How To Vacuum Bag Small Molded Parts Instructions
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HOW TO VACUUM BAG SMALL MOLDED PARTS
Vacuum Bagging Small Molded Parts
Step 1 |
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We will start by making up the vacuum bag. In the "Basic Vacuum Bagging System Set-Up Instructions" we covered using bag clips to make up a basic vacuum bag. That method works well but in this tutorial I will cover an alternate method, using bag seal tape. This method alos works well and takes only slightly longer.
Cut a length of vacuum bag tube about 12 inches longer than the length of the mold. Cut a length of Bag Sealant Tape that is 2 inches longer than the width of the bag tube. |
Step 2 |
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Roll the cut length of sealant tape up so the sticky side
is out. This makes the tape much
easier to control while you are placing it on the bag tube. |
Step 3 |
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Place the tube flat on a table. Stick the end of the
sealant tape to the inside of the tube. Start the end about 1 inch past the fold line on the edge of the
tube. The tape should also be about ½
inch in from the end of the tube. The
flat table will help prevent any wrinkles in the bag while you are sticking
down the tape.
The sealant is very sticky and once pressed down on
the bag, it is nearly impossible to remove. |
Step 4 |
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After the end is started, unroll the bag seal along the end
of the tube. Keeping all wrinkles out
of the bag, press the sealant into place as you go. |
Step 5 |
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Once the bag seal is in place it should extend about an
inch past the fold line on the corner of the bag. Repeat the same steps to put the bag seal in the other end of
the tube. Leave the paper backing on
the sealant in place until you are ready to close the bag. |
Step 6 |
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Cut two porous release film (peel ply) and two breather fabric layers a little
smaller than the inside dimensions of the nylon vacuum bag. Also prepare the ¼” vacuum line that will
run from the bag to the vacuum regulator. Wrap a short length of bag sealant around the vacuum line about two
inches from end on the line. The vacuum line
sealant is lined up with the bag sealant in the end of the bag when the bag is
closed. The tube will extend inside
the bag and breather must be wrapped around the end of the tube providing a
continuous path for all the air to exit the bag. |
Step 7 |
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A two part fiberglass mold was made from a wooden
pattern. Because this mold has many
tight corners a pair of silicone rubber inserts were made to force the carbon
fiber into all the corners of the mold. The inserts are slightly smaller than the mold to allow for the
thickness of the carbon fiber layers. This was accomplished by applying a thin layer of sheet wax to the
surface of the mold before the silicone inserts were made. For a larger part the silicone insert
would only be made for the areas near the tight corners. |
Step 8 |
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The carbon fabrics are wet out completely in the molds and
the silicone rubber inserts are pressed into place over the wet lay up.
Breather then porouse release film (peel ply) layers are placed in the bottom of
the bag.
The molds are now placed in the bag with plenty of space
for the bag to pull down around the molds.
Next the second layer of porous release film (peel ply) then breather are added
on top. |
Step 9 |
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The bag is sealed by removing the paper backing from the
sealant, and pulling the ends of the sealant strip so there are no wrinkles
in the bag when it is pressed down against the sealant.
The breather material must be wrapped around the end of
the vacuum line.
Start the vacuum pump. The excess epoxy will be forced out
of the lay up. |
Step 10 |
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After the epoxy has cured the edges of the parts are
trimmed and the halves are joined with a strip of carbon fabric.
Instead of silicone rubber inserts, fiberglass inserts can be molded to serve the same purpose. Silicone rubber molding compound is difficult to find in small quantities and typically has a short shelf life. |
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Prices are in US dollars and subject to change without notice.
