Core77

How is the Exterior of the New Mac Pro Made? Impact Extrusion

By Rain Noe - June 14, 2013

in Object Culture

Man I can't get over that new Mac Pro. And while we all know the "thermal core" part is made from extruded aluminum, how is the exterior (which is also aluminum) made? It's obviously not extruded, as it's got that inward-curving lip up top, and it wouldn't make sense from an efficiency standpoint to CNC-mill the entire thing out of a billet; there would be too much waste. Any guesses?

According to Don Lehman, it's made using the production method known as impact extrusion. Conceptually, the process is more similar to blowmolding than proper extrusion, except a metal punch takes the place of compressed air, and the material used is metal rather than plastic. Here's a quick look at impact extrusion as performed by Illinois-based Best Metal Extrusions, on a product significantly smaller than the Mac Pro. (Looks like a cigar holder, but your guess is as good as mine.)

Here's something a little closer in size to the Mac Pro:

Okay, so what's going on here? As you can tell by seeing the guy in the first video inserting the slug with his bare hands, it goes into the die cold. A punch shaped like the negative space of the final object slams downward and, with brute force, forces the material to fill the space of the die. This is why I say it's conceptually similar to blowmolding, and in fact it's how SIGG makes their fee-yancy aluminum bottles.

Why use impact extrusion versus regular extrusion? Because you can get a closed surface (like the bottom of the SIGG bottle) integrated with the sides; with regular extrusions you'd just get a tube. In the case of the Mac Pro, the additional surface is the lipped top, and we assume it goes through a CNC mill afterwards for the top cutout, the purty bevel, the connector cutouts and the nice finish.

Rendering or no, that bevel looks pretty hot

In the first few minutes of this next video, you can see a horizontally-oriented press using impact extrusion to whip out batteries. (The vid is four-minutes-plus, but you needn't watch more than the first few seconds to get the idea.)

The thing I love about seeing impact extrusion in action is how fast the material kinda "squirts" up out of the die. Check out this vid of shiny aluminum cans being made by the same company that does the batteries, Beijing Holland Trading Co.:

In any case, back to the Mac Pro—this thing looks suh-weet in video:

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powers

11 years ago

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It would be sweet if Apple did a "making of" video for this like they did for the original "unibody" MBPs.
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Shadley

11 years ago

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I initially thought hydro forming....
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Jesse

11 years ago

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This is a great post! I would love to see more insight into the process behind today's most innovative products like this from Core 77. Thanks.
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Nigel

11 years ago

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Don't quote me on this, because I'm having trouble getting firm confirmation, but from the wording, this new Mac Pro is only assembled in the US. The parts will still be made in China, I'm assuming. So I don't expect the manufacturing technique has anything to do with the assembly location change.

Impact extrusion is freaking awesome though, I had no idea about it until now!
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Derek

11 years ago

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Isn't that a chamfer, not a bevel?
http://en.wikipedia.org/wiki/Bevel
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Aaron

11 years ago

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I would have thought it was drawn, then the top opening cnc milled out.

Guess I was wrong too.
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slippyfish

11 years ago

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Great.

So, is there anything about the tooling or process that might bias this product toward US domestic manufacture? Can impact extrusion happen overseas just as well as here?
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goodmaei

11 years ago

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One more for ya: scuba tanks
http://www.youtube.com/watch?feature=player_detailpage&v=qAgSU6BCpsY#t=91s

I would have guessed metal spinning at first glance. Guess I'd be wrong.
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Eric

11 years ago

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Yes, that is a very good assumption, scuba tanks are made the same way along with gas cylinders, except those products have additional steps to re-curve the other end. They could also start with an extruded cylinder and then form the top edge with heat and a die or use some sort of a spin form technique.
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Thijmen

11 years ago

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I've worked as an process engineer in the aerosol industry for a while where impact extrusion is top choice for producing the cans. Awesome to see such a big cylinder with what looks like something of a 3 millimetre thick wall. The machines we used were spec'd up to about 1,700 metric tonnes (with a wall thickness of only .5 mm) so the one producing the imac must be one hell of a machine!
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