Introduction to Metal Casting Processes

Questions and Answers

What is an advantage of shell mold casting over sand casting?

Reduced labor skills requirement

Superior surface finish and good dimensional accuracy (correct)

Lower tooling cost

Ability to cast large parts

What is a limitation of shell mold casting?

Ability to cast only small parts

Low surface finish

High equipment and pattern cost (correct)

Requires high labor skills

What is the advantage of using small sand particles to form the die in sand casting?

Increases die permeability

Enhances surface finish (correct)

Increases part size

Reduces tooling cost

What is a characteristic of centrifuging casting?

Utilizes inertial forces resulting from die rotation Signup and view all the answers

What is an advantage of re-usable sand in sand casting?

Minimizes overall process cost Signup and view all the answers

What is a limitation of sand casting?

Low surface finish and dimensional accuracy Signup and view all the answers

What is a characteristic of shell mold casting?

Has low capital outlay on the sand preparation plant Signup and view all the answers

What is an advantage of shell mold casting?

Lower cleaning costs and no labor skills requirement Signup and view all the answers

Which of the following materials can be used to make expandable molds in casting processes?

Sand resin Signup and view all the answers

What is the purpose of a pattern in casting processes?

To form the mold cavity Signup and view all the answers

What is the difference between the cope and the drag in sand casting?

The cope is the upper portion of the mold, while the drag is the lower portion. Signup and view all the answers

What is the function of a core in casting processes?

To form internal holes in the casting Signup and view all the answers

What type of casting process uses a centrifugal force to distribute the molten metal?

Centrifugal casting Signup and view all the answers

Which of the following casting processes uses a pattern made of polystyrene?

Lost foam casting Signup and view all the answers

In a composite mold, which types of materials are combined?

Expandable and permanent materials Signup and view all the answers

What is the main difference between sand casting and shell mold casting?

Sand casting produces a rougher surface finish than shell mold casting. Signup and view all the answers

Study Notes

Introduction to Metal Casting Processes

Metal casting is a process where molten metal is poured into a mold cavity to form the final part upon solidification
Molds can be made from different materials, including expandable metals (sand, resin, ceramic, gypsum) and permanent metals (grey cast iron, steel, bronze, graphite)

Types of Casting Processes

Expandable casting processes use a pattern to make mold cavities, with materials like metals, wax, and polystyrene
Cores can be inserted into the mold cavity to make parts with internal holes, made of sand mixed with binder materials
Three types of casting processes will be covered in this experiment: sand, shell mold, and centrifuging casting

Sand Casting Process

Mold is made of sand, with a pattern used to make internal die cavities and cores used to form internal holes in the final castings
Die is divided into two portions: cope (upper) and drag (lower)
Pattern is also divided into two portions, one for the cavity in the cope section and one for the cavity in the drag portion
Re-usable sand can be used to minimize overall process cost
Sand casting process can be used to cast almost any metal type with no limitations on part size and low tooling cost
Surface finish and dimensional accuracy of the final parts are low, requiring some finishing operations
Surface finish can be enhanced by using small sand particles to form the die, but this reduces die permeability and may cause casting defects

Shell Mold Casting Process

Expendable mold casting process, where molten metal is poured into a heat-cured mold that is non-reusable and in the form of a shell
Shell is made from silica sand with a resin binder
Two shells are held together and brokered when the final part is solidified
Superior surface finish and good dimensional accuracy are advantages of this process over sand casting
Can be used for a wider range of alloys with greater die design flexibility than die-casting and lower cost than investment casting process
Secondary machining operations are often not required, and casting cracks are minimized by mold collapsibility
Process can be mechanized for mass production
Limitations include high equipment and pattern cost, low part size, and formation of noxious fumes that must be extracted
Shell mold casting process is characterized by low capital outlay on sand preparation plant, good space utilization, low sand-metal ratio, and lower cleaning costs