Casting Lab

Objective

Observation of the procedure and basic elements of the lost foam sand casting process.

Results

Object..................................Styrofoam Dimensions......................After Metal has Cooled

Large Balls..........................Diameter of 1.42"...............................1.39"

Small Balls..........................Diameter of 1.00"............................... 0.95"

Heart..................................w=5.9",h=5.82".................................w=5.7", h=5.3"

Square Thing........………..Bottom=1.9" x 1.9" x 1.9"……..Bottom=1.89" x1.88"x

……………………………………………………………….………..not measurable

...........................................Top=1.9" x1.9" x 1"……………….Top=not measurable

"h" with Thin Section ........h=2.28" wt=1.08.............................h=2.26" wt=1.10"

......................................….ht=.59" hb=.59"............................ht=.59" hb=.657"

......................................….web=.14" wb=.95"........................web=.14" wb=1.06"

Discussion of Results

The casting process in this particular lab consisted of making bronze castings with a lost foam casting procedure. The first step is to make styrofoam molds of the desired object. Included in this is providing for runners, sprues, and risers necessary for the entrance and distribution of the molten metal. After the molds are made, the mold packing sand must be mixed. This consists of adding small amounts of water to fine silica sand and mixing it until the sand is of the correct moisture and consistency for casting purposes. The sand is then packed into a container large enough to enclose the mold. With about a one inch floor of sand, the mold is placed into the container and covered with more packed sand. When the mold is covered so that only the top of the riser is visible, the sand is formed into a cone shape such that the molten metal will be funneled into the riser.

We made five objects out of foam that we used for the lab analysis. The first was a series of large balls (diameter - 1.42") connected end to end. The second was a series of smaller balls (diameter - 1.00") connected in the same way. The third object was a heart-shaped solid rod with an overall width of 5.9" and a length of 5.82". We also made a cubical object with side dimensions of about 2". The last object we made was a "C" shape with a thin walled web in the center. As can be seen from the data, the general trend was for the dimensions to shrink on the actual casting. As the molten bronze evaporates the foam and fills the cavity, the bronze then cools and shrinks in the process.

There were several varying parameters that we attempted to experiment with. In the series of balls, we wanted to see what the effect of having one runner had on the end product. We found that the bronze filled the cavity fairly well. On one of them, the metal was poured in with a slight hesitation. The evidence of this is clearly visible by examining the casting. There is definite parting line where the molten metal filled in the cavity where the cooling metal stopped. The heart was another demonstration of the effect of having only one runner. The results were even more pronounced with this one. The effect was similar to a short-shot in molding. Only a little more than half of the cavity was filled with bronze. The "C" shaped object was intended to show how a thin walled section would cast. The results showed us that it worked very well.