(1) Hot Air Module (HAM) Units. HAM units
and level of pressure used can signiicantly alter the
are generally controlled either manually or in con-
quality and resulting strength of a repair. There are
junction with a hot bonder controller. They can be
two general types of pressure: positive and negative.
used to heat large areas of any contour or material.
Positive pressure is produced by physically exerting
HAMs supply controlled heat to over 900 ºF. HAMs
an external force onto an object (repair) such that
lend themselves very well to heating and curing of
it is compacted as it reacts against another object
materials that require no contact such as paints and
(tooling or the component being repaired) to resist
the pressure. Negative or vacuum pressure is a
term used when an object (the repair) is exposed
to a conined vacuum environment (supported by
(2) Heat Guns.
a tool or component) while allowing the surrounding
atmospheric pressure to exert a compaction force onto
the object (repair). Most ield level bonded repairs
and repairs are fabricated from materials that are
involve the use of vacuum pressure to compact as
processed using various temperature and pressure
well as to remove volatiles and air from the repair.
proiles. Pressure is required to shape repair patches
Refer to igure 6-41 for a comparison of the pressure
to a part contour, to remove volatiles and entrapped
levels produced using an autoclave, shot bags, and
air from the repair patch and bondline, and also holds
negative vacuum pressure.
the repair in place while it is being cured. The type
Figure 6-41. Pressure Levels Produced Using Various Pressure Methods (Sheet 1 of 4)