3D printing for functional parts

3D printing for functional parts

This step-by-step tutorial explains how to approach 3D printing for functional parts, focusing on practical decisions from design to testing. Functional parts are components you expect to carry load, fit with other parts, or operate under heat and wear, so the aim here is to give repeatable steps that reduce wasted prints and speed iteration. I assume you have a basic desktop FDM printer and CAD skills, and I will cover design guidelines, material selection, slicer settings, printer calibration, post-processing and simple tests you can run at home or in a small workshop.

Step 1 — design with function in mind. Start by defining the loads, fit tolerances and the environment your part will face, for example compressive or shear loads, exposure to heat, chemicals or moisture, and whether precision fit is required for fasteners or bearings. Use features such as fillets to reduce stress concentration and add ribs to increase stiffness without heavy infill. For assemblies, add clearance for mating parts — a common starting clearance is 0.2 mm for sliding fits but test and adjust for your machine. Consider printing orientation early, because layer direction strongly affects strength perpendicular to layers, and plan for fastener bosses or heat-set inserts if you need robust threaded connections.

Step 2 — choose the right material. PLA is easy to print and dimensionally stable for non-loadbearing or indoor parts, but it softens near 60 degrees Celsius so avoid it for heat-exposed uses. PETG balances toughness and temperature resistance and bonds well between layers, making it a good general-purpose choice for functional parts. ABS and ASA offer higher temperature resistance and better impact behaviour but need an enclosed build space to avoid warping. Nylon is very strong and wear-resistant but hygroscopic, so store and dry it properly before printing. Consider composite filaments such as carbon-fibre or glass-filled nylons for higher stiffness, and check manufacturer data for tensile strength and heat deflection temperature when making a final material choice.

Step 3 — orientate and set slicer parameters for strength. Orientate the part so the primary load paths are parallel to the layers where possible, to exploit layer adhesion strengths, or set layers to run through critical features to avoid delamination. Increase wall/perimeter count to prioritise shell strength over infill for many designs — three to five perimeters is a good baseline for functional parts. Use a higher infill percentage where compressive strength matters, and choose infill patterns such as gyroid or cubic that distribute loads evenly. Keep layer height lower for finer feature resolution and better tensile properties, and adjust print temperature to promote strong inter-layer bonding while avoiding stringing or oozing. Plan supports where necessary but design your part to minimise overhangs and support removal that could compromise surfaces.

• Layer height: 0.12–0.2 mm for strength and resolution trade-off.
• Perimeters: 3–5 walls for structural parts.
• Infill: 20–60% depending on load, choose gyroid or cubic for even strength.
• Print temperature: follow filament specs and calibrate for best bonding.
• Print speed: moderate speeds to maintain bonding and dimensional accuracy.

Step 4 — calibrate the printer and run test prints. Before committing to a final print, calibrate bed levelling and first layer height for consistent adhesion, and perform an extrusion multiplier test to confirm the correct filament flow. Print small test coupons such as tensile bars, single-wall cylinders and threaded inserts to verify fit and strength, and consider a temperature tower if you need to dial in the best print temperature for mechanical properties. Measure printed dimensions with callipers and compare to your CAD model, then adjust slicer scaling or design clearances as required. If you use retraction and bridging settings, tune them on simple geometries to reduce stringing and sagging on functional features.

Step 5 — post-processing, assembly and validation. Many functional parts benefit from modest post-processing such as sanding mating faces for a better fit, tapping or heat-inserting brass threads for repeated assembly, or annealing parts printed in suitable materials to increase heat resistance and relieve internal stresses. Chemical smoothing for ABS can improve fatigue life in certain applications but must be done safely and in a well-ventilated area. Assemble the part with the intended fasteners and run real-world tests that simulate actual loads and cycles; document failures and iterate the CAD design, material choice or print orientation as necessary. Keep a build log with print settings and test outcomes to speed future iterations and avoid repeating failed configurations.

Final notes and resources: approach each functional print as an experiment with measurable variables, change one parameter at a time and keep records to build a reliable workflow for your printer and materials. If you would like more project examples and community-tested advice, visit the Maker & DIY section of this site for related guides and build notes at Maker & DIY. Follow safety guidance when printing and post-processing, and iterate carefully to turn prototypes into dependable parts. For more builds and experiments, visit my main RC projects page.