Abstract: Process and apparatus, applicable to new or existing machinery for additive manufacturing, based on Fused Deposition of thermoplastic material deposited in subsequent layers one on top of another, wherein the process can be carried out preventing abnormal conditions in which the old layer about to receive a new layer has a surface temperature below a desired limit, that is below which bond strength is compromised and the resulting part defective. This feature is particularly useful in large envelope parts where the previous layer zone, which is about to receive a new layer thereon, has reached a surface temperature below said threshold limit. The apparatus comprises a heating system featuring multiple stationary heating elements, each one of them selectively powered in order to adjust delivered energy in direction and in intensity according to layer path and extruder speed.

Abstract: A fiber placement head with secondary compaction arrangement is provided. The fiber placement head includes a frame, at least one heating module mounted to the frame, and a primary compaction roller mounted to the frame. The secondary compaction arrangement includes a secondary idle compacting roller, operating after the primary compacting roller, performing a post retracing on the tows just applied by the primary compaction roller. The secondary compaction arrangement may also include an additional (secondary) heating module interposed between the primary and secondary compaction rollers. Re-heating and re-pressing the tows addresses those tows which are insufficiently bonded to a working surface due to the tow being insufficiently tacky.