from turbocharger modifiers.