Certifying additive manufactured parts for aerospace how difficult is it?
You may want to start qualification process to your printed components of your additive manufacturing operations. The good news is that the procedure is similar to what you are used to certifying your machined and formed parts.
In order to develop a high-level understanding of the qualification process it is important to discern the differences between typical certification processes and additive manufacturing certification processes as they pertain to parts, materials, and process.
Conducting your first article inspection report for printed parts will work the same way as in any other process. However, additive manufacturing allows for unique design features to be realized, and these features must also be qualified. These parameters include:
- Part infill
- Ergonomic and complex geometries
- Consolidated meshes
Infill parameters, like most internal part geometries, are often qualified through destructive testing methods. While the external geometry of a machined part is often qualified with linear measurement methods, complex geometries of a printed part may require more advanced measurement techniques, such as CMM or optical scanning to be qualified.
Material behavior in printed parts is sometimes non uniform and generally anisotropic. The tool path of a metal printed part can affect the cooling rate of material in different regions of the part, which may create material irregularities. Powder-based (e.g. SLS) printers often create porous parts that affect material behavior. Most commonly, the print orientation introduces anisotropic behavior in the part itself. With these considerations in mind, parameters that should be qualified include:
- Anisotropic behavior
Microscopy measurement techniques are generally accepted to qualify porosity and material density parameters. Material density and anisotropic parameters together can be qualified through traditional material testing (e.g. Tensile, hardness, and compression testing) as long as material non uniformity is accounted for. Consider experimenting with multiple load directions to gain a more thorough understanding of your material anisotropy.
Machine process controls largely govern the yield, and are often included in the qualification process. Common process controls that are unique to additive manufacturing are listed below:
- Printer resolution
- Printing temperature
- Printing travel speed
These process controls for additive manufacturing, like for machining methods, are qualified through proper documentation of the printer’s settings across a range of inputs. Be sure to familiarize yourself with the appropriate input ranges and tolerances for your printer’s specific technology.
Now you know (generally) how to qualify your printed parts. Though the process to qualify a printed part is similar to the process to qualify a machined or formed part, there are several key differences that are important to address.
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