Increasing laser coupling using proactive layer height control
in direct laser deposition

 

 

Laser Assisted Net Shape Engineering - Proceedings of the LANE 2004

 

 

Eamonn Fearon,K.G. Watkins, M C Sharp
The Laser Group, The University of Liverpool, Liverpool, United Kingdom, L69 3GH, UK
Lairdside Laser Engineering Centre, Merseyside, England

Abstract: Direct Laser Fabrication (DLD) is a blown-powder laser deposition process that can be used to quickly produce fully-dense metallic prototypes by a layered manufacturing method. DLD can also be used to repair or modify high-value components. In common with other laser deposition processes, variation in the process parameters, variation in the process parameters (ie traverse speed., powder flow rates etc) often cause height errors in the built part. Layer height control methods are therefore a continually investigated field.
Research carried out at Liverpool University has resulted in a non-feedback layer height controlling process based on controlling the shape of the powder streams emitted from a four-port side feed nozzle. This method limits deposited layer height by causing a sharp reduction of catchment efficiency in the vertical plane at a fixed distance from the powder feed nozzle, and is therefore capable of depositing a consistent layer height in spite of power, powder flow or process velocity variation. A further effect of limiting the powder cloud in this way is a refinement of the top of the powder cloud interface. This interface refinement can be shown to have beneficial effects on laser power coupling into the workpiece.
This paper shows how this refinement of powder cloud shape can be achieved and discusses the increased coupling effects in terms of existing thermal models of the laser cladding process.

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