Laser direct metal deposition process of thin-walled parts using variable spot by inside-beam powder feeding

The purpose of this paper is to improve the forming efficiency and quality of unequal-width parts fabricated by laser direct metal deposition technology, some experiments were designed.

A new method by varying laser spot was adopted to fabricate unequal-width single track using one scanning rather than multi-track overlapping in the way of the inside-beam powder feeding, and the thin-walled parts were fabricated layer by layer. The theoretical model among layer thickness of z-axis, height of single track and the section curve order of single track was established.

The top surface unevenness of the thin-walled parts could be compensated automatically within the laser defocusing ranges from −2.5 to −5 mm and from 0.5 to 2.5 mm. The growth rate with the large width/height ratio was more than the small ratio, while the set height of the single track was uniform. The problem of non-uniform growth rate could be solved based on a stepped single-track method. The thin-walled parts with the smooth top surface was fabricated layer by layer which had a continuously variable width from 1 to 3 mm by splicing the laser defocusing range.

The shapes of the to-be-fabricated parts affect variable laser spot process in practical applications. For example, it will be difficult to apply variable laser spot process on the parts with the hole features.

This paper provided a guidance for forming unequal-width parts by laser direct metal deposition based on the inside-beam powder feeding.