Page 36 - 3D Metal Printing Fall 2017

3D
Q&A
BY CAITLIN OSWALD
Additive Manufacturing
Q&A Question:
so, the initial leadtime with 3D printing can be drastically shorter. The same holds true for raw-material orders. Depending on the material and enve- lope, the raw material blank’s long lead- time can be reduced by 3D printing the part. Another good indication that the part is a candidate for leadtime reduc- tion: when there’s a need for design iter- ations. 3D printing accomplishes design options quickly and even simultaneously.
Question:
What makes my part a candidate for cost reduction using 3D printing?
Answer:
Buy:Fly ratios provide a quantitative tool for identifying whether a part may be a good candidate for cost reduction. The ratio describes how much material must be purchased up front in the raw-material state, versus the amount of material that ends up in the end-use application. For complex shapes, where the final part geometry resembles only a shell of the overall material envelope, the part may have cost-reduction potential. This possi- bility increases with innovative geometric nesting of parts during the build, enabling the 3D printer to optimize the quantity of parts printed simultaneously.
Another method for determining whether a part is a good candidate for cost reduction: Count the number of setups required to machine the part con- ventionally, versus the amount of setups needed to finish only the part’s critical interfaces. Why? 3D printing can build the majority of the necessary features, leaving only value-added machining to complete the part. For parts with many
CAITLIN OSWALD
line-drilled/plug-welded ports, or lighten- ing holes/features, 3D printing can elimi- nate the need to touch those surfaces.
Part-count reduction offers another strategy for determining cost-reduction potential. However, from a systems-engi- neering perspective, identifying the many cost savings resulting from part-count reduction can be difficult. Besides those associated with removing certain inter- face features from machining, cost reduc- tions are associated with reducing inven- tory, inspections, installation steps and the overall administrative costs to route and handle additional part numbers. Also, combining parts not only reduces parts count, it increases design options for strengthening weak structural points. For example, by combining parts where the bolt-hole radius has the highest stress concentration, with adjacent parts, the bolt-hole and bolt can be removed and the load can be spread over a larger area.
Low-volume production, legacy spare parts and part-feature customization offer three more cost-saving opportuni- ties. In low-volume production, 3D print- ing can help reduce the need to main- tain an inventory of seldom-needed parts. In addition, when expensive tool- ing is required, recouping those tooling costs may take years. By reducing or eliminating the initial tooling, even if the per-piece price is more expensive, cost savings can result in the long run. So, too, is the case with legacy spares. With these, old tooling may no longer be available, or the manufacturer has gone out of business. Where a total order numbers only one or two parts, 3D metal printing can generate significant savings compared to upfront costs associated
When does it make sense to 3D print?
Answer:
That depends on the function, appli- cation and end-use. All too often I see companies trying to employ 3D printing as a process-substitution strategy, and then being surprised to find that the cost and leadtime are the same or greater than with the conventional process.
When designers create part models to be cast or machined, it’s rarely a good idea to force it into a 3D-printing space as-is. Instead, the team needs to sit back and ask, how will 3D metal printing ben- efit this application?
Question:
What makes my part a candidate for leadtime reduction using 3D printing?
Answer:
You have a few ways to determine this. The most obvious: when the con- ventional part requires long leadtime for tooling, molds or dies. Months for procuring a mold can drop to just a few weeks for a 3D-printed as-built part, though expect a leadtime for post-pro- cessing, especially if tight-tolerance needs require machining setups. Even
Caitlin Oswald is an additive-manufacturing specialist with LAI International, Inc., a contract manufacturer of precision-engineered finished components and subassemblies for the aerospace, defense, energy, medical and industrial markets: coswald@laico.com; 612/300-8722; www.laico.com.
Please e-mail questions for Caitlin related to 3D metal-printing best practices for material selection, machine parameters, quality control, etc. to bkuvin@pma.org.
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