Jefferson Spivey has been building and marketing his Sabertooth survival knives since 1968. In that time, the handle design has only changed a few times so when a change does take place, Spivey insists that the design be perfect. 

The latest version was designed in CAD and Spivey liked the way it looked so he released the tooling for production. His only mistake was not having a prototype built of the new design.

Scan_Mesh_DataUpon receiving the first production pieces, Spivey proceeded to assemble the handles to a blade discovering that it didn’t feel right. The handle seemed too thick in the finger area, but some associates insisted he proceed with production. Spivey didn’t feel right selling a design he felt wasn’t perfect, so he turned to Absolute Geometries to produce a new CAD model.

Absolute Geometries used 3D Laser Scanning to produce a digital replica of the modified handle by scanning it with a Faro Laser Scanarm, which captures thousands of 3D measurement points per second and creates what is known as a point cloud model. 

From the point cloud model, Absolute Geometries created new CAD surfaces of the modified area by converting the point cloud model into a 3D mesh file. The mesh file was created by attaching points together to form triangle surfaces that have a surface normal, then cross sectioned and used as a guide to create the new surfaces. The new surfaces were incorporated into the original CAD model and then verified to the original scan data using Rapidform XOV – a computer-aided inspection software that uses scan data to verify as-built parts. 

The scan data was aligned with the CAD model so differences could be identified, verifying that the modified CAD model matched the hand crafted handle that Spivey had created as closely as possible. The data was aligned and a 3D Color Deviation model highlighted any areas that did not match.  

Reference dimensions were taken at several areas to verify the deviation and to produce smooth tangent surfaces. The new surfaces proved to be accurate and a Rapid Prototype model was created. 

Deviation_modelAn Objet Eden500V 3D Printer was used to build a detailed model of the new design. Parts were built in .0006” layer thickness and .0016” resolution. A UV sensitive resin was printed onto a platform and cured with a UV light bulb attached to the back of the print head. After one layer is “printed”, the platform lowers and the printing process is repeated until the part is complete. The Objet prototype was assembled to a blade and this time Spivey was very pleased with the feel.   

To keep from completely rebuilding the tool cavity, the tool maker dropped the parting line and then used EDM to burn in the new surfaces.  New handles that met Spivey’s specifications where then produced.  Without 3D Scanning and Rapid Prototyping, it would have been very difficult to turn Spivey’s hand modified handle into production parts.  Looking at a design in CAD is never the same as holding it in your hand. 

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