How heat sink prototyping works: CNC vs extruded samples, cost, lead time, thermal validation, and how to move from a prototype to a production die safely.
Heat Sink Prototype and Sample Service: What to Expect
Direct answer: A heat sink prototype should be CNC machined from plate or bar, not extruded. CNC prototyping costs USD 80-450 per part depending on size and features, ships in 5-10 working days from an approved drawing, and requires no tooling. Extruded samples only make sense once you have committed to a die, and they always come from the die trial, which means they are not thermally or dimensionally representative of production.
CNC prototype vs extruded sample
| CNC prototype from plate | Extruded die-trial sample | |
|---|---|---|
| Tooling required | None | Full die, USD 800-3,500 |
| Quantity that makes sense | 1-50 | 5-20 (the trial run) |
| Lead time | 5-10 working days | 15-25 working days including die |
| Fin geometry | Straight fins only; aspect ratio limited by tool reach | True extrusion geometry including thin dense fins |
| Thermal representativeness | Close but not identical: alloy and fin thickness are controlled, surface finish differs | Not representative: die-trial fins run oversize and the surface is not anodised the same way |
| Dimensional representativeness | Machined to drawing, tighter than production | Die-trial profile sits on the tight side of tolerance |
| Cost per part | USD 80-450 | USD 15-60 plus the die |
The practical sequence is CNC prototype to validate the thermal design, then die, then production. Skipping the CNC stage means paying for a die before you know whether the geometry works.
What a prototype actually validates
Be clear about what a prototype can and cannot prove, because the answer determines whether it was worth the money.
- It validates geometry and fit. Mounting holes, clearance to neighbouring components, connector access and enclosure depth. This is the highest-value use of a prototype and the one most often skipped.
- It validates thermal performance within reason. A machined prototype with the same fin count, fin thickness and base thickness will get within 10-15% of an extruded production part, because the geometry is the same even though the manufacturing route differs.
- It does not validate the production surface finish or anodising. Prototypes are often left bare or hand-anodised.
- It does not validate die feasibility. A CNC prototype can be machined with fin aspect ratios that no extrusion die could produce at volume. Do not design the prototype in isolation from the intended process.
Cost of a prototype heat sink
| Prototype type | Indicative cost | Lead time |
|---|---|---|
| Small machined heat sink, under 100 x 100 mm, straight fins, 1 pc | USD 80-150 | 5-8 working days |
| Medium machined heat sink, 150 x 150 mm, machined base and tapped holes | USD 150-280 | 7-10 working days |
| Large machined heat sink, over 200 mm, multiple setups | USD 280-450 | 8-12 working days |
| Prototype with heat pipes or vapour chamber | USD 350-900 | 12-20 working days |
| Prototype cold plate with machined channels and fittings | USD 400-1,200 | 12-20 working days |
| Small batch, 10-20 pcs, same design | 60-70% of the single-unit price each | 8-12 working days |
These are indicative ranges for 2026 Chinese supply. A prototype is priced by machine hours and setups, so the number of faces you machine matters more than the part's mass.
Thermal validation: what to measure and how
A prototype that is only checked for fit is half tested. The thermal test that actually informs the design decision has four inputs and one output.
Inputs: dissipated power in watts, ambient temperature, airflow in metres per second or cubic feet per minute, and the thermal interface material and its bond line thickness. Output: the temperature rise from ambient to the heat sink base, from which you derive thermal resistance in C/W.
Test it at the power level you expect, not at a convenient level. Thermal resistance is not constant across power; radiation and convection both change with temperature. A heat sink measured at 10 W can look competent and fail at 50 W.
Two practical notes. Measure the base temperature at the centre of the component footprint, not at the edge of the heat sink, or you will measure spreading as if it were interface resistance. And record the airflow at the fin inlet, not at the fan outlet, because the two differ substantially once the air has passed through the enclosure.
Moving from prototype to production without a surprise
- Freeze the design against the production process. Before you release the drawing for tooling, confirm that the fin thickness and pitch you prototyped are achievable by the extrusion die you are about to buy. A 0.6 mm fin is easy to machine and expensive to extrude.
- Ask for a DFM report on the die. The supplier should comment on fill, bearing, die strength and expected tolerance drift. This is free and it is where most die problems are avoided.
- Insist that the first article comes from a production run. Die-trial parts are not production parts, for the reason in the table above.
- Keep the prototype as the visual and fit reference. Agreement on "meets the sample" is easier to enforce than agreement on a drawing with a dozen tolerances.
- Validate the anodised part. Anodising changes dimensions by micron-level amounts and changes the contact face. Test the finished part, not the bare one.
Frequently asked questions
Can I get one sample for free?
Not for a new design. Free samples exist for standard catalogue profiles where the factory already holds stock. For a new machined heat sink, the sample is machined to order and is charged. Some suppliers credit the sample cost against the first production order; ask.
How accurate is a CNC prototype thermally?
Within roughly 10-15% of the production extrusion if the geometry and alloy match. The difference comes from surface finish, anodising and small deviations in fin thickness.
Can you prototype a heat sink with heat pipes?
Yes, but expect a longer lead time and a higher cost, because pipe bending, sintering and press-fit assembly are separate operations. Budget 12-20 working days.
Do I need a prototype if I am buying a standard profile?
Usually not. Ask for a stock sample instead, which is faster and cheaper, and test it thermally. Standard profile samples are often free or charged at freight only.
Send a STEP file and the application conditions and we will tell you whether a CNC prototype is the right next step or whether a stock profile sample will answer the question.
Heat sink sourcing guides
- Aluminum Heat Sink Price per kg: 2026 Cost Breakdown
- Custom Heat Sink MOQ and Lead Time by Process
- Heat Sink Extrusion Die Cost and Tooling Amortisation
- Heat Sink RFQ: What to Send for an Accurate Quote
- Heat Sink Tolerance and Flatness: What to Specify
- Heat Sink Surface Finish Options and Cost Impact
- Heat Sink RoHS, REACH and UL Compliance Explained
- Heat Sink Volume Pricing: How Breakpoints Really Work
- Heat Sink Packaging, Shipping and DDP Terms
- Heat Sink Supplier Audit and Second Sourcing
- Heat Sink Thermal Test Report: What the Data Package Contains
