User manual

Z406 System User Manual Z Corporation
www.zcorp-users.com 71
Preparing and Pouring the Silicone Mold
Preparing the silicone is relatively easy but must be performed properly to ensure a good mold. Pay
close attention to the mix ratio of the two components of the silicones. Be sure to prepare a large
enough volume to completely encase the pattern. The open time
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of RTV silicone is typically 1-2
hours (see your product’s Technical Data Sheet for specific information) allowing enough time to
carefully mix and prepare the liquid rubber.
Though mixing can be done by hand, it is difficult to
determine if both components are thoroughly combined in
large volumes. The use of a Jiffy
®
Mixer is recommended.
Mixing the components together will whip air into the
mixture. Air trapped in the mixture must be degassed, which
separates the air out of the silicone mixture. Place the
mixture in a vacuum chamber and degass. Removing the air
until a minimum of 27” Hg has been reached (vacuum
chambers and casting systems are commercially available for a range of budgets). Note that the
volume of the mixture will increase dramatically until all of the air has been removed. Choose a
container that holds approximately 3 times the volume of the mixed silicone.
Once the de-gassing is complete; pour the silicone mixture slowly into the mold box, letting it run
smoothly around the pattern. Take your time to decrease the chance of air being trapped anywhere.
Best practice is to de-gas the mold after the silicone has been poured to remove any air that was
introduced.
Manufacturers of Vacuum Chambers and Casting Systems
BJB Enterprises (www.bjbenterprises.com/equipment
)
Innovative Polymers (http://www.innovative-polymers.com/)
MCP Equipment (www.mcp-group.com)
Removing the Master Pattern and Creating the Parting Line
Remove the mold box from around the mold. Using a razor
blade or scalpel, begin to cut the mold open at the gate and
vent. This will begin to create the parting line for the mold.
Cutting in a smooth zigzag motion will make the mold halves
easier to re-assemble in preparation for urethane casting.
Slowly cut deeper to the edge of the pattern. Keep in mind
where the mold parting line will be on the pattern. The parting
line should be placed on an edge of the part to avoid witness
lines (flash
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from the cast urethane).
When the cut is finished, the mold halves should easily separate and the
master pattern can be removed.
Mold Preparation and Casting
Spray mold release onto all areas that will be exposed to the casting
material and place the mold halves together. Use tape, rubber bands, or
clamped boards to hold the mold together, preventing the cast urethane
from leaking through the parting line. Do not squeeze a soft mold too
6
Open Time – The amount of time it takes to gel or double in viscosity.
7
Flash – Cast material that has squeezed into the space between mold halves, typically at the parting line.