The Complete Guide to 3D Printing for Engineers (2026)

What's Inside This Guide

Chapter 1

What Is 3D Printing?

3D printing — formally additive manufacturing (AM) — is any process that builds a three-dimensional object by depositing material layer by layer, guided by a digital model (typically an STL or 3MF file sliced into 2D cross-sections). Unlike CNC machining (subtractive) or injection molding (formative), AM adds material only where needed, which enables geometries impossible to achieve with traditional methods: internal channels, lattice structures, topology-optimised lightweighting, and consolidated assemblies.

The seven commercially relevant AM processes fall into three families:

Extrusion-based (FDM): Melts and deposits thermoplastic filament through a heated nozzle.
Photopolymerisation (SLA, DLP): Uses UV light to selectively cure liquid resin.
Powder-based (SLS, MJF, DMLS/SLM, Binder Jetting): Selectively fuses or binds particles in a powder bed.
Metal extrusion (Metal FFF): Extrudes metal-polymer composite filament, then debinds and sinters to full density.

For a detailed breakdown of each technology's physics, trade-offs, and real cost data, read our Types of 3D Printing: Complete Technology Comparison.

Chapter 2

All 7 Technologies at a Glance

Side-by-side comparison of tolerance, resolution, surface finish, and cost across every commercial AM process. *Cost ranges are for typical small-to-medium parts (50–200 cm³).

Process	Typical Tolerance	Layer Height	Min Feature	Surface Finish (Ra)	Cost per Part*
FDM	±0.5 mm	100–300 µm	0.8 mm	10–25 µm	$5–$50
SLA	±0.05–0.15 mm	25–100 µm	0.2 mm	1.5–4 µm	$10–$80
DLP	±0.05–0.10 mm	25–100 µm	0.3 mm	2–5 µm	$8–$60
SLS	±0.3 mm	100–120 µm	0.7 mm	6–12 µm	$20–$150
MJF	±0.3 mm	80 µm	0.5 mm	5–10 µm	$15–$120
DMLS/SLM	±0.05–0.1 mm	20–60 µm	0.4 mm	6–15 µm	$200–$2,000+
Metal FFF	±0.5 mm → ±1%	100–200 µm	1.0 mm	8–20 µm	$50–$500

For detailed cost breakdowns, material properties, and DFM guidelines per technology, see the deep-dive chapters below.

Chapter 3

Polymer 3D Printing Technologies

Four processes cover 90%+ of polymer AM applications — from $200 desktop prototyping to $500k production lines.

FDM

FDM — Fused Deposition Modeling

The workhorse of desktop and industrial prototyping. FDM melts thermoplastic filament through a heated nozzle, tracing each layer's cross-section. It offers the widest material range of any polymer AM process — from commodity PLA to aerospace-grade PEEK — and the largest build volumes (up to 914 × 610 × 914 mm on Stratasys F900). Trade-off: visible layer lines and anisotropic mechanical properties.

Tolerance

±0.5 mm (±0.02 in.) typical

Layer height

100–300 µm

Cost range

$5–$50 (prototype)

Best for

Rapid prototyping, functional testing, large parts, jigs & fixtures

Materials: PLA, ABS, PETG, Nylon, PC, PEEK, PEI (Ultem)

Read the full FDM guide

SLA

SLA — Stereolithography

A UV laser (405 nm) traces each cross-section on a vat of liquid photopolymer resin, curing it layer by layer. SLA delivers the best surface finish of any polymer AM process — layer lines are nearly invisible at 25 µm resolution. Modern desktop SLA uses inverted (bottom-up) architecture. Trade-off: most resins are brittle and degrade under prolonged UV exposure.

Tolerance

±0.05–0.15 mm (±0.002–0.006 in.)

Layer height

25–100 µm

Cost range

$10–$80 (prototype)

Best for

Visual prototypes, fine features, medical models, master patterns for casting

Materials: Standard, Tough, Flexible, High-Temp, Castable resins

Read the full SLA guide

SLS

SLS — Selective Laser Sintering

A CO₂ laser selectively sinters nylon powder layer by layer. No supports needed — unsintered powder acts as its own support, enabling complex geometries (internal channels, interlocking assemblies). SLS parts are near-isotropic and approach injection-molded strength in PA12. It's the dominant process for functional polymer production parts.

Tolerance

±0.3 mm (±0.012 in.) typical

Layer height

100–120 µm

Cost range

$20–$150 (production)

Best for

Functional prototypes, end-use parts, living hinges, snap-fits, small-batch production

Materials: PA12, PA11, Glass-filled PA, Carbon-filled PA, TPU

Read the full SLS guide

MJF

MJF — HP Multi Jet Fusion

HP's proprietary powder-bed process jets fusing and detailing agents onto nylon powder, then fuses each layer with an IR lamp. Build time depends on Z-height, not part count — filling the build plate doesn't increase print time. MJF delivers near-isotropic properties with finer detail than SLS (600 dpi XY resolution). Lower per-part cost than SLS at volume.

Tolerance

±0.3 mm (±0.012 in.) typical

Layer height

80 µm

Cost range

$15–$120 (production)

Best for

Production parts at volume, fine features in nylon, batch production (100–10,000 units)

Materials: PA12, PA11, TPU, PP

Read the full MJF guide

Chapter 4

Metal 3D Printing Technologies

Two pathways to metal additive parts — laser powder bed (DMLS/SLM) for production density, and bound metal deposition (Metal FFF) for accessible cost.

DMLS/SLM

DMLS/SLM — Direct Metal Laser Sintering

A high-power laser (200–1,000 W) fully melts metal powder in an inert-gas-shielded chamber (argon for most alloys, nitrogen for steels). DMLS produces fully dense (>99.5%) metal parts with mechanical properties that meet or exceed wrought equivalents after HIP treatment. Requires extensive supports (anchors to build plate, manages thermal stress) and post-processing (stress relief, wire EDM removal, CNC finishing of critical surfaces).

Tolerance

±0.05–0.1 mm (±0.002–0.004 in.) as-built

Layer height

20–60 µm

Cost range

$200–$2,000+ per part

Best for

Aerospace brackets, medical implants, conformal cooling inserts, lightweight topology-optimized parts

Materials: Ti-6Al-4V, Inconel 718/625, 316L SS, AlSi10Mg, 17-4 PH, Maraging steel

Read the full DMLS/SLM guide

Metal FFF

Metal FFF — Bound Metal Deposition

Metal FFF (Desktop Metal, Markforged Metal X) extrudes a metal-polymer composite filament, then debinds and sinters the "green" part into a fully metal component. The process prints in a standard office environment — no inert gas chamber, no loose metal powder. Parts shrink ~16–20% during sintering. Metal FFF costs 5–10× less than DMLS for comparable geometries, but tolerance and density (96–99%) are lower.

Tolerance

±0.5 mm (±0.02 in.) green; ±1% post-sinter

Layer height

100–200 µm

Cost range

$50–$500 per part

Best for

Functional metal prototypes, tooling inserts, low-volume production at 5–10× lower cost than DMLS

Materials: 17-4 PH, 316L, H13, Ti-6Al-4V, Copper

Read the full Metal FFF guide

Chapter 5

How to Choose the Right 3D Printing Process

Start with your requirements — surface finish, mechanical properties, production volume, and budget — then use this decision matrix.

Scenario	Recommended	Why
Fastest, cheapest prototype (visual only)	FDM	Lowest cost, largest build volume, widest desktop availability
Best surface finish / fine detail	SLA or DLP	25 µm layers, near-injection-mold surface quality
Functional nylon parts (snap-fits, hinges)	SLS or MJF	No supports, near-isotropic PA12/PA11, production-grade strength
Production batch (100–10,000 nylon parts)	MJF	Build time independent of part count, lowest per-part cost at volume
Fully dense metal parts (aerospace, medical)	DMLS/SLM	99.5%+ density, Ti-6Al-4V / Inconel, meets ASTM standards after HIP
Metal prototypes (office-safe, lower cost)	Metal FFF	5–10× cheaper than DMLS, no loose powder, good for tooling & prototypes
3D Printing not ideal — tight tolerances on simple geometry	CNC Machining	±0.025 mm, superior surface finish, wider material range for metals

For the full decision tree with cost crossover tables and material-specific recommendations, see our Types of 3D Printing comparison.

Chapter 6

3D Printing vs CNC Machining

These aren't competing technologies — they're complementary. The decision comes down to geometry complexity, tolerance requirements, volume, and material.

Choose 3D Printing When:

Complex geometry (internal channels, lattices, undercuts)
Low volumes (1–500 parts) where tooling cost can't be amortised
Rapid iteration — design changes without retooling
Topology-optimised or weight-reduced structures
Consolidated assemblies (reduce part count)

Choose CNC Machining When:

Tight tolerances needed (±0.025 mm vs ±0.05–0.5 mm for AM)
Superior surface finish (Ra 0.4–1.6 µm vs 1.5–25 µm for AM)
Specific metal alloys not available in AM powder form
Production volumes >50 identical metal parts
Material certifications required (mill certs, traceability)

The Hybrid Approach

Many teams use both: 3D print for prototyping and design validation, then CNC machine the production version for tighter tolerances and better surface finish. This gives you the speed of AM and the precision of subtractive manufacturing.

For detailed cost crossover analysis, tolerance comparison tables, and material compatibility charts, read our full 3D Printing vs CNC Machining article.

Chapter 7

3D Printing Materials by Process

The process determines your available material universe. Here are the most common materials for each technology.

FDM

PLA — prototyping, low cost
ABS — functional, heat-resistant
PETG — chemical resistant, food-safe
Nylon (PA6/PA12) — tough, flexible
PC — high impact, transparent
PEEK/PEI — aerospace-grade, 260 °C HDT

SLA / DLP

Standard resin — visual prototypes
Tough resin — ABS-like impact
Flexible resin — 50–80 Shore A
High-Temp resin — HDT 238 °C
Dental/castable resin — investment casting

SLS / MJF

PA12 — workhorse nylon, ~48 MPa
PA11 — bio-based, more ductile
Glass-filled PA — higher stiffness
Carbon-filled PA — ~80 MPa, lightweight
TPU — flexible, elastomeric
PP (MJF) — chemical resistant

DMLS / SLM

Ti-6Al-4V — aerospace, medical
Inconel 718/625 — high-temp turbines
316L SS — corrosion resistant
AlSi10Mg — lightweight structures
17-4 PH — hardened tooling
Maraging steel — mold inserts

Metal FFF

17-4 PH — general purpose
316L SS — corrosion resistant
H13 tool steel — injection mold inserts
Ti-6Al-4V — medical, aerospace
Copper — thermal management

For full property tables (tensile strength, elongation, HDT, density) and process-specific material guides, visit our Materials Library or the Material Selection Guide.

Chapter 8

Design for 3D Printing (DFM)

Designing for AM is different from designing for CNC or injection molding. These six rules apply across all processes.

Minimum wall thickness

FDM ≥1.2 mm, SLA ≥0.6 mm, SLS/MJF ≥0.8 mm, DMLS ≥0.4 mm. Thinner walls risk warping or incomplete fusion.

Orientation matters

All 3D printing processes are anisotropic to some degree. Z-axis (inter-layer) strength is 20–60% lower than XY for FDM; 5–15% lower for SLS/MJF. Orient critical load paths in the XY plane.

Support strategy

FDM and SLA/DLP require supports for overhangs >45°. SLS and MJF are self-supporting (unsintered powder). DMLS requires extensive metal supports to manage thermal stress.

Holes and clearances

Design holes ≥0.5 mm (SLA), ≥1.0 mm (FDM/SLS/MJF), ≥0.4 mm (DMLS). For press-fit tolerance, add +0.1 mm to nominal diameter and verify with test coupons.

Escape holes for powder processes

SLS, MJF, and DMLS require escape holes (≥4 mm diameter) for enclosed hollow sections. Without them, trapped powder adds weight and can't be removed post-build.

Shrinkage compensation

SLS parts shrink ~3.0–3.5%. MJF ~2.7%. Metal FFF ~16–20% during sintering. DMLS ~0.05–0.1%. Your service provider should compensate in slicing, but verify on first articles.

Process-specific DFM is critical

These are universal rules. Each technology has additional, process-specific design constraints. See our DFM Best Practices: 15 Rules for the complete guide, or the individual technology guides (FDM, SLA, SLS, MJF, DMLS, Metal FFF) for process-specific rules.

Common Questions

Frequently Asked Questions

What is the most accurate 3D printing technology?

SLA and DLP deliver the tightest tolerances (±0.05 mm) and finest surface finish (Ra 1.5–4 µm) among polymer processes. For metals, DMLS/SLM achieves ±0.05–0.1 mm as-built. For production-grade accuracy on simple geometries, CNC machining (±0.025 mm) still outperforms all AM processes.

How much does 3D printing cost per part?

It depends on the process and material. FDM parts start at $5–$50 for prototypes. SLS/MJF production parts typically cost $20–$150 each. Metal DMLS parts range from $200 to over $2,000 depending on alloy, volume, and post-processing. At low volumes (1–50 parts), 3D printing is almost always cheaper than injection molding or CNC. The crossover point where injection molding becomes cheaper is typically 500–5,000 parts for plastics.

Which 3D printing technology is best for production parts?

For polymer production, MJF and SLS dominate. MJF excels at batch production (100–10,000 units) because build time is independent of part count. SLS offers a wider material range including glass-filled and carbon-filled nylons. For metal production, DMLS/SLM is the standard for aerospace, medical, and high-performance applications.

Can 3D printed parts replace injection molded parts?

For volumes under 500–5,000 units, absolutely. SLS and MJF nylon parts approach injection-molded PA12 strength (tensile ~48 MPa for SLS PA12 vs ~50 MPa for molded PA12). They won't match the surface finish of a polished mold, but for functional parts, the mechanical properties are comparable. Above 5,000 units, injection molding's per-part cost drops below AM.

What is the strongest 3D printing material?

For polymers: PEEK (tensile strength ~100 MPa, HDT ~260 °C) via FDM, or carbon-fiber-filled nylon via SLS/MJF (~80 MPa). For metals: Ti-6Al-4V via DMLS (UTS ~1,050 MPa after HIP) or Inconel 718 (~1,240 MPa). Strength always depends on print orientation and post-processing.

3D printing vs CNC machining — when should I choose each?

Choose 3D printing when you need complex geometry (internal channels, lattices, topology-optimized shapes), low volumes (1–500 parts), or rapid iteration (design changes without tooling). Choose CNC machining when you need tight tolerances (±0.025 mm), superior surface finish, specific metal alloys not available in AM, or production volumes over 50+ identical parts in metals. Many projects use both — 3D print for prototyping, CNC for production.