engineering-skills/additive-manufacturing/references/process-parameters.md

AM Process Parameters — Technical Guide

Important premise

The parameters listed are optimized starting points based on consolidated best practices. Every machine, material lot, and geometry requires fine-tuning. Never use unvalidated parameters on critical parts without preliminary testing (coupons).

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FDM/FFF — Parameters by Material

General structure of FDM parameters

Layer height     → Z resolution and speed (25–75% nozzle diameter)
Line width       → Usually = nozzle diameter (0.4mm standard)
Print speed      → mm/s (perimeters < infill < travel)
Temperature:
  - Nozzle (T_e)  → Material melting
  - Bed (T_b)     → First layer adhesion, anti-warping
  - Chamber (T_c) → Required for high-temperature materials
Cooling fan      → Rapid solidification (good for bridging/overhangs, bad for layer adhesion)
Retraction       → Stringing prevention

Parameter table by material

Material	T_nozzle (°C)	T_bed (°C)	T_chamber (°C)	Layer height	Perimeter speed	Cooling	Retraction
PLA	195–220	50–65	—	0.1–0.3mm	40–60 mm/s	100%	1–5mm / 25–45 mm/s
PETG	230–250	70–85	—	0.1–0.3mm	35–50 mm/s	30–50%	3–6mm / 25–35 mm/s
ABS	230–250	90–110	40–60°C	0.1–0.3mm	40–60 mm/s	0–10%	4–6mm / 25–45 mm/s
ASA	240–260	90–110	40–55°C	0.1–0.3mm	35–55 mm/s	10–20%	4–6mm / 25–45 mm/s
PA12	240–260	70–90	45–65°C	0.1–0.25mm	30–50 mm/s	0–10%	6–8mm / 20–35 mm/s
PC	260–290	100–120	60–80°C	0.1–0.25mm	30–50 mm/s	0–10%	4–6mm / 25–40 mm/s
TPU (Shore 95A)	220–240	30–50	—	0.15–0.3mm	20–35 mm/s	20–50%	0–2mm (direct)
PEEK	360–400	120–140	90–120°C	0.1–0.2mm	20–40 mm/s	0%	2–4mm / 20–30 mm/s
CF-filled (PA-CF)	250–270	70–90	45–65°C	0.15–0.25mm	30–45 mm/s	0–10%	Hardened nozzle required

Material-specific FDM notes

PLA:

• Fan: always high → improves bridging and overhangs
• Warping: minimal on flat surfaces; avoid air drafts
• Pre-drying: rarely necessary (but recommended for filament >1 year old or stored in humid conditions)

PETG:

• High stringing → reduce temperature, increase retraction, increase travel speed
• Excellent bed adhesion on glass + glue stick → may stick too well (use release agent)
• Reduced fan → improves interlayer adhesion

ABS / ASA:

• Severe warping without enclosure → do not attempt on open-frame printers for parts >50mm
• Critical first layer: precise bed leveling, first layer speed 20–30 mm/s, precise Z offset
• Fumes: mandatory ventilation

PA (Nylon):

• Pre-drying MANDATORY: 70–80°C / 4–8h before printing (hygroscopic filament)
• Store in dry box during printing
• Warping on large parts → enclosure + brim

PEEK:

• Requires all-metal hot end (no PTFE above 260°C)
• Heated enclosure mandatory
• Pre-drying: 120°C / 4h
• Slow cooling after printing (do not open enclosure immediately)

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SLA / DLP / MSLA — Parameters

Main parameters

Parameter	SLA (laser)	DLP	MSLA
Layer thickness	25–100 µm	25–100 µm	25–100 µm
Exposure time (normal layers)	Depends on laser power	2–8 sec	2–6 sec
Bottom layers	5–10	5–10	5–10
Bottom exposure	3–5× normal	3–5× normal	3–5× normal
Lift speed	30–150 mm/min	30–200 mm/min	30–200 mm/min
Lift distance	5–8 mm	4–7 mm	4–7 mm
Anti-aliasing	N/A	4–8×	4–8×

SLA/DLP practical rules

• Layer height and detail: 25–50 µm for maximum detail (dental, jewelry); 100 µm for fast prototypes
• Exposure time: always calibrate with a test matrix (exposure test) for each resin and lot
• Over-exposure → loss of detail, oversized dimensions
• Under-exposure → layers don't adhere, print failure
• FEP film: replace when cloudy or scratched — causes failures and worse surface quality
• Resin temperature: 25–30°C optimal; cold resin (<20°C) → more viscous → adhesion problems

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SLS / MJF — Process Parameters

SLS — Main parameters (EOS P396 as reference, PA2200/PA12)

Parameter	Typical value	Effect
Layer thickness	100–120 µm	Standard; 60 µm for some premium materials
Part bed temperature	168–172°C (PA12)	Critical: too low → warping; too high → hard cake
Laser power	21–25 W	Calibrated by manufacturer — do not modify without validation
Scan speed	5000–8000 mm/s	High speed → energy per unit area
Energy density (ED)	0.015–0.025 J/mm²	ED = Laser power / (scan speed × hatch × layer)
Hatch spacing	0.25–0.35 mm
Refresh rate (fresh powder)	30–50% per build	Mixes virgin powder with recycled powder

Powder bed temperature — the most critical SLS parameter

• Operating window: ±2°C from the optimal point
• Too cold → distortions, curl, delaminations (curl effect)
• Too hot → excessive cake, lost detail, powder difficult to separate
• The chamber heating and cooling profile affects quality → follow manufacturer curve

MJF (HP) — Differences vs SLS

• Faster process (single pass of agents + IR fusion)
• Key parameters: controlled by HP — less parameter freedom for the user vs SLS
• User parameters: orientation, nesting, packing density
• Optimal packing density: 8–12% for PA12 (impacts mechanical properties)

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LPBF / DMLS — Process Parameters

Fundamental LPBF parameters

Parameter	Symbol	Unit	Role
Laser power	P	W	Total available energy
Scan speed	v	mm/s	Beam travel speed
Hatch spacing	h	µm	Distance between adjacent passes
Layer thickness	t	µm	Powder layer thickness
Energy Density (VED)	E = P/(v×h×t)	J/mm³	Synthetic indicator — not sufficient alone

Typical values by alloy (reference EOS M290 / SLM Solutions 125HL)

Alloy	P (W)	v (mm/s)	h (µm)	t (µm)	VED (J/mm³)
AlSi10Mg	340–370	1300–1600	130–190	30	40–65
Ti-6Al-4V	175–280	1000–1300	100–140	30	50–90
316L	200–280	700–1000	100–150	40	60–100
17-4PH	200–260	800–1100	100–150	40	55–90
Inconel 718	200–285	800–1000	100–130	40	65–110
Inconel 625	200–250	800–1100	100–140	40	55–90

Note: These are indicative ranges. Every machine and powder lot requires optimized parameters. The machine manufacturer provides certified parameters — use those as the baseline.

Scan strategies

Strategy	Description	Use
Alternating stripes	Alternating bands at 90° layer by layer	Standard, isotropic
Chessboard	Checkerboard with rotation	Reduces distortion on large parts
Island scanning	Random islands	Reduces residual stresses, large parts
Contour + infill	Perimeter + fill separately	Improves surface Ra (slow, precise contour)
Rotation per layer	Angle rotation (e.g. 67°) each layer	Improves isotropy, modern standard

Atmosphere parameters

• Inert gas: Argon or Nitrogen (AlSi10Mg prefers Nitrogen; Ti and superalloys → Argon)
• O₂ target: < 0.1–0.5% vol (depends on machine and material)
• High O₂: powder oxidation → inclusions → degraded mechanical properties

Build orientation and nesting parameters

• Build height: minimize → less time, less gas consumption, less risk of distortion
• Nesting: optimize chamber fill to reduce cost per part
• Distance between parts: ≥ 5mm (powder must flow between parts)

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Parameter → Defect Correlation

Defect	Probable cause	Correction
Gas porosity (spherical)	Dissolved gas in powder, moisture	Powder pre-drying, gas purity
Lack-of-fusion porosity (irregular)	VED too low	Increase P, reduce v or h
Solidification cracking	Susceptible alloy, excessive VED	Reduce VED, modify strategy
Warping / distortion	Residual stresses, inadequate supports	Optimize orientation, stress relief
Balling	v too high, oxidized surface	Reduce v, check atmosphere
Delamination	t too high, P too low	Reduce layer thickness, increase P
Stringing (FDM)	T too high, insufficient retraction	Reduce T, increase retraction
Warping FDM	Low bed temperature, no enclosure	Increase bed temperature, enclosure, brim
Visible layer lines SLA	Layer height too high	Reduce to 25–50µm, post-sanding