Friction welding tooling

Friction welding tooling includes a cassette (2,4) for holding a component (6) which is to be welded with great accuracy to a clamped workpiece. The cassette is carried on the distal end of an oscillator arm (8) and urged against the workpiece surface so the cassette has to transmit the frictional heating and weld forming forces to the component. The component (6) must be clamped accurately and securely by the cassette for accurate welding. The cassette comprises a base portion (2) and a floating cap (4). The base portion carried by the oscillator arm (8) has locating features (15,16) to position the component (6) accurately. The floating cap (4) has similar locating features (13,16) but locates entirely on the component (6). The cap (4) is then securely clamped to the base portion (2) with a force transmitting wedge (22) inserted by opposing faces (24,25) in a load path.

The invention concerns friction welding tooling. In particular it relates 
to a part of the tooling which clamps a component which is to be welded to 
a separately clamped workplace. 
In the manufacture of BLISK's, integrally bladed discs, and BLUMS's, 
integrally bladed drums, for gas turbine engines accuracy of location of 
the blade or blade blank is of prime importance. The blades may be 
friction welded to the disc as a finished item or as a part-finished item, 
ie as a blade blank to be subsequently finished by mechanical or chemical 
machining processes. In either case when the blade (which term is 
hereinafter used to include a blank) is clamped into a holding cassette it 
is important that it is accurately located in the cassette prior to 
commencement of the welding operation. 
The blade cassette or tooling of immediate interest consists of a cassette 
base member and a demountable cap. The cassette is carried at a distal end 
of an oscillator arm which produces the friction generating movement and 
is connected to a weld-pressure generating ram. In order to load a fresh 
blade into the cassette prior to the commencement of a welding operation 
the cap is removed, the blade inserted and the cap replaced. Any 
misalignment or movement of the blade when the cap is refitted therefore 
results in an error in the orientation of the blade when it is welded. The 
invention seeks to overcome this drawback by providing a floating cap. 
According to the present invention there is provided friction welding 
tooling comprising clamp means adapted to accurately clamp a component 
which is to be welded to a workpiece, the clamp means including a base 
member adapted to accurately locate the component and a demountable cap 
adapted to accurately locate on the component and which may be attached to 
the base member in order to apply a clamp force to the component, the base 
member and the cap being formed with reference faces which are spaced 
apart to form a gap in a load path between the base and the cap, and a 
spacer member adapted to be forcibly inserted into the gap to render the 
load path rigid. 
Preferably the base member and the cap are formed with V-notch features 
adapted to engage edges of the component for accurate location. Preferably 
also the reference faces are non-parallel and form a tapering gap and the 
spacer member for insertion in the gap is wedge shaped.

Referring now to the drawings the friction welding cassette illustrated is 
adapted for use as part of the tooling and friction welding apparatus 
described and illustrated in our co-pending patent application filed 
herewith (Ser. No. 08/570,010, filed Dec. 14, 1995). 
The cassette of the accompanying drawing comprises a cassette base member 2 
having a demountable cap 4 which is mounted on the base member 2 to apply 
a clamp load to a component 6. In this example the component 6 comprises a 
blade blank, but it might be a finished or part-finished blade, which is 
to be friction welded to the periphery of a disc (not shown) for a rotary 
BLISK stage of a gas turbine engine axial flow compressor. A finished or 
part-finished blade would include a shoulder or platform to provide a 
substantive feature for clamping purposes. In order to achieve this the 
cap 4 is arranged to "float" with respect to the cassette base 2 so that 
the entire clamp force is applied to the component through the cap. The 
invention has for its principal objective the provision of such a floating 
cap and means for carrying the loads which arise during various phases of 
the whole welding operation. 
As is described in greater detail in the above mentioned co-pending 
application the cassette base member 2 is mounted at the distal end of an 
oscillator arm 8, and a weld-pressure generating force W is applied in the 
direction indicated by an arrow in FIG. 2 by a ram 9. 
The component 6 is clamped between confronting faces of the cassette base 2 
and the cap 4. The confronting faces consist of complementary arrangements 
of surfaces which in combination provide the required accurate location of 
the component and the cap itself. The face of the base member 2 comprises 
two parallel plane surfaces 12b and 14b which are spaced apart by two 
unequal angled surfaces 15b and 16b. To match the cross-section of the 
component with which this piece of tooling is designed to operate the 
included angle between the faces 15b,16b is a right angle. This right 
angle extends across the width of the base member thereby constituting a 
V-notch in which an edge of the component is located. 
The confronting face of the cap is formed similarly to engage the opposite 
side of the component. This face also comprises two parallel plane 
surfaces 12c and 14c spaced apart by two unequal angled surfaces 13c and 
16c. Again the included angle between the faces 13c,16c is formed as a 
right angle to match the component and extends across at least part of the 
width of the cap thus constituting a V-notch which in this instance is 
used to locate the cap on the component. This arrangement is best seen in 
FIG. 1. 
The dimensions of these faces, in particular the notch faces, of the base 
and cap are selected so that when the component and cap are in place on 
the cassette base a narrow gap remains between the parallel faces 12b,12c 
and 14b,14c. Thus, when the cap 4 is fitted to the cassette base member 2 
the whole of the clamping force is applied to the component, or blade 
blank in the example, which is thereby firmly clamped. If the component is 
not of uniform rectangular section, ie as in a part-finished or finished 
blade it is preferred to provide the component with a locating shoulder 
which is engaged with the notch faces. Thus all forces are exerted through 
the notch faces and the shoulder portion of the component. In the case of 
a part finished airfoil blade for a gas turbine engine no forces are 
exerted through the finished airfoil portion. 
The demountable cap 4 is clamped to the base member 2 by means of eight 
bolts, each of which carries reference 10. Eight clearance holes 11 are 
drilled through the flanks of the cap 4, see FIG. 1 to receive the bolts 
10. Preferably bolts 10 include shoulders or thrust washers to bear 
against the exposed cap face. The clearance holes ensure that the bolts 10 
exert no lateral forces on the cap. The cap 4 is located by engagement 
with the component before the clamp force is applied by tightening the 
bolts 10 to their holding force. The preferred method of fitting the cap 
is first to butt it against the backing plate 18, for which purpose a heel 
is provided at the adjacent edge of the cap comprising two slightly raised 
regions 19, 19' against which the cap can be pivoted into position on the 
component or component shoulder. 
For reasons explained in the co-pending application vertical forces exist 
in the cassette during welding and frictional heating phases which also 
pass through the cap. (In the frame of reference of the drawings a 
vertical direction extends from the top of the page to the bottom, or vice 
versa.) In order to avoid movement of the cap thereby disturbing the 
positive location of the component 6 it is therefore necessary to make 
some provision in the mounting of cap 4 to carry these forces. Since the 
cap is floating it follows that in the vertical direction it does not abut 
any portion of the cassette. In order to provide the required load path 
the cassette base 2 is formed with a step or shoulder 20 opposite an upper 
edge 21 of the cap. Direct contact between the shoulder 20 and the edge 21 
is avoided by arranging for a gap when the cap is in position. A spacer 
member or floating wedge 22 is then inserted into the gap and clamped 
firmly in position thereby providing the load path. 
The step 20 has a lower face 23 which forms one side of the gap and has a 
second, upper face 24 which, with respect to the reference directions, is 
formed horizontally. Three, in this example, clearance holes are drilled 
in a perpendicular direction downwardly from face 24 in line with 
clearance slots in wedge 22 and tapped holes in the cap 4. When the wedge 
22 has been inserted into the gap bolts 34 are inserted through these 
holes and tightened to hold the wedge in place. 
Preferably the reference faces 23,25 on the base member and cap 
respectively are formed non-parallel to ensure that the spacer member 22 
can be inserted after the cap has been clamped into the component 6. In 
the illustrated embodiment the face 24 on the base forms a right angle 
with plane surface 12b. The surface 25 on the cap, however, slopes 
downwards; that is the internal angle between that face and face 12c is 
less than a right angle. Thus, when the cap 4 is clamped in position the 
faces 24,25 form an inwardly tapering gap. The wedge 22 is formed with 
correspondingly tapering faces to fit into this gap. A pair of studs 26,28 
project outwardly through the gap from two holes drilled and tapped in the 
face 12b to receive the studs. The wedge 22 is drilled through at the same 
spacing with clearance holes for the studs. The outer ends of the studs 
are also tapped to take self-locking nuts 30,32 to apply end load for 
inserting the wedge. 
In use, the sequence of operations to fit the cap 4 to the cassette body 2, 
having placed the blade in position is: first position cap against the 
backing plate 18, second insert and tighten bolts 10, and third fit the 
wedge 20 and locking nuts 30,32. The wedge is first fitted, after the cap, 
by sliding it onto the studs 26,28 and then forcing it into the gap by 
tightening the self-locking nuts 30,32. Finally the wedge is held securely 
by the holding bolts 34.