Aftercompleting the process of casting, the pattern can be molded and formed successfully.However, the pattern has three types of defects. Thefirst one is rough surface finish that is caused by four factors such as thetypes of sand, the properties of sand (dry or moist) and the sand is not packedtight enough in the metal box that effects the surface of pattern. Also, permeabilityis another factor that cause the rough surface finish. For example, if thepermeability level is too high, the mold metal may penetrate the boundary wallof the mold and mix with the sand grains which are along with the casting moldwall. Consequently, the area of mixing sand grains and mold metal will become arough surface finish.Anothertype 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 saidthat the Pits are the outcome of poor porosity. The pits are caused by gasseswhich floating at the top surface of the pattern during melting.
Thelast type of defect on the pattern is Porosity (pinholes that go through thewall of the casting). Generally, porosity is caused by dissolved gas escapingand the process of gas formation and solidification during casting. For example,if the level of moisture is too high, the molten metal may transform themoisture to liquid or stream and cause porosity in the pattern. This type ofdefect can be seen as small holes on the surface of the pattern. 2) How couldyou improve the lab handout or casting activity?Inmy opinion, the lab handout and casting activity are already well organized.
The activity is interesting and amazing as we can learn and practice theprocess of casting. The best thing is that the activity is like a groupactivity but we perform the casting by individual. We can learn deeply andeffectively. Honestly, so far, I have nocomment to improve the Lab 2 since we learned well and acquired the processcasting.