What is Design for Additive Manufacturing (DfAM)?

Production companies worldwide are recognizing that 3D printing is becoming a vital component in building resilient and market-leading supply chains. A “perfect storm” of factors has made this technology increasingly attractive for businesses leading to:

Improved production machines: Modern production machines are now significantly more reliable and user-friendly, making in-house manufacturing more accessible.
Advanced materials: The materials available today offer technical properties comparable to standard options, including both hard and elastomeric polymers.
Global access to reliable producers: The availability of dependable manufacturers worldwide, specializing in quick turnaround and series-quality parts, has expanded significantly.

Over the past five years, these advancements have scaled rapidly, creating an ideal moment for businesses to seize this opportunity.

The remaining challenge lies in the relative novelty of the technology. While engineers today generally understand the basics of 3D printing, there is still a significant gap in universal knowledge of the necessary design criteria. In contrast, injection molding benefits from well-established design optimization courses and advanced software systems like MoldFlow analysis, which help ensure part success. For additive manufacturing, design principles are gradually becoming more standardized and aligned with improvements in machine reliability.

Design for Additive Manufacturing - the key to successful 3D printed products

This article, along with the accompanying series of guides, provides a concise overview of core design principles for 3D-printed products, commonly known as Design for Additive Manufacturing (DfAM). These principles include a set of design guidelines and best practices developed by engineers to optimize parts for industrial applications. When paired with advancements in machinery and materials, as described earlier, DfAM accelerates the growth of additive manufacturing.

Because each 3D printing technology operates differently, the DfAM principles discussed here are tailored specifically to powder-based manufacturing, with a particular focus on HP Multi Jet Fusion technology. Developed by Hewlett Packard, a leader in consumer and industrial printing,

this technology is designed to deliver reliable, series production. Since its introduction in 2016, HP Multi Jet Fusion has become a market leader in both plastic and metal manufacturing.

Using DfAM to ensure first-round success for MJF products

The conventional wisdom to “never change a running system” has its place in the manufacturing world – but market pressures on price and speed along with the advantages of additive manufacturing are proving this saying out of date. While 3D printing has been part of manufacturing for 35 years, the bulk has been fringe use primarily for prototyping applications. The industrial ecosystem which has arrived with reliable machines, performant materials, and sound principles for design for additive manufacturing is still new territory for most businesses. This is why now is the right time to utilize 3D printing to gain personal success in your organization and a competitive edge.

These initial design for additive manufacturing guidelines help set the design expectations at the outset of the product development process to ensure that the selected item has the maximum chance of success before being produced by a contract manufacturer like Endeavor 3D. Understanding these principles is also a key communication tool internally for other design engineers, product owners, management teams, or end-customers to eliminate surprises or delays. When these core principles are in place from part selection to design approval, then the risk is almost fully removed from production.

The graph above illustrates several key business advantages of 3D printing. First, it significantly reduces product development costs by enabling multiple design iterations to be tested simultaneously during each phase. Second, it accelerates time-to-market by eliminating the need for injection molding or vacuum casting tooling, allowing for turnaround times as quick as 5–7 days. Without tooling constraints, designers and engineers can easily and cost-effectively update designs at any stage of the product lifecycle. Additionally, advancements in 3D printing machines and materials enable the production of parts suitable for end-use applications, delivering immediate value to your organization.

In our experience, once the principles of design for additive manufacturing are understood, the gains begin accumulating faster and faster. The design cycle length will continue to decrease since key design principles are already accounted for in the concept phase. However, the biggest advantage comes when the knowledge from the first part can improve the production of an entire group of similar products. For example, when you have determined proper tolerances for fastening systems on custom piping placed on specialty pump systems, an entire customer

segment can potentially be served by those custom pipes. Each routing geometry (the middle) would have the geometries adjusted for installation in their plant. The critical connection points can be reused to fit the pump systems based on that initial validation phase. Using the HP Multi Jet Fusion system, 3D printed parts can support a wide range of industries and applications. Many of these represent quick wins that help ensure success and secure organizational buy-in. This article serves as a toolbox, highlighting key design principles to achieve optimal 3D printing results and avoid common pitfalls on the path to bringing your products to life.

The Basics: 5 Quick Wins Using Design for Additive Manufacturing (DfAM)

When designing for HP Multi Jet Fusion (MJF), there are five key factors to consider for achieving optimal results. While not exhaustive, these guidelines highlight the most common use cases where MJF excels, delivering fast and effective outcomes:

Strong, Functional Parts: HP MJF is ideal for producing durable components like brackets, casings, and covers.
Optimal Part Size: Best results are achieved with small to medium-sized parts (5–25 mm) that have a compact form.
Complex Geometries: The more intricate the geometry, the greater the advantage of 3D printing, as traditional tooling costs rise disproportionately with complexity.
Moderate Detail Resolution: Parts should avoid extremely fine details, targeting a minimum feature size of 0.3 mm.
Production Volumes: MJF is most efficient for mid-sized parts in quantities of 5–500 and smaller components in runs of 1,000–5,000.

By keeping these considerations in mind, you can maximize the benefits of HP MJF for your designs.

Multi-fusion parts that have proper design for additive manufacturing processes can quickly move from production into products and machines.

1. Proper use of Wall Thickness in MJF

The first rule of thumb is to ensure that critical walls meet the baseline thickness for stability and that corners are rounded to improve performance.

The process of fusing layers in HP Multi Jet Fusion relies on a baseline wall thickness of 3mm in the X-Y and 5mm in the Z direction of the design to guarantee strength. Smaller dimensions are possible but often require a “calibration print” to ensure a good output. Smaller features are also potential fail-points so when aiming towards series products it is important to land in the middle of the tolerance spectrum.

For larger surfaces that experience direct pressure, the thickness should be increased or fitted with a ribbing structure similar to injection molded parts. Having consistent wall thickness throughout the part helps to ensure dimensional accuracy. When areas require more thickness for the function, they are more susceptible to warping (curling). Sometimes this is unavoidable when the thickness is needed for structural stability in the end application. A good example is when post-milling or machining of the 3D-printed parts is required for assembly operations. Whenever possible, these elements should be made lightweight using these design principles.

Because of the nature of the process, the weight (volume) of the part has one of the most significant effects on the total cost of the part. Reducing mass and working with structural ribbing not only brings a better output from printing but also directly improves the business case. This becomes even more important the more parts you produce. Often a 3D printed part can be cost-competitive into the 100s or low 1000s of parts with an efficient design.

More information about ensuring accuracy using design for additive manufacturing is in the sixth part of this series.

2. DfAM Tolerance Requirements for MJF

The second rule to ensure is that the design accounts for standard MJF tolerances to ensure first-round wins.

Typically, a part prepared for Multi Jet Fusion using principles of design for additive manufacturing can expect to meet IT Grade 13 accuracy (DIN 16742 TG6 – TG7 ) standards for part manufacturing. The highest accuracy is always on the X-Y plane because that is where the print head is depositing the bonding agent. Critical features should always be placed in that orientation. In the best cases, they are also noted in advance to ensure that the in-house production or an external printing service can optimize for those features when preparing production.

Tighter tolerances are achievable using scaling of particular features within a design. This requires close communication with the production team to ensure that the expectations are clearly defined and taken into account. Typically, 1-3 iterations would be produced with slightly different scaling factors to reach the optimal fit for series production. In some cases, you can get to a level of 0.15 mm for select features after accounting for placement within the machine.

The guidelines in the Ensuring Accuracy Article provide an excellent approach to improving performance.

3. Designing for Snap Fits and Inserts in MJF

The third rule is to focus on rules for creating accurate connections to best integrate with the entire mechanical system.

A single part isn’t valuable unless it performs properly in the surrounding system. The primary polymer materials available on the MJF System are Nylon PA11 and PA12. These are robust, engineering-grade plastics that can be used as strong parts in functioning machines. Here is a listing of the key watch points to ensure function.

Working with snap fits there are a few basic design rules to follow to engineer

a good connection. First, sharp edges can be challenging since the fusing of powder cannot form sharp edges reliably. By designing fillets on the top and lip of the part – the MJF machine will fully print the part at full strength. Next, by optimizing the build orientation, the area in the design requiring the most accuracy can be favored as required.

The second rule is that depending on where accuracy is most critical, the part should be printed in a different orientation. The critical geometry should be on the X-Y plane and that should be communicated to the production floor. A third consideration is that fusing plastic is slightly less stable than full-injection molded material. The difference is not as dramatic as other processes, but particularly if the snap is thin, a performance test should be used to validate the design. Some rules of thumb for calculating the strength are in the detailed guidelines.

Another important connection method is working with metal inserts. Here there is a simple guideline for creating the hole sizes (as the process tends to err on being slightly smaller than the CAD model). Having enough material surrounding the insert is also critical to ensure long-term strength in the part. When those rules of thumb are followed, then MJF parts can be used as direct replacements to cast parts. Depending on how often torque will be applied on the insert, there are a few different types that are recommended. The details are included in the article about joining elements.

For applications that do not require regularly removing and reinserting the connecting part, 3D-printed threads can be designed directly. The main factor is the resolution of the threads which need to be produced. 3D printing is particularly interesting for large, non-standard thread types where one-off cutting tools can easily run in the thousands of euros and be relatively inconsistent in placement compared to 3D printing. For standard sizes of screw threads, the shape can be cut directly into the part like any other plastic.

4. Designing Interlocked Moving Elements using MJF

The fourth design concept to guarantee consistent movement and eliminate the work of adding subcomponents is to directly design and 3D print interlocking elements.

One of the more interesting advantages of 3D printing is designing fully articulating parts directly from the 3D printer. The basic principle is that a hinge element or moving ball joint is added to the original design file as a fully enclosed system. There is then an opening at the bottom or front of the design so that the unfused powder falls out of the moving joint after a minimal amount of use. The part then has a secure joint without requiring any additional hardware.

For complex assemblies, this is particularly interesting because if the design of individual elements changes, they can be printed as a complete unit rather than coordinating multiple parts in an assembly. Particularly when manufacturing spare parts or products with variable demand volumes, that eliminates the risk of using legacy parts from an older design and eliminates keeping a separate stock of hardware for assembly operations.

More ideas for optimizing parts with interlocked elements can be found in the article on assembly consolidation.

5. Joining Rules for Oversized Parts in MJF

The last rule of thumb is to not shy away from producing large parts by using proper joining techniques.

One of the remaining hurdles for additive manufacturing is building capacity and size. As the volume of the part grows, the price increases more quickly in 3D printing – similar to quickly raising costs of tooling. For large sized parts, they often no longer fit in the build chamber requiring splitting of the parts (HP MJF 5200 series: 380 x 284 x 380 mm). The solution is to use joining methods that originally are known for woodworking. This increases the surface area for gluing the part to ensure a strong bond and uses overlapping geometries to ensure a tight and accurate fit of the parts.

Successfully joining parts and achieving structural strength comes from two steps. First, the design for additive manufacturing principles for accuracy and tolerances needs to be used while preparing the interlocking joining areas. This ensures that the design has slight tolerances so it will fit properly while still having a tight fit. It is also important that the parts that will connect are printed in the same orientation so that any process deviations occur to both pieces equally. The second step is using a time-tested joining method to work with larger surface areas for gluing to ensure the strength of the connection. This means, there is not a straight cut, but instead, teeth, corners or ledges that provide structural strength similar to traditional woodworking designs. In fact, our experience is that when the part uses design for additive manufacturing principles, any part breakage due to impact or weight overload will occur somewhere else on the part since the engineered joint with bonding through glue is particularly robust. We have many additional tips and examples in the detailed article on designing for accuracy.

Capturing Early Wins Using Design for Additive Manufacturing

Adding 3D-printed parts to your production portfolio is a short journey away. As illustrated above, the key principles known as Design for Additive Manufacturing have been developed and validated by capable engineers over the past decades. When those rules of thumb are followed in the design, there is a very high likelihood of success. Those DfAM rules combined with advances in machines and materials have made 3D-printed parts robust and reliable to compete head-to-head with conventionally produced parts. When you partner with a contract manufacturer to review the design and scale production reliably and cost-effectively, it has never been easier to add 3D printing to your company.

When these“quick win” applications have won acceptance within your organization, the next step is to add specialty functionality and design elements that are unique to additive manufacturing. This will help you gain a competitive market advantage alongside the pure business advantages from the quick wins. Those DfAM features have a more difficult learning curve in the initial design phase but remove processing steps later in the value chain or unlock strong performance advantages for your products.

The pathway is clear. When will you pick up your 3D-printed quick win?

What is Design for Additive Manufacturing (DfAM)?