Vacuum Casting

[SRD-Series] [SRD i-Series] [ECS-Series] [HT-Series] [On-The-Fly Degassers] [Batch Degassing Tanks] [Curative Melters] [Urethane Casting] [Resin Transfer Molding] [Vacuum Potting & Encapsulating] [Vacuum Chambers]

Manual to Continuous Flow-Through
Vacuum Potting and Vacuum Encapsulation Systems

Dispense air-free, accurately metered, mixed and dispensed
epoxies and urethanes into APT vacuum chambers for
superior penetration and void-free vacuum cast parts.

Vacuum-potted components ranging in size from automotive ignition coils to large MRI body-
imaging coils often require air-bubble and void-free penetration of the mixed epoxy—around
every turn of wire and under hard-to-reach overhanging ledges.

When connected to one of our ECS-Series or HT-Series metering, mixing and dispensing
machines, our complete vacuum potting and encapsulating systems are equipped to precisely
control your formulation’s ratio, shot-size and output rate — to deliver air-free material into
your molds at precisely preset and controlled vacuum levels. The resin degassing tanks
connected to the dispensing machine can be equipped for either batch or continuous thin-
film resin degassing.

Typically, digitally-controlled vacuum at better than 0.5 mmHg is continuously drawn on the
resin materials in the supply tanks, while high-voltage components to be potted inside the
vacuum chamber are also digitally maintained at a precise vacuum level to insure bubble-free
casting of on-ratio, abrasive-filled mixed material, into those mold cavities. High-voltage
electrical and electronic components demand vacuum potting, however other critical air-free
applications, including vacuum-assisted RTM, utilize vacuum casting to produce void-free parts.

APT’s metering and mixing systems feed air-free mixed material to both standard and custom-
built vacuum chambers to produce the highest quality, void-free parts. What size or type of
chamber is right for your application? Our people can work with you to select one of our
existing manual or automatic chambers or we can design one that meets your specific
application requirements.

Your vacuum chamber can be as simple as a small chamber with a front-opening door. On
the other hand, for high volume output, if you need to minimize the time spent cycling from
vacuum to vent, our continuous flow-through vacuum chamber includes three chambers and
four automatic doors. This system allows the center chamber to be maintained under constant
vacuum (i.e., no vacuum/vent cycles) to maximize pour time inside the center chamber. These
systems include automatic valves for connection to the vacuum pump and for venting vacuum
to ambient pressure.

Vacuum Potting System.jpg (32431 bytes)

Shown below is a dual-box vacuum chamber. While parts are being automatically poured inside
the chamber on the left, an identical chamber on the right lowers its automatic elevator base to
permit finished potted parts to be removed. Note that there are four individual shutoff nozzles
at the top of each chamber to allow the system to sequentially pour into each mold cavity. Due
to the absence of air, it can take a while for the mixed material to flow by gravity and fill voids
down inside the assemblies. Multiple-pass pouring eliminates over-filling by allowing you to make
a series of programmed shot volume displacements into each mold cavity (including a final
“top-off” shot), just prior to opening the chamber and removing the parts.

Dual Vacuum Chamber.jpg

The two chambers shown below have front-opening doors, lighted sight-ports, automatic
vacuum valving and mixed material inlet valves. The vessel on the left has a manual
turntable inside the box, plus a vacuum-sealed horizontal rod running through the chamber,
which lets the operator accurately position the shutoff nozzle over each mold cavity. The
larger chamber on the right has a 36″ diameter hinged door.

Chamber with Pour Tube Positioning Rod30 Dia. Vacuum Chamber

When potting trays of parts with numerous cavities, digitally controlling a single pour nozzle
often answers the need to eliminate maintenance on multiple pour nozzles. In the fully automatic
vacuum boxes shown below, a single pour nozzle is driven from part-to-part with a servomotor-
controlled, X-Y-Z Axis, pour tube positioning system. With these systems, automatic conveyors
index a mold or tray of molds into the pour chamber or the operator simply places a long tray of
parts to be potted on the z-axis base inside the chamber and presses the start button. Sensors
at the edge of each tray detect that tray’s identifier and communicate with the PLC to automatically
preset the ratio, shot-size, output-rate and all indexed movements of the pour nozzle from one
mold cavity to the next. At the end of the automatic sequence, the chamber is vented, the door
automatically opens and the tray of parts is removed for post curing.

Chamber with Programmable X-Y-Z Axis Pour Tube Positioner

Vacuum Levels Required for Degassing Resins
and Potting Components Under Vacuum:

30″ Vacuum = 0.0 mmHg (Torr) = 0.0 microns = Perfect Vacuum
0.05 mmHg (Torr) = 50 microns
0.1 mmHg (Torr) = 100 microns
0.5 mmHg (Torr) = 500 microns (Resin is degassed at 50 to 500 microns to vacuum
pot and encapsulate high voltage components.)
1.0 mmHg (Torr) = 1,000 microns (In-chamber vacuum levels from 500 to 1,000
microns are required for most vacuum potting and encapsulating applications.)
2.0 mmHg (Torr) = 2,000 microns
5.0 mmHg (Torr) = 5,000 microns (2 to 5 mmHg is needed to make low to medium
viscosity resins visibly air-free. This range of vacuum levels is five to ten times
better than 29″ of vacuum.)
10.0 mmHg (Torr) = 10,000 microns (Very little degassing is done at this level.)
29″ Vacuum = 25.4 mmHg (Torr) = 25,400 microns (Not a sufficient
vacuum level for degassing most epoxy and urethane resins.)
28″ Vacuum = 50.8 mmHg (Torr) = 50,800 microns
15″ Vacuum = 381 mmHg (Torr) = 381,000 microns
0″ Vacuum = 762 mmHg (Torr) = 762,000 microns = Ambient Air

Light-Beam Vacuum Trap

Light-Sensing Vacuum Traps Eliminate costly vacuum pump rebuilding and cut downtime. This liquid trap stops foamed resin from flooding the vacuum pump while degassing. When the glass-tube receiver has just 30ccs of resin inside, the light-beam and reflector sense it, the valve closes, an alarm sounds and the flood of resin stops. The receiver (see inset) comes apart four pieces for easy cleaning.

Vacuum Pump

Vacuum Pumps 11-, 20-, 55-, 100-CFM and larger are available from APT. Complete assemblies include a motor-starter, a manual switch mounted on the control panel, a bleed valve and an analog gauge on the tank lid, plus plumbing to the tank. An optional electronic vacuum sensor, mounted on the tank lid with an automatic control valve, can hold preset vacuum setpoints on material in the tank. Preset vacuum levels can optionally be entered at the operator-interface control panel on the meter/mix machine.

The Heateroll - Drum Rolling/Melting Oven

The Heateroll® - 55-Gallon Drum Heating/Melting Oven Melts one drum, fast. The combined heating and rotating action of the The Heateroll® typically preheats drums 6 to 8 times faster than conventional “stand-up” drum heating methods. Operates with ceramic-enclosed infrared heaters. Saves energy and minimizes thermal degradation of the material. Inset shows the Heated Compartment, which slides over the drum, in the closed position. Temperature Range: 90oF to 200oF. Keeps filler in suspension.

Note: Resins typically require precise (± 2°F) temperature-control, agitation and vacuum degassing to significantly lower the resin’s viscosity and surface-tension – to remove all the air and dissolved gasses – prior to metering, mixing and dispensing into molds inside chambers. APT’s Batch Tanks and Continuous Thin Film Deaerators prepare the resin materials for short-run vacuum casting and continuous vacuum casting. Various levels of vacuum degassing (down to the micron level) are required for different applications.

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