3D Printing Conformal Cooling SLM / DMLS March 14, 2026 · 14 min read · By MouldNova Engineering Team

Conformal Cooling & 3D Printing: Which Process, Which Material, and What It Actually Costs

What this article covers:

Table of Contents

  1. Why 3D Printing Is the Only Option
  2. SLM vs. DMLS vs. Binder Jetting: Which Process for Mold Inserts?
  3. The SLM Manufacturing Process — Step by Step
  4. Material Selection: 420 SS vs. 18Ni300 vs. CuCrZr
  5. Design-for-3D-Printing Rules for Conformal Channels
  6. Real Project: 3D Printed Conformal vs. Drilled Conventional
  7. What Does It Cost? Real Price Ranges
  8. FAQ

Why 3D Printing Is the Only Option for Conformal Cooling

The phrase "conformal cooling" is sometimes used loosely to mean "better cooling." But in manufacturing terms, it has a precise meaning: cooling channels that conform to — follow the surface of — the mold cavity at a constant offset distance.

That geometric requirement immediately rules out all conventional subtractive manufacturing methods:

SLM 3D printing process for conformal cooling insert production
Selective laser melting builds conformal cooling inserts with complex internal channels
Manufacturing MethodCan Make Conformal Channels?Why Not
Gun drilling✗ NoOnly straight-line paths possible; cannot bend around geometry
CNC milling✗ NoTool access requires open geometry; cannot machine enclosed internal channels
EDM (wire or sinker)✗ NoRequires electrode access; cannot create fully enclosed 3D curved channels
Baffles / bubblers✗ WorkaroundExtends straight channels into cores, but cannot truly follow complex surfaces
Vacuum brazing (split mold)⚠ PartialChannels milled in two halves and brazed; limited to near-planar geometries, bonding reliability concerns
SLM / DMLS metal 3D printing✓ YesBuilds geometry layer by layer; channels created during print with no access constraints

The physics of why this matters: a conformal channel maintains a constant offset of 8–15mm from the mold surface, regardless of how curved or deep the part geometry is. A drilled channel, by contrast, can only approach within ~25–30mm of complex surfaces before structural risk becomes unacceptable — and often cannot reach deep core tips at all.

The key insight: In a conventional mold, cooling channel placement is determined by what the drill can reach. In a 3D printed conformal mold, channel placement is determined by what the part actually needs. That shift — from tool-access-constrained to thermally-optimized — is what drives the 30–70% cycle time reductions.

SLM vs. DMLS vs. Binder Jetting: Which Process for Mold Inserts?

Several metal additive manufacturing processes can create internal channels. Not all are suitable for injection mold inserts that must withstand 50–150 MPa injection pressure, 50+ HRC hardness, and millions of cycles. Here's the comparison:

ProcessDensityAchievable HardnessSurface Finish (as-built)Suitable for Mold Inserts?
SLM (Selective Laser Melting)99.5–100%Up to 54 HRC (after HT)Ra 4–8 μm✓ Best choice
DMLS (Direct Metal Laser Sintering)95–99%Up to 52 HRC (after HT)Ra 4–10 μm✓ Excellent
EBM (Electron Beam Melting)99%+Up to 35 HRC (Ti alloys)Ra 25–35 μm (rough)✗ Too rough, limited materials for molds
Binder Jetting + sintering96–98%Up to 45 HRCRa 3–6 μm⚠ Limited — shrinkage control challenging for precision molds
DED (Directed Energy Deposition)99%+Up to 50 HRCRa 10–30 μm (very rough)✗ Poor for fine channels; mainly for repair/cladding
Standard choice

SLM (Selective Laser Melting)

  • Full melt — near 100% density
  • Best mechanical properties
  • Highest pressure integrity for channels
  • Available in 420 SS, 18Ni300, CuCrZr
  • Typical build rate: 5–20 cm³/hr
  • Our primary process at MouldNova
Also excellent

DMLS (Direct Metal Laser Sintering)

  • Sintering (partial melt) — 95–99% density
  • Slightly lower strength than SLM at same material
  • Wider equipment availability globally
  • Available in similar material range
  • In practice: SLM vs DMLS results nearly identical
  • Industry often uses terms interchangeably
Practical note: In day-to-day industry use, "SLM" and "DMLS" are used interchangeably by most mold shops and suppliers. Both refer to powder bed fusion with a laser, and both can produce mold inserts of equivalent quality. The academic distinction (full melt vs. sintering) matters less than the specific equipment, parameter settings, and post-processing of a given supplier.

The SLM Manufacturing Process — Step by Step

Understanding the full manufacturing chain helps you specify correctly, avoid surprises, and communicate accurately with your supplier. Here's exactly what happens between your CAD file and a finished 3D printed conformal insert:

3D printed conformal cooling inserts on metal printer build plate
Conformal cooling inserts on the build plate after 3D printing
1

Design Review & DFM (Design for Manufacturing)

Channel routing is checked for: minimum wall thickness, bend radius compliance, support structure requirements, and powder removal path. Channels with no exit for loose powder must be redesigned — trapped powder causes hot spots and blockages. Critical: every conformal channel needs a clear powder evacuation route.

1–2 working days
2

Support Structure & Build Orientation

The insert is oriented in the build chamber to minimize supports inside channels (supports inside a cooling channel cannot be removed). Overhangs >45° require supports; channel geometry is designed to avoid this. Build orientation also affects surface finish on critical mating faces.

4–8 hours (engineer time)
3

SLM Printing

Layer thickness: 30–60 μm (finer = smoother surface, longer build time). Laser power: 200–400W depending on material. Build atmosphere: inert argon gas to prevent oxidation. Typical print time for a 150×150×100mm insert: 18–36 hours. Multiple inserts are nested in one build to reduce cost per part.

1–3 days (print time)
4

Stress Relief Heat Treatment

SLM-printed parts have high residual stress from rapid heating/cooling of the laser. Parts are stress-relieved at 450–600°C before removal from build plate. Skipping this step causes distortion during CNC machining. This is a non-negotiable step — ask any supplier whether they do it.

1 day
5

Powder Removal & Channel Cleaning

Loose powder is blown and vibrated out of all channels. Internal channel inspection via borescope camera confirms channels are clear. Ultrasonic cleaning removes residual powder from channel walls. Blocked channels = dead zones in cooling = hot spots in the mold.

4–8 hours
6

CNC Finish Machining

All mating surfaces (parting line, ejector pin holes, guide pin bores) are machined to drawing tolerance. The as-printed surface Ra 4–8 μm is only acceptable for non-mating areas. Mating surfaces are machined to ±0.05–0.1mm. This is where insert dimensional accuracy is finalized.

2–4 days
7

Hardening Heat Treatment

420 SS: vacuum hardening at 1,020–1,050°C, quench, double temper at 200°C → 50–52 HRC. 18Ni300: age hardening at 490°C for 6 hours → 50–54 HRC (no quench needed — dimensional stability is excellent). CuCrZr: solution annealing + aging — achieves different hardness profile.

1–2 days
8

Polishing & Final Inspection

Cavity surface polished to required specification: texture mold (VDI standard), polished mold (SPI B1–A1), or technical surface. CMM dimensional inspection, hardness testing, channel pressure test at 1.5× operating pressure, and photography for delivery report.

1–3 days
10–16Total working days CAD → finished insert
30–60μmSLM layer thickness
±0.1mmDimensional accuracy on mating surfaces
8Manufacturing steps — all in-house at MouldNova

Want to know the lead time and cost for your specific insert?

Share your STEP file and mold drawing. We'll quote within 24 hours with a full breakdown: print time, material, post-processing, and delivery.

Request a Quote WhatsApp Us

Material Selection: 420 SS vs. 18Ni300 vs. CuCrZr

The choice of print material is the single biggest factor in both cost and performance of a conformal cooling insert. Here's the decision framework we use across 13 industries of production experience:

Property420 Stainless Steel18Ni300 (Maraging Steel)CuCrZr Copper Alloy
Hardness after HT50–52 HRC50–54 HRC~28–32 HRC
Thermal conductivity~24 W/m·K~25 W/m·K~320 W/m·K
Yield strength~1,500 MPa~1,900–2,000 MPa~500–600 MPa
Corrosion resistanceGood (stainless)Moderate (requires coating for corrosive plastics)Good
Wear resistanceGoodExcellentPoor — not for abrasive materials
Relative cost$$$$$$
Best applicationGeneral purpose: most injection moldsHigh-cavitation, high-pressure, long-run moldsTargeted inserts: deep cores, hot-runner zones, max heat extraction

When to choose 420 Stainless Steel

420 SS is the default choice for 70–80% of conformal cooling applications. It delivers 50–52 HRC hardness (equivalent to conventional mold steel), excellent corrosion resistance for processing PVC, flame-retardant ABS, or other corrosive plastics, and the lowest cost of the three options. If you're not running a specialized application, start here.

When to upgrade to 18Ni300 Maraging Steel

The 300-grade maraging steel provides ~30% higher yield strength than 420 SS and the highest hardness (54 HRC achievable). This matters for:

When to use CuCrZr Copper Alloy

CuCrZr's thermal conductivity (320 W/m·K) is 13× higher than steel. This makes it uniquely effective for specific locations: deep core tips where steel inserts still create a thermal bottleneck, hot-runner gate areas where rapid heat removal prevents gate drool, and thick sections where even conformal steel channels can't extract heat fast enough.

Do not use CuCrZr for entire mold inserts if processing glass-filled, mineral-filled, or any abrasive plastic. Its 28–32 HRC hardness means it wears 3–5× faster than hardened steel. Use it for targeted inserts in high-heat, low-wear zones only.

Design-for-3D-Printing Rules for Conformal Channels

3D printing enables geometry that machining cannot — but it has its own constraints. These rules are specific to conformal cooling channels in metal SLM printing, and violations are the most common cause of print failures or post-print surprises:

RuleValueWhy It Matters
Minimum channel diameter4mm (6mm recommended)Channels <4mm are difficult to clear of sintered powder and risk blockage. See channel design rules
Maximum channel diameter12mmLarger requires support structures inside channel — hard to remove
Self-supporting overhang angle≤45° from verticalOverhangs >45° inside channels require supports that cannot be removed
Powder evacuation routeRequired for every channelChannels with no exit = trapped powder = blockage during pressure test
Minimum wall (channel to surface)≥1.0 × channel diameterThinner walls risk crack propagation under injection pressure cycling
Minimum wall (channel to channel)≥0.8 × channel diameterThinner inter-channel walls risk deformation during heat treatment
Transition from channel to fittingGradual taper, not abrupt stepAbrupt cross-section changes create turbulence dead zones — reduces cooling efficiency
Build orientation (channel axis)Avoid horizontal channels parallel to build plateHorizontal channels need internal supports — prefer channels running diagonally or vertically
The most common mistake we see: Customers design conformal channels that terminate in a blind dead end on one side — no exit for powder. During printing, the metal powder inside the channel partially sinters to the walls. On removal from the build plate, the channel looks fine externally, but internally it's blocked. This only shows up during pressure testing or, worse, during first use on the press. Always design a clear evacuation path for every channel section.

Optimal build orientation strategy

Build orientation affects three things: support structure amount (cost), surface finish on specific faces, and dimensional accuracy in Z vs. XY. General rules for mold inserts:

Real Project: 3D Printed Conformal vs. Conventional Drilling

Automotive — Glass-Filled PA66 Deep Core Insert

Core insert for structural door bracket — 52mm core depth, 8-cavity mold

The original conventionally drilled mold had straight channels that could not enter the core at all — a bubbler insert was used, but the bubbler created a single cooling point rather than distributed cooling. Core tip temperature ran 38°C hotter than the surrounding mold steel. This caused premature ejection warpage and a reject rate of 18%.

3D printed conformal approach: 18Ni300 maraging steel insert. Conformal channels wrapped around the core at 10mm offset from tip, spiraling from tip to base. Channel diameter 8mm, pitch 20mm. Total channel length per insert: 640mm. Build time: 28 hours. Post-processing: 6 working days.

−42%Cycle time
38°C → 4°CCore tip temperature differential
18% → <1%Warpage reject rate
5 monthsInsert cost payback period

What Does It Cost? Real Price Ranges

Most articles about conformal cooling 3D printing avoid discussing cost. Here is our actual pricing structure, which reflects the costs of SLM printing + full post-processing at our Ningbo facility. European and North American suppliers typically charge 2–3× these figures for equivalent inserts.

Small Insert — ≤100 × 100 × 80 mm (420 SS, standard conformal channel)

SLM printing (material + machine time)$380–520
Stress relief + hardening heat treatment$80–120
CNC finish machining (mating surfaces)$180–280
Polishing (cavity surface, SPI B2 standard)$60–150
Inspection + pressure test + report$40–60
Total: Small insert$800–1,200

Medium Insert — 100–200 mm cube (18Ni300, complex conformal channel)

SLM printing (material + machine time)$900–1,500
Stress relief + age hardening$120–180
CNC finish machining$400–700
Polishing (SPI A2 standard)$200–450
Inspection + report + pressure test$80–120
Total: Medium insert$1,800–3,000

Large Insert — >200 mm cube (18Ni300 or 420 SS, multi-zone conformal)

SLM printing$2,200–4,500
Heat treatment$200–350
CNC machining (multiple setups)$800–1,800
Polishing$400–900
Full inspection package$150–250
Total: Large insert$4,000–9,000

For reference: a conventionally machined insert of equivalent size typically costs 40–60% less. The conformal cooling premium is recovered through cycle time savings. For a detailed breakdown, see our metal 3D printing cost guide. For a mold running 100,000+ shots/year, the payback period for this premium is typically 3–8 months.

Cost reduction tip: Nesting multiple inserts in one SLM build significantly reduces per-part cost — machine setup is amortized across all parts in the build. If you're ordering multiple inserts, always ask your supplier to batch them in a single build. We typically see 15–25% cost reduction when 3+ inserts are built together.

Ready to Get a Quote for Your Conformal Cooling Insert?

Send your STEP file and mold drawing. We'll confirm the build approach, material recommendation, and quote with full cost breakdown within 24 hours.

Request Quote — 24hr Response Chat on WhatsApp

Frequently Asked Questions

Why is metal 3D printing the only way to make true conformal cooling channels?
Conformal cooling channels must follow complex 3D curved paths that cannot be accessed by any drilling or milling tool. Metal 3D printing (SLM/DMLS) builds the insert layer by layer, creating internal channels of any geometry during the build process — no post-drilling required. Conventional alternatives (baffles, bubblers, vacuum brazing) are workarounds that approximate conformal cooling but cannot match its temperature uniformity.
What is the difference between SLM and DMLS for conformal cooling?
SLM (Selective Laser Melting) fully melts the powder, achieving near-100% density. DMLS (Direct Metal Laser Sintering) sinters particles at slightly lower energy, achieving 95–99% density. For mold inserts requiring 50+ HRC and high injection pressure resistance, SLM is technically preferred. In practice, both processes produce equivalent mold inserts, and the industry uses the terms interchangeably. The specific equipment, parameters, and post-processing of a given supplier matter more than the SLM vs. DMLS distinction.
Which material should I use for 3D printed conformal cooling inserts?
420 stainless steel: best for most applications — 50–52 HRC, good corrosion resistance, lowest cost. 18Ni300 maraging steel: best for high-cavitation, high-pressure, or long-run molds — highest strength (50–54 HRC), minimal dimensional change during heat treatment. CuCrZr copper alloy: use only for targeted inserts in maximum-heat zones — 13× higher thermal conductivity than steel, but softer (28–32 HRC) and more expensive. Do not use for full inserts in abrasive plastic applications.
How long does it take to 3D print a conformal cooling mold insert?
SLM printing time for a typical insert (150×150×100mm): 18–36 hours. Total lead time from CAD file to finished insert: 10–16 working days including: design review (1–2 days), printing (2–3 days), stress relief (1 day), powder removal (half day), CNC machining (2–4 days), hardening (1–2 days), polishing (1–3 days), inspection (1 day). Rush lead times (8–10 days) are available for simple geometries.
What does a 3D printed conformal cooling mold insert cost?
From MouldNova (China-based, full-service): Small insert (≤100mm cube): $800–1,200. Medium insert (100–200mm cube): $1,800–3,000. Large insert (>200mm): $4,000–9,000+. European/North American suppliers typically charge 2–3× these prices. The premium over conventional machined inserts (60–120% more) is recovered through cycle time savings — payback typically 3–8 months for molds running >100,000 shots/year.

Related Articles & Pages