

Ask HN: How does Apple manufacture iPhones/iPads (School Discussion) - jason_slack

Hello HN'ers.<p>My 12 year old son, 7th grade in Social Studies class is discussing "push" vs "pull" manufacturing and of course his first question is  what does Apple/Foxconn do.<p>Can anyone shed light on how Apple/Foxconn manufactures devices?<p>Push manufacturing - is a "make to stock" philosophy. Utilizing Push a quantity of products is made without knowing if anyone really wants them. So it would be possible to have a number of unfinished products still on the assembly line, half made. Employee 1 could perform his/her piece of the process 80 times in a given say, while Employee 2 is backlogged and may only get 40 done.  So there are 40 products still waiting to be finished.<p>Pull manufacturing - is a "make to order" philosophy.<p>I dont want to confuse him by stating that companies usually utilize a happy medium of both "Push" and  "Pull" and the factors that drive that decision.<p>I also dont really want comments that say it doesn't matter since Apple sells out of devices quicker than they can be made so neither philosophy applies.<p>Does anyone have thoughts on the manufacturing ideology and maybe assembly line specifics I can talk to him about?
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mechanical_fish
It sounds like your son might not have the time, energy, or desire to actually
read _The Goal_ :

<http://en.wikipedia.org/wiki/The_Goal_(novel)>

... although I could perhaps have read that book when I was twelve or thirteen
-- it is highly approachable, perhaps even by a child; if you can solve logic
puzzles you can read this book -- and if I had I would have _really_
understood modern manufacturing. This is the book that my buddy the fab
manager has on his shelf.

There is a chapter of _The Goal_ in which the protagonist _literally_ learns
about how manufacturing works by helping a Scout troop of 12-year-olds move
faster on their cross-country hike. You need to go to the library and read
just that chapter. Then maybe have your son read it.

If you want a detailed summary of what the book is about I can't do better
than Wikipedia:

<http://en.wikipedia.org/wiki/Theory_of_Constraints>

(though that is _way_ less readable than Goldratt's book) and if you want a
summary of the summary it would go something like this:

Modern manufacturing is closer to your "pull" description than to "push".
Everyone hates inventory of finished goods, and they hate inventory of half-
finished goods even more. So the goal is to make stuff only as fast as it is
being sold.

You control how fast you make stuff by controlling how much material you put
into the factory at step zero. And you decide _that_ by measuring every step
in the process and figuring out the slowest step. The slowest step is the
constraint. In your example, it's Employee 2. Because Employee 2 can only make
40 widgets per day, your factory can only make 40 widgets per day. This leads
to a bunch of important management facts:

A) To avoid having half-finished inventory piling up on the assembly line,
don't start more than 40 widgets' worth of work in a day. Anything extra will
be wasted anyway. Have Employee 1 only work half the time. Or, equivalently,
give Employee 1 only 40 widgets' worth of raw material each day. (In the real
world, of course, every step has less than 100% yield, so maybe you start 50
widgets in order to end up with 40 widgets entering step two.)

B) If you need more widgets per day, you need not upgrade everything in the
factory. You need only upgrade Employee 2. Hire Employees 2b and 2c and 2d.
Or: Notice that Employee 1 is now only working half the time. Perhaps if
Employee 1 was _less_ efficient, but in a particular way that made Employee 2
_more_ efficient, it would speed up Employee 2, which would speed up the whole
factory. Have Employee 1 work part time cranking out her 40-or-so widgets and
spend the rest of her time fetching coffee and tools for Employee 2.

C) Eventually you will find that you've upgraded Employee 2 to the point that
he is no longer the constraint. The constraint will move. Maybe it will now be
Employee 1. If so, get to work upgrading Employee 1, or making _her_ job go
faster. Or maybe you've moved the constraint completely out of the factory:
You can now make more parts than your salespeople can sell and the constraint
is the marketplace, in which case you need to make some commercials and attend
more trade shows.

~~~
jason_slack
Thank you for the reply. Very informative and the book looks like a good read.

I do sort of take offense that you state " It sounds like your son might not
have the time, energy, or desire to actually read The Goal:"

How can you even state something like that? He was asking a question based
upon a social studies conversation. Nothing about time energy or desire. He
has this thread open in his browser to read the replies folk post and I think
you have been rude with that statement.

Again though your description and links were beneficial and I can find the
book on Amazon

