How to Design 3D Prints: Software, DfAM, Advanced Strategies

Additive Manufacturing (AM), or 3D printing, marks a shift from traditional subtractive methods to a layer-by-layer approach that builds physical objects directly from digital models. Originally used for prototyping, AM has evolved into a viable production tool across industries such as aerospace, automotive, medical, and consumer products. It utilizes material forms like filament, resin, or powder to create complex parts with a high level of speed and material efficiency.

AM’s core benefits include unmatched design freedom, rapid prototyping, reduced material waste, and potential for mass customization. Among the seven AM process categories defined by ISO and ASTM, this guide focuses on key technologies relevant to engineers: Fused Deposition Modeling (FDM), Stereolithography (SLA), Selective Laser Sintering (SLS), Multi Jet Fusion (MJF), and Direct Metal Laser Sintering (DMLS), also called Selective Laser Melting (SLM).

This guide is tailored for design and hardware engineers aiming to produce functional AM parts. It covers the relationship between process, material, and geometry, while introducing essential Design for Additive Manufacturing (DfAM) rules. Topics include material selection, CAD-to-print workflow, advanced design techniques, post-processing, and common pitfalls—empowering users to fully leverage AM's capabilities.

Design for Additive Manufacturing

DfAM ensures parts are designed to suit the 3D printing process

Design for Additive Manufacturing (DfAM) is vital for engineers aiming to harness the full potential of their 3D printer. Unlike traditional Design for Manufacturability (DfM), which suits subtractive or formative processes, DfAM emphasizes functional geometry and material efficiency—adding material only where needed. It takes advantage of additive’s strengths, including geometric freedom and part consolidation.

Common 3D CAD or 3D modeling software tools like SolidWorks, Fusion 360, and Siemens NX serve as DfAM foundations. Advanced features such as mesh editing, topology optimization, lattice structures, and simulation tools help optimize designs for printability, strength, and efficiency. Direct modeling enables fast iterations tailored to AM-specific constraints.

Key design rules for printed parts include maintaining appropriate wall thickness—typically over 0.8 mm for FDM, and 0.4–0.5 mm for SLA. Powder-based methods like SLS and DMLS have their own minimums. Proper orientation affects strength, accuracy, and support needs. Minimizing build height shortens print time, while aligning critical features with the build direction can improve mechanical performance.

Overhangs over 45° in FDM and DMLS usually need support, whereas powder-bed systems like SLS are more forgiving. And features such as chamfers, fillets, and teardrop holes can reduce or eliminate support requirements. Bridges and small unsupported spans are limited—typically around 5 mm in FDM and 2 mm in DMLS.

3D printers also have limits in terms of detail: small features like holes and pins need careful sizing—minimum 1 mm in FDM, smaller in SLA or DMLS. Threads are often better added post-print, while clearances are crucial to avoid fused parts, especially in tight-fitting or moving assemblies.

DfAM Summary Table

Material Selection and Design

Selecting the right material in additive manufacturing (AM) directly affects the design of a part. Material properties—such as stiffness, strength, thermal resistance, and chemical compatibility—determine how the part will perform and how it should be designed. For example, a flexible material like TPU requires different design considerations compared to a rigid material like Nylon or a high-performance material like PEI. The material guides key design features, including wall thickness, support structures, and part orientation.

Material-driven design considerations include:

• Support structures: Materials that warp, such as ABS, may need more support or a specific part orientation to avoid defects.

• Part orientation: Strong materials like PEI benefit from adjusting orientation to maximize strength and reduce warping.

• Surface finish: SLA resins often need smoother finishes, so designs may require specific supports that are easy to remove without damage.

Besides strength and flexibility, a material’s behavior during printing influences design decisions. Thermoplastics like ABS may warp or shrink when cooling, which could require thicker walls, specific orientations, or the use of a heated bed to prevent issues.[1] On the other hand, SLA resins are more brittle, so designs need more uniform wall thicknesses and effective support structures to avoid breakage. Nylon and PETG, often used for functional parts, need designs that account for stress distribution and long-term durability.

For metal materials such as stainless steel or titanium, design must account for factors like thermal conductivity and internal stress. Metal parts may need specific adjustments for post-processing, such as heat treatment.

Recommended reading: Understanding CAD File Types: A Comprehensive Guide for Digital Design and Hardware Engineers

Designing 3D Prints Step by Step

3D design software can be difficult to use for beginners

Designing a 3D print using a CAD program or other design software involves several steps, from selecting the right software to exporting a print-ready file. This guide breaks down the process into clear, simple steps.

1. Choose the Right CAD or Modeling Software

Your 3D design journey starts with picking the appropriate software. For beginners, Tinkercad is an excellent browser-based tool with drag-and-drop functionality. It’s ideal for basic models like keychains, nameplates, or simple enclosures. For more advanced users, Fusion 360, SolidWorks, Blender, or FreeCAD offer powerful modeling tools for engineering parts, artistic models, and assemblies. Fusion 360, in particular, strikes a good balance between ease of use and professional features like parametric design and simulation.

2. Define the Purpose of the Part

Before modeling, consider what your part is for. Will it be decorative, structural, mechanical, or wearable? Understanding its function will help determine what material you’ll use and how strong or flexible the part must be. For example, parts under stress need thicker walls or reinforced features, while a simple figurine can be hollow and lightweight.

3. Model the Object Thoughtfully

Using your chosen software, start building the object using basic shapes or sketch-based geometry. (Further modelling basics are explained in the next section.) Keep these tips in mind:

• Use consistent units (mm or inches) and precise dimensions.

• Maintain minimum wall thickness (typically 0.8 mm or more for FDM printing).

• For snap-fit parts or enclosures, leave clearance gaps—about 0.2–0.5 mm is typical depending on your printer’s accuracy.

• Avoid sharp inside corners, which can be hard to clean or print accurately.

4. Account for Overhangs and Bridges

Overhangs are features that extend outward and are not supported beneath. Most printers struggle with overhangs greater than 45°, and bridges (horizontal spans) beyond 5 mm may sag if unsupported.[2] Use techniques like:

• Chamfers instead of sharp 90° overhangs.

• Teardrop or diamond-shaped holes instead of circular holes in horizontal surfaces.

• Design parts in a way that minimizes the need for external supports.

5. Add Details with Printability in Mind

Text, holes, pins, and small features should be sized with the printer's resolution in mind:

• Text should be at least 0.4 mm high and 0.5 mm wide to remain legible.

• Holes should be ≥ 1 mm for clean resolution.

• Avoid overly fine threads—use inserts or post-processing to add threads for mechanical parts.

6. Design for Print Orientation and Strength

Orientation affects strength, surface quality, and print time. For FDM prints:

• Parts are strongest along the layer lines, so align structural elements accordingly.

• Orient large, flat surfaces parallel to the build plate to prevent warping.

• Hollow or enclosed shapes should include escape holes for trapped resin or powder in SLA/SLS processes.

7. Export the Model for Printing

When your design is complete, export it in a 3D printable format, typically STL or 3MF. An STL file is the most common but does not include color or material data. 3MF is more modern and can store additional information like print settings or units.

8. Slice the Model Using Slicing Software

Use a slicer like Ultimaker Cura, PrusaSlicer, or Bambu Studio to prepare the model for printing. The slicer converts your 3D model into layers and generates G-code, which your printer reads to know how to move.[3] Key settings include:

• Layer height (affects detail and print speed)

• Infill density (affects strength and weight)

• Supports (for overhangs)

• Brim or raft (for bed adhesion)

9. Save and Print

Once slicing is complete, save the G-code file to an SD card or send it to your printer wirelessly (if supported). Monitor the first layers carefully to ensure good bed adhesion, which is critical for a successful print.

Recommended reading: How to Make a 3D Model for Printing

3D Modelling Basics

Creating a 3D print-ready part begins with establishing the basic shape in your CAD software. First, start by sketching a 2D profile of the part on a selected plane, using tools like line, circle, or rectangle to define its outline. Once the basic sketch is ready, use features like "extrude" or "revolve" to convert the 2D sketch into a 3D object, adding depth or curvature. For more complex geometries, you can combine multiple sketches or use Boolean operations to add or subtract material.

After establishing the main body of the part, refine the design with features like holes, fillets, or chamfers. Holes can be created with the "extruded cut" tool, ensuring they have the correct diameter for the intended functionality. Fillets and chamfers can be added to edges to improve strength or ease of assembly. It’s also important to consider the thickness of walls, as parts that are too thin might not print well or could fail under stress. Many CAD tools allow you to measure wall thickness directly or display warnings for parts that fall below a certain threshold.

Using the "mirror" or "pattern" tools can help replicate symmetrical parts or structures without manually redesigning them. Additionally, optimizing internal features, such as adding ribs or lattice structures, can strengthen the part while reducing material use.

Advanced 3D Printing Design Strategies

Lattice structures are often deployed in aerospace metal AM

Advanced design strategies in additive manufacturing (AM) go beyond basic printability to unlock the full potential of 3D printing. These techniques—topology optimization, generative design, lattice structures, and integrated geometries—allow for complex designs for parts that are lighter, stronger, and more efficient than those made with traditional manufacturing.

Topology optimization and generative design use software to remove unnecessary material or generate multiple design options within defined constraints. Engineers input load conditions, boundary limits, and performance goals (e.g., minimizing weight or maximizing stiffness), and the software outputs organic-looking geometries optimized for performance. These designs are ideal for AM, which can produce their complex shapes with ease. They’re commonly used in aerospace, automotive, and robotics for lightweighting and part consolidation—replacing multi-part assemblies with a single, optimized component.

Lattice structures are intricate 3D frameworks made from repeating cells like gyroids or tetrahedrons. They drastically reduce weight while maintaining structural integrity.[4] Lattices can be tailored for specific stiffness, strength, or energy absorption, and even used for specialized applications like heat exchangers, sound dampening, or bone implants. However, they must be designed with the printing process in mind—ensuring that powder or resin can be removed from inside and that minimum printable strut thicknesses are met.

Complex geometries and part integration represent another strength of AM. Parts can include internal channels for fluid flow or conformal cooling in tooling, eliminating the need for traditional drilling or welding. Enclosures for electronics can include integrated features like vents, mounts, and cable guides in a single print. Engineers often turn to biomimicry for design inspiration, emulating efficient natural structures.

Conclusion

3D printing represents a major shift in engineering, allowing the creation of complex, optimized parts that are difficult or even impossible to produce using traditional manufacturing methods. Additive manufacturing’s ability to build geometrically intricate and functionally efficient structures gives designers more freedom, especially in fields like aerospace, automotive, and healthcare, where lightweight and high-performance parts are often needed.

To make the most of these possibilities, designers need a solid understanding of both the design principles and the limitations of 3D printing technologies. Design for Additive Manufacturing (DfAM) ensures that parts are not only functional but also printable without issues like warping or weakness. Factors such as wall thickness, part orientation, and support structures need careful attention to produce reliable and high-quality prints.

By combining advanced software with a sound understanding of AM processes, engineers can design parts that push the boundaries of what's possible. And as 3D printing continues to improve, its role in product design will only grow, offering more ways to create efficient, creative, and sustainable solutions.

References

[1] Ramian J, Ramian J, Dziob D. Thermal deformations of thermoplast during 3D printing: warping in the case of ABS. Materials. 2021 Nov 21;14(22):7070.

[2] Jiang J, Stringer J, Xu X, Zhong RY. Investigation of printable threshold overhang angle in extrusion-based additive manufacturing for reducing support waste. International Journal of Computer Integrated Manufacturing. 2018 Oct 3;31(10):961-9.

[3] Coburn J. Ultimate Beginner’s Guide to 3D Printing [Internet]. 2017

[4] Chouhan G, Bala Murali G. Designs, advancements, and applications of three-dimensional printed gyroid structures: a review. Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering. 2024 Apr;238(2):965-87.