A recent interview with Daniel Lazier, Strategic Application Engineer, at Markforged, covers tips on getting the most out of your additive manufacturing project.
Here are a few points from the interview.
1. Increasing yield to same time and money.
Yield, in the context of additive manufacturing, is a function of feature parameters and process parameters. For example, with the Markforged systems, you can improve yield by considering the process itself, (which is fused filament fabrication (FFF)), and designing features that can be self-supporting. This means reducing the need for overhangs that require additional support.
Another example is to consider the path the nozzle will take to place material. As Lazier notes, “We see users shifting their mindset from one of the number of cuts, which is a very CNC focused mindset, to a more additive mindset where you’re only depositing material in the places where you need it, taking into consideration constraints like gravity and so on. There are efficient ways to place material, which can speed up the build process, improving yield.
Also, consider using inlay lattice patterns rather than a solid build. Internal lattice patterns offer support using a minimal amount of material, reducing build time and cost.
2. Software for planning an additive layout.
Traditional CAD software programs did not always optimize for an efficient additive printing layout. Newer programs, such as generative design or topology optimization, help designers think about creating designs for additive manufacturing technologies.
These programs will take design parameters on load, thermal, or aerodynamic requirements, for example, and then output oftentimes alien-looking features that optimize the solution to a problem.
Then, slicer software aids in determining part settings and how to print the geometry. Noted Lazier, “Markforged offers a slicer program known as Eiger. Eiger includes the ability to customize a lattice structure that’s built up in the internal feature of the part. So, the outer shell is as designed, but the interior of the part may look like a honeycomb or a triangular truss structure.”
3. Tips on geometry.
With traditional manufacturing, an engineer might prototype the whole project several times before building the design. But with additive technology, because users pay for the material used, they can prototype sections of a design until they get it right, and then prototype the whole design.
“I can just break out little features, like say I have a really complicated connector,” says Lazier. “In fact, just yesterday, I was designing a sample part that I wanted to fit together like a Lego almost so that the two pieces come together with a subtle adherence to one another.
“In that case, I can just break out that unique feature, and then I’ll iterate on it a couple of times. I might fill up a build plate with 10 iterations in one print and then in a matter of a few hours, I can obtain the part that I need that points to that feature complexity.”
Lazier cites a recent example from a Siemens’ client. “They developed this really neat looking cutback tool to service their gas turbines. And they needed unique and complex holding surfaces for the circular saw that was going to be part of that tool.
“When they went through the process of iterating, it wasn’t so much like they were taking the whole entire saw and printing it every time, they were just printing out bits and pieces that had a feature complexity. Rather than take a print that might take a day and make it 10 times in 10 days, they took a 30-minute subsection and did that 10 times taking five hours instead.”
4. Material choices.
The Markforged printer works differently than other metal 3D printers. It’s an extrusion process using a feedstock material composed of metal powder. Once the part is built layer by layer, it goes into a deep binder tank that removes the polymer component of the part. Then the part is placed in a furnace that solidifies the metal particles into a final physical body. Other additive processes using metal may involve laser sintering, where sections on a bed of metal powder are fused with the laser.
“The factors that would lead me down one road or another,” notes Lazier, “the physical characteristics that I’m generally looking at are things like size and where I’m going to need support overhangs. Those constraints actually look really different from those two print systems, where, with something like laser sintering, I’m generally going to be most concerned with a factor like heat.
“Several software packages model how things might work as a function of heat in that relatively intense chamber. With the Markforged process, we consider how the heat in the furnace will affect geometry, and how to support or combat potential slumping as a function of geometry.”
In addition to metals and polymers, designers can also consider composites. Continuous fibers, for example, can often have strength on par with metals.
“Our continuous carbon fiber, for example, performs like 6061 aluminum in terms of tension and flexural strength.”
Such a material is useful in applications needing strength but is light in weight.
In a decision tree, when might a designer choose between metal and a composite? Composite parts like traditional composite laminate structures generally perform really well in the plane that those laminate fibers are laid, but in the inter-layer adhesion, that’s going to be an area of potential vulnerability in the design, says Lazier.
“I might point an engineer toward a metal print system in a case where I have lots of different accesses that could be subject to loading conditions. Relatedly, hardness is a big characteristic where we’re going to make sure that we identify metal as the right use case. And going along with that, temperature.”
Polymers, of course, work well in applications with lower temperatures.
Many times, though, a part is better made with multiple materials. “We see lots of customers employing strategies like hybrid parts. For example, size can be a big constraint for metal, but not so much for a polymer composite. We see our customers taking really, really big sections of their part, like say an end effector that needs to withstand a lot of load in one axis. They might print a majority of that arm in a composite, and then produce the tip or the contact point that needs to be custom in metal, and then bond the two together, either through bolts or an adhesive or other kind of binding agent.
One of the material aspects to consider with composites is fiber direction. “There’s a bit of a learning curve with composites. This material has fibers laid in a plane, so where the design will experience mechanical load becomes a design criterion.
“When I was first trained in this technology, it was kind of like being on a roller coaster, and then all of a sudden that roller coaster can now go off the rails, where I could point that continuous fiber in that plane, in any direction that I’d like, which is almost like a superpower, being able to that specifically dictate how a part is going to respond to mechanical stresses.”
Other challenges include the “two-axis problem,” where fibers will be laid in a laminate structure that is two-dimensional. The implementation or use of external components off the shelf components, like pins or bolts to restrain that part in the Z-axis, it’s going to be a super useful strategy long-term.
“We design parts in the 2D layer by layer format, but those parts need to perform in the 3D world. That being the problem statement, one of the most potent solutions we have for that using off-the-shelf components like bolts. And for a couple of cents, I’ve solved this problem where I no longer have this type of vulnerability in this part.