It is abundantly clear that additive manufacturing (AM), whether in plastic, metal, or human tissue, is a manufacturing game changer. But as with any manufacturing method, design for that method must be considered. In that case of digital manufacturing, we get to let down our hair and let go of having to consider those pesky tool paths. It’s liberating!
However, I know I should still be cautiously optimistic. Just because I can build internal cavities and crazy organic shapes (non-rectangular), I still need to consider the 3D printing process types, materials, and methods.
Changing the way we think of the design-to-manufacture process saves time in making part and assembly drawings, saves costs in machining or molding complex surface geometry, and again saves time in final assembly.
AM is the only manufacturing method that demands 3D model-only product definition
Looking at possible use cases (product outputs) that leverage 3D printing manufacturing techniques, I offer the following categories for end products as a result of numerous AM processes. Do you have more to share? Please share a comment.
Additive manufacturing production level process categories
Functional prototype:
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- Form, fit, function evaluation
- Changes may be required to the actual design to accommodate for 3D print materials versus the final manufactured product materials.
- Generally not concerned with product life, outgassing or regulatory considerations of this end item.
- Exact geometry (model precision) is important, but because the end item is merely a prototype, the overall geometric accuracy may not be critical.
Final part:
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- The product’s final surface geometry dimensional accuracy affects performance of the end item.
- This product is considered to be “digitally manufactured.”
- Repeatable manufacture of the end item.
- Build parts on-demand, and just-in-time.
- Can take advantage of “Design for No Assembly” (see more detail below).
- Exact geometry (considering model precision and geometry translation quality) is critical.
Molds:
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- Serving as the inverted geometry impression of a part.
- Could be part of the manufacturing process for injection molding, cast urethane, or casting.
- Complex geometry can be directly input into a CAM (Computer-Aided Manufacturing) without the need for dimensions on a 2D drawing.
- Exact geometry (considering model precision and geometry translation quality) is critical.
Sculpture:
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- Artistic representation of shape and color.
- Final surface geometry dimensional accuracy is generally not important.
- The end item product result is only important to the human eye.
AM final part example
"Design for No-Assembly" is a concept credited to Sridhar Kota, Professor of Mechanical Engineering at the University of Michigan. It’s my belief that Design for No-Assembly is a concept to which AM is best suited.
Kota states:
When neighboring parts don't have to be different material, then you should combine them. Even if there is relative motion between parts, you can combine them by exploiting the material's elasticity.
Kota's statement captures the design intent and practice of a principal use of a single 3D printed part, as shown in my design of a complex air duct.
This air duct requires complex geometry, easily depicted in a 3D model but not trivial to replicate with standard manufacturing techniques (even if machined with a 6-Axis CNC machine using a ball end mill). The air duct could be split into two halves and cast or injection molded, but then draft angles would need to be added. The initial setup and mold manufacture is cost prohibitive if this air duct is a one-of a kind build (or only manufactured in low quantities).
A single 3D model that results in a moving, working, and real-world rudder printed as a single part. This is an excellent example of Kota’s “Design for No-Assembly”
This direct transfer of 3D geometry lends itself to increased accuracy and prevents human error when transferring and interpreting drawings. In fact, no drawing interpretation is required. When complex surfaces are involved, it is paramount that data is transferred directly from the originating model and directly into the manufacturer’s tools, thus eliminating errors incurred during drawing interpretation.
Stay tuned for a follow-on blog post that will describe this air duct with appropriate MBD tolerances for 3D printing manufacture.
