Sand complexity like a car engine. Apparatus/Tools 1. Casting

Sand Casting   

Sand casting
is a process of casting a desired shape with sand as the molding material. The
term sand casting often refers to the product of the casting process and may
not be confused in places. This process is used to produce parts of machinery
of commercial use (lathe, miller).

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The process
of sand casting can be used to produce hollow objects with a desired cavity and
even objects of increased complexity like a car engine.

Apparatus/Tools

1.      Casting
Flask

The casting flask is a two-part box that serves as the
holder for the sand while the molten metal is poured into the cavity.

The two parts include:

                                
i.           
Cope

Cope
is the top part of the flask which sits right on top of the drag and is the
area where the shape of riser, gate, holes are made.

                              
ii.           
Drag

Drag
is the lower part of the flask. It is the part where the major cavity of the
mold exists

2.      Foundry
Sieve

Foundry sieve is used to filter the sand from
impurities.

3.      Rammer

The rammer is used to ram the sand in the flask so
that the sand packs together perfectly. This also helps in the finishing touch
of the casting.

4.      Vent rod

Vent rod is used to create holes in the mold so that
the gases in excess can escape when the metal is poured into the mold.

5.      Lifter

Lifter is used to lift the pattern from the mold once
the sand has set.

6.      Draw spike

Serves as the same function as the lifter except that
for this you need to create a hole in the pattern to lift it

7.      Trowel

Trowel is used to lift the sand and pour it into the
flask

8.      Slicks

Are used to create the shape of the riser and runner.

9.      Tong

Is used to lift the container of molten metal and pour
it in the mold.

Many more tools can be used in the process but for the sake
of simplicity the number will be kept slim.

Procedure

1.      Start by
mixing the sand mixture. The sand in our lab was molasses sand. Molasses helps
the sand to be in the desired shape and also stick so that it does not fall
apart like a house of cards.

2.      Put the
drag upside down and the pattern upside in it. Apply parting sand so that the
molasses sand does not stick to the pattern and the ground.

3.      Fill the
drag with sand. Use a rammer where necessary to compress the sand. When done
even the sand with a pipe.

4.      Turn the
drag upside down so that now it faces the right way up. Pot cope above it and
apply a second layer of parting sand. Leave holes for the riser and runner
using pipes and then pour more sand over it and even it using a pipe.

5.      Remove the
pipes and lift the cope and put it on the side. Make the gating system so that
the metal actually reaches the mold cavity. Now remove the pattern with the
help of a lifter and if necessary use a tapping stick.

6.      Time to
melt the metal. Take some scrap metal and melt it in a crucible in a furnace.
Once done use a lifter to pour the metal in the mold.

7.      Wait for
the metal to settle down then break the mold but be careful not to touch the
casting as it will still be hot. Take a poker and use it to clean the mold of
sand and then pour water over it to cool it down.

8.      The casting
will still need some finishing to look presentable. Do filing and polishing of
the casting.

 

 

 

 

Casting
Defects

Many defects can be produced during the casting process. The
most common of them being

1.      Cold shuts

2.      Misrun

3.      Cold shots

4.      Shrinkage
Cavity

Diagrams