Ivoclar Vivadent IPS d.SIGN - Manual (Page 29)

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... and the properties of the alloy used.
The frameworks are contoured according to the static requirements…
Finishing the metal framework
The cast metal framework is finished using tungsten carbide
metal burs or ceramic-bonded grinding instruments. The
marginal area of the framework is reduced up to the inner
edge of the chamfer or shoulder preparation (labial or
circular) to make room for the ceramic shoulder. Contouring
The framework reflects the reduced anatomical tooth shape
(see 'Functional support of the veneering ceramic' on page
24). In this way, the ceramic material may be applied in even
layers and is adequately supported. For that purpose, the
properties of the different alloys (e.g. firing stability) must be
taken into consideration.
– Use reduced pressure when working with softer
alloys.
– Work in one direction only to avoid overlapping and
inclusions in the metal surface.
– Do not use diamond grinding instruments. Diamond
particles may be trapped in the alloy and cause bubbles
in the ceramic material during firing.
– Undersized metal frameworks result in increased
shrinkage of the veneering ceramic and require
additional corrective firings.
– If the metal framework is too small, the veneering
ceramic is not adequately supported, which may lead to
cracks and delamination, particularly in very thick ceramic
layers.
... or ceramic-bonded grinding instruments.
Cast metal frameworks are finished using tungsten carbide metal burs…