Mechanisms: Ode to the Zipper

Look around yourself right now and chances are pretty good that you’ll quickly lay eyes on a zipper. Zippers are incredibly commonplace artifacts, a commodity item produced by the mile that we rarely give a second thought to until they break or get stuck. But zippers are a fairly modern convenience, and the story of their invention is one that shows even the best ideas can be delayed by overly complicated designs and lack of a practical method for manufacturing.

Try and Try Again

US Patent #504,307. One of the many iterations of Judson’s design. Like the others, it didn’t work.

Ideas for fasteners to replace buttons and laces have been kicking around since the mid-19th century. The first patent for a zipper-like fastener was issued to Elias Howe, inventor of the sewing machine. Though he was no slouch at engineering intricate mechanisms, Howe was never able to make his “Automatic, Continuous Clothing Closure” a workable product, and Howe shifted his inventive energies to other projects.

The world would wait another forty years for further development of a hookless fastener, when a Chicago-born inventor of little prior success named Whitcomb Judson began work on a “Clasp Locker or Unlocker.” Intended for the shoe and boot market, Judson’s device has all the recognizable parts of a modern zipper — rows of interlocking teeth with a slide mechanism to mesh and unmesh the two sides. The device was debuted at the Chicago World’s Fair in 1893 and was met with almost no commercial interest.

Judson went through several iterations of designs for his clasp locker, looking for the right combination of ideas that would result in a workable fastener that was easy enough to manufacture profitably. He lined up backers, formed a company, and marketed various versions of his improved products. But everything he tried seemed to have one or more serious drawbacks. When his fasteners were used in shoes, unexpected failure was a mere inconvenience. If a fastener on a lady’s dress opened unexpectedly, it could have been a social catastrophe. Coupled with a price tag that was exorbitantly high to cover the manual labor needed to assemble them, almost every version of Judson’s invention flopped.

Zipping up. Source: Dominique Toussaint (Wikipedia)

It would take another decade, a change of company name, a cross-country move, and the hiring of a bright young engineer before the world would have what we would recognize as the first modern zipper. Judson hired Gideon Sundback in 1901, and by 1913 he was head designer at the Fastener Manufacturing and Machine Company, newly relocated to Meadville, Pennsylvania after a stop in Hoboken, New Jersey. Sundback’s design called for rows of identical teeth with cups on the underside and nibs on the upper, set on fabric tapes. A slide with a Y-shaped channel bent the tapes to open the gap between teeth, allowing the cups to nest on the nibs and mesh the teeth together strongly.

Sundback’s design had significant advantages over any of Judson’s attempts. First, it worked, and it was reliable enough to start quickly making inroads into fashionable apparel beyond its initial marketing toward more utilitarian products like tobacco pouches. Secondly, and perhaps more importantly, Sundback invented machinery that could make hundreds of feet of the fasteners in a day. This gave the invention an economy of scale that none of Judson’s fasteners could ever have achieved.

Putting Some Teeth into It

Continuous process for forming metal zippers. Source: How Products Are Made

The machinery that Sundback invented to make his “Separable Fastener” has been much improved since the early 1900s, but the current process still looks similar, at least for metal zippers. Stringers, which are the fabric tapes with teeth attached, are formed in a continuous process by a multi-step punching and crimping machine. For metal stringers, a coil of flat metal is fed into a punch and die to form hollow scoops. The strip is then punched again to form a Y-shape around the scoop and cut it free from the web. The legs of the Y straddle the edge of the fabric tape, and a set of dies then crimps the legs to the tape. A modern zipper machine can make stringers at a rate of 2000 teeth per minute.

Plastic zippers are common these days, too, and manufacturing methods vary by zipper style. One method has the fabric tapes squeezed between the halves of a die while teeth are injection molded around the tape to form two parallel stringers. A sprue connected the stringers by the teeth breaks free after molding, and the completed stringers are assembled later.

Zippers have come a long way since Sundback’s first successful design, with manufacturing improvements that have eliminated many of the manual operations once required. Specialized zippers have made it from the depths of the oceans to the surface of the Moon, and chances are pretty good that if we ever get to Mars, one way or another, zippers will go with us.

Aluminum No Match For 3D Printed Press Brake Dies

If you’re looking for a get-rich-quick scheme, you can scratch “Doing small-scale manufacturing of ultralight aircraft” off your list right now. Turns out there’s no money in it. At least, not enough money that you can outsource production of all the parts. Not even enough to setup a huge shop full of customized machining tools when you realize you have to make the stuff yourself. No, this sounds like one of those “labors of love” we always hear so much about.

So how does one do in-house manufacturing of aircraft with a bare minimum of tools? Well, since you’re reading this on Hackaday you can probably guess that you’ve got to come up with something a bit unorthodox. When [Brian Carpenter] of Rainbow Aviation needed a very specific die to bend a component for their aircraft, he decided to try designing and 3D printing one himself.

Printing a die on the Zortrax M200

He reasoned that since he had made quick and dirty dies out of wood in the past, that a 3D printed one should work for at least a few bends before falling apart. He even planned to use JB Weld to fill in the parts of the printed die which he assumed would start cracking and breaking off after he put it through a few cycles. But even after bending hundreds of parts, wear on the dies appears to be nearly non-existent. As an added bonus, the printed plastic dies don’t mar the aluminum pieces they are bending like the steel dies do.

So what’s the secret to printing a die that can bend hundreds of pieces of aluminum on a 20 ton brake without wearing down? As it turns out…not a whole lot. [Brian] attributes the success of this experiment to designing the die with sufficiently accurate tolerances and having so high of an infill that it may as well be solid plastic.

In fact, the 3D printed die worked out so well that they’ve now expanded the idea to a cheap Harbor Freight brake. Before this tool was going more or less unused as it didn’t have features they needed for the production of their parts, namely a radius die or backstop. But by 3D printing these components [Brian] was able to put the tool back to work.

We’ve previously covered the art and science of bending sheet metal, as well as a homebuilt brake that let’s you do it on a budget even Rainbow Aviation would scoff at. So what are you waiting for? Go build an airplane.

Thanks to [Oahupilot] for the tip.

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Retrotechtacular: 1950s Televisions Were Beasts

Television has been around for a long time, but what we point to and call a TV these days is a completely different object from what consumers first fell in love with. This video of RCA factory tours from the 1950s drives home how foreign the old designs are to modern eyes.

Right from the start the apparent chaos of the circuitry is mindboggling, with some components on circuit boards but many being wired point-to-point. The narrator even makes comments on the “new technique for making electrical connections” that uses a wire wrapping gun. The claim is that this is cleaner, faster, and neater than soldering. ([Bil Herd] might agree.) Not all of the methods are lost in today’s manufacturing though. The hand-stuffing and wave soldering of PCBs is still used on lower-cost goods, and frequently with power supplies (at least the ones where space isn’t at a premium).

It’s no surprise when talking about 60+ year-old-designs that these were tube televisions. But this goes beyond the Cathode Ray Tube (CRT) that generates the picture. They are using vacuum tubes, and a good portion of the video delves into the manufacture and testing of them. You’ll get a glimpse of this at 3:20, but what you really want to see is the automated testing machine at 4:30. Each tube travels along a specialized conveyor where the testing goes so far as to give a  few automated whacks from corks on the ends of actuators. As the tube gauntlet progresses, we see the “aging” process (around 6:00) when each tube is run at 3-4 times the rated filament voltages. Wild!

There’s a segment detailing the manufacture of the CRT tubes as well, although these color tubes don’t seem to be for the model of TV being followed during the rest of the films. At about 7:07 they call them “Color Kinescopes”, an early name for RCA’s CRT technology.

During the factory tours we get the overwhelming feeling that this manufacturing is more related to automotive than modern electronic. These were the days when televisions (and radios) were more like pieces of furniture, and seeing the hulking chassis transported by hanging conveyors is just one part of it. The enclosure plant is churning out legions of identical wooden consoles. This begins at 11:55 and the automation shown is very similar to what we’d expect to see today. It seems woodworking efficiency was already a solved problem in the ’50s.

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Sonoff Factory Tour is a Lesson on Life in Shenzhen

Judging by the popularity of “How It’s Made” and other shows of the genre, watching stuff being made is a real crowd pleaser. [Jonathan Oxer] from SuperHouse is not immune to the charms of a factory tour, so he went all the way to China to visit the factory where Sonoff IoT devices are made, and his video reveals a lot about the state of electronics manufacturing.

Test jig for six units at once

For those interested only in how Sonoff devices are manufactured, skip ahead to about the 7:30 mark. But fair warning — you’ll miss a fascinating discussion of how Shenzhen rose from a sleepy fishing village of 25,000 people to the booming electronics mecca of 25 million that it is today. With growth supercharged by its designation as a Special Economic Zone in the 1980s, Shenzhen is now home to thousands of electronics concerns, including ITEAD, the manufacturers of the Sonoff brand. [Jonathan]’s tour of Shenzhen includes a trip through the famed electronics markets where literally everything needed to build anything can be found.

At the ITEAD factory, [Jonathan] walks the Sonoff assembly line showing off an amazingly low-tech process. Aside from the army of pick and places robots and the reflow and wave soldering lines, Sonoff devices are basically handmade by a small army of workers. We lost count of the people working on final assembly, testing, and packaging, but suffice it to say that it’ll be a while before robots displace human workers in electronic assembly, at least in China.

We found [Jonathan]’s video fascinating and well worth watching. If you’re interested in Sonoff’s ESP8266 offerings, check out our coverage of reverse engineering them. Or, if Shenzhen is more your thing, [Akiba]’s whirlwind tour from the 2016 Superconference will get you started.

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Taking a Guitar Pedal From Concept Into Production

Starting a new project is fun, and often involves great times spent playing with breadboards and protoboards, and doing whatever it takes to get things working. It can often seem like a huge time investment just getting a project to that functional point. But what if you want to take it to the next level, and take your project from a prototype to a production-ready form? This is the story of how I achieved just that with the Grav-A distortion pedal.

Why build a pedal, anyway?

The author, shown here with bandmates.

A long time ago, I found myself faced with a choice. With graduation looming on the horizon, I needed to decide what I was going to do with my life once my engineering degree was squared away. At the time, the idea of walking straight into a 9-5 wasn’t particularly attractive, and I felt like getting back into a band and playing shows again. However, I worried about the impact an extended break would have on my potential career. It was then that I came up with a solution. I would start my own electronics company, making products for musicians. Continue reading “Taking a Guitar Pedal From Concept Into Production”

Danielle Applestone: Building the Workforce of 2030

You wake up one morning with The Idea — the one new thing that the world can’t do without. You slave away at it night and day, locked in a garage expending the perspiration that Edison said was 99 percent of your job. You Kickstart, you succeed, you get your prototypes out the door. Orders for the new thing pour in, you get a permanent space in some old factory, and build assembly workstations.  You order mountains of parts and arrange them on shiny chrome racks, and you’re ready to go — except for one thing. There’s nobody sitting at those nice new workstations, ready to assemble your product. What’s worse, all your attempts to find qualified people have led nowhere, and you can’t even find someone who knows which end of a soldering iron to hold.

Granted, the soldering iron lesson is usually something that only needs to happen once, but it’s not something the budding entrepreneur needs to waste time on. Finding qualified workers to power a manufacturing operation in the 21st century is no mean feat, as Dr. Danielle Applestone discussed at the 2017 Hackaday Superconference. Dr. Applestone knows whereof she speaks — she was the driving force behind the popular Othermill, serving as CEO for Other Machine Co. and orchestrating its rise to the forefront of the desktop milling field. Now rebranded as Bantam Tools, the company is somewhat unique in that it doesn’t ship its manufacturing off to foreign shores — they assemble their products right in the heart of Berkeley, California. So finding qualified workers is something that’s very much on her mind on a daily basis.

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Erika Earl: Manufacturing Hacks

Many of us will have casually eyed up the idea of turning a project into a product. Perhaps we’ve considered making a kit from it, or even taking it further into manufacture. But building a single device on the bench is an extremely different matter from having a run of the same devices built by someone else, and in doing so there are a host of pitfalls waiting for the unwary.

[Erika Earl] is the Director of Hardware Engineering at Slate Digital, and has a lengthy background in the professional audio industry. Her job involves working with her team to bring high-quality electronic products to market that do not have the vast production runs of a major consumer electronic brand, so she has a lot of experience when it comes to turning a hacked-together prototype into a polished final device. Her talk at the 2017 Hackaday Superconference: Manufacturing Hacks: Mistakes Will Move You Forward examined what it takes to go through this process, and brought her special insights on the matter to a Hackaday audience.

She started her talk by looking at design for manufacture, how while coming up with prototypes is easy, the most successful products are those that have had the ability to manufacture as a consideration from the start of the design process. Starting with the selection of components, carrying through to the prototype stage, and through design reviews before manufacture, everything must be seen through the lens of anyone, anywhere, being able to build it.

At the selection of components for the Bill of Materials level, she made the point that high quality certified components can be the key to a product’s success or failure, contributing not only to reliability but also to it achieving certification. In her particular field, she often deals with components that can be close enough to the cutting edge to be prototypes in their own right. She mentioned the certification angle in particular in the context of exporting a product, as in that case there is often a need to be able to prove that all components used to meet a particular specification.

When it comes to the prototype stage, she made the point that documentation is the key. Coming back to the earlier sentence about anyone anywhere being able to build the product, that can only be achieved if all possible stages of manufacture are defined. She mentioned an example of a product in which the prototypes had had PCB fixing screws tightened by hand; when the factory started using electric screwdrivers the result was damaged PCBs and broken tracks.

The design review should look at everything learned through the prototype stage, and examine everything supplied to the manufacturer to allow them to complete their work. She describes finding support documentation containing a poorly hand-drawn schematic, and seeing an electronic assembly in which a piece of gum had been used to secure something. She also made the point that another function at this point is to ensure that the product is affordable to produce. If any parts or procedures are likely to cost too much, they should be re-examined.

After the talk itself as described above there is a Q&A session where she reveals how persistent and cheeky she sometimes has to be to secure sample parts as a small-scale manufacturer and delivers some insights into persuading a manufacturer to produce prototypes at a sensible price. And yes, like most people who have tried their hand at this, she’s had the nightmare of entire runs of prototype boards returned with a component fitted incorrectly.

The talk is embedded in its entirety below the break, and represents an extremely interesting watch for anyone starting on the road to manufacturing, particularly in the electronic world. If this describes you, take a look!

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