3D Printing Pro-Tips: Design Guidelines and Post-Processing for FDM, SLS, and SLA

Mohamad Yousif
5 days ago
3 min read

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In the modern world of mechanical design, 3D printing has transformed from a rapid prototyping novelty into a powerful manufacturing method. Whether you’re validating a concept, producing functional parts, or creating molds for low-volume manufacturing, knowing which 3D printing technique to choose — and how to design for it — is crucial.

Each method has its own strengths, limitations, and design considerations. Let’s break down the three most common 3D printing processes used in engineering and product development today: FDM, SLS, and SLA.

1. FDM (Fused Deposition Modeling)

How it works:FDM printing builds parts layer by layer by extruding melted thermoplastic filaments such as PLA, ABS, or PETG through a heated nozzle.

Best used for:

Low-cost prototypes
Fit and assembly testing
Large, non-aesthetic components

Design Guidelines:

Minimum wall thickness: 1.2–1.5 mm for structural integrity.
Orientation: Place overhangs at ≤45° to minimize the need for supports.
Holes and gaps: Avoid designing holes smaller than 2 mm as they may close up due to material flow.
Tolerances: FDM accuracy typically ranges from ±0.3 mm to ±0.5 mm.

Design Tip in SolidWorks:Use the “Draft Analysis” tool to check for overhangs and unsupported surfaces. You can also define printing orientation and clearances by creating custom reference planes during the design stage.

Post-Processing:

Support removal (mechanical or soluble)
Sanding and smoothing for visible layer lines
Vapor smoothing for ABS to improve surface finish
Painting or coating to enhance durability and aesthetics

2. SLS (Selective Laser Sintering)

How it works:A laser fuses nylon or composite powder layer by layer, forming a strong, functional part without the need for support structures.

Best used for:

Functional prototypes
Complex geometries
Batch production of mechanical parts

Design Guidelines:

Minimum wall thickness: 1 mm for small features, 2 mm for large flat surfaces.
Clearances: Minimum 0.2 mm between moving parts to prevent fusing.
Embossed details: At least 0.5 mm deep for clarity.
Orientation: Use SLS freedom to design parts as a single assembly or interlocking joints.

Design Tip in SolidWorks:SLS allows organic, topology-optimized designs, so consider using SolidWorks Simulation + Topology Study to reduce weight while maintaining strength.

Post-Processing:

Bead blasting to remove residual powder
Dyeing for uniform color
Polishing or coating for smoother finishes
Heat treatment (optional) for improved mechanical performance

3. SLA (Stereolithography)

How it works:SLA uses a UV laser to cure liquid resin, producing highly detailed and smooth parts ideal for presentation models or master patterns.

Best used for:

High-detail prototypes
Visual and cosmetic parts
Master models for casting

Design Guidelines:

Minimum wall thickness: 0.8–1 mm
Supports: Required for most geometries; design flat bases to reduce marks.
Drain holes: Include 2–3 mm holes to allow uncured resin to escape from hollow areas.
Tolerances: Excellent precision, typically ±0.1 mm.

Design Tip in SolidWorks:When designing for SLA, use the “Shell” feature to hollow out parts and reduce resin use. Apply fillets to edges that connect to supports to make post-processing easier.

Post-Processing:

Support removal and sanding
UV curing to fully harden the resin
Priming and painting for appearance models
Clear coating for transparent parts

Choosing the Right Process

Process	Materials	Accuracy	Surface Finish	Strength	Cost	Applications
FDM	PLA, ABS, PETG	±0.3–0.5 mm	Fair	Moderate	Low	Concept Models
SLS	Nylon, PA12, Composites	±0.2 mm	Good	High	Medium	Functional Parts
SLA	Resin	±0.1 mm	Excellent	Moderate	Medium	Aesthetic Models

Design and Beyond

At The SolidWorks Expert, we help clients move from CAD to prototype seamlessly.Using SolidWorks, we design parts optimized for 3D printing — accounting for print orientation, material behavior, and post-processing requirements — ensuring faster production, higher quality, and reduced trial and error.

Conclusion

3D printing isn’t one technology — it’s a toolkit of solutions.Understanding how each process works, what it’s best for, and how to model your designs accordingly can save both time and cost while unlocking better performance.

Whether it’s FDM for quick validation, SLS for functional parts, or SLA for precision models, the key is the same:Design smart, print efficiently, and refine with purpose.