I tell people “We can only make closures 4 mm small [height].”
…because I predicted my competitor’s actions. They would attack the height.
But, I really like a ZS closure height of 6 mm because, per testing, that is a good optimization of size, tensile strength, water tightness, and just overall durability.
6 mm is the height of 4 pennies stacked on top of one another.
If your waistline increased 6 mm then would you notice?
Well…the optimal (in my opinion) ZS zipper will stick out 6 mm from your body.
That’s the smallest size (4 mm) we can make with heavy gauge sheet metal- 0.5 mm and above metal thickness.
But, we can use medium weight sheet or heavy foil, which is anything above 0.10 mm. Or, said differently, 5 mil foil.
If the metal is bent and holds the shape, then we can use it. This also depends on metal hardness. So, 1/4 hard steel will be weaker than full hard steel.
And, using around 50% less thick endoskeleton material results in a thickness decrease of 0.25 mm on each half of closure, 0.5 mm overall. But, there’s also the thickness of polymer exoskeleton to consider.
We can get to 2.5 mm tall closures. This is the height of a YKK size 5 metal zipper.
Oh, and the YKK size 5 metal zipper has a tensile strength of well under 180 lbF. The maximum crosswise tensile strength of a size #10 YKK zipper is 800 Newtons or 180 lbF.
Whereas the Zipr Shift closure is above 180 lbF in tensile strength. The closure with 0.5 mm thick, half hard (steel) metal had a tensile strength of over 400 lbF.
I believe this is already happening, competitors attacking the perceived height of my closure.
There’s an interesting action from YKK. They’re trying to update the ASTM D2061 standard to include the dimensions of zippers.
(It’s a publicly available link via the Free Standards Tracker email or RSS so I’m not in violation of copyright- it’s a free AND public link.)
After their 83 years of zipper use, they (YKK) now think it’s reasonable to include specific dimensions in the standard.
When all zippers are the same, this wouldn’t matter.
All zippers are the same = All zipper dimensions are the same.
I’m sure most companies who use zippers don’t know the tensile strength of zippers. They never had a choice of zipper strength.
If they did then they’d know that YKK’s perceived superior strength is false.
There is no significant difference in strength between the zippers of any mainstream zipper maker- SBS, YKK, Ideal, Dunlop, etc.
I laugh because that’s a predictable response.
Adding dimensions to the standard will serve to further make the standard specific to their zipper type. (Because there’s more than one type now with ZS.)
But, I’m sorry. Sheet metal is extremely versatile as far as tensile strength.
And, ZS’s closure depends on material stiffness (force to bend) and not shape (tiny parts slipping past one another.)
Extra full hard puzzle piece zipper teeth will slip past one another just as easily as dead soft puzzle piece zipper teeth.
The separation or gaps between the teeth and coils (i.e. not being a continuous structure) is what hurts the tensile strength.
That’s why it’s a design weakness.
The shape and size doesn’t matter for the ZS closure.
Only the stiffness of the metal endoskeleton matters. No matter how tall I make it, the trend of changing size doesn’t drastically alter the strength.
A 0.5 mm thick half hard metal endoskeleton and 10 mm tall closure has roughly the same strength as a 0.5 mm thick half hard metal endoskeleton with 4 mm tall closure.
There are no interlocking parts so the size of the parts doesn’t really matter.
You have to bend metal so only the metal matters.
Changing the metal to make it stiffer is the only thing that changes the strength.
The exoskeleton is merely functional to keep the structure continuous, hermetic, and inert.
Give them hope and then snatch it away…
I’m so good at this.
Predicting the Army’s awful corruption and now (potentially) predicting the plight of my competitors.
But, it doesn’t matter anyway.
I’m not interested in updating the standard because I’d have antitrust issues if my closure sets/becomes the standard.
Plus, people don’t notice two extra millimeters anyway. Especially not when they realize it’s watertight under pressure and much stronger than its predecessors.
(Per my focus groups, people noticed when my closure was 8 mm tall but not before that. And, that’s smaller than the size of a YKK BDM zip which is 9.5 mm tall.)
It’s funny how business works. Everything you say could end up in your competitors ears…