The Alphacam project was undertaken for a leading aerospace component manufacturer and focused on the machining of 2 mm diameter holes at 4 mm nominal pitch centers around the circumference of liners fitted to turbofan engines.

The composite liner is mounted on a rotary indexing table. The angles of the machine’s drill heads are determined using machined templates that divide the parts into three separate drilling zones. Typically, components are mounted ‘bell mouth’ down and indexed in approximately 1/2 degree increments. The comb of drills produce a series of holes in rings around the part’s circumference. The drill heads are then stepped in the vertical axis and readjusted to account for the taper of the components before the process is repeated.

The accurate positioning and orientation of the drilled holes is complicated by the non-uniform geometry of the job. The liners are not true cones. They are not circular in cross section and their profiles are not completely straight, resulting in complex compound geometry, which the programming system takes into account.

With a maximum angular tolerance of +7 degrees on the normality of each hole to the local surface, it was necessary to calculate the maximum, average and minimum curvature and slope at each location —and compensate for the variations accordingly.

In operation, the customer initially imports CATIA geometry into the programming application in IGES format. Following specification of the hole parameters, the system automatically determines the drilling sequence and generates machine code. It takes around 25 minutes for the system to create all the geometry for the hole matrices, with a further 35 minutes required to complete the final programming.

Planit Group
www.planit.com

:: Design World ::

Source: :: Design World ::