Heat Sinks and ISO 2768 General Tolerances: how the two fit together
Heat Sinks is a machined or extruded finned body that carries heat away from a component. It is used for power electronics, LED assemblies and any enclosure that generates heat. This entry explains what it is, what the numbers on a data sheet mean, and what to put on a drawing.
It is written from the point of view of the buyer and the drawing office: the values that are realistic in production, the ones that cost money, and the way the result is verified. Where an industry sets the requirement, automotive is used as the example: a fixed takt, because a late delivery stops the line.
How the two fit together
Heat Sinks and ISO 2768 General Tolerances are specified together more often than separately. Heat Sinks is a machined or extruded finned body that carries heat away from a component, while ISO 2768 General Tolerances is a standard that sets the tolerance for dimensions that have no individual tolerance on the drawing; one produces the result and the other controls or finishes it.
Sequence
The order matters. Heat Sinks sets the requirement, and the work with ISO 2768 General Tolerances is carried out to meet it; stating the result without the control is what leaves a drawing open to interpretation.
What to specify
| Specification | Typical value |
|---|---|
| Aspect | Note |
| This entry | Heat Sinks – ±0.05 mm on the mounting face |
| Related entry | ISO 2768 General Tolerances – ±0.2 mm for medium over 6 to 30 mm |
| Material | 6063-T5 aluminium |
| Finish | Ra 1.6 µm on the contact face |
| Documentation | in-house approval with dimensional reports |
A combined note for the drawing
Where both apply, state the result and let the route follow: the tolerance, the finish and the verification. Specify flatness on the mounting face, not just a thickness tolerance
Applications
Heat Sinks is used for power electronics, LED assemblies and any enclosure that generates heat, and in practice it appears most often in power supplies, motor drives, LED luminaires, telecom enclosures.
How it fits into a machining route
Heat Sinks is produced by whichever route reaches it most reliably, and it is usually the reason the rest of the part is dimensioned the way it is. Datums are chosen so that this feature is measured from what it actually has to be square or concentric with.The route is fixed before the first part is cut, and it is the route rather than the individual setting that holds the result: fin count and the machining time on the base. Where a drawing calls for something the route cannot hold economically, that is raised at quotation rather than after the parts are made.
Standards, documentation and what is issued
The documentation requirement is in-house approval with dimensional reports. Material is supplied against a certificate where the application calls for it, inspection results are recorded with the job, and the records are kept so that a repeat order can be compared with the first instead of being measured from scratch.
Flatness check on a plate, plus a visual check of the fins is the verification step. Where a customer format or a standard report is required, it is agreed before the batch starts, because a report written after the event is a report nobody can use.
Frequently asked questions
What tolerance should be specified for Heat Sinks?
±0.05 mm on the mounting face is realistic in production. Tightening it beyond the functional requirement increases cost without improving the part.
Which material is usually used?
6063-T5 aluminium is the usual choice, supplied against in-house approval with dimensional reports.
How is the result verified?
Flatness check on a plate, plus a visual check of the fins, with the results recorded so a repeat order can be compared with the first.
What is the most common mistake?
Fins so thin that the tool deflects and they vary in height.
How long does it take and what does it cost?
A realistic cycle is 20 to 90 minutes depending on the fin count, and the cost driver is fin count and the machining time on the base.
Related capability
If you are specifying Heat Sinks on a drawing and want a second opinion on the route, send the model and the quantity. The first response is a manufacturability review with the likely risk points and a quotation, so the decision can be made on facts rather than on a price alone.
Machining, inspection and documentation are handled in one place, which is why the dimensional report and the material certificate arrive with the parts rather than after them.
Related entries
These entries sit next to Heat Sinks in the encyclopedia: Bearing Housings, Hydraulic Manifolds, Surface Roughness. Reading them together gives a fuller picture of how the process, the material and the measurement affect each other.
