Motion Planning for Cladding Operations in a 5-axis LENS Machine

This paper presents a motion planning approach for some basic part shapes that require 5-axis motion control in a LENS machine. The paper discusses an approach that allows a cladding layer to be deposited on a cylindrical or a semi-spherical part for re-build operations. For cylindrical parts, the deposited layer could take the form of a tube, a spiral, or stepped/tappered tube. The approach allows arbitrary values for the parameters of these layers, and automatically translates the part parameters into a motion control program to run the LENS machine. The developed methodology was tested on an Optomec 850 machine, and the results were successful. INTRODUCTION The Laser Engineered Net Shaping (LENS) process developed at Sandia National Laboratories and commercialized by Optomec Design Company of Albuquerque, New Mexico, is one of the first successful techniques for direct metal deposition. The LENS process distinguishes itself from the stereolithography process and other common rapid prototyping processes in the following ways: 1. The LENS process fabricates metal and/or ceramic parts rather than polymer parts. 2. Parts are built by fusing powdered metals and ceramics with a high-powered laser, directly creating dense metal and ceramic parts in the LENS machine without need for post-processing in a furnace. 3. Parts are built on a base and unsupported overhangs cannot be built. Only upwardfacing features can be built unless the part is manipulated with multi-axis control. A LENS machine delivers powder directly to the beam/powder interaction region on the substrate. A high-powered Nd:YAG laser melts the powder, solidifying it to the substrate. The LENS machine scans the entire x-y cross-sectional slice from the CAD model, steps in the z-axis, and then repeats the process over again until the part is fabricated. This paper discusses a method to plan the motion of a 5-axis LENS machine that allows a cladding layer to be deposited on a cylindrical or semi-spherical part. For cylindrical parts, the deposited layer could take the form of a tube, a spiral, or stepped/tapered tube. The capability to deposit the cladding layers is important in part rebuild operations.