SLS Post-Processing and Inspection Checklist

Direct answer

SLS post-processing and inspection should be planned from the part function backward. Start with the surfaces that must fit, move, seal, bond, or remain visible. Then define the finishing route, measurement method, acceptance criteria, and evidence needed for release. This prevents a cosmetic finish from being chosen before the engineering requirements are understood.

What is SLS post-processing?

SLS post-processing is the set of operations performed after powder-bed production to clean, smooth, coat, mark, assemble, or otherwise prepare a nylon part for its intended use. Inspection is the parallel quality step that confirms the part matches the agreed drawing, model, appearance, and functional requirements.

Which post-processing route fits the part?

1. Depowdering and cleaning

Every SLS project begins with removal of loose powder and inspection of openings, cavities, and interfaces. For complex parts, the RFQ should identify areas where retained powder would affect assembly, airflow, movement, or cleanliness.

2. Surface smoothing or cosmetic finishing

Sanding, blasting, tumbling, vapor or chemical smoothing, and coating can produce different visual and tactile results. The correct choice depends on the geometry, target appearance, edge definition, and whether text, small features, or mating surfaces must remain sharp.

3. Coating, painting, or marking

If coating is required, define the coating type, color reference, gloss target, masking boundaries, and any post-coating inspection. Do not treat a finish description as proof of chemical, UV, wear, or weathering performance unless the project includes evidence for that requirement.

4. Inserts and assembly

Threaded inserts, bonded components, heat-set elements, or multi-part assembly may be added after printing. The RFQ should identify torque, service access, adhesive, or replacement requirements rather than assuming a printed thread is always the best solution. See the guide on threaded inserts in SLS parts.

What should be inspected?

A useful inspection plan separates general checks from critical-to-function checks.

Inspection area	Example questions	Evidence to define
Geometry	Does the part match the latest CAD revision?	Revision, datum scheme, measurement method
Interfaces	Do mating, mounting, or moving features fit?	Critical dimensions and functional check
Appearance	Are visible surfaces and boundaries acceptable?	Approved sample, finish reference, defect limits
Openings and cavities	Is loose powder removed from required areas?	Cleaning method and visual or functional check
Assembly	Do inserts, fasteners, or bonded parts work as intended?	Assembly procedure and acceptance criteria
Packaging	Is the part protected from damage or contamination?	Packaging standard and handling notes

The table is a planning framework, not a universal tolerance or acceptance specification. Project drawings, material data, process capability, and customer requirements govern the final criteria.

When should inspection requirements be fixed?

Set them before production whenever possible. A practical sequence is:

1. Mark critical dimensions and surfaces on the drawing or 3D model.
2. Separate cosmetic requirements from functional requirements.
3. Define the measurement method and reference datums.
4. Agree which findings require rework, concession, or rejection.
5. Confirm whether first-article, sample, or batch records are needed.
6. Review a representative finished sample before scaling the same route.

What information should be included in an RFQ?

For a reliable review, include:

• Latest CAD and drawing revision
• Quantity and intended use
• Material family or preferred grade, if known
• Critical dimensions, interfaces, and visible surfaces
• Finish target, color, coating, or marking requirements
• Inspection method and report expectations
• Packaging, labeling, and delivery destination
• Photos or samples of the desired finish when appearance matters

See How to Prepare a Better RFQ for SLS 3D Printing and SLS End-Use Nylon Parts: Qualification Checklist.

Limits and project-specific validation

Post-processing is not a substitute for design validation. A finish may improve appearance while changing edge definition, surface texture, or local dimensions. Likewise, a visual inspection cannot prove load capacity, sealing, chemical resistance, or long-term durability. Those requirements need their own test method and acceptance evidence.

For complex assemblies, also review common reasons SLS parts fail in testing, SLS design guidelines, and SLS robot grippers and EOAT.

Release checklist

Before approving shipment, confirm:

• Correct CAD and drawing revision
• Required powder removal completed
• Finish and masking checked against the approved reference
• Critical dimensions measured with the agreed method
• Inserts or assemblies function as intended
• Defects and concessions documented
• Packaging matches the project requirement

Need a project review? Send the CAD revision, quantity, material preference, finish target, critical features, inspection plan, and delivery requirements for an engineering review.