Report On The Manufacturing Process Step
Based on the product which is the flag’s stand base, we redesigned the early manufacturing
process from welding process to the lost foam casting process. Theprocess of lost foam are
1) The formation of foam pattern
7) Extract pattern from flask
1) The formation of foam pattern.
The pattern is made from expanded polystyrene foam. Since the pattern’s geometry of
flag base is simple, so it can be cut using a hot-wire foam cutter. The size of the pattern
must be exactly same with the size of actual product. These polystyrene is suitable to
make for any geometry of pattern.
For clustering process, the individual patterns need to be attached to the gating system.
Number of patterns per sprue is dependent on part size and/ or configuration.
Next, the foam cluster is coated with ceramic investment, also known as the refractory
coating, via dipping, brushing, spraying or flow coating. Coating parameters are verified
before coating cluster. Coating is mixed continously to maintain properties. This coating
creates a barrier between the smooth foam surfaces and the coarse sand surface.
Secondly, it controls permeability, which it can allows the gas created by the vaporized
foam pattern to escape through the coating and into the sand. Controlling permeability is
a step to avoid sand erosion. Lastly, it can forms a barrier so that molten metal does not
penetrate or cause sand erosion during pouring of aluminium.
4) Drying/dry coating
To ensure the coat is dried, so the coated pattern is placed in an oven at temperature range
of 49 – 60 °C for 3 to 5 hours.
After the coating dries, the cluster is placed into a flask or mold and fill the flask with the
un-bounded sand. The sand is then compacted using a vibration table if we use machine,
but since the process is done manually, the compaction can be forced by using a clamp.
The pattern cluster must be totally surrounded and structurally supported by sand without
being distorted or causing dimensional changes.bSand fill and compaction are important
keys to success of the process and must not be taken lightly.
Before casting, the aluminium used was melt until the temperature reach around 600 °C –
650 °C. After the aluminium is melt, pour it into the polystyrene pattern through the
sprue. The pouring process must be done quickly and carefully to avoid the temperature
droped of melted aluminium. The high temperature of melted aluminium will vaporize
the foam polystyrene and perfectly reproduced the shape of pattern. Gases formed from
the vaporized pattern permeate through the coating on the pattern, the sand and finally
through the flask. Any leftover product from the vaporized polystyrene material is
absorbed into the molding sand.Lastly the casting solidifies in the sand mold.
Casting is allowed to cool in sand for the some period. When the cast is cool already, the
mold is dumped out and the cluster product is taken out. The loose sand and coating can
be removed. The sprue are removed. For finishing, trim the sprue and aluminium residue
around the flag base with machine.
The most important environmental impacts during the casting are the large use of energy
and all kinds of emissions and dust. The lost foam casting has the advantages of reduction
in capital investment and operating costs, cores ara not required, and the most important
is no binders or other additives are required for the sand which is reusable are one of the
important environmental impacts that never found on the other type of casting process.
Besides, due to the extra energy required to vaporize the polystyrene, there will be a large
thermal gradient present at the metal-pattern interface as the casting is being poured. At
the same time, there will reduced the wasted of energy release to the environment.
This process is advantageous for relatively complex shapes or castings that would
normally require coring. It is also very dimensionally accurate, maintains a good surface
finish, requires no draft and has no parting or join lines. As a result there is no flash and
so very little fettling is required.
Lastly, this process also suitable to be known as sustainable process because the lost
foam casting process can be known as environmentally advantageous process due to the
long tool life which is the dry sand is reusable.