Heatsinks · CNC Machined
CNC machined heatsinks
CNC machined heatsinks are milled from solid or plate aluminum for shapes extrusion and bonding cannot make — curved bases, embedded channels, pin fins and precise mounting patterns — at prototype and low-volume quantities with no tooling charge.
When to choose CNC machined
A CNC machined heatsink is the right call when the geometry cannot be extruded or bonded: a contoured base that wraps a device, internal coolant channels, a dense array of pin fins, or a low quantity where a die is not justified. We machine from 6061 or 6063 plate, or from a near-net extrusion, to cut material and cycle time while holding tight tolerances.
Where volume is high and the fin shape is simple, an extruded sink is cheaper — see our extruded heatsinks page. CNC is the flexible default for complex, low-run and prototype thermal parts.
Typical specs
- Positioning: ±0.01 mm
- 3 / 4 / 5-axis milling
- Pin fin dia: ~1–3 mm typical
- Finish: anodized II/III
Exact travel, MOQ and lead time confirmed against your drawing.
How a CNC machined heatsink is made
- Program from model. The STEP or IGES file is set up in CAM; datum and critical surfaces are defined so milling holds your callouts.
- Rough & face. The block is squared and the mounting face is faced flat before features are cut.
- Cut fins. Straight plate fins are end-milled; pin fins are drilled or milled as an array of posts — only machining can produce them.
- Machine features. Holes, threads, pockets, locating bosses and embedded channels are cut in the same setup where possible.
- Deburr & finish. Edges are broken and the part is anodized (clear or black) or left as-specified.
- Inspect. Critical dimensions are checked against the print before shipping.
Capability & typical specs
Numbers below are typical production ranges; confirm exact limits against your drawing and order.
| Parameter | Typical capability |
|---|---|
| Positioning tolerance | ±0.01–0.05 mm |
| Axes | 3 / 4 / 5-axis |
| Pin fin diameter | ~1–3 mm typical |
| Surface finish (milled) | Ra 0.8 µm typical |
| Materials | 6061, 6063, 6082 plate |
| Finish | Anodize II/III, bare, powder |
Pin fins — the CNC advantage
A pin fin heatsink uses a grid of short posts instead of straight fins. Because each post is a separate feature, air can approach it from any direction, so pin arrays outperform straight fins in low-airflow and omnidirectional cooling. Pin fins cannot be extruded or bonded — they are milled, drilled or punched, which is why they are a CNC-only construction.
Pin fins suit compact, high-power parts where straight extruded fins would choke: RF and power modules, motor drives, and sealed enclosures with weak internal flow. Typical pin diameter is about 1–3 mm with pitch set by tool and machine; we pick diameter and height to your thermal target and envelope rather than to a catalog value.
Thermal & design notes
Design for CNC machined heatsinks
- Start from near-net stock (plate or extrusion) when volume allows — it cuts cycle time and scrap versus a solid block.
- Define one datum and the critical mounting face so all features are referenced to it; this is what holds ±0.01 mm where needed.
- Size pin fins for your flow. Smaller, denser pins help in still air but add pressure drop under a fan — match to the actual airflow.
- Keep features machinable. Avoid slots narrower than the end mill; tell us the smallest internal radius and we set tooling.
- Call out the thermal target. A resistance or power/ΔT figure lets us propose fin type and density instead of guessing from shape.
CNC machined vs extruded vs skived
| Need | Best choice |
|---|---|
| Complex shape, low volume, no tooling | CNC machined |
| Low cost at volume, simple fins | Extruded (see extruded heatsinks) |
| Very thin, tall straight fins, no bond line | Skived (see skived fin) |
| Pin fin array | CNC machined only |
These are process choices, not competitors. Many programs use a machined base with extruded or bonded fins, or a CNC prototype that later moves to extrusion at volume.
How to specify a CNC machined sink
Send the STEP file with datum, critical dimensions and surface finish, plus your thermal target (resistance or power and ΔT) and airflow. For a prototype we confirm material, pin or fin geometry and lead time; for production we also confirm quantity and any inspection level. No tooling charge applies — you pay per part, not per die.
Where CNC machined heatsinks are used
Power electronics
IGBT and converter sinks needing contoured bases and precise mounting at prototype and low volume.
RF & microwave
Sealed modules where pin fins cool in weak internal airflow.
Medical & optical
Laser and imaging parts where flatness and clean finish matter.
R&D / NPI
Design-validation builds before a die is cut, then ported to extrusion at scale.
Frequently asked questions
What is a pin fin heatsink and when do I need one?
A pin fin heatsink uses a grid of short posts instead of straight fins. Air can reach each post from any direction, so pin arrays cool better than straight fins in low or changing airflow and in compact sealed boxes. Pin fins are milled or drilled, not extruded, so they are a CNC construction. Choose them when straight extruded fins would choke or when the envelope is tight and omnidirectional cooling helps.
Skived or CNC machined — which fin?
Skived fins are thinner and taller for maximum straight-fin density and have no bond line, so they lead on pure conduction through the fin base. CNC wins on shape freedom: curved or contoured bases, embedded channels, pin fin arrays and features skiving cannot make. If you need the thinnest tall straight fin in a simple slab, skived is usually better; if the part is complex or low-volume, CNC is.
Why pick CNC over extrusion?
Extrusion is cheaper at volume but locked to a die and to straight-fin geometry. CNC has no tooling charge and makes contoured bases, pin fins, internal channels and tight-tolerance features that extrusion cannot. For prototypes, low runs and complex shapes CNC is the default; for high volume with simple fins, extrusion wins on cost. We can take a CNC prototype and move it to extrusion later.
What tolerance can CNC hold on aluminum?
A typical positioning tolerance is about ±0.01–0.05 mm, with milled surfaces around Ra 0.8 µm. Tighter values are possible on critical features — define the datum and the callouts that matter and we hold those, rather than over-specifying the whole part.
Is there a tooling charge or minimum order?
No die cost — CNC is made to print, so you pay per part. Minimum order depends on setup and material, not a die; prototypes of a few pieces are normal. Confirm exact MOQ and lead time against your drawing and quantity.
What do you need to quote a CNC machined heatsink?
The STEP/IGES model with datum and critical dimensions, material, finish, thermal target and airflow, and quantity. A drawing gets the tightest quote; for a prototype we can often quote from the model alone and confirm details in a DFM note.
Quote a CNC machined heatsink
Send the model and thermal target — we machine to print, no tooling charge.