Andrew Huang's Blog, page 34

Winner, Name that Ware April 2015

The Ware for April 2015 is a control board from a Keyence VE-7800 SEM, which I bought with some friends for a steal at a used equipment shop. Unlike my previous SEM adventure, this one is in good working order.

Nobody guessed it correctly, but I liked Dave Z’s analysis, and also Paul Campbell’s comment about two engineers at war. It’s a nice mental image :) However, the fact that Christian Vogel picked up on the vacuum flange in the background, that was really subtle, so I’ll declare him the winner. Gratz, email me for your prize!

Name that Ware April 2015

The Ware for April 2015 is shown below.

Have fun!

Winner, Name that Ware March 2015

The Ware for March 2015 is a PC AT Single T4 4 Meg Transputer board assembly. Jim is the winner, congrats! Email me to claim your prize.

The Heirloom Laptop’s Custom Wood Composite

The following is an excerpt from a recent Novena backer update that just got published. I thought the tech bits, at least, might be interesting to a broader audience so I’m republishing them here:

With mainline laptop production finally humming along, bunnie was able to spend a week in Portland, Oregon working side by side with Kurt Mottweiler to hammer out all of the final open issues on the Heirloom devices.

We’re very excited about and proud of the way the Heirloom laptops are coming together. In a literal sense, Heirloom laptops are “grown” – important structural elements come from trees. While we could have taken the easy route and made every laptop identical, we felt it would be much more apropos of a bespoke product to make each one unique by picking the finest woods and matching their finish and color in a tasteful fashion. As a result, no two Heirloom laptops will look the same; each will be beautiful in its own unique way.

There’s a lot of science and engineering going into the Heirloom laptops. For starters, Kurt has created a unique composite material by layering cork, fiberglass, and wood. To help characterize the novel composite, some material samples were taken to the Center for Bits and Atoms at MIT, where Nadya Peek (who helped define the Peek Array) and Will Langford characterized the performance of the material. We took sections of the wood composite and performed a 3-point bend test using a Instron 4411 electromechanical material testing machine. From the test data, we were able to extract the flexural modulus and flexural strength of the material.

Heirloom composite material loaded into the testing machine

I’m not a mechanical engineer by training, so words like “modulus” and “specific strength” kind of go over my head. But Nadya was kind enough to lend me some insight into how to think about materials in this context. She pointed me at the Ashby chart, which like some xkcd comic panels, I could stare at for an hour and still not absorb all the information contained within.

For example, the Ashby chart above plots Young’s Modulus versus density of many materials. In short, the bottom left of the chart has bendy, light materials – like cork – and the top right of the chart has rigid, heavy materials, like Tungsten. For a laptop case, we want a material with the density of cork, but the stiffness of plastic. If you look at the chart, wood products occupy a space to the left of plastics, meaning they are less dense, but they have a problem: they are weak perpendicular to the grain, and so depending on the direction of the strain, they can be as yielding as polyethene (the stuff used to make plastic beverage bottles), or stiffer than polycarbonate (the stuff layered with glass to make bulletproof windows). Composite materials are great because they allow us to blend the characteristics of multiple materials to hit the desired characteristic; in this case, Kurt has blended cork, glass fiber, and wood.

The measurements of the Heirloom composite show a flexural strength of about 33 MPa, and a flexural modulus of about 2.2-3.2 GPa. The density of the material is 0.49 g/cm3, meaning it’s about half the density of ABS. Plotting these numbers on the Ashby chart shows that the Heirloom composite occupies a nice spot to the left of plastics, and provides a compromise on stiffness based on grain direction.

The red circle shows approximately where the Heirloom composite lands. To be fair, measurements still revealed some directional sensitivity to the composite; depending on the grain, the modulus varies from about 2.2GPa to 3.2 GPa (and the diameter of the red circle encompasses this variability); but this is a much tighter band than the 10x difference in modulus indicated for pure woods.

Another thing to note is that during testing, the material didn’t fail catastrophically. Above are the graphs of load vs. extension as plotted by the Instron testing machine. Even after bending the material past its peak load, it was still mostly intact and providing resistance. This result is a bit surprising; we had expected the material, like normal wood, would break in two once it failed. Furthermore, after we reset the test, the material bounced back to its original shape; even after bending by over 10mm, once the load was removed you could barely tell it went through testing. This high fracture toughness and resilience are desireable properties for a laptop case.

Of course, there’s nothing quite like picking up the material, feeling its surprising lightness, and then trying to give it a good bend and being surprised by its rigidity and ruggedness. The Heirloom backers will get the privilege of feeling this firsthand; for the rest of us, we’ll have to settle with seeing circles on Ashby charts and graphs on computer screens.

If you want to see more photos of the Heirloom laptop coming together, check out the image gallery at the bottom of the official Crowd Supply update!

Name that Ware, March 2015

The Ware for March 2015 is shown below.

Thanks to Dale Grover for sharing this ware! I had read about this one as a lad, but never laid hands on one…

Winner, Name that Ware February 2015

The Ware for February 2015 is a logic board from an HP 16600 series logic analyzer. Megabytephreak is the winner, thanks for the clear analysis and also helping answer other reader’s questions about the metal fill for etch concentration normalization!

Name that Ware, February 2015

The Ware for February 2015 is shown below.

Eep! I’m late! I blame Chinese New Year.

This one was a tough one to crop: too much makes it too obvious, too little makes it impossible to guess. However, I’m betting that someone out there could probably recognize this ware even if I downsampled all of the part numbers and manufacturer’s logos.

Thanks again to dmo for sharing this ware. I’ll miss visiting your lab!

Winner, Name that Ware January 2015

Judging this one was tough. There were a lot of perfectly good guesses (and some pretty hilarious ones :), but because the advertised purpose of this ware is so weird, sound engineering reasoning need not apply.

What I’m told is that you install this on an electric bike to prevent the motor from burning out. I….don’t really think that’s effective, nor do I really believe it. At the very least, stacking capacitors like this while connecting them with thin copper traces to a terminal block and then wiring them with a long pair of wires to a battery seems to nullify any benefit of equalizing the ESR of capacitors by using a banked array of different values.

Although I think Jeff’s explanation (use as a power filtering cap in car audio) is a much more likely reason…I liked ingo’s thought process in reviewing the ware — knowledgeable, yet skeptical. So I’ll declare ingo as the winner…congrats, email me for your prize!

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:



Compressed sawdust pellets, used to fuel the ingot smelter

and this:



Rice, used to feed the workers

And turn it into this:



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 figure within 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 orientation by 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 the objects 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 the difference 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 designer wouldn’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 trying to 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 and largely 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 opposite happens 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 mirror surfaces 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!

Name that Ware, January 2015

The Ware for January 2015 is below.

“I love capacitor”

but why?

Been in Shenzhen the past two weeks, trying to beat Chinese New Year deadlines, improve my Chinese, and learn more about manufacturing and supply chains. So far, so good. Will have more updates soon!