3D printing (aka additive manufacturing) has gone far beyond making prototypes quickly. It is now entrenched in manufacturing, and examples abound:
- The Juno spacecraft, built by Lockheed Martin and NASA and currently completing its mission in orbit around Jupiter, carries a dozen 3D-printed waveguide support brackets.
- Activated Research Co. used 3D Printing to develop a new design for its Polyarc gas chromatography catalytic microreactor, bringing it to market in just 15 months.
- Raytheon uses 3D printing for rocket engines, fins, and control components for guided missiles, creating parts in hours rather than days.
- Boeing set a world record in 2016 by building the largest 3D-printed item ever made, a fixture used in building 777 airplanes, reportedly cutting weeks off its manufacturing time.
- Brunswick Corp. relied on 3D printing for air conditioning grills on its Sea Ray yachts, eliminating the need for disposable tooling and speeding product development.
- This air-conditioning grill for Sea Ray yachts was 3D printed.
In these cases, results included greater functionality, lower weight, and reduced manufacturing costs, and oftentimes all three. Here are six design considerations that made these benefits possible:
1. Optimize the Design
Well-designed 3D-printed parts follow many of the same rules as those made with injection molding. These include: Use gradual transitions between adjoining surfaces. Eliminate large differences in cross section and part volume. Avoid sharp corners that often create residual stress in finished workpieces. Watch that thin unsupported walls don’t grow too tall, or they may buckle or warp. And surfaces with shallow angles tend to leave ugly “stair-stepping” that makes them unsuitable for cosmetic features; flatten them out when possible.
2. Throw Out Tradition
The most dramatic 3D-printed part designs leverage 3D’s ability to create “organic” shapes, such as honeycombs and complex matrices. Don’t be afraid to use these shapes, provided doing so creates a lighter, stronger part. Nor should you fear placing holes (and lots of them) in your design. With traditional manufacturing, drilling holes in a solid block of material increases part cost and waste. Not so in the additive world, where more holes mean less powder and less processing time. Just remember, 3D-printed holes don’t need to be round. Quite often, an elliptical, hexagonal, or free-form hole shape would better suit the part design and be easier to print.
GE uses several innovative 3D-printed parts in its LEAP jet engine.
3. Consider Next Steps in the Design Cycle
Just because you can print parts with lots of holes, however, doesn’t mean you should, especially if the plan is to make lots of such parts later. Because 3D printing offers tremendous design flexibility, it’s easy to paint yourself into a corner by not considering how parts will be manufactured post-prototyping. Based on examples at the start of this design tip, an increasing number of companies are finding 3D printing suitable for end-use parts, but many parts will transition from printing to machining, molding, or casting as production volumes grow. That’s why it’s important to perform a design for manufacturability (DFM) analysis early in the design cycle, assuring cost-effective production throughout the part’s life cycle.
4. Avoid Secondary Operations
Plastic parts produced using SLS need no support structures during the build process, so post-processing is usually limited to bead blasting, painting, reaming, tapping holes, and machining critical part features. Direct metal laser sintering (DMLS), on the other hand, often requires extensive scaffold-like structures to support and control movement of the metal workpiece; without them, surfaces may curl and warp. This is especially true with overhanging geometries such as wide T-shapes, which require build supports beneath the arms which will have to be machined or ground away, thus increasing cost and lead time. The story is similar but less dramatic with SL, where cured resin supports are easily removed with a hand grinder and some sandpaper. Where possible, parts should be oriented to reduce these overhangs and other unfriendly features.
Brunswick Corp. used 3D printing to make air-conditioning grills on its Sea Ray yachts, eliminating the need for traditional tooling.
5. Watch the Tolerances
Designers and engineers should avoid “over-tolerancing” parts because it may force them to be built using thinner layers (increasing build time and cost), and will often call for secondary machining operations to meet overzealous print dimensions. Because 3D printing offers so many opportunities for part count reduction, there’s less need for super-accurate fits between mating surfaces anyway—just one more example of how this technology reduces manufacturing costs.
Some parts produced with DMLS require hand finishing. Well designed 3D printed parts minimize post-production steps that add cost and time.
6. Look at the Big Picture
3D-printed parts might cost more upfront, but don’t let that scare you. With additive, you have tremendous potential for part count reduction, reduced weight and greater structural integrity, lower assembly costs, internal passages for cooling or wiring, and other features not possible with traditional designs. Also, keep in mind that fixtures, molds, and other types of tooling are not needed with 3D printing, eliminating costs that might not be directly associated to the price of the individual parts. Focusing on the part’s price tag, rather than product function and “the big picture,” may leave you designing the same parts you did yesterday, eliminating opportunities to reduce overall manufacturing costs.
This was written by Eric Utley, applications engineer at Protolab. If you have any questions regarding 3D printing, please feel free to call a Protolabs application engineer at (877) 479-3680 or e-mail at [email protected]