
Aggressive design caused Samsung Galaxy Note 7 battery explosions - kilohotel
https://www.instrumental.ai/blog/2016/12/1/aggressive-design-caused-samsung-galaxy-note-7-battery-explosions
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mehuser
> But, the battery also sits within a CNC-machined pocket -- a costly choice
> likely made to protect it from being poked by other internal components.
> Looking at the design, Samsung engineers were clearly trying to balance the
> risk of a super-aggressive manufacturing process to maximize capacity, while
> attempting to protect it internally.

Seems like really vague speculation. Any evidence this is not pseudo-
engineering nonsense?

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akshed
Hi, I'm Anna Shedletsky, the author of the post linked above. I spent six
years as a product design engineer at Apple, designing very similar products
and making similar design decisions that Samsung engineers needed to make.

Typical smart phone / tablet type products use a stamped metal frame ($) to
stiffen the product and support the display. A few phones use die-cast
magnesium frames ($$). A CNC'ed pocket ($$$$) is a significant cost adder for
this product (larger starting billet, longer cycle time, and thousands of CNC
machines required) -- so this choice was clearly made for a reason.

Additionally, the fact that the battery is surrounded on five sides by a
machined pocket cuts into battery volume -- most products just rely on an air
gap (0.5-1mm) between the battery pouch and the next nearest component that
could poke it during assembly and usage. Take a look at some other product
teardowns on iFixit, and you'll see this (example from iPhone 7:
[https://d3nevzfk7ii3be.cloudfront.net/igi/fJI2bhqYXg4CMNPi.h...](https://d3nevzfk7ii3be.cloudfront.net/igi/fJI2bhqYXg4CMNPi.huge))

They added significant cost to the product and sacrificed a little battery
capacity to have that pocket. I hypothesize that it was for battery safety
given the aggressive design.

~~~
burfog
What about forging? Rough out the shape from AlZnMgCu1,5 (EN AW-7075) alloy,
heat to 450°C, and slam it between a pair of dies.

Compared to cast or machined parts, you get a 20% higher strength-to-weight
ratio from the forging. The cycle time is decent I think, perhaps 3 per second
with a 0.06 second contact time in the dies.

~~~
mritun
Tolerances are poor with forging.

