Remember Groundhog Day? Not the day in February but the movie starring Bill Murray. In it Murray plays a character forced to live the same day over and over. This gives him the opportunity to try different things until he hits on the magical combination of actions that sets him free.
Design is a lot like that, or at least it should be. Good designers keep iterating, exploring new ideas, refining their design until they come up with a solution that best satisfies all the constraints. As we all know though, in the real world, unlike in Groundhog Day, time is in short supply. To meet production deadlines the designer is forced to settle for something less than optimal.
Generative design tackles that problem head-on. It lets the designer explore far more potential solutions than is humanly possible, especially when the boss is breathing down his neck! Here we’re going to explain what generative design is and what it does for manufacturers and product engineers. Then, because here at Wiley we’re metal fabricators, we’ll share some thoughts on what it means for our industry.
Finding the Optimal Solution in Generative Design
At the end of February Tiki Talk covered a weird looking seat bracket that GM had 3D printed, and we mentioned that they’d used generative design to create its shape. (“How Additive Manufacturing is Being Used in Sheet Metal Fabrication” if you missed it.)
In generative design an engineer defines the design goal along with constraints like mounting faces, material, maximum weight and loads expected. Then software works out solutions to this problem and presents them to the engineer. So far so good, but maybe you’re wondering how that leads to those organic shapes. Let’s dive deeper.
Generative Design Basics
A few years ago CAD companies starting talking about something called, “topology optimization.” This is a tool for deciding where material is needed in a component and where it isn’t. Having produced a design in CAD, the engineer tells the system about the forces that will be applied and software works out the load paths. With this information the engineer can delete material where it’s not contributing to strength and add some where it is.
Generative design automates this process, taking the design through a huge number of iterations until it arrives at a set of solutions. (You might also see it described as “physics-driven design” because it’s applying physics to design optimization.) But that’s not all it does.
To create those weird shapes generative design is using “form synthesis.” This frees it from the constraints of conventional manufacturing processes. The software grows structures around “preserve” and “obstacle” regions the design engineer defines in CAD to create the most efficient shape it can come up with.
As you might imagine, generative design needs a lot of computing power. For that reason, generative products like Autodesk’s Fusion 360 do the actual processing in the cloud and send only the results back to the engineer.
Generative and Additive
It’s all very well coming up with these designs, but someone has to make them, and that’s where additive comes in. Additive manufacturing, (3D printing), builds these structures, in metal or polymers, piece by piece. In fact it’s the only way most products designed generatively could be produced.
Additive has some limitations of course. There are minimum wall thicknesses to maintain, overhangs are hard to produce, and support structures are often needed. However, these constraints can all go into the initial model, ensuring that the final design is printable.
Driving Forces behind Generative Design
Helping designers explore more options in less time is laudable, especially if you are a designer, but it’s not what’s really pushing this technology forward. The big thing is lightweighting, followed by part consolidation.
The aerospace and automotive industries are both very big on lightweighting. Less mass translates to higher payloads, improved performance and better fuel efficiency. The GM seat bracket for example is 40% lighter than the conventional equivalent and also 20% stronger.
The other point to note about that bracket is that it combines eight parts into one. Part count reduction has a lot of benefits for a company like GM. Tolerance stack-ups are avoided and there’s less waste because you’re never overstocked with one component and out of another. It also simplifies purchasing, inventory management and so on. Now admittedly, the part isn’t in production, but these are the factors driving interest in generative design.
Generative Design in Metal Fabrication
So far generative design has been developed with the intention of using additive methods to make the parts. There is recognition though that generative could fit with more conventional processes, and this is something the CAD companies are working on.
Casting is an obvious candidate. The value of generative lies in putting material only where it’s needed, so why not design casting dies and molds with it? We could even imagine 3D printing sand patterns with all sorts of complex features.
In the subtractive realm, (our fancy word for machining,) 5-axis milling looks a good fit with generative design. Following complex cutting paths, a mill could hollow-out ribs and cavities to, again, leave material only where it’s needed.
The same goes, in our view, for fabrication. Fabricated structures use a lot of bracing to create stiffness. Generative design could perhaps help in optimizing the size and location of that bracing.
Then there are sheet metal parts that have bends added for stiffness. Generative design could help identify where material can be taken out. Feeding that information to a turret punch or laser cutter, we could then remove what’s not needed before the blank goes into a press brake or folder.
In short, to the question, “Is there a place in metal fabrication for generative design?” we say, “Why not?”
New Appearance, Higher Performance
Design should be an iterative process, but it’s a fortunate designer who has time to explore multiple options. Generative design puts that freedom back into the process. When combined with additive manufacturing it results in weirdly organic shapes that no human designer would ever conceive. Stronger and lighter than the results of human design effort, products created by generative design will look like nothing we’ve seen before, and some might even be fabricated!