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How is this manufactured? I'm stumped

How is this manufactured? I'm stumped

How is this manufactured? I'm stumped

(OP)
I'm working on a project that requires a heat sink for a high power LED. The unit shown in the linked images works well, the problem is that I can't figure out how it was manufactured and I need to create something similar but customized to this project.

This heat sink is from a fairly high volume product. The material is aluminum, and it's anodized. The part is not machined, there are very sharp inside corners that they would never bother with since they serve no purpose. There is 0deg draft on any of it, so it's not die cast. As far as I know you can't metal injection mold aluminum, so that's ruled out. There's no way a high volume part would be sand cast.

Am I missing something? Is there some sort of automated high volume equivalent to sand casting? The bottom face is smoothed with a secondary operation, but the rest of it can be a bit rough. I have Googled everything I can think of with no success.

Any ideas?

http://files.engineering.com/getfile.aspx?folder=4...
http://files.engineering.com/getfile.aspx?folder=e...
http://files.engineering.com/getfile.aspx?folder=9...

RE: How is this manufactured? I'm stumped

themilkmaid (Mechanical)
You can investment cast Aluminum. and do modified die casting. See IRstuff's second link electronics cooling etc.,
B.E.





)

You are judged not by what you know, but by what you can do.

RE: How is this manufactured? I'm stumped

The fully radiused edges of the fins contraindicate routing the entire unit from a solid billet.
Those fins could be extruded and sheared to length at a pretty decent rate.
... then bonded or brazed to the contact plate, using a positioning fixture of some kind.


I can't quite eliminate impact extruding the whole thing from a slug a little thicker than the contact plate, but I'd expect a little bigger radius at the root of the fins.
... or maybe the part is smaller than I imagine it; there's no dimensional context in the photos.


The finish texture looks like a fine powder coat that wasn't sintered quite enough to make it run.


Or, the finish texture could be an artifact of selective laser sintering of the whole thing from aluminum powder. ... but I can't imagine that being fast enough for production, unless someone found a way to make it deposit metal as fast as flame/arc spraying.


... If I had one guess as to how the part in the photo was made, I'd go with SLS, and not real fast.


For a low-tech contrast, ISTR that at least some radial engine cylinder heads of WWII vintage had their super-fine fins cut from solid forgings by mechanical reciprocating hacksaws. ... a technology which is not amenable to the exact geometry you've illustrated, but offers a possibility.




Mike Halloran
Pembroke Pines, FL, USA

RE: How is this manufactured? I'm stumped

While it would be possible to make the part using diffusion bonding or furnace brazing, I don't think either process would be economical for mass production of a consumer product.

Looking at the photos, another possibility might be making the part using sintered aluminum powder.

RE: How is this manufactured? I'm stumped

What about laying up a custom feeder of flat stock (and the one little bar) through a form and friction welding the circular back on? This would then be advanced through the form and cut to give the desired fin length before the process would repeat for the next part.

RE: How is this manufactured? I'm stumped

Vibration welding was my thought as well.

RE: How is this manufactured? I'm stumped

(OP)
Thanks everyone! I think IRstuff and berkshire nailed it, investment casting. I never thought of investment casting as a high-volume process but I am now reading about it being used in automotive. According to the design guides you can get thin wall, there's no draft required, and tolerances are good.

(Sorry about the lack of scale, FYI it's about a 3" diameter)

RE: How is this manufactured? I'm stumped

If you have a say in the matter, design for diecasting or impact extruding. Your parts will be a fourth the cost.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: How is this manufactured? I'm stumped

(OP)
KENAT, I'm probably ordering in batches of 5000. Annual volume will depend on sales of the product.

RE: How is this manufactured? I'm stumped

Oh, well in that case I don't think my suggestion will work for production.

However, if you need to do prototyping it may be of use, I've dealt with these guys before http://aljcast.com/ but there are other places too.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: How is this manufactured? I'm stumped

(OP)
Good contact, thank you KENAT.

RE: How is this manufactured? I'm stumped

Definitely forged. I have had good experience with these guys for custom heat sinks. Malico

I have used them for prototype qtys and am just getting into production volumes in the mid 100's. They should have no problem with 5000 pcs lots.

They also have state side reps that are very responsive.

RE: How is this manufactured? I'm stumped

(OP)
Thanks hendersdc!

RE: How is this manufactured? I'm stumped

Themilkmaid:
I’ll bet you could take a piece of 3"x3" bar stock, say 2' long; mill 1/8" slots every 1/4" o/c along the length; mill the slots 2.8-2.9" deep, with a round toothed saw blade; heat the continuous side sufficiently to form the entire bar around a piece of 2" pipe, without significant cracking in the continuous material. Then oven braze the whole formed doughnut to a base plate.

RE: How is this manufactured? I'm stumped

It may have been sand shell cast?

Shell casting

www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

RE: How is this manufactured? I'm stumped

I've used Radian a looong time ago. They were pretty helpful and have a nice gallery of custom heatsinks and how they were manufactured.

RE: How is this manufactured? I'm stumped

Medeski,

We used Radian in the past too, it actually turned out they were just reselling the Malico heat sinks (at a significant mark up).

RE: How is this manufactured? I'm stumped

Really? Wow, I didn't realize that. The last time I had any contact with Radian was three jobs ago, so almost 12 years now. It was a custom heatsink project and all the engineering support and purchasing was done through Radian's California office, but I do seem to recall the actual fabrication being done overseas. I wonder if they were a reseller of Malico back then too.

RE: How is this manufactured? I'm stumped

I took a look at the websites for the companies that forge these heat sinks from aluminum or copper. The aspect ratios for the pins and fins they can achieve are quite impressive. I'd also like to know how they produce these forgings without draft and with sharp corners.

I'm familiar with the squeeze casting process used to produce larger aluminum components, like wheels, using higher strength alloys that cannot be made using conventional casting processes. The "forging" process used here seems like it might be similar. The aluminum preform is heated to a plastic condition (just below its melting point), and then it is rammed into a steel mold under high pressure. The primary limitation appears to be the total mass of the material being forged. It seems to be limited to parts weighing just a few ounces.

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