Electronics > Projects, Designs, and Technical Stuff
general heat sink rules for fin dimensions
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coppercone2:
those are too expensive for me, I want to get entertainment from the mill

you can't make them without weird equipment unfortunately and the development kits are expensive

as much as I want to, I can't afford this
https://www.ebay.com/i/183203665283?

their like 10$ each if you buy singles

https://www.digikey.com/products/en/fans-thermal-management/thermal-heat-pipes-vapor-chambers/977?FV=1880003%2Cffe003d1&quantity=0&ColumnSort=1000011&page=1&k=heat+pipe&pageSize=500&pkeyword=heat+pipe

less for smaller ones. maybe
T3sl4co1l:
The thickness and length of a fin can be derived from the heat spreading length of the material.

Thin fin radiators have frequent pipes, while thick fins are typical for longer heatsinks with heavy solid backplates.  Thicker fins or more frequent pipes are required for forced air.

Fin spacing similarly is driven by pressure drop.  The pressure drop of convection is very small so the fins need to be widely spaced.  There is much more time for thermal diffusion to occur, carrying heat into the thickness of the airflow, so this isn't a big deal.  Forced air can afford more pressure drop, and so shorter, denser fins are acceptable.

Tim
duak:
Coppercone2, what type of milling machine are you using?  For small end mills on the order of 1 mm you need a machine with tight ways and a fast spindle and have to watch the feed and speed carefully.  If fed too fast or if the end mill loads up with chips it'll break like glass.  Depending on the shape and spacing of the fins, it's probably better to use a slitting saw instead of an end mill.
MosherIV:
Most commercial heatsinks use extruded shapes. Meanung all straight lines and shapes.

How about machining concentric rings into a block.
I am no mathmetician or mechanical engineer but I would have thought you can get more surface area with circles than straight lines.

Not ecomonical to machine circles unless there is good reasons or necessity.

More thoughts rather than absolute facts.
ejeffrey:
Straight lines are better for airflow than concentric rings.  And almost any heatsink whether forced air or natural convection ultimately relies on airflow to remove heat.
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