Designing For Additive Manufacturing

The process with which a part will be manufactured considerably impacts its design, and product designers rely on years of experience and comprehensive process design guidelines to design parts specifically for the manufacturing process with which they will be produced. Typically it’s a collection of parts that come together to make the final assembly, and every one of those parts is designed with the manufacturing process in mind that the design engineer deems will produce the most economical result while simultaneously maintaining the intent behind the design – form, fit, and function. This process of designing for the manufacturing process is aptly called Design for Manufacturing (DFM), and typically, when we discuss DFM, we’re talking about it in the context of legacy manufacturing processes like milling, turning, or injection molding, to name a few.

In contrast to more traditional subtractive methods which involve removing parts of a block of material to make an object, additive operates by adding material together – sintering a bed of powder, or by selectively polymerizing a liquid resin, for instance – to form the final shape, and with that comes numerous materials, technologies, and software solutions that shape, to some extent, the design process. But perhaps the factor that most contributes to how product designers and engineers design for additive is the ‘design freedom’ the technology offers them and the opportunities for design innovation it provides. 

Just as with traditional processes, it is essential here that the design is contextualized for the technology in order to derive the most benefits. Competing for cost with an existing design – or in other words – bringing over a part from a legacy process to an AM process ‘as-is’, is likely to be a losing battle, save for a few exceptions. Designing specifically for AM will ensure fully functional designs that deliver, through the design freedoms offered by the technology, on multiple requirements for the lowest cost.

This article we will look at the broader picture of design for additive manufacturing (DfAM), the various design opportunities that additive provides and the cost and performance benefits of additive.

Where are you in your product development cycle?

The first thing to consider when starting out is where you are along the product development cycle. While it’s ideal to completely design for AM, real world applications can be less than ideal. When setting out, ask yourself: does the part or product you’re working with have a set design? Is it a part (or an assembly of parts) that could potentially benefit from moving over from a legacy process to an additive process? Is the design in its conceptual stages and the limits are as far as the technology (and your imagination) can take them?

Early on in the development cycle you will have more opportunities to utilize AM fully, since the final part design at this stage isn’t set. You can think about design completely within the context of additive. It is at this stage that you can gain the most performance and cost benefits from additive, by making use of complex designs (such as those possible with latticing or unorthodox geometries), and further lightweighting using lighter weight materials and methods like topology optimization to trim the fat while maintaining or improving on performance fidelity.  

In cases where the product design is set, perhaps due to a form-fit-function constraint of an existing design its trying to accommodate (like a car seat bracket designed for a particular vehicle, for instance – in this case unitized using generative design), there may be opportunities to combine assemblies with additive – potentially saving on weight, material, and assembly costs (typically all three). HP, for instance, consolidated a coolant extraction shoe for its printer line from 7 parts to a single part. The shoe was originally machined and assembled from its individual parts, and consolidated with AM using HP’s multi jet fusion process. This switch to additive resulted in 95% cost reduction and 90% weight reduction.

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Additionally, if you’re at an even later stage in the product development cycle, you may spot opportunities for lightweighting particular parts by using complex lattice structures to maintain or improve on the part’s performance and produce cost savings by using less material.

Designing for Performance: Complex Designs

As mentioned earlier, the largest value you can get from additive is the design freedom inherent to the technology. With legacy processes like Machining or Injection Molding, designing complex geometries requires equally complex (and typically much more costly) setups and tooling. In many cases, these complex designs may not be feasible, both from a technical and economical point of view.

With AM, you can use topology optimization or AI generated design to reduce the mass of a part, increase its surface area, or improve its mechanical fidelity by using complex lattice structures – producing more economical, lighter-weight parts, with better heat transfer capabilities or excellent shock absorption, among other improvements in mechanical properties – depending on the requirements of your specific application.

Let’s look at these methods with a bit more scrutiny.

Topology Optimization

Topology optimization (TopOp) allows you to optimize a part through material reduction. It enables rapid design exploration and improved development productivity. A design engineer provides constraints at the beginning stages of the design process, including materials to be used, expected loads the part will see when in use, and other governing factors, such as the volume of space a part can occupy – to name a few – and the TopOp software will deliver the engineer designs optimized around those parameters, refining the geometry of the part in a collaborative (and iterative) process between software and engineer until a final part design is reached.

Topology optimization can drastically reduce product development times and produce manufacturable parts that meet performance objectives or improve upon existing performance capabilities while minimizing the mass of the part and overall assembly. AM allows you to create parts that have been topology optimized to a level of complexity that may not have been previously manufacturable, allowing you to draw even more benefit from the technology.

Generative Design

Topology optimization is itself an example of generative design, but when we discuss generative design today, we are primarily talking about AI driven design based on biomimicry. Generative design is a design process that uses artificial intelligence to generate and explore a wide range of design solutions. But unlike topology optimization, AI driven generative design doesn’t require a human-designed model to begin the process, as a result broadening the potential part design outcomes.

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When generative design is combined with an innovative technology like additive, it opens up a world of possibilities for the future of product development. An engineer simply sets the constraints on the design and the software will run simulations and remove material not carrying loads through the part, returning hundreds, if not thousands or millions, of manufacturable designs. 

Lattice Structures

Latticing plays a large role in AM applications as well for its ability to produce lighter weight components with high strength-to-weight ratios, large surface areas (for heat exchange applications, for instance), excellent shock absorption, among other mechanical benefits. Less material used in latticed parts also translates to lower costs. We looked at the role lattices play in product design in our article on lightweighting in electric vehicles.

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Designing for Assembly: Parts Unitization

Within the umbrella of designing for additive, much like with DFM in general, you can also look for opportunities to design for assembly (DFA) optimization. Designing for assembly is the process of designing with the goal of minimizing the total number of parts that make up the final product. This results in a product that is easier to assemble, in turn saving time and money.

Designing for assembly in the context of additive manufacturing through parts unitization opens up opportunities that have previously been infeasible with traditional processes due to the complexity of the designs allowed by AM. With AM, combining the assembly of four or eight or twelve components into a single part is not out of the realm of possibilities. 

In addition to simplifying assembly, parts consolidation helps trim down your supply chain and improves product performance.

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Conclusion: Benefits and Cost Savings When Designing for Additive

As is often the case, design for additive manufacturing is used to lightweight parts and assemblies by using techniques like topology optimization, generative design, parts unitization, and latticing, reducing the cost of materials and the total volume to build. Less volume to build equates to smaller build times, and therefore lower machine costs. In the case of parts unitization, you’re also saving money on assembly time.

DfAM also reduces the amount of support material needed, further increasing savings on material costs, build time, and post-processing.

Additive enables you to take products to market much faster than previously possible, shaving weeks and months off of your lead times. In some cases the technology can be used for bridge production when the final product will be manufactured using another process, helping you expedite your time to market.

In addition to cost benefits, additive allows you to produce parts that perform better, by allowing you to create unique geometries only feasible with additive, and helping you produce lighter weight parts with better heat transfer capabilities, improved internal flow channels, among others. Lightweighting parts has already seen significant headway in the aerospace industry because of its downstream effect of saving money on fuel costs when a plane is in operation. These same benefits extend to other industries and applications.

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Designing for additive is the value multiplier of additive manufacturing. Bringing over an existing design as-is is almost certainly to be a losing battle, simply because the part or product was designed for a different manufacturing process. There are certain exceptions to the rule but they are far and few in between. To garner the most benefits from additive, you must start with DfAM.