Page 80 - My FlipBook
P. 80
:
form and rubbing it over tlie model. The ring which acts as a matrix dur-
ing the process of casting the model so shapes its base that no further
investing is required for swaging (Fig. 88 B and C).
The best soft plungers for swaging matrices into models are made
of velum rubber, and these are so constructed that they press the foil from
the center of the cavity to the margins (Fig. 89). They are constructed
by forcing a piece of plastic modeling compound through the cylinder
Fig. 88.
Fig. 89. Fig. 90.
of the swaging device with the metal plunger. The end that conforms
to the face of the plunger remains unchanged while the opposite end is
carved to any desired form. The modeling composition is then invested
in plaster of Paris so that a mould will be constructed in two sections.
After the modeling composition has been removed the mould is filled with
velum rubber and vulcanized at a temperature of 310° F. for ninety
minutes.
The technique of constructing a matrix by
swaging it into the model of the cavity is as follows
Swagina matrices
Invest the model in the ring of the swaging device in
In eavitv models.
modeling composition so that the center of the cavity
is equidistant from the periphery (Fig. 88 A). An-
form and rubbing it over tlie model. The ring which acts as a matrix dur-
ing the process of casting the model so shapes its base that no further
investing is required for swaging (Fig. 88 B and C).
The best soft plungers for swaging matrices into models are made
of velum rubber, and these are so constructed that they press the foil from
the center of the cavity to the margins (Fig. 89). They are constructed
by forcing a piece of plastic modeling compound through the cylinder
Fig. 88.
Fig. 89. Fig. 90.
of the swaging device with the metal plunger. The end that conforms
to the face of the plunger remains unchanged while the opposite end is
carved to any desired form. The modeling composition is then invested
in plaster of Paris so that a mould will be constructed in two sections.
After the modeling composition has been removed the mould is filled with
velum rubber and vulcanized at a temperature of 310° F. for ninety
minutes.
The technique of constructing a matrix by
swaging it into the model of the cavity is as follows
Swagina matrices
Invest the model in the ring of the swaging device in
In eavitv models.
modeling composition so that the center of the cavity
is equidistant from the periphery (Fig. 88 A). An-
