The historically high cost of prepreg-based composite parts is often due to the painstaking hand layup that is required to create them. “It will be impossible to sustain composite part manufacturing levels that meet stringent quality standards if commercial OEMs rely only on manual labor,” contends John Melilli, VP of Accudyne Systems Inc. (Newark, Del.), whose company recently custom-built a tape-laying system that automates layup of thermoset prepreg.
According to Melilli, this “part-purpose” system — that is, a simple machine that addresses the manufacture of a single part rather than a more complex machine that can do many types of parts — provides a more affordable automated solution for small- to medium-sized, relatively simple parts. The machine has a 60-ft/18.5m-long, flat steel vacuum table and a carriage mechanism that moves from one end to the other under closed-loop servo control. The carriage contains three prepreg heads capable of laying down any combination of thermoset prepreg in the zero or longitudinal direction from either end of the machine, each fed by a spool that can hold a material roll up to 25 inches/625 mm in diameter and 12 inches/300 mm wide. Material can be unidirectional tape, woven fabric or ±45° bias prepreg. In addition, the carriage holds two rolls of auxiliary material, such as peel ply, foil or vacuum bagging film. Each head is individually controlled by the machine’s operating system. Accudyne optimizes machine efficiency by making the heaviest components stationary, in this case, the table, while lighter elements (the heads) move. (On a smaller part-purpose system, the tape head was fixed while a lighter layup table moved; see end note). To minimize downtime during material changeout, an automated “turret loading system” allows an operator to load new material rolls while the machine is operating, with only a 90-second production delay as spools are automatically exchanged. Material lay down rates of 100 ft/min (30.48 m/sec) and between 50 lb to 60 lb (22.7 kg to 27.2 kg) per hour have been achieved. Typically, Melilli says, a finished charge can be produced in 15 minutes. Reportedly, edge position is accurate to ±0.030 inch/0.75 mm and start/stop accuracy is ±0.030 inch/0.75 mm. When complete, the flat “charge” or blank can be formed to final shape in a number of processes.
For more on this smaller system, see “Related Content,” at left.