Cracked Mac bruises Apple?

By: 
July 11, 2001


Tuesday, October 31, 2000

Cupertino, CA--It's not easy being beautiful. Like a beauty
queen with a blemish, the Power Mac G4 Cube from Apple has drawn some catty
comments from a few users who contend that the computer's acrylic enclosure
tends to develop unattractive cracks.

Maybe Apple has it coming. After all, the company's fervent
descriptions of the Cube's beauty, while arguably true, just about dare people
to look for flaws. Now a few sharp-eyed folks think they've found them, and
their disappointed Internet postings describe the appearance of small cracks in
Cube's surface. Thoughts about Apple's just desserts aside, though, these
alleged defects raise a more important question for the plastics engineer. Are
the cracks real?

Probably not. Apple makes a strong case that the untrained
consumer's eye can easily mistake the normally visible traces of the molding
process for stress cracks. "They're not cracks at all, they're mold lines,"
insists Linda McNulty, director of Apple's desktop products. Indeed, the design
of the two-piece enclosure does make the mold, or weld, lines just about
impossible to hide through design practice.

The main housing component, which defines the 8 x 8 x 8-inch
Cube's shape and surrounds the Cube's sheet-metal enclosed core, is crystal
clear. Acrylic's optical clarity helps create the impression that the core
floats above your desktop, but clear plastics tend to reveal their weld lines
more readily than colored or painted materials. Also, the Cube is meant to be
viewed from all angles, preventing Apple's engineers from hiding the weld line
in back of or beneath the housing.

The second enclosure component posed its own weld-line problems.
This ribbed white vent panel, which forms the cube's top, features five
different openings for screws and computer hardware. Each of these results in
more weld lines and no out-of-the-way place to hide them, according to McNulty.

Weld lines may be inevitable in many plastic parts, but McNulty
reports that plenty of engineering effort went into minimizing their visual
impact. She says some of the mold lines were incorporated into the design. "We
intentionally lined up the mold lines with the centers of the screws," she says.
Apple also tried to lessen the lines by molding the 9-mm thick acrylic walls at
high injection pressures (20,000 psi). Finally the company experimented with
several different gate locations during a tooling development process that took
12 months.

For more information on the Cube specifications, visit www.apple.com.

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