Extended tool machines circuit board rack

Citation

(2002), "Extended tool machines circuit board rack", Aircraft Engineering and Aerospace Technology, Vol. 74 No. 4. https://doi.org/10.1108/aeat.2002.12774dab.004

Extended tool machines circuit board rack

Keywords: Tooling, Circuits, Machining

To cut narrow slots in die cast aluminium racks for housing printed circuit boards in Tornado aircraft, a long-reach, right-angle milling head has been manufactured by Centreline Machine Tool for GJT Precision Engineering, Glenrothes, UK (www.gjt.co.uk), an approved subcontractor supplying the Tornado chassis to BAE Systems (Figure 1).

Figure 1 Drawing of the extended, right-angle milling head manufactured by Centreline for machining Tornado PCB racks

The challenge was to impart sufficient stiffness to the 30mm wide tool, which measures 375mm from the cutting tool centreline to the taper gauge line, to avoid flexing and consequent lack of accuracy during machining.

The required rigidity was achieved in part by supporting the tool about one third the way along its length by means of a cowl mounted on the head of the Fadal machining centre and located on the bearing cap, around the spindle and concentric with its centreline. The bending moment and hence the deflection at the tool tip are therefore said to be proportionately reduced. Additionally, whereas the standard BT 40 taper has a 44mm diameter, the cowl is fixed at three points on a PCD (pitch circle diameter) of 127mm, thereby reportedly nearly trebling the effective support at the spindle nose.

The milling cutter is held in a 7mm diameter collet chuck and the drive is via 10 sets of helical ground gears to a pair of helical bevel gears which turn the drive through 90 degrees. The speed and direction of rotation of the tool are the same as those of the spindle.

Details available from: Centretine Machine Tool Company Limited. Tel: +44 (0) 24 7635 4111; Fax: +44 (0) 24 7635 4222; E-mail: sales@centreline.com; Website: www.centrefine.com