Amann Girrbach argovent 2 Mode D'emploi page 38

F R E Q U E N T L Y A S K E D Q U E S T I O N S ( F A Q )
Questions on the gas pressure and the gas
retort
E N
Question: May the gas pressure be increased at
the gas fittings in order to achieve lower oxide
results?
Answer: To facilitate oxide-free results, the gas
pressure during sintering may be adjusted
between 1.5 bar and 2.0 bar. A higher gas pressure
leads to a higher argon consumption.
Question: What needs to be observed when
assembling the components?
Answer: Pay attention to clean sealing surfaces.
Due to possible residual dusts/deposits on the cir-
cumferential sealing surfaces, tolerances in the
oxidation result can occur.
Questions on the float sintering disc
Question: Why does the sintering result increas-
ingly worsen when frequent, consecutive float sin-
tering runs are performed?
Answer: The best protective-gas coverage with
the highest argon concentration is achieved when
sintering with a pearls and powder mixture. For
sintering runs only on the float sintering disc with-
out pearls, the protective-gas coverage is lowest,
yet sufficient. Frequent switching between float
sintering and pearl sintering benefits a most uni-
form, oxide-free result of both procedures, and is
therefore recommended.
Question: What if the separating disc would be
used for float sintering instead of the float sinter-
ing disc?
Answer: The separating disc may not be used as
float sintering disc, as is does not have a ground
(smooth polished) surface.
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Question: What can be done against selective
burn-in spots on the surface of the float sintering
disc, which can no longer be removed with normal
polish?
Answer: Selective burn-in spots, for example, can
be polished out using a rubber roller for zirconium
oxide. This does not influence the flatness of the
plate.
Question: Does the separating disc always have
to be below the float sintering disc when the sin-
tering height is not sufficient?
Answer: The separating disc with a minor amount
of pearls and powder benefits the result of the
float sintering. When more height is required, the
float sintering disc can also be placed on the bowl
bottom by itself. It separates the frame from the
bowl bottom. With this procedure, a somewhat
increased oxidation can occur.
General sintering tips
_ For large-span work, never connect all
crowns/pontics with connectors to the stabi-
liser. Connecting each second connector alter-
nately and symmetrically is sufficient. Always
connect end parts.
Recommended connector strength:
rear 3.0 mm, centre 2.5 mm, front 2.0 mm.
Otherwise, too many strong connectors at the
frames often generate too high tensile stress,
resulting in frame distortion. The crowns lift off
of the float sintering disc and the bridge may
warp.
_ Normal bridges from 3 units on can also be sin-
tered with several sintering pearls on the float
sintering disc, without additionally attached sta-
bilisers, in the case that even a deep pearl
embedding is not sufficient as support (for
heavy pontics next to thin-walled crowns, etc.).