3D Printing Services in China: SLA, SLS, and FDM Compared

The three mainstream 3D printing processes used by Chinese service bureaus are SLA (stereolithography), SLS (selective laser sintering), and FDM (fused deposition modeling). SLA gives you the smoothest surfaces and finest detail, SLS delivers the strongest functional nylon parts without support structures, and FDM is the cheapest route for large parts and early prototypes. Most product developers get this choice wrong by defaulting to whatever their supplier offers — the right call depends on what the prototype needs to prove.

China hosts a dense concentration of professional 3D print bureaus — especially around Shenzhen and Dongguan — with turnaround times measured in days and pricing well below Western providers. If you are ordering printed parts from China for the first time, it helps to have someone on the ground vetting bureaus and managing the process, which is exactly what a sourcing partner like CN Ally does alongside full factory coordination.

This guide compares the three processes on the metrics that matter, and covers pricing, file preparation, quality checks, and IP protection when printing in China.

How SLA, SLS, and FDM Actually Work

All three build parts layer by layer, but the mechanics are completely different — and those mechanics dictate what each process is good at.

SLA cures liquid photopolymer resin with a UV laser (or projector, in DLP variants), hardening each layer in place. Because it works with liquid rather than extruded plastic, SLA captures extremely fine detail — layer heights run from roughly 0.025 to 0.15 mm, the thinnest of the three processes. Every part needs supports for overhangs, plus a solvent wash and UV post-cure before it is usable.

SLS spreads a thin layer of polymer powder — usually nylon — across the build area and fuses each cross-section with a laser. Unfused powder acts as a natural support, so no support structures are needed: complex geometries, interlocking components, even printed-in-place moving assemblies are all achievable. Typical layer heights: 0.06 to 0.15 mm.

FDM extrudes melted thermoplastic filament through a nozzle, tracing each cross-section — the simplest and most accessible process, with layer heights typically between 0.1 and 0.3 mm. Chinese bureaus also run industrial-grade FDM machines in engineering materials like polycarbonate and Ultem (PEI).

How Do SLA, SLS, and FDM Compare Side by Side?

Here is the practical comparison — tolerances, materials, surface finish, and cost, based on the published specifications of major bureaus and printer manufacturers.

Decision factor · SLA · SLS · FDM

• Typical accuracy: ±0.1–0.2 mm · ±0.2–0.3 mm · ±0.3 mm
• Layer height: 0.025–0.15 mm · 0.06–0.15 mm · 0.1–0.3 mm
• Surface finish: Smooth, near injection-molded quality (Ra ≈ 1.5–3 μm) · Matte, slightly grainy (Ra ≈ 6–10 μm) · Visible layer lines (Ra ≈ 10–20 μm)
• Common materials: Standard, tough, clear, castable, high-temp resins · Nylon PA11/PA12, glass-filled nylon, TPU · PLA, PETG, ABS, ASA, PC, TPU, Ultem
• Mechanical strength: Moderate; standard resins can be brittle · Strong and near-isotropic; best for functional parts · Strong in the XY plane, weaker between layers
• Support structures: Required for overhangs past ~45° · None needed — powder supports the part · Required for overhangs past ~45°
• Post-processing: Wash, UV cure, support removal, optional sanding/painting · Depowdering, media blasting · Support removal, sanding, optional acetone smoothing
• Relative part cost: Medium · Medium-high · Low
• Best for: Visual prototypes, clear parts, dental/jewelry models, fine detail · Functional prototypes, snap-fits, living hinges, small-batch end-use parts · Large parts, jigs and fixtures, early-stage form studies

Surface-finish and tolerance figures reflect published service-bureau data — see Sinterit's FDM vs SLA vs SLS comparison and JLC3DP's rapid prototyping guide for the underlying specs — and vary with part size and geometry. Treat any supplier's numbers as quoted under controlled conditions and validate with your own test parts.

Which 3D Printing Technology Should You Choose?

The honest answer: pick the process by what the prototype has to prove, not by habit or by what is cheapest.

Choose SLA when appearance matters most: investor demos, packaging prototypes, clear light-pipes, jewelry and dental models, and anything with fine engraved text or 0.2-mm walls. If the part must look like the final molded product, SLA gets closest.

Choose SLS when the part has to work like the final product. Nylon SLS parts are strong, tough, and nearly isotropic — the go-to for functional testing of snap-fits, living hinges, ducts, and brackets. With no supports to block or damage fine features, SLS also handles the most complex geometries: nested parts, internal channels, lattices. It is the natural choice for small nylon production batches, typically tens to low hundreds of units.

Choose FDM when size and budget dominate. A large enclosure or an early form study rarely needs 25-micron layers — FDM prints big and cheap. Engineering materials like ABS, ASA, and polycarbonate give reasonable functional performance; just orient the part so loads run along the layers, not across them.

What Drives the Price of 3D Printing Services in China?

Chinese bureaus often undercut Western pricing substantially, but the pricing logic is the same everywhere. Five factors dominate the quote:

1. Material volume and machine time. Most bureaus price by part volume (resin or filament consumed) plus machine occupancy. A bulky, hollow-looking part that eats hours of build time costs more than a dense, compact one.

2. The process itself. FDM parts are generally the cheapest per unit, SLA sits in the middle, and SLS commands a premium — the machines cost far more and powder handling adds overhead. Metal processes (SLM, binder jetting) are a separate tier entirely.

3. Batch size and nesting. 3D printing loves batches. An SLS build can nest dozens of parts in one powder bed, so ordering 30 units often costs little more per part than ordering 5 — sometimes the unit price drops dramatically once the bed is full. SLA and FDM scale less aggressively but still reward quantity.

4. Post-processing and finishing. Support removal is baked into the base price; sanding, primer, painting, plating, or assembling multi-part builds are billed separately. A showroom-quality painted SLA model can cost several times the raw print.

5. Tolerance and inspection requirements. Standard tolerances (±0.2–0.3 mm) are free; tighter tolerances, CMM inspection reports, and first-article documentation add labor cost. Specify these only when the part genuinely needs them.

Always ask Chinese bureaus for an itemized quote — material, machine time, finishing, shipping — rather than a single number. It makes quotes comparable and exposes where one vendor is padding.

How to Prepare Your Files for a Chinese 3D Print Bureau

Most quoting friction traces back to files that are not quite print-ready. A clean handoff gets you faster, cheaper quotes:

• Send STEP or STL. STEP preserves more information than triangulated STL and is the preferred interchange format. Avoid absurd tessellation settings — sub-0.05 mm chord tolerance adds megabytes without improving the print.
• Check watertightness. Mesh files with holes, inverted normals, or non-manifold edges print badly or get rejected. Run a mesh repair in your CAD tool or a utility like Meshmixer before sending.
• Respect minimum wall thickness. Rough guidance: 0.8 mm for FDM, 0.5 mm for SLA resin parts, and around 0.7–1.0 mm for SLS nylon. Below that, parts warp or fail — especially thin walls in nylon.
• State the critical dimensions. Highlight which faces mate, which holes take fasteners, and the tolerance those features need. A one-page PDF callout sheet saves more back-and-forth than a paragraph of email text.
• Specify material by name, not by brand. Write "PA12 nylon" or "ABS-like resin" rather than a proprietary filament brand the bureau may not stock.
• Flag the surface finish. "As-printed" is cheapest; note explicitly if you want sanding, dyeing, or paint, and include a color reference (RAL or Pantone) for painted parts.

Units are a classic trap: confirm millimeters before quoting. A 25.4× scaling surprise is an expensive one.

How Do You Verify Print Quality?

You cannot inspect a part in person, so build the checks into the order:

Ask for photos before shipping. A reputable bureau photographs finished parts on request — general views plus close-ups of critical features. Review supports-removal scars and surface finish against what you ordered.

Define an acceptance checklist up front. List the critical dimensions with tolerances, the expected material, and the finish level. A third-party inspection is the reliable option for larger runs: an inspector measures parts with calipers or a CMM, checks surface quality, and flags defects before the shipment leaves China.

Run a first-article check on your own bench. Fit-test parts against mating components, load-test snap-fits and hinges, and check flat faces for warping — one bad detail discovered now saves a full reorder.

Watch for common failure modes. In SLA: uncured resin trapped in hollow sections, support marks on cosmetic faces. In SLS: powder trapped in internal channels, dimensional drift on long thin parts. In FDM: layer delamination under load across the build direction, elephant's foot on the first layers.

How Do You Protect Your IP When 3D Printing in China?

Sending CAD files overseas makes many product teams nervous. The risk is real but manageable with basic discipline:

Use an NNN agreement, not just an NDA. China's standard protection instrument is the NNN (non-use, non-disclosure, non-circumvention) agreement, enforceable in Chinese courts — a Western NDA template carries little weight there. Have it in place before any files change hands.

Compartmentalize the files. Share only what the bureau needs: the geometry for the current iteration, not the full product assembly. For sensitive parts, splitting a product across two bureaus means no single vendor holds the complete design.

Watermark or version-tag your exports. Embedding a part number and date in the filename or a non-critical surface makes leaks traceable and discourages casual reuse.

Register design rights early in China. A Chinese design patent (外观设计专利) is inexpensive and gives you real enforcement leverage. It is far easier to secure before any disclosure than after.

These are baseline precautions, not legal advice — for high-value IP, consult counsel experienced in Chinese manufacturing law. And if managing vendor vetting plus IP paperwork feels like overhead you did not budget for, this is exactly the kind of ground work a sourcing agent handles routinely: qualified bureaus, signed agreements, and controlled file flows.

How to Choose a 3D Printing Service Bureau in China

Dozens of bureaus compete on price; the differentiators are reliability and process range:

• Process coverage. A bureau running SLA, SLS, FDM, and ideally MJF or metal under one roof lets you split jobs (visual + functional) without re-qualifying vendors. Ask which machines they actually own versus outsource.
• Material range and traceability. Legitimate bureaus name their materials (e.g., genuine PA12, engineering resins) and can tell you the powder refresh policy for SLS. Vague answers about "nylon-like" materials are a warning sign.
• Engineering feedback. Good bureaus review your files and flag printability problems before quoting — thin walls, unsupported overhangs, trapped powder risks. A bureau that quotes blind ships surprises.
• Quality documentation. Ask whether they can provide dimensional reports and what their rework policy is. ISO 9001 certification is a useful baseline for production-scale work.
• Communication in your timezone. Confirm response hours and whether an English-speaking engineer — not just a sales rep — reviews your order.
• Start with a paid trial. One small, representative part tells you more than a hundred reviews. Evaluate turnaround, accuracy, finish, and packaging before committing volume.

A factory audit — or at minimum a video walkthrough of the production floor — is worth doing once you plan recurring orders. It confirms the machines on the website are the machines in the building.

Frequently Asked Questions

How much do 3D printing services in China cost?

Pricing depends on process, material volume, part size, finishing, and batch quantity. Roughly: FDM is cheapest, SLA sits in the middle, and SLS costs more per part — though SLS unit costs drop sharply when the build bed is full. Get itemized quotes from two or three bureaus and compare material, machine time, finishing, and shipping separately.

Is SLA or SLS better for functional prototypes?

SLS, in most cases. SLS nylon parts are strong, tough, and nearly isotropic, which makes them suitable for snap-fits, living hinges, and load-bearing test parts. SLA wins on surface finish and fine detail but standard resins are relatively brittle. If a prototype must both look good and survive functional testing, order one of each and compare.

What file format do Chinese 3D printing bureaus accept?

STEP and STL are the universal standards; most bureaus also accept native SolidWorks, Fusion 360, and Rhino files. STEP is preferred over STL because it preserves exact geometry. Include a short specification note covering material, critical dimensions, tolerances, and finish so the bureau quotes accurately.

How long does 3D printing take in China?

Simple SLA and FDM parts are frequently quoted at 2–4 business days plus shipping; SLS takes a few days longer for cooling, depowdering, and finishing. Painting or assembly adds more time. Express shipping from China typically takes another 3–7 days — plan for roughly one to two weeks door to door.

Can I 3D print end-use parts in China, or is it only for prototypes?

Yes — especially in SLS nylon. Bureaus regularly run batches of tens to hundreds of functional parts: jigs, fixtures, housings, replacement components. For larger volumes, compare per-unit cost against injection molding; additive usually loses its advantage once tooling costs can be amortized.

Do I need to worry about my design being copied?

Manageable with the right precautions: an NNN agreement enforceable in China (not a generic NDA), sharing only the geometry the bureau needs, and registering a Chinese design patent before disclosure. An agent that vets bureaus and manages file flows adds another layer of control.

Your Decision Rule: Pick the Process in Five Minutes

If you take one thing from this comparison, make it the decision flow product teams actually use:

1. Does it need to look like the final product? → SLA (or SLA for the visual parts, something else for the rest).
2. Does it need to survive real loads, snaps, or hinges? → SLS nylon.
3. Is it big, simple, or just a form study? → FDM, and spend the savings on a second iteration.
4. Still torn? → Order the critical part in two processes and compare on your bench. Data beats theory.

Once you know the process, shortlist bureaus on process coverage, engineering feedback, and a paid trial part — then scale. And if you would rather skip the trial-and-error of vetting vendors across the language barrier, reach out at hi@cnally.com: CN Ally finds and manages reliable 3D print bureaus in China, with inspections and freight handled alongside, so your prototypes arrive on spec and on schedule. The process page shows how a typical engagement runs.