A hybrid tool serves as a form on which constituent materials are applied
for bonding or curing into a part in a desired configuration. It also
serves as a holder for the bonded or cured materials in the originally
applied position during subsequent machining. The hybrid tool is made by
fabricating a face sheet of composite material having a facing surface
configured to the reverse of a desired shape of one surface of a part to
be made on the tool. The actual part will be laid up on the facing
surface, cured while on the tool, and even trimmed before release. Base
structure of the tool holds the facing surface of the face sheet in the
desired shape, and includes ground-engaging pads that define an "A" datum
plane. The tool aligns a reference plane of the face sheet parallel to the
datum plane. A substantially continuous groove in the face sheet, used for
trimming the part, opens in the facing surface. Edge trimming of the part
on the tool is performed using a CNC machine tool following a part program
to move a cutter extending into the groove to engage the full thickness of
the part. The groove corresponds in space to the position represented by
the cutter path of travel in the part program because of the accurate
spatial relationship of the face sheet reference plane and the datum
plane. One embodiment of the invention includes filling the groove in the
facing surface with a foaming, self-skinning sacrificial material and
covering the facing surface of the tool with a caul sheet. The tool is
heated to cure the foaming material, which fills the groove and forms a
hard, smooth surface skin, flush with the facing surface of the tool to
support the part during lay up. A series of skin plies are laid-up to form
a tool-side skin, and other components of the part are laid-up on the
tool-side skin. A vacuum bag is sealed to peripheral regions of the facing
surface of the tool around the laid-up skin and components. An
adhesive/resin matrix in the skin and components is bonded/cured in the
conventional manner within the vacuum bag to produce a rigid integral
assembly. The vacuum bag is removed, uncovering the rigid integral
assembly for trimming. A cutter of a machine tool is guided on a
predetermined path around the facing surface of the tool, running in the
foam-filled groove below the facing surface of the tool and cutting a
peripheral edge around the rigid integral assembly. After trimming, the
rigid integral assembly is removed from the facing surface of the tool.
