What is compression engineering? Describe its importance in AM process.
"Compression engineering" is not a formal or widely recognized field of study. However, the term likely refers to a few distinct concepts that are critical in engineering and manufacturing. In the context of additive manufacturing (AM), the term is most relevant in two key areas: the mechanical properties of the final part and the physical processes that occur during printing.
1. Compressive Strength and Part Performance
In a general engineering context, compression refers to the application of a force that reduces the volume or size of a material. Compressive strength is a material's ability to withstand this type of load without failure.
Importance in AM: For AM, this is a critical aspect of Design for Additive Manufacturing (DfAM). AM parts are being increasingly used for end-use applications, and their mechanical properties must be well-understood.
Structural Integrity: Many AM parts, such as brackets, jigs, fixtures, and aerospace components, are designed to bear significant compressive loads. Knowing a material's compressive strength is essential for ensuring the part will not deform or fail under service conditions.
Anisotropy: 3D printed parts often exhibit anisotropic behavior, meaning their mechanical properties, including compressive strength, can vary depending on the orientation in which they were printed. Engineers must account for this by orienting the part to withstand the primary compressive loads.
Lattice Structures: AM's unique ability to create intricate internal lattice structures is a form of compression engineering. These structures can be optimized to provide a high level of compressive strength and stiffness while significantly reducing the part's weight.
2. Physical Processes and Quality Control
"Compression" can also refer to the physical forces or processes involved in certain AM methods.
Importance in AM:
Powder Bed Compaction: In processes like Binder Jetting and Powder Bed Fusion, a fresh layer of powder is spread and compacted before the next layer is added. The density of this powder bed has a direct impact on the quality of the "green" part and the final sintered part. A well-compacted bed leads to a more uniform part with less porosity.
Fused Deposition Modeling (FDM) and Layer Bonding: In FDM, the deposited material is often compressed or flattened by a roller mechanism or the nozzle itself. This compression helps to fuse a new layer to the previous one, expelling any trapped air and improving the part's overall strength and density.
Residual Stress: As AM parts are built, they undergo heating and cooling cycles, which can induce internal residual stresses. These stresses can be compressive in some areas and tensile in others, potentially leading to warping, cracking, or dimensional inaccuracies. Understanding these forces is a critical part of process optimization.