Casting Flashcards
What is the gate on a casting mold?
an opening that allows molten metal to enter the mold cavity and shape the final product
Foundry sand is really a mixture of what two components?
Sand and Clay
What are the most common clays used in Foundry sand?
Bentonite and Fire Clay
What type of sand is usually used for aluminium casting? (in combination with clay)
Silica Sand
What is ‘Tempering’ foundry sand?
The process of adding an appropriate amount of water, for natural
bonded sands or oil for synthetic sands to allow the clay to hold the grains of sand together.
What are the 5 basic steps to sand casting? (simplified)
- Prepare the Mould
a) Make the Pattern
b) Make the mould cavity
2) Prepare material for casting
3) Pour metal into mould: metal of proper temperature is introduced rapidly so the sprue is kept full.
4) Metal is allowed to solidify.
5) Mould is broken up to remove the casting, and sand is reclaimed for reuse
What is the riser base on a casting mold?
vertical channels that provide a continuous flow of molten metal to eliminate shrinkage as solidification occurs during the casting process
What is the runner on a casting mold?
connected channels that convey the molten metal to different parts of the mold.
What is the sprue on a casting mold?
a channel through which molten metal is poured into the mold
What is the core on a casting mold?
a pre-formed insert that shapes the inside of a casting. Cores are often used to create cavities or hollow sections in a casting
What is the parting line on a casting mold?
the border line between the two halves of the mold
What are saw kerfs used for?
Helps to remove waste stock
Helps to create irregular contour
What is a shrink rule?
a scaled ruler used to account for dimensional changes in a casting as it cools. The shrink rule’s divisions are larger than a standard ruler to account for shrinkage allowance.
How large should the runner be if it is a 1 runner mold?
4 times the size of the choke
How large should the runner be if it is a 2 runner mold?
2 times the size of the choke
What are the 4 characteristics Foundry Sand must exhibit?
- Permeability - to allow gasses produced during pouring of molten metal to pass or vent through the mold. Permeability is inversely related to the percentage of clay content.
- Green Compressive Strength - the structural integrity of the sand grains held together by the clay. This determines how the mold will withstand handling and the forces of molten metal entering the mold cavity. Green Compressive Strength is directly related to the percentage of clay content and moisture.
- Dry Strength - upon contact with molten metal the mold dries rapidly. The sand must resist the forces of the metal to prevent erosion, cracking, and other deterioration of the mold cavity.
- Flowability - the ability to conform to the shape of the pattern as the mold is made. This is governed by the size and shape of sand grains and clay content.
________ a process which mixes the sand and clay with a heavy roller with a kneading action.
_________ helps maintain high green compressive
strength.
Mulling
What is a swab and what is it used for?
a small brush with long hemp fibers used to moisten the sand around the edge of a mold before removing the pattern.
