Additive Manufacturing

Additive Manufacturing

1. History

   • Previously termed Rapid Prototyping (RP) - orginally named RP as the technique was originally used to create prototypes of ideas, however as the technology has advanced the term is inadequate and doesnt describe the process entirely. Technical comittee in ASTM International agreed a new name should be adopted.

2. Uses of AM Parts

   • Originally used to develop models
   • The 3 F's - AM is used to allow simple production of accuracy and quality of the final product. Form, Fit and Function. Form - Initial models used to understand the basic principlas of the model. Fit - Increase in accuracy during development meant components can be built to the required tolerances. Function - improved material properties meant that parts could now properly be handled and assesed to the final mechanism.

3. Generic Process of CAD to Part

   • 1. CAD - All AM parts start from a software model, detailing the geometry of the final product. The output must be a 3D solid or surface . Reverse engineering such as laser scanning can be used to create this representation.
   • 2. Conversion to STL - All AM machines accept the STL file format as a de facto standard - the file describes the enternal surfaces of the original CAD model and provides the basis for the calculaiton of the slices.
   • 3. Transfer to AM Machine and STL File Manipulation - The STL file with the part details needs to be transferred to the AM machine and gernal manipulations of the file may take place to ensure the correct size, shape, position for building.
   • 4. Machine Setup - The AM machine needs to be set to the correct parameters before processing the STP file e.g. energy source, layer thickness and timings.
   • 5. Build - An automated process which the machine carries out without much supervision. Only superficial monitoring is required to ensure there are no errors during the build, such as running out of material/ powder/ software glitches.
   • 6. Removal - Once the part is built it needs to be removed, i.e. unlocking safety mechanisms of the machine which protects the user from extreme temperatures or any moving parts.
   • 7. Postprocessing - Once removed from the machine the part may need to be cleaned before initial use. They may also be weak and any support structures must be removed carefully.
   • 8. Application - The part may now be used however additional paiting or refinement of the product may need to take place, to ensure optimal texture and finish.

4. Wohler Report

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