I'm trying to locate web resources or personal/professional
knowledge on how modern multi-platter 3.5" hard drives are
assembeled... A general procedure list or set of instructions would be
the preferred answer
format... I'm specifically interested in the head portion of the
assembly. (How are the spring-loaded heads safely moved from the outer
portion of the platters to the inside portion [landing/parking zone]
without scraping the heads across the platter? ... I'm sure they have
specialized tools to do this, but I'm curious about the
details/functionallity of these tools)... Thanks!

NHDW --

Your question asks about manufacturing and also how heads are kept
away from the platter.  There's relatively little that's easily
available on the Internet about how the assembly process flows, but a
lot on drive structure.

Though the assembly of hard drives is largely done offshore, often in
Malaysia, several of the key component suppliers are here in the U.S.,
including Hutchinson Technology (NASDAQ: HTCH), a company in a small
Minnesota town that dominates the manufacture of suspension assemblies
that hold the hard drive heads.  Hutchinson explains the functioning
of the head on its pages in a fashion that I hope answers many of your
questions about the heads and their movement.  The heads and
suspensions effectively use the Bernoulli principal to draw the heads
close to the surface of a rapidly-spinning disk -- without touching
the surface:
Hutchinson Technology
"Suspension Primer"
http://www.htch.com/primer.asp

"Product Overview"
http://www.htch.com/p_overview.asp

In addition, the heads are installed retracted, then the armature is
allowed to move over the surface only when the platter is spinning. 
The spinning platter draws the heads closer using the air pressure. 
The heads are flying so close to the surface that minute amounts of
dirt can cause a head crash, as can movement or vibration.

Another excellent general description of the hard drive, which treats
the overall structure, is on the Howstuffworks pages:
How Hard Disks Work
"Inside a hard drive" (undated)
http://computer.howstuffworks.com/hard-disk2.htm

Electronic Business has an excellent overview of the hard disk
business, which profiles leaders and emerging technologies, should you
wish to do further research on manufacturers' pages or investigation
into particular technologies:
Electronic Business
"When Slower is Better" (March 1, 2003)
http://www.reed-electronics.com/electronicnews/index.asp?layout=article&articleId=CA279298&title=Search+Results&publication=e%2Dinsite&webzine=e%2Dinsite&text=seagate&rid=0&rme=0&cfd=1


Google search strategy:
"Hutchinson Technology"
Seagate
"manufacturing hard drives"

Please let me know if anything is unclear via a clarification request
before rating this answer.

Best regards,

Omnivorous-GA

---

Request for Answer Clarification by nhdw-ga on 07 Aug 2003 19:48 PDT

Good Answer... Thanks... Can you clarify one thing though? In the
answer you said:

> In addition, the heads are installed retracted, then the armature is
> allowed to move over the surface only when the platter is spinning.
> The spinning platter draws the heads closer using the air pressure.
> The heads are flying so close to the surface that minute amounts of
> dirt can cause a head crash, as can movement or vibration.

Can you clarify what you mean by retracted? My interpretation of this
is that (to initally place the heads onto the platters,) the platters
need to be spinning and all of the heads on both sides of each disc (8
heads for a 4-platter drive, for example) need to be simultaneously
lowered onto the spinning surface... Is this correct?

---

Clarification of Answer by omnivorous-ga on 08 Aug 2003 00:17 PDT

NHDW --

The armature, which holds the suspension assembly (and heads) are
retracted with a mechanical interlock when power is withdrawn from the
drive.  This is to prevent the suspension from contacting the disk
surface accidentally.  It's much like mechanical interlocks on a car's
steeing wheel -- if the car is off the wheel can't be turned.  Drives
weren't always designed this way: we old-timers remembered when disk
heads had to be parked with a software command.

As the disk platters come up to a certain RPM, the armature is
advanced over the platter's surface.  Now the suspension -- which is
in fact a precision-etched spring -- is allowed to do its work of
keeping the head flying at just the right height above the platter,
thanks to the Bernoulli effect drawing the heads close to the platter
with lower air pressure.

Best regards,

Omnivorous-GA

I'm still searching for the process used to initially advance the
armature (heads, suspension, etc) over top of the platters, but a ton
of great information was given here. Definitely worth it.

Any harddrive that I've taken apart parks the heads on the outside of
the platter, not the inside.  The armature is spring loaded to return
to this area without power.  I assume the rotational inertia of the
platters maintains the "air cushion" while the armature snaps back
when power is unexpectedly removed.

The picture shown in the howstuffworks.com link seems to corroborate
my understanding.

Bradley