|
Lawton Pattern's
ability to manufacture patterns with varying degrees of function
and cost affords the opportunity to analyze alternative molding
processes to determine if greater value can be afforded to our customers.
By partnering with several different alliances, we have the capability
to analyze the possible value opportunities afforded by the lost
foam, foam cast, full mold, and foam mold processes.
|
Lost
Foam
Lost
foam is considered by many to be the process of the future.
While currently being utilized by some organizations, it is
our opinion that it's full potential is not being realized.
The lost foam process involves:
- Molding
foam shapes that are direct replicas of your desired parts.
- Coating
the shape with a thin layer of ceramic coating.
- Embedding
the foam shape in dry unbound vibrated sand
- Pouring
metal into the mold dissipating and replacing the foam shape.
|
 |
Two of the major
benefits of the lost foam process are part integration and near
net shapes. While the traditional world of lost foam is capable
of fitting parts into a 32" cube, Lawton is be able to go beyond
that and deal with iron and aluminum parts that fit into a 48" X
96" flask. This would equate to up to 500 lbs. in aluminum and up
to 1500 lbs. in iron.
The value afforded
from the lost foam process is enhanced by our capability to cut
foam shapes accurately and expeditiously, saving our customers enormous
amounts of time and money compared to traditional methods by which
high cost aluminum tooling is initially created.
 |
Foam
Cast
Foam cast
is a process similar to investment casting. Foam patterns
are coated with a ceramic shell then the foam is dissipated
from the shell in a high temperature oven. The foam cast process
is an offshoot of the lost foam process, which is incompatible
with steel or high carbon metals due to the carbon content
in the polystyrene (plastic). The process typically focuses
on small, intricate shapes that fit within a 32" cube. Lawton
is constantly pushing the envelope on this and to date we
have been able to pour stainless steal castings weighing as
much as 2000 lbs., fitting in a 60" cube.
|
While a more
complex and costly process than Lost Foam, there are many advantages
that are derived from the foam cast process. These advantages include:
- Part integration
- Complex shape
friendly
- More near
net size
- Higher ductile
modularity
- Thinner wall
castings
|
Foam
Molding
Foam molding
is a process used almost exclusively in a no-bake (chemically
bonded sand) system primarily for medium (100 lb.) to large
(100 ton) complex castings that require some level of core assistance.
Lawton Pattern is capable of building a foam pattern very similar
to a no-bake production pattern. Typically there are far less
core boxes required as much of the foam is physically removed
from the mold without damaging the mold. With this advantage,
back draft and cored areas need not be omitted from the pattern
via loose pieces and core boxes. |
 |
The foam molded
pattern pictured to the right is that of a transmission made of
foam painted with a latex paint and then converted with a release
agent to enhance removal from the mold. Typically these are "one
shot" patterns that can be manufactured at 25% to 75% of the cost
of wood tooling with similar delivery benefits.
 |
Full
Mold
Full mold
patterns are typically large non-complex shapes as depicted
in the picture to the left. The pattern is gated, coated,
and encapsulated in no-bake sand. Metal is poured into the
mold and the foam is dissipated. Again, this is a "one shot"
pattern requiring no core boxes.
Castings
weighing near 100 tons have been poured in this process with
typically a 50% to 75% savings in pattern cost and time.
|
Some typical
castings poured in this process are mill heads, counter weights,
forming dies, plenums, cylinders, machine beds, large gearing, etc.
|
