5 common mistakes when designing parts for additive manufacturing

Designing for additive manufacturing (AM) can be challenging and it’s easy to make mistakes when designing parts for AM because there’s often conflicting requirements. There are many ways AM designers can improve their skills. They can participate in classes, find inspiration from other designs and practise on example problems. To improve, designers need to learn from their own mistakes too. 

With this in mind, here are 5 common mistakes that engineers should avoid when designing parts for additive manufacturing:

1. Not designing for the process
2. Build orientation as an afterthought
3. Underestimating the cost of post-processing
4. Not being aware of the latest CAD tools
5. Not looking at systems-level design

1) Not designing for the process

One of the biggest mistakes that designers make is failing to design for the additive manufacturing process. Additive manufacturing (AM) is often slower and more expensive than traditional manufacturing processes such as machining or casting. Therefore if we 3D print exactly the same parts that we make in traditional ways, the printed parts are likely to be more expensive.

In order to make AM a cost-effective process we need to design specifically for the process. This means designing for minimal material usage. We need to ensure that only material that is required for the function of the part is used in the design. To do this we can use advanced design techniques such as lattice generation and topology optimisation.

As designers become more experienced, they tend to move from designing for the additive manufacturing process in general to designing for a specific additive manufacturing process. For instance,  FDM and SLA are two common polymer additive manufacturing processes, however, the parts produced from these processes are very different.

As you get more confident with design for AM (DfAM), you should start to consider the type of process that you will use early on in the design process and then tailor the geometry towards that.

2) Build orientation as an afterthought

If you fail to account for the build direction early in the design phase you can add substantially to the cost of the part. Typically, the build orientation should be clear to the manufacturing engineer because certain geometry features often indicate the designers thinking.

Finding the right build orientation is often tricky. This is because build orientation is often a compromise between:

• Build time
• Support structure usage
• Packing density on the build plate

One of the challenges with build orientation is that CAD systems lack inbuilt manufacturing awareness. To get an understanding of the packing density and support structure usage, we often have to export the parts into “build pre-processing software.” We then evaluate the build conditions so are likely to need to return back and forth to our CAD system to make changes.

This iterative process can be inefficient but is a necessity to optimise our designs for 3D printing.

3) Underestimating the cost of post-processing

The third mistake that we commonly see is underestimating the difficulty of post-processing AM parts, especially metal parts. After the part has come out of the printing machine without any build defects, the work is often far from over. If the part requires post-machining and inspection, we must ensure that the parts can be fixtured and machined effectively.

Post-processing of AM parts is particularly challenging because we have often optimised the design using computational algorithms that generate complex organic geometry. This means that often there are no straight or flat areas for fixturing parts in the CNC machine.

Designers can make post-processing easier by considering how they will remove excess powder, cut away support structures and machine interfacing features to tolerance as a key part of the design process.

4) Not being aware of the latest CAD tools

This is a slightly controversial point because it’s not always a requirement to have the latest CAD tools to design parts for additive manufacturing.

However, the design for AM software market is evolving rapidly, and providers are constantly providing new and innovative solutions for simplifying the AM process to create lighter, more efficient, cheaper to manufacture printed parts.

There is now a wide range of software solutions ranging in complexity and price. All providers have dedicated applications engineers who can demonstrate how to use their software for your specific applications.

Whilst you can feasibly design optimised parts for AM using a basic set of CAD tools, it’s a good idea to trial new software from time to time to keep up to date with the latest trends in the industry. This means you can see how new features could be used to optimise your design process.

At Gen3D, we offer Sulis, which has inbuilt high performing CAD tools at entry-level prices. For more information on how to use our bespoke lattice and flow design software, check out the software page on our website. 

5) Not looking at systems-level design

The final item on our list of mistakes when designing parts for AM is that designers often fail to question the design requirements. All too often we look to optimise material usage to the gram, however, bigger gains can often be made by questioning the design problem itself.

Part consolidation is one of the big advantages of AM and systems-level design thinking can help find assemblies that are prime candidates for optimisation.