CPT International 04/2017

PRESSURE DIE CASTING
with conventional equipment could
achieve,” Schlotterbeck points out.
The desired target was a wall thickness
of 0.15 mm. The main focus, however,
was the question of how far one
could approach this level with the
conventional possibilities of a normal
die-casting foundry. For this reason,
a standard high-tech W80 Zn-RC
hot-chamber machine was used for the
casting experiments at the Frech Technical
Center (Figure 2). This had the
complete standard equipment without
any special accessories. The alloy
used for the experiments was commercially
available ZL 5, and HF alloy was
also used for comparative purposes. No
vacuum support was used. Instead, a
passive venting system with a double
‘scrubbing board’ – made of steel and
not CuBe – was selected. A 15-year-old
modular training mold was used for
the experiments, with wall thicknesses
of 0.28 mm, 0.2 mm and 0.15 mm.
With appropriate operation it was possible
to achieve different wall thicknesses
with this whilst also testing the
effects of different casting channel and
gating systems, cross-sections and ventilation.
The mold’s tempering channels were
designed according to conventional
calculation rules. A heating/cooling
Figure 3: Bright chromium-plated dish made of die-cast zinc alloy ZL 5 with a wall
thickness of just 0.2 mm.
system for magnesium that could attain
media temperatures of up to 300 °C
was used in order to be able to achieve
higher mold temperatures for particular
experiments. A variety of mold inserts
was used or ‘readjusted’ for the
various wall thicknesses. Due to positional
tolerances, the limit was already
reached at 0.2 mm with this mold: values
of between 0.13 and 0.22 mm were
measured during the experiments with
this casting wall thickness. These differences
in wall thickness were adapted
using subsequent machining.
Results
“A total of 25 series of experiments
were carried out with this equipment,”
Schlotterbeck explains. The main process
parameters – such as pressure, pis-
Figure 4: Comparison between two dishes made of zinc alloys ZL 5 and HF alloy,
HF alloy
Figure 5: The mold: The double ‘scrubbing
board’ for passive venting is at the
top. The insert for a fan-shaped gate is
below.
20 Casting Plant & Technology 4 / 2017