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Additive manufacturing has transformed demanding sectors such as aerospace, where every gram matters and every component must meet strict performance standards. But its impact doesn't end with the ability to print complex geometries or reduce part weight: one of its most strategic applications is in how these parts are designed and assembled.
3D printing is no longer just a prototyping tool. Today, it is an integral part of the production and assembly workflow. Understanding how assemblies are optimized in this context is key for any technical professional seeking reliable results, especially when working with technologies like FDM, SLA, SLS, or metal.
One of the greatest contributions of additive manufacturing is the possibility of consolidating parts. For example, in the aeronautical sector, GE redesigned a fuel nozzle originally composed of 20 welded parts and printed it as a single unit. Result: 25% less weight and a radical decrease in assembly failures.
However, in many cases, the most appropriate approach is not to consolidate, but to divide the model. Why? To overcome print volume limitations, optimize orientation for mechanical strength, avoid supports, or print with different materials. In these cases, it becomes critical to plan how these parts will be joined after being printed.
3D printed parts rarely offer the same dimensional precision as machined ones. Therefore, when designing joints (such as tenon and mortise), it is advisable to add clearances. A slightly larger hole or a smaller tenon can compensate for deviations inherent to the process.
To ensure a correct fit, it is recommended to:
Undersize holes if post-processing (precision drilling) is intended.
Add registration pins or guide grooves that help align parts during assembly.
Avoid printing threads directly; it's better to provide holes for inserting nuts or metal threads.
Depending on the part's use, assembly may require screws, adhesives, or mechanical snap-fit systems. Each method imposes design requirements:
For screws, it is recommended to design threaded holes or use inserts.
For bonding, it is essential to ensure flat, clean, and parallel surfaces that allow for good adhesion and pressure during adhesive drying and curing.
High-resolution 3D scanning is increasingly integrated into the design and assembly workflow. It allows existing parts to be precisely digitized for replication, adaptation, or integration into new systems. This is especially useful in contexts such as:
Reverse engineering of parts without blueprints.
Dimensional verification before assembly.
Designing custom components that need to fit into a pre-existing system.
Ideal for functional prototypes and technical parts in materials like ABS, Nylon, PC, or PEI (e.g., ULTEM™ 9085 for aerospace use). Good practices for assemblies include:
Printing holes slightly undersized and then machining them.
Orienting critical assembly faces to maximize precision in the XY plane.
Applying brim or raft to improve adhesion in large parts and prevent warping deformations.
Its high precision makes it excellent for parts with many details or delicate fits. But its relative fragility requires additional care:
Avoid excessively tight press-fits that can cause cracks.
Use technical resins (tough, high-temp) if greater mechanical resistance is required.
Reinforce screw areas with washers or inserts if considerable torque is to be applied.
Ideal for functional assemblies. It allows printing without supports, which facilitates the design of internal geometries and movable parts. SLS parts have:
Excellent mechanical homogeneity (almost isotropic).
Slightly rough surfaces that may require sanding in contact or movement areas.
Possibility of directly printing articulated assemblies or with sliding fits.
Metal printing (DMLS/SLM) can completely eliminate some assemblies by consolidating parts. But when assembly is needed:
Traditional processes are used: drilling, tapping, milling, welding.
It is common to combine printing and machining to ensure critical tolerances in joining areas.
Thermal (stress relief) and surface post-processing is key to preparing contact or fit areas.
3D printing is only one part of the process. For a part to meet the technical and functional requirements of sectors such as aerospace or advanced industry, it is essential to apply appropriate post-processing and assembly techniques. From improving finishes to ensuring robust joints, these steps determine the final product quality.
Parts printed by FDM require the first step of removing supports, brims, or rafts. This is done with cutting pliers or deburring tools. To eliminate layer lines, progressive grit sandpaper, files, or rotary tools are used. For materials like ABS or ASA, chemical smoothing with acetone vapor allows for a smooth finish close to injection molding.
It is also common to rework holes or critical surfaces through drilling or light milling, especially on parts that will be assembled. Having a basic post-processing kit – cutters, sandpaper, rotary tool, gloves, safety glasses – is advisable even for non-industrial work.
In resin printing, post-processing begins with cleaning in isopropyl alcohol to remove resin residue. Then, UV curing is performed (in a dedicated station or with controlled sunlight) to complete polymerization. From there, support marks are removed with fine sandpaper, and primer or paint can be applied, not only for aesthetics but also to block UV rays that could yellow the part over time.
Nylon powder parts come out with a matte and slightly porous surface. The usual first step is blasting with microspheres or sand to remove adhered powder and smooth the surface texture. Then, immersion dyeing, mechanical polishing (tumbling), or even chemical vapor smoothing can be applied. In demanding applications, epoxy sealing or thermal annealing can improve resistance or watertightness.
In technologies like DMLS or SLM, parts are usually printed with metal supports that are removed by mechanical cutting or wire EDM. Subsequently, a stress relief heat treatment is performed, which is essential to eliminate residual stresses.
To meet tight tolerances, functional surfaces (holes, flat faces, housings) are machined after printing. This may include tapping, milling, or grinding. In sectors such as aerospace, shot peening is used to improve fatigue resistance and smooth surfaces.
After post-processing, the use of 3D scanners or CMMs (coordinate measuring machines) allows for verification that the part complies with the CAD geometry. Only after passing this control can the part proceed to assembly.
Bonding is effective and simple for plastics. Cyanoacrylate is ideal for PLA, while two-part epoxies allow filling gaps or joining parts with relaxed tolerances. For materials like ABS, solvent welding with acetone offers a more homogeneous bond.
To achieve a solid bond:
Surfaces must be flat, clean, and dry.
Light sanding is recommended to increase adhesion.
Applying pressure (using a press or clamps) during adhesive drying improves bond quality.
For removable joints or those subjected to load, metal inserts (heat-set inserts) are the best option. They are inserted with a soldering iron and provide durable threads in PLA, ABS, or PETG parts.
In resin parts or thin areas, you can use:
Embedded nuts (designing hexagonal cavities).
Direct threading if the material allows (with caution).
Whenever screwing into printed parts:
Design reinforcements to prevent crushing breakage.
Use washers or conical washers if there is a risk of sinking.
Snap-fits or sliding fits allow assemblies without hardware. Widely used in housings, covers, or non-structural elements. They require testing, as the flexibility of the part depends on the material and printing direction (especially in FDM).
For metals, many printed parts can be welded to others if the subsequent heat treatment is respected. For polymers like PP or PE, which are difficult to glue, friction welding or heat welding can be an alternative.
An underutilized but effective technique: printing assembly jigs or fixtures. They serve to precisely position parts during gluing or screwing. In small batches or complex assemblies, designing a specific jig in 3D printing speeds up the process and improves quality.
Additive manufacturing does not end when the part comes out of the printer. Mastering post-processing and assembly is what turns a good design into a functional and professional final product. From correctly preparing a surface to selecting the appropriate adhesive or screw, every detail counts to ensure reliability and durability.
These strategies are not only valid for the aerospace sector. Industrial engineers, product designers, or advanced makers can apply them to improve their developments. The key is to understand 3D printing as part of a complete manufacturing workflow, where each stage – from design to final inspection – adds quality.
At Filament2Print, you will find not only printers, filaments, resins, or sintering powders, but also post-processing tools, 3D scanners, and everything you need to ensure your parts are ready for assembly. Because printing is just the beginning. The real value lies in how all the pieces eventually fit together.
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