completing the process of casting, the pattern can be molded and formed successfully.
However, the pattern has three types of defects.
first one is rough surface finish that is caused by four factors such as the
types of sand, the properties of sand (dry or moist) and the sand is not packed
tight enough in the metal box that effects the surface of pattern. Also, permeability
is another factor that cause the rough surface finish. For example, if the
permeability level is too high, the mold metal may penetrate the boundary wall
of the mold and mix with the sand grains which are along with the casting mold
wall. Consequently, the area of mixing sand grains and mold metal will become a
rough surface finish.
type of defect on the pattern is pits (defects on the surface of the casting). Naturally,
the pits and porosity are related to each other. In other word, it can be said
that the Pits are the outcome of poor porosity. The pits are caused by gasses
which floating at the top surface of the pattern during melting.
last type of defect on the pattern is Porosity (pinholes that go through the
wall of the casting). Generally, porosity is caused by dissolved gas escaping
and the process of gas formation and solidification during casting. For example,
if the level of moisture is too high, the molten metal may transform the
moisture to liquid or stream and cause porosity in the pattern. This type of
defect can be seen as small holes on the surface of the pattern.
2) How could
you improve the lab handout or casting activity?
my opinion, the lab handout and casting activity are already well organized.
The activity is interesting and amazing as we can learn and practice the
process of casting. The best thing is that the activity is like a group
activity but we perform the casting by individual. We can learn deeply and
effectively. Honestly, so far, I have no
comment to improve the Lab 2 since we learned well and acquired the process