Laboratory # 6
Aluminum Sand Casting
Time of Presentation 2:00pm 12/11/98
Final product was turned in to Dr.Salimian
Sand casting, and indeed metal casting I one of the worlds oldest
form of manufacturing, it dates as far back as 4000 BC . Sand molds are
good examples of expendable mold, they generally provides an economical or
cost effective means of producing most parts because the sand can be
broken up and reused. Apart from being cost effective, sand casting
enables the manufacture of products with intricate parts. There is no
limit to size , shape or weight of the products manufactured
By sand casting. " Typical cast products are engine blocks, crankshaft,
piston, valves , railroad wheels
And ornamental artifacts." ( Kalpakijain 262) Also, in spite of the
impacting manufacturing processes today. Kalpakijian identified two
trends that are presently having a large impact on the casting
Industry. One is the fact that the casting industry is continuously
undergoing mechanization and automation of the casting process. This
trend has resulted in the use of advance machinery and automated process
control to replace the traditional methods of casting. The second trend
The industry is the continuous improvement of the quality of casting
resulting in product with
Very close tolerance.
For this laboratory project, we are required to cast on aluminum
dog using a sand mold ( Sand casting). To achieve the desired result, we
made an impression in the sand using the pattern with
Similar shape and dimension of the required product. After the making of
the mold, the aluminum
Was melted and poured into the mold via the sprue. The molten metal was
left to sodifiy and the product removed by breaking the sand mold. This
is the typical procedure that is adhered to in all metal casting process.
The design philosophy for this lab takes into consideration that
the design should not only serve the function, but must also have the
ability to facilitate or favor the casting process. This is especially
important due to the fact that the castings have work hardened surface and
cause significant tool wear in post cast machining. After selecting a
pattern (the dog), it must be evaluated; noting the size and shape, the
contours, and overall appearance of the metal piece. These observations
play a critical role in deciding where to create sprues, runners, and
in-gates. The size of the drag and cope was not big enough to allow much
room to "play" with. Therefore, we decided to place the pattern in a
slanted orientation. This is to ensure that the molten metal has more
room to flow evenly into the cavity. We decided to create the sprue at
the bottom, flat base of our pattern. This is a good starting position
for the molten metal to be poured. We noticed that the chosen pattern had
a great deal of detailed lines. So, the sand must be firmly rammed. We
also noticed that the pattern did not come in two halves, but had a small
depression shape at the bottom. So when the drag is turned upside down,
there is no match for the lower half. We also knew when filling the cope
with sand, we must not ram too firmly otherwise the pattern on the bottom
will be destroyed.
THEORY AND CALCULATIONS
Sand casting is an art form. It is a form of expression that is
simple and effective in itself. It is the casting of material into molds
made in sand, with the intention of having the casting itself pick up a
layer of sand on the surface. In sand casting, one achieves an object,
when viewed from different angles to reflect many different things.
Practically anything can be used to make an impression. Ordinary kitchen
tools, objects around the house, even rocks can be used in some kind of
casting. The objects made by this process are used in various manners.
Wall plaques are the most popular, but there is no reason why other things
of more useful purposes are not possible.
As stated earlier, the project involved a sand mold to make an
1. First task was the making of the sand mold required for the casting
2. To accomplish this sand mold making process, synthetic sands were used
to make the drag and the
Cope. The process of making the drag part of the mold involved the use of
a wooden plane board, a flask and a parting powder.
3. The parting powder is uniformly distributed over plane board,
4. The half part of the pattern is placed on top of the board and the
uniform distribution of the parting
powder over the wooden plane is repeated.
5. After the board is uniformly sprayed with the parting powder, the
synthetic sand is in like manner
Distributed over the surface of the board and half of the pattern
6. The Sand is about half of inch high up the drag, the sand is
compacted by pressing on it with a flat
wooden material. The uniform sand spraying then continue with the
repetition of the compacting
process at every half or one inch increment of the sand height.
7. The Process continues until the entire drag flask is filled with sand.
8. After the drag is made, it is turned upside down and the second half of
the pattern is placed on top of
the drag half.
9. The sprue and open riser pattern are pushed about one quarter of an
inch inside the drag to ensure
rigidity of the pattern.
10. After positioning the sprue and the open riser, the flask for the cope
is placed on top of the drag and
parting powder once again sprayed uniformly over the pattern and
the inserts for the sprue and
11. The cope is then sand filled the same way as the drag, After sand
filling cope, an area around the top of the sprue and open riser inserts
were caved out ot facilitate the removal of these inserts.
12. After the removal of the sprue and open riser inserts, the plane
wooden board is used to cover the
Exposed surface, then the cope is turned upside down to expose the side
with the pattern
13. The two channels are made one from the sprue position to the pattern
and the other from the open
Riser position to the pattern.This will enable the flow of molten metal
from the sprue to the mold and out through the open riser.
14. With the aid of the screw, the patterns are removed both from the
drag and the cope leaving behind
the mold cavity.
14. The cope is placed on top of the drag such that the two cavities are
in contact with each other.
15. Now the mold is ready for pouring of the molten aluminum metal.
16. The molten aluminum which has been in the furnace prior to this time
is now poured down the basin in the mold cavity.
17. About three to five minutes after the pouring, the sand mold is broken
and the casting removed.
18. The casting was cooled for 5 min in water.
19. The sprue and the open riser were hatched sawing off and edges were
smoothed with a file.
This experiment used Analytical theory of sand casting is produced
when molten metal is poured at atmospheric pressure into a cavity formed
in a compacted molding sand. In typical
Ferrous casting, the mold would be bonded with 6 to 8 percent western
bentonite mulled with
2 to 3 percent water. Patterns would be reusable, but the sand molds
would be broken from the casting after the solidified casting had cooled
sufficiently. The sand would be returned to the muller for recycling by
mulling with some new clay and water to reactivate the old clay. Sand
the external geometry of a casting, whereas cores define the interior or
Sand casting accounts for more than 90 percent of all metal
poured, on a tonnage basis. It can be an extremely high production process
.The process requires a high investment in plan facilities and sand
handling equipment to make such production rates possible ( they hire
Morgan state Industrial engineering ) . Sand casting is versatile and is
capable of making parts ranging from small knobs to huge radiotelescope
bases weighing more than 200,000 lbs.
Discussion of Corrections and Results
After the removal of the aluminum product from the mold, it was
analyze for errors and defects
. A drawing of the final product is was present in the presentation. Some
of the major defects observed
on the casting include metallic projections, cavities and incomplete
casting. The metallic projections were more prominent at the parting line
sections of the casting. They were produced because
the drage and the cope were not tightly closed together, therefore some
molten metals escaped
from the parting line and soldified to form metallic projection on the
casting. Example of metallic
projections, cavities were also noticed on the casting. Both external and
internal cavities such
as blowholes and pinholes respectively were observed on the casting. An
example of the blowhole
is seen on one side of the casting and an example of a pinhole occurred at
the bottom or base of the product. These cavities must have resulted
form defect in the sand mold. A third type of defect
not noticed on the product as incomplete runs which resulted from the
premature cooling of the metal
before it reached the end of the mold cavity. These misruns are attributed
to slow pouring speed and not insufficiency of the molten metals since
there was enough molten metal left over after the pouring.
Although we encountered some problems in the course of the
laboratory project , further
Analysis of the aluminum casting showed that it was dimensionally
consistent with the required product. Some of the problem encountered
included the breaking off of the some tips of the sand
Mold during the process of removing the pattern. This problem was
corrected by patching the affected area with synthetic sand. The surface
finish was excellent.
After receiving the final product, there were a few imperfections.
Firstly, the surface of the pattern had several small holes. This is
known as macroporosity, which may be amplified by the evolution of gas
before and during solidification. Ventilation holes should have been made
in the cope and drag to allow circulation of airflow. Secondly, much more
emphasis was placed on the ramming process instead of creating runners and
in-gates which would allow a more continuous, uniform flow of molten metal
into the mold cavity without turbulence. Also, ramming excessively
(especially in the drag) caused the pattern to stiffen in the sand and
made removal difficult; another sprue had to be created near the head of
the pattern. Parts of the pattern that was disturbed and did not quite
match the original. However, thorough ramming made the detailed lines and
shapes appear clearly.
The overall process was shown to be effective, yet time consuming.
Ramming the sand took the greatest amount of time and effort. Automated
process would improve efficiency and quality of castings, and may reduce
the amount of defects. Also, the removal of the gates, runners, and
risers is better automated to produce high surface quality. By using the
hacksaw and file, the surface quality is reduced; its finish is not as
smooth as the original. Eventhough, the permeability* of the sand was
good, it was not excellent. There was a lot of moisture content present
in the sand. Safety factors played an important role in this laboratory
exercise. Especially when removing the cast from the sand, the metal is
still extremely hot (the instructor performed the actual pouring of the
metal into each mold).
Tooling lead time is long Facilitates complex shapes
Tooling cost is high Allows hollow parts
Design changes are costly and time-consuming Allows use of hard
Reduces material waste
* The ability of the molding sand to allow gases to pass through
El Wakil, Sherif. Processes and Design for Manufacturing: Second Edition;
Publishing Company, Boston; 1998.