|
 Vacuum bagging is
actually a very simple process. What you are doing is letting
atmospheric pressure provide the clamping force. Whether you
are vacuum bagging veneer or composites, the process is the same.
You enclose your project in a sealed bag, evacuate all the air and
create a vacuum. When a vacuum is created, atmospheric
pressure applies pressure from all directions onto
whatever you are vacuum bagging. The amount of pressure is
determined by the amount of vacuum created, so the pressure can be
increased or decreased by adjusting the amount of vacuum.
At sea level atmospheric pressure is
14.7 pounds per square inch (29.92" Hg). This
amounts to over 2100 pounds of even and uniform pressure per
square foot. As altitude increases atmospheric pressure decreases.
For example, at 2000 feet above sea level the maximum pressure would
be 13.67 pounds per square inch (27.82" Hg), a 7 percent
decrease. At 4000 feet above seal level it would be 12.69
pounds per square inch (25.84" Hg), a 14 percent decrease from sea
level. Although the atmospheric pressure has gone down, it is still
capable of producing over 1800 pounds of pressure per square foot at
4000 Feet above seal level.
Vacuum bagging can be used for flat or curved
projects, as well as complica ted shapes when using composites.
To create a vacuum you can use a vacuum pump or
vacuum generator. Both of which will work for vacuum
bagging.
Vacuum pumps come in a variety of sizes and
designs so there are a lot of choices. They are
measured in how much vacuum they can produce and how much air volume
they can evacuate.
One thing to keep in mind when purchasing a vacuum
pump or vacuum generator, is that there is really not much
benefit in purchasing one that has a large CFM rating. The
only benefit is that it would evacuate the air from the bag
faster. After all the air is evacuated from the bag, all you
are doing is maintaining vacuum.
Our vacuum pump creates up to 24" Hg of vacuum and
evacuates 1.2 CFM @ 0" Hg. It was designed to be economical to
purchase, able to run for several hours at a time so no
additional expense would be incurred by having to purchase expensive
control valves. It also has adjustable vacuum so you can
control how much pressure you are applying, an integrated filter,
and a vacuum gauge.
A vacuum generator is
driven by an air compressor, and they come in different
sizes. You need to know how much air volume it will take
to make it function properly, and if your air
compressor can produce the needed amount of air
volume. Our vacuum generator uses only 1.8 CFM
@ 65 PSI, evacuates 1 CFM @ 0" Hg. and creates up
to 26" Hg of vacuum.
This size vacuum generator can be
operated by most small shop compressors, and you can control
the amount of vacuum by adjusting the air pressure with a
regulator (which is the best method) or by turning the
control valve on the generator to lower the amount of air
volume entering the generator.
With vacuum bags there are several
choices. First you have many choices in the size of the
bag. Mostly this decision will depend on what you are vacuum
bagging, and how much you want to invest in a vacuum bag.
Vinyl is the most economical vacuum bagging material
and it comes in several thicknesses. The most common being
either 20 or 30 mil in thickness. The other vacuum
bagging material is polyurethane. It is much more
resilient, stretches more than vinyl, is more durable, and
also comes in different thicknesses, the most common being 20
or 30 mil. With the additional benefits comes more cost which
is sometimes twice that of the same thickness of vinyl vacuum
bags. Our vacuum bags are made from premium grade 20
mil vinyl, with great elasticity, and
durability. They have a 1/4" solid seam which you will
find almost  indestructible.
| 
