Engineering Studies
Home > Engineering Studies > Personal and Public Transport > Forming processes - sand casting
Engineering materials
Forming processes – sand casting
This unit addresses aspects of the following syllabus outcomes:
Outcomes:
H1.2 differentiates between properties of materials and justifies the selection of materials, components and processing in engineering.
H2.1 determines suitable properties, uses and applications of materials in engineering
Source: Board of Studies (1999) Stage 6 engineering studies syllabus preliminary and HSC courses. Sydney, Board of Studies
This unit covers the process of sand casting for producing components from raw metallic materials. Other metal casting methods include gravity die casting and pressure die casting.
Sand Casting
Introduction
Sand casting is used to make large parts (typically from iron, but also from bronze, brass and aluminium alloys). In sand casting molten metal is poured into a mould cavity formed out of sand (natural or synthetic). The processes of sand casting are discussed in this section, include patterns, sprues and runners as well as design considerations.
Activity 1
Visit the web site efunda
engineering fundamentals 
website, select sand casting and locate
the necessary information to complete the following statements.
The cavity in the sand is formed by using a ______________ (an approximate duplicate of the real part), which are typically made out of _________, sometimes _________.
The cavity is contained in an aggregate housed in a box called the ___________.
A __________ is a sand shape inserted into the mould to produce the internal features of the part such as _________ or __________________. Cores are placed in the cavity to form holes of the desired shapes. A core print is the region added to the pattern, core, or mould that is used to locate and support the core within the mould. A ____________ is an extra void created in the mould to contain excessive _____________________. The purpose of this is to feed the molten metal to the mould cavity as the molten metal solidifies and shrinks, and thereby prevents ____________ in the main casting.
Source: Efunda Engineering fundamentals http://www.efunda.com
Activity 2
Use the diagram below and the efunda
engineering fundamentals web site to insert the missing terms in the following statement.
The Moulding Process:
In a two-part mould, which is typical of
sand castings, the upper half, including the top half of the pattern, flask,
and core is called ____________ and the lower half is called ___________.
The parting line or the parting surface is ___________ or ____________ that separates the cope and drag.
The drag is first filled partially with _____________, and the core print, the cores, and the gating system are placed near the ___________________.
The cope is then assembled to the drag, and the ___________ is poured on the _____________, covering the ____________, core and the _____________________.
The sand is compacted by _______________ and ________________________.
Next, the cope is removed from the ____________, and the ___________________ is carefully removed.
The object is to remove the pattern without __________________ the _______________. This is facilitated by designing a draft, a slight angular offset from the vertical to the vertical surfaces of the pattern. This is usually a minimum of _________________, whichever is greater.
The _______________ the surface of the pattern, the more the ______________ to be provided.
Source: Efunda Engineering fundamentals http://www.efunda.com
Activity 3
Visit the web site efunda
engineering fundamentals to research answers for the following questions:
- Name the part of the gating system, which supplies the molten material to the mould cavity.
- Name the following:
- The vertical part of the gating system connected to the pouring cup.
- The horizontal part of the gating system connected to the pouring cup.
- The extensions to the gating system. What do these do?
- Describe what size the cavity is made and why this is done. Describe how this is achieved.
- Describe how shrinkage is managed.
- What sort of surface finish results from a sand casting and what is done to deal with surface impurities, which may occur as a result of the casting process?
Design Considerations:
Activity 4
Use the web site efunda
engineering fundamentals to indicate some simple design considerations which
could be implemented when sand casting.
|