11/26/2015 A Tale of Two Zippers « bunnie's blog http://www.bunniestudios.com/blog/?p=4364 1/16 « Name that Ware, January 2015 Winner, Name that Ware January 2015 » A Tale of Two Zippers Recently, Akiba took me to visit his friend’s zipper factory. I love visiting factories: no matter how simple the product, I learn something new. This factory is a highly-automated, vertically-integrated manufacturer. To give you an idea of what that means, they take this: Ingots of 93% zinc, 7% aluminum alloy; approx 1 ton shown and this:
Transcript
11/26/2015 A Tale of Two Zippers « bunnie's blog
http://www.bunniestudios.com/blog/?p=4364 1/16
« Name that Ware, January 2015
Winner, Name that Ware January 2015 »
A Tale of Two Zippers
Recently, Akiba took me to visit his friend’s zipper factory. I love visiting factories: no matter how simple the
product, I learn something new.
This factory is a highly-automated, vertically-integrated manufacturer. To give you an idea of what that means,
they take this:
Ingots of 93% zinc, 7% aluminum alloy; approx 1 ton shown
Compressed sawdust pellets, used to fuel the ingot smelter
and this:
Rice, used to feed the workers
And turn it into this:
11/26/2015 A Tale of Two Zippers « bunnie's blog
http://www.bunniestudios.com/blog/?p=4364 3/16
Finished puller+slider assemblies
In between the input material and the output product is a fully automated die casting line, a set of tumblers and
vibrating pots to release and polish the zippers, and a set of machines to de-burr and join the puller to the slider.I think I counted less than a dozen employees in the facility, and I’m guessing their capacity well exceeds a
million zippers a month.
I find vibrapots mesmerizing. I actually don’t know if that’s what they are called — I just call them that (I figurewithin minutes of this going up, a comment will appear informing me of their proper name). The video below
shows these miracles at work. It looks as if the sliders and pullers are lining themselves up in the right orientationby magic, falling into a rail, and being pressed together into that familiar zipper form, in a single fully automated
machine.
720p version
If you put your hand in the pot, you’ll find there’s no stirrer to cause the motion that you see; you’ll just feel a
strong vibration. If you relax your hand, you’ll find it starting to move along with all the other items in the pot. The
entire pot is vibrating in a biased fashion, such that the items inside tend to move in a circular motion. This pushes
them onto a set of rails which are shaped to take advantage of asymmetries in the object to allow only theobjects that happen to jump on the rail in the correct orientation through to the next stage.
Despite the high level of automation in this factory, many of the workers I saw were performing this one
operation:
720p version
This begs the question of why is it that some zippers have fully automated assembly procesess, whereas others
are semi-automatic?
The answer, it turns out, is very subtle, and it boils down to this:
I’ve added red arrows to highlight the key difference between the zippers. This tiny tab, barely visible, is thedifference between full automation and a human having to join millions of sliders and pullers together. To
understand why, let’s review one critical step in the vibrapot operation.
We paused the vibrapot responsible for sorting the pullers into the correct orientation for the fully automatic
process, so I could take a photo of the key step:
As you can see, when the pullers come around the rail, their orientation is random: some are facing right, some
facing left. But the joining operation must only insert the slider into the smaller of the two holes. The tiny tab,
highlighted above, allows gravity to cause all the pullers to hang in the same direction as they fall into a rail
toward the left.
The semi-automated zipper design doesn’t have this tab; as a result, the design is too symmetric for a vibrapot to
align the puller. I asked the factory owner if adding the tiny tab would save this labor, and he said absolutely.
At this point, it seems blindingly obvious to me that all zippers should have this tiny tab, but the zipper’s designerwouldn’t have it. Even though the tab is very small, a user can feel the subtle bumps, and it’s perceived as a
defect in the design. As a result, the designer insists upon a perfectly smooth tab which accordingly has no
feature to easily and reliably allow for automatic orientation.
I’d like to imagine that most people, after watching a person join pullers to sliders for a couple minutes, will be
quite alright to suffer the tiny bump on the tip of their zipper to save another human the fate of having to manually
align pullers into sliders for 8 hours a day. I suppose alternately, an engineer could spend countless hours tryingto design a more complex method for aligning the pullers and sliders, but (a) the zipper’s customer probably
wouldn’t pay for that effort and (b) it’s probably net cheaper to pay unskilled labor to manually perform the
sorting. They’ve already automated everything else in this factory, so I figure they’ve thought long and hard about
this problem, too. My guess is that robots are expensive to build and maintain; people are self-replicating andlargely self-maintaining. Remember that third input to the factory, “rice”? Any robot’s spare parts have to be
cheaper than rice to earn a place on this factory’s floor.
However, in reality, it’s by far too much effort to explain this to end customers; and in fact quite the oppositehappens in the market. Because of the extra labor involved in putting these together, the zippers cost more;
therefore they tend to end up in high-end products. This further enforces the notion that really smooth zippers
with no tiny tab on them must be the result of quality control and attention to detail.
My world is full of small frustrations similar to this. For example, most customers perceive plastics with a mirror-
finish to be of a higher quality than those with a satin finish. While functionally there is no difference in the plastic’s
structural performance, it takes a lot more effort to make something with a mirror-finish. The injection molding
tools must be painstakingly and meticulously polished, and at every step in the factory, workers must wear white
gloves; mountains of plastic are scrapped for hairline defects, and extra films of plastic are placed over mirrorsurfaces to protect them during shipping.
For all that effort, for all that waste, what’s the first thing a user does? Put their dirty fingerprints all over the
mirror finish. Within a minute of coming out of the box, all that effort is undone. Or worse yet, they leave the
protective film on, resulting in a net worse cosmetic effect than a satin finish. Contrast this to a satin finish. Satin
finishes don’t require protective films, are easier to handle, last longer, and have much better yields. In the user’s
hands, they hide small scratches, fingerprints, and bits of dust. Arguably, the satin finish offers a better long-term
customer experience than the mirror finish.
But that mirror finish sure does look pretty in photographs and showroom displays!
This entry was posted on Monday, February 9th, 2015 at 4:43 am and is filed under Made in China, The Factory Floor. You canfollow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
They still are costly though but I think you can get this done for less than $1000.
Reply
YellowApple says:
February 10, 2015 at 4:35 am
That would be the case if each zipper factory had to produce its own solution to this
problem.
Instead, this seems to be a good realm for some plucky Silicon Valley startup to build the
thing and spread the programmer costs over dozens of installations.
Reply
Jerry Biehler says:
February 16, 2015 at 11:08 am
There are companies like Keyence that make self-contained machine vision packages thatcan be set up in the field by non-programmers through a built in GUI in a very short period.
It would take longer to install it than have it set up to reject parts in the wrong position.
Reply
10. OrenT says:
February 9, 2015 at 3:30 pm
I have been mesmerized by such feeders since I first saw them at a factory for drip irrigation emitters some
30 years ago. There was a lot of creativity in the design of the barriers for pushing the incorrectly orientedparts back into the bowl. I remember many of them made use of strategically placed compressed air
nozzles.
I think a bifurcation in the path of the pullers and one or two compressed air nozzles should do the trick.
Air flow can reliably distinguish ring-first pullers and apply torque to nudge them right or left.
Reply
hawkeyeaz1 says:
February 10, 2015 at 10:13 am
I think you are on to something. An optical sensor trips for the zipper presence, a pin or burst of air
will rotate or flip the zipper. Minimal hardware, thus minimal cost and maintenance.
Reply
11. A Tale of Two Zippers « Adafruit Industries – Makers, hackers, artists, designers and engineers!
Nice insight article. The point about the manual component though; I wouldn’t feel sorry for the labourer
so long as he has the choice to be there. If a machine took over the role, then he would have to find workelsewhere and perhaps there is no elsewhere for this person? It’s an age old argument, but worth
highlighting.
Reply20. How zippers are made | SteevAK says:
February 12, 2015 at 6:52 am
[…] love learning stuff like this. The nuances and complexity of making even the simplest things can be
amazing. This line in […]
Reply
21. Hiroo Yamagata says:February 12, 2015 at 9:17 am
Hi, I’m surprised that no one already pointed this out (I would, like you, have imagined within minutes),
but your “vibrapot” is called a “deburring maching” among people in the know.
Reply
22. Hiroo Yamagata says:February 12, 2015 at 9:17 am
deburring machine, I meant.
Reply
23. Peter G. says:
February 12, 2015 at 9:57 am
How about having the tabs ride horizontally past two nylon-tipped probes that attempt to slide through the
two holes. The one that wins will cause the other one to retract. Gravity then pulls down the other end,with the smaller hole, creating the desired alignment. As the dangling tab passes over the vertical feed rail,the winning probe is retracted.
Or feed the tabs into a rotating carousel with slots that will accept the full length of the tab in the desiredorientation, but only to the depth of the large ring end if the tab goes in the other way, leaving the
misaligned tabs sticking up. Then let the tabs ride in these slots past a cutout in the rail around the carouselthat will allow the misaligned tabs to fall back into the bowl.
Or feed the tabs horizontally along a rail and use a microswitch or photocell to detect when the leadingend of the tab is large instead of small, then activate a flipper to pop the tab back into the bowl.
Any of these solutions could be locally engineered and implemented within days.
. png
Reply
24. Noumenon72 says:February 12, 2015 at 4:13 pm
As someone who used to make those gloss finishes on plastic, yes, it was always demoralizing to see our
products come back with fingerprints all over them. And then thermoformed into a beer cup.
Also, my experience with all these suggestions people are tossing off is that having management implement
one of your suggestions is usually a humiliating experience as you see how much extra work it causes andhow little it helps.
Reply
Ay Dee Jay says:February 13, 2015 at 10:06 pm
It’s the old “why can’t you just” uninformed outsider dilemma. I’m sure one of them will strike goldand become a rock star of factory automation
Reply
25. Noob says:February 13, 2015 at 12:12 am
Why not just make the pullers symetrical? Do you really need a small end of the zipper? Then it would notmatter which end of the puller is joined with the slider.
Reply
Ay Dee Jay says:
February 13, 2015 at 10:08 pm
It’s been done, and produces an inferior product. This has all been thought out far more than anynoob could imagine :D
Why not put the tab at the side with the smaller holes, let gravity drop them upside down then make therail further down the line to flip them before assembly into the slider? This way the user doesn’t feel thebump. If not a tab, then two smaller dots/tabs near the smaller hole, which would have the same result
without effecting the slider design.
Reply
27. Adrian Meli says:February 13, 2015 at 6:57 am
Enjoyed the post. Makes you appreciate zippers more.
Satin finishes were actually quite a breakthrough! You see, they take work: you have to abrade the moldsjust right. But that’s something you do once per mold, not once per part.
I actually worked at a place where they transitioned from black satin to “piano black”, and it washeartbreaking.
On displays, it’s even dumber: satin finishes reduce glare. But no, everything has gone mirror-finish…
Reply
f4eru says:
February 27, 2015 at 4:45 pm
Not everything is mirror finish !
Yes, theese mirror screens are a pain in the ass.But every business latop has a matte screen.Just buy some used pro laptops, for example fujitsu lifebook, and you ge4t some nice matte
screens, not that customer mirror crap.
Reply
30. penny thought says:February 14, 2015 at 9:20 am
A little top slide to reject the ones with the large hole first, run them through again. Double the speedsomewhere else though to make up for less efficiency, or have them cascade to another conveyer for a
second try.. maybe
Reply
penny thought says:
February 14, 2015 at 9:21 am
Yeah, push it off onto another conveyer going in the opposite direction
Reply
31. Realist says:
February 14, 2015 at 4:48 pm
> save another human the fate of having to manually align pullers into sliders for 8 hours a day
… by making the job go away altogether? I’m not sure he’d thank you for that.
Reply
Splash says:
February 23, 2015 at 11:01 pm
That’s exactly what I was thinking. I’m sure if you asked the person with the zipper job he wouldnot want his work to become automated.
Reply32. Be afraid of the smart toaster - MyFeedly.info says:
February 17, 2015 at 5:03 am
[…] Design | A tale of two zippers […]
Reply
33. ray says:February 22, 2015 at 5:51 am
After watching a person join pullers to sliders for a couple minutes, I’m glad they have a job that feedsthem and their families.
Reply34. Lazy Reading for 2015/02/22 – DragonFly BSD Digest says:
Steve Jobs would surely disagree with you on the tabs and mirror-finish as well as many other designerswho pride themselves with obsessive attention to detail
