a. Vertical Cuts. These cuts are used to cut
adhesive (See the system speciic technical
replacement core sections from honeycomb core stock
material. The cuts are made along the core cell axis
using a core slicer or an end sharpened core knife.
(4) Inspect the core cells for areas of rolled over
A Mylar template deining the damage cut out shape
core cell walls. Finish sand any rolled over
and containing the part ribbon direction should be
areas using 180-240 grit abrasive paper and
used as a guide in cutting the core section. The core
a sanding block.
slicer or knife tends to dull rapidly and should be reg-
ularly sharpened to facilitate cutting. Core densities
(5) Vacuum the machined core surface to
higher than 6.0 PCF require a signiicant application
remove sanding residue.
of force for slicing.
c. Foam Core. Foam core can easily be removed
b. Angle Cuts. These cuts are made at an angle
with a face sheet or by itself. Hole saws or routers
to the core cell axis and require core stabilization.
can be used. Replacement foam core can be shaped
Core stabilization is provided by bonding or tacking
with hand tools such as knives and scissors.
the replacement core in place on the part prior to
machining. The part surface is then used as a guide in
(1) Use hole saw pilot drill to make a hole in the
machining the core to the required shape. Machining
center of the damaged skin area. Set the
is performed using a 0 degree router motor, a router
blunt pilot in the hole saw 1/8" beyond the
holder and the burr special core cutter. After the core
cutting edge of the hole saw or long enough
is stabilized in place, use a hand held hacksaw blade
to engage the previously drilled pilot hole in
to perform an initial rough cut on core (to within 0.5
the damaged skin. Cut through damaged
inch of the part surface) to remove excess material.
skin and core close to the opposite skin but
not cutting into it. The blunt tip pilot will pre-
vent cutting into the undamaged back side
(1) Install the burr cutter in router motor. Adjust
router motor in router holder so that cutting
edge of burr cutter is lush with outer mold-
line (OML) surface of part.
(2) Pry off damaged skin plug and remove core
material down to the opposite face skin.
(2) Using the part surface as a guide, carefully
(3) Remove any remaining X-CorŪ pins
machine core lush with OML surface of part.
attached to the opposite face sheet using a
Start by machining around the core periph-
pair of pliers.
ery. Use caution during machining not to cut
into the part skin or to undercut core.
(4) Use carbide router bits because PMI foam
tends to be fairly abrasive.
(3) Use a straight edge which extends beyond
the machined core and onto the part sur-
(5) Use high RPM while machining, up to 15,000
face to check that the surface of the replace-
ment core is lush with the surrounding part
surface. If the core surface is higher than
d. Spoiling Core. This procedure can be used
the part surface, inish sand using 180-240
for spoiling honeycomb or foam core for fastener
grit abrasive paper and a sanding block. If
installation, rapid densiication, or to repair a small
the core surface is lower than the part sur-
face, bring it lush by surface illing with paste