Unusual metal machining process?

Milled from both sides simultaneously with gang tooling and then formed. Small stuff like this is also frequently sintered metal.

The fins are only 0.7mm thick and no sign of machining marks just a slightly granualar looking surface on the concave side of each vane and a smooth surface on the convex side. I don't see how a milling process can be involved. Are you saying the original bulk would have been about 4 + (2x27mm ) wide ? , the fins are about 27mm along the curve. A milling process would not leave those 5 degree or so off axis cuts along the spine.

-- General electronic repairs, most things repaired, other than TVs and PCs

Diverse Devices, Southampton, England

Yeah, they are milled straight and then roll formed in place. Bar stock is pulled through a machine that does both sides and both operations at the same time.

Sure it would. You form grind the tools/cutters and gang them on an arbor. You are thinking of this as a milling operation done vertically from the top. It isn't. It's done horizontally with multiple cutters on an upper and lower arbor as a long length of stock is pulled through.

I didn't see a ground plane on the heat sink but if there is one it's bonded after the long bar has been cut to individual lengths and in a furnace. Like I said, a lot of this stuf is pressed and sintered as well. Depends on the material and - most importantly - quantities. Hardened carbide dies aren't cheap whereas wire cutting the forming sections and grinding the gang tooling is.

I have a heat sink similar to that somewhere. To me it looked like something done similar to a metal shaper not going through, leaving the chip attached to base metal. I'm not sure how the process works but I've seen video of aluminum cans being made by a small piece of aluminum being pressed in a die and flowing around a punch. Perhaps the fins heat enough to be formed while being cut?

This is an end on view

the granularity which probably suggests a shearing action. Looks as though the first operation was 4 knife cuts about 2mm deep (assuming 9mm thick slab to start with ) which when chiselled? up give those (2 sense) tapering ends to the knife cuts The lines on the spine probably show a guillotine to chop to length. The back face of these vanes is quite smooth in appearance mainly.

-- General electronic repairs, most things repaired, other than TVs and PCs

Diverse Devices, Southampton, England

I'm not sure what the process is actually called, but I call it "shaving." It's probably done on something like a shaper, as one other poster suggested. It's certainly not milled or sintered.

I've often wondered if heat sinks made like this were any good, because the integrity of the shaved off material is suspect in my mind. If the material is cracked, it won't have the same thermal conductivity. It's possible that this can be okay if the right alloy is used.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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I've never seen such a heatsink with a broken vane. There is a variant where the tip of each vane is sharply turned into a spiral before the main run of the curved vane.

I amagine it is all done just immediately after the extrusion, the knife cuts and then the 5 degree set chisel action on both sides , then chopped to length.

A very efficient process in the sense of no material loss in machining.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

If the texture in the photo is accurately portrayed on my computer screen, it's machined with wirecut EDM. Not cheap, but the best way to do it in small quantities.

If it's a high-production part, then it's something else.

-- Ed Huntress

Would that process give the alternating surface appearance effect? There's not much point in taking a photo of the other end showing the appearance of the convex sides of the vanes as it looks like polished aluminium except for about 5mm at the open end of each vane. That has an appearance half way between polished and that granular appearance, so probably won't show up in a pic.

What I don't understand is why the "polished" looking faces look just that. with not the slightest trace of any striations from a cutting action, I will try looking under a microscope.

I assumed the process was producing one cut surface and one cleaved process like a chisel or plane-blade. If it was done at the same time as extrusion then relatively light forces of a knife through butter.

-- General electronic repairs, most things repaired, other than TVs and PCs

Diverse Devices, Southampton, England

I'm afraid I don't follow what you mean by alternativing surfaces. If you explained it earlier in the thread, sorry, I missed it.

That suggests EDM. The EDMed surface texture is non-directional and just grainy, looking at it under a microscope. It can range from coarse to the naked eye, to highly polished.

Do you know if this thing is something made special, in small quantities, or is it a production piece?

I looked under a x30 microscope and both surfaces show striations, at that level of viewing, in the sense of chisel cuts if produced like that.

There were 10,000s to millions of them produced for mainlly Sony makes of domestic hi-fi amplifiers of the 1970s and 80s.

-- General electronic repairs, most things repaired, other than TVs and PCs

Diverse Devices, Southampton, England

cuts

PCs

It could be a casting using a lost wax process. The wax model is typically cast in wax from a master mold, then the wax is invested in a plaster mold, burned out and the aluminum poured in. This shape would lend itself well to that process.

-Mike

That wouldn't be wire EDM, then. Fine striations suggest extrusion. And that quantity suggests they weren't cut, except that they were sliced off from the extrusion.

-- Ed Huntress

But not that quantity, Mike. That would be too high for a non-structural aluminum part. The cost would be at least 20 times the cost of extrusion -- probably more like 100 times the cost.

-- Ed Huntress

It`s a process called 'Skiving'

Ron(UK)

So it does, which begs the philological question - what's the connection with the work-shy ?

-- General electronic repairs, most things repaired, other than TVs and PCs

Diverse Devices, Southampton, England

So that means that the dole office is full of orthogonal planers?

Ron

Ed,

If you will forgive my hopping in here, These heatsinks were popular in Japanese consumer electronics about thirty years ago. They always looked shaped to me. The bright surface is formed as the curls are cut. The "polish" was just a nice finish.

Kevin Gallimore

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I guess I should look again, Kevin. When the quantities get as large as they were described, the usual method today is extrusion. From my quick look at the photos it looked like a difficult production-broaching job. I don't know what our Brit friends mean by "skiving" (in the US, the term is traditionally applied to a form-turning operation that's like scraping).

Anyway, I'll take another look.

-- Ed Huntress