Jeremy Rubin's Blog

Here you'll find an assorted mix of content from yours truly. I post about a lot of things, but primarily Bitcoin.

categories: Bitcoin, Shenzhen Journey.

Zipper Factory Tour

Shenzhen Adventure Day 19

The Zipper factory tour was courtesy of Daniel Liang. This was one of the more detailed tours; there’s a whole lot that goes into a zipper! Daniel’s factory is also super large as it is essentially end-to-end, raw materials go in such as bulk plastic and metal, and finished spools of zipper material and zips come out.

Filament Making

Filaments are used to make the plastic zipping ribs.

They start out as raw plastic pelts.

If a black color is desired, a small amount of dye pellets are added.

The pellets go into the hopper (far left) to be melted down/mixed and then extruded.

Unfortunately, I didn’t get great pictures of this part, but the filaments are pulled through, cooled, and then spooled.

Maybe this picture will help you, but I can’t really make sense of it.

Tape Weaving

Tapes are woven from some nylon/cotton thread. I’m not sure if this is made on site or not, but I think if I recall it is a separate factory.

The thread goes into weaving machines.

Weaving machine, slowed down many times.

Many arrays of weaving machines. Each machine weaves several tapes at once.

Zip Integrating

These machines knit in the filaments into a plastic zipper. This is either onto a woven tape, or standalone (both are pictured below).

Slider Making

A Zipper Slider starts out looking like this:

Raw metal.

The metal is melted down and sent to die casting molds.

Die casting machines cranking out zips.

Live die casting, metal refil pouring in the background.

They make a lot of sliders!

Die cast pieces coming out of the mold.

Then the pieces go through multiple polishing phases.

Separated pieces going into the polisher. One of ~5 polish phases.

Lastly, some assembly of the flap and the zip.

Putting together the zipper metal components by hand.

Less specialized zipper assemblies are automated.

The alignment process involves a properly shaped “needle” and a vibrating, spinning bowl.


Chord spindling machine. Back and forth makes it tidy for sale!

Chord spindling machine release.

Leather Factory Tour

Shenzhen Adventure Day 17

Today we visited the PrimeAsia Leather Factory.

Welcome to PrimeAsia A warm welcome.

A ‘real’ welcome.

The leather comes in to the factory pre-treated. The tannery is (typically) these days co-located with the slaughterhouse. At the tannery they chrome treat the raw leather and then put it in a shipping container to wherever it is going.

Pile of raw leather “wet blues”, waiting to be processed

Quality Inspection

The leather is then cut through the middle (ie, reducing the thickness) to a top-grain piece and a suede piece.

The suede leather is then buffed down to standardize thickness. (the top-grain needs no buffing as it is cut to the right size).

The leather dust is then captured and put into random products, like asphalt.

Leather dust

The leathers are then dyed in these big tumblers. They can do any color – they mix chemicals on site.

Oh that tumbler was just a baby, for color testing and sample runs. No. This is a tumbler:

Look at the people to get a sense of scale

The dyed leather comes off the line

Post Processing

There’s a myriad of leather post processing steps depending on the finished product.

You can turn a cow into a crocodile:

This is done by melting a plastic sheet into the leather.

You can embed thermal-color change wax:

Bright pink dyed and super soft suede:



A really cool section was the testing facilities. This ensures the quality of the finished product.

There are machines that can test the rigidity, flexibility, waterproofness, etc.

Water Purification

Leather is notorious for pollution. At PrimeAsia, they have a big and fancy water purification plant on-site.

We start our tour from the control panel

Water starts out a bit frothy (I believe it’s a bacterial processing phase)

Water is cleaner!

Clean water comes out here.


Leather is cheaper than I thought. It was maybe $100 for a whole pelt.

There’s no natural leather color. After chrome tanning, all leather is blue-gray.

Shenzhen Maker Faire

Shenzhen Adventure Day 14

We were lucky enough to overlap our stay with the Shenzhen Maker Faire!

Panorama of  the faire

Panorama of  the faire

There were a lot of drones…

Drones! Drones everywhere

I even ran into some friends!

Lizhou Sha MIT ‘18

Deb Weinswig, my cousin!

We finished off the day at the Hackaday pizza party.

What struck me most is that we were like an hour out of the city by subway but it still looked like this:


The amount of construction in the region is insane.

How is Shenzhen so green?

Shenzhen Adventure Day 13

Watering trucks! Saw this during a night out. They go around and spray down all the fancy greenery.

Engineering Query at King Kredie

Shenzhen Adventure Day 12

Inside the King Kredie Engineering Query room

On Day 9 I mentioned that we had submitted our boards for Engineering Queries, but I didn’t quite explain what those are.

When you’re working with a good manufacturer, they don’t just blindly produce what you tell them, they will go through and verify certain properties of the design to make sure it will come out as expected, or even tell you ways you can save costs that you may not have thought of. This is because:

  1. they want your future business
  2. they’re just good people
  3. they don’t make more money on the more expensive process

3 can happen because a different process may have no different labor cost, but just a material cost which they don’t mark up. This is an important point to keep in mind when working with various manufacturers – they will pass savings on to you if possible!

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