Plenty of materials take the heated edge of a laser beam quite well, but many others don’t. Some release toxic fumes; others catch fire easily. For all the materials that don’t cut well (PVC and FR4, we’re looking at you!) and for those that do (hello, acrylic and Delrin) they’re each reacting to the heat of the laser beam in different ways. Lucky for us, these ways are well-characterized. So let’s take a look at how a laser cutter actually cuts through materials.
MakerBot is not dead, but it is connected to life support waiting for a merciful soul to pull the plug.
This week, MakerBot announced it would lay off its entire manufacturing force, outsourcing the manufacturing of all MakerBot printers to China. A few weeks ago, Stratasys, MakerBot’s parent company, released their 2015 financial reports, noting MakerBot sales revenues have fallen precipitously. The MakerBot brand is now worth far less than the $400 Million Stratasys spent to acquire it. MakerBot is a dead company walking, and it is very doubtful MakerBot will ever be held in the same regard as the heady days of 2010.
How did this happen? The most common explanation of MakerBot’s fall from grace is that Stratasys gutted the engineering and goodwill of the company after acquiring it. While it is true MakerBot saw its biggest problems after the acquisition from Stratasys, the problems started much earlier.
“String Art” is the name of the art form that transforms thousands of nails and just as many feet of thread into unique masterpieces. Some artists have developed techniques to create photorealistic string art works, but until now, there was no way around the tedious and time-consuming manufacturing process. Depending on the size, it can take months to complete a single piece by hand.
Did [TobiasWeis] build a mirror that’s better at reflecting his image? No, he did not. Did he build a mirror that’s better at reflecting himself? We think so. In addition to these philosophical enhancements, the build itself is really nice.
The display is a Samsung LCD panel with its inconvenient plastic husk torn away and replaced with a new frame made of wood. We like the use of quickly made 3D printed brackets to hold the wood at a perfect 90 degrees while drilling the holes for the butt joints. Some time with glue, band clamps, and a few layers of paint and the frame was ready. He tried the DIY route for the two-way mirror, but decided to just order a glass one after some difficulty with bubbles and scratches.
A smart mirror needs an interface, but unless you own stock in Windex (glass cleaner), it is nice to have a way to keep it from turning into an OCD sufferer’s worst nightmare. This is, oddly, the first justification for the Leap Motion controller we can really buy into. Now, using the mirror does not involve touching the screen. [Tobias] initially thought to use a Raspberry Pi, but instead opted for a mini-computer that had been banging around a closet for a year or two. It had way more go power, and wouldn’t require him to hack drivers for the Leap Motion on the ARM version of Linux.
After that is was coding and installing modules. He goes into a bit of detail about it as well as his future plans. Our favorite is programming the mirror to show a scary face if you say “bloody mary” three times in a row.
USB power supplies are super cheap and omnipresent. They are the Tribble of my household. But they’re not all created equal, and some of them may even be dangerous. I had to source USB power supplies for a product, and it wasn’t easy. But the upside is that I got to tear them all apart and check out their designs.
In order to be legitimate, it’s nice (but not legally required) for a power supply to have UL approval. Some retailers and offices and building managers require it, and some insurance companies may not pay claims if it turns out the damage was caused by a non-UL-approved device. UL approval is not an easy process, though, and it is time consuming and expensive. The good news is that if you are developing a low voltage DC product, you can pair it with a UL approved power supply and you’re good to go without any further testing necessary.
If you are going for FCC approval and are having unintentional emissions testing done (which is more likely than UL as it’s a legal requirement for products that meet certain qualifications), the testing has to be done on the whole solution, so the power supply must be included in the testing, too.
Sourcing cheap electronics in large quantities usually ends up in China, and specifically Alibaba. First, we started with a how-low-can-you-go solution. This wasn’t even a power adapter; it was a power “adapteP”, and the whole batch was mis-printed. Quality control could not be a high priority. After cutting it open, it wasn’t terrible, and it had all the necessary parts. It was surprising how much of it was through-hole, which indicates that the assembly was done mostly by people. That happens when factories are cheaper, hire inexpensive labor, don’t invest in technology, and don’t care as much about quality.
There are certain things you should look for in a power supply to determine the level of risk:
So this first adapter? Isolation distance was fine because it was two separate boards, but there was no fuse and no protective tape between components. The connectors were all secure, but the label didn’t make any promises. As for performance, output at 5.34V under my product’s load meant it was a little outside of USB spec (5.25V limit), but not dangerous. On the scope it was ringing with a peak at 5.5 V at 4 kHz.
Of course, sourcing this supply for a second batch proved tricky, and we wanted the USB plug to come out the side instead of the front so it would have a thinner profile against a wall. Additionally, we needed UL approval for a client. Our second attempt was surprisingly successful. This adapter had UL certification, with a number to look up. Note that just having a number isn’t enough; many companies will just put someone else’s number on their product and assume nobody will bother to check. So when you do look it up, and find a different manufacturer, a different enclosure, and it looks more like a refrigerator than a USB power supply, don’t be too surprised. But no, this particular one was great! The label had a company name on it, model number and specs, and certifications that could be verified. Let’s tear it open!
Sweet sweet silicon meat inside an ABS shell! Components wrapped in protective tape, two PCBs for isolation, and even a special injection-molded plastic piece to add additional protection. Components are labeled, and what’s this, an IC to control the oscillation instead of a feedback winding on the transformer? Fancy! It’s pretty clear that this power supply is good, and I’d trust this one.
Comparing this one to the others, there were so many noticeable little details that are important and clearly thought-out. Take, for example, the connection between the prongs and the PCB. On the previous board, it was made with wires soldered by hand. Solid, but time consuming and prone to failure or quality issues. This adapter has metal contacts that snap into the case very solidly so that the prongs cannot get loose. The connection to the PCB is via the springiness of the metal, but notice that the PCB has pads specifically designed to maximize the surface area of that connection. On the next PCB you’ll see no such effort.
Some components were covered in shrink tube, tape, or non-conductive grey adhesive. The assembly was tight with no room for components to shake loose or accidentally touch. And the output was perfect. 4.9 Volts with nary a ripple.
But this is China, and component sourcing problems are a thing, so I guess I shouldn’t have been surprised when these supplies were no longer available. In retrospect, maybe these were unsold overstock, or possibly QC rejects. That would explain why they were only slightly more expensive than the others. And so we moved on to another supplier; one that could pad-print our logo on top.
At first glance these power supplies appeared identical. But close inspection reveals slight differences in the style around the USB and the raised ridges on the underside. The label was completely different, and gone was the number next to the UL logo. There was no company name on the supply either, and the company we purchased from turned out to be a reseller and not the OEM. Also, why was the output 4.7-5V, and why did my scope say 5.5V (but surprisingly stable)?
Inside was a completely different beast. Using a single PCB, the creep distance was about a millimeter. You can see the white line meandering through the bottom of the PCB that shows the high and low sides. The USB port wasn’t soldered to the PCB except by the four signal/power pins (see the bottom side lower left and the hanging USB connection pins), and there was a capacitor with really long uncovered leads and the positive side dangerously close to the USB shell. There was almost no protective tape, no shrink tube on the leads, and no protection in case of a short.
In the end, I wouldn’t trust the two non-UL supplies with anything worth more than a few bucks, and certainly not my cell phone. I’d have really big reservations about reselling them to customers who don’t know the difference. The UL-approved one was great, but the other two are only good for powering low-current-draw devices that are not sensitive to voltage. Also, finding a reliable supplier in China is HARD.
Check out a much more thorough analysis of this and pretty much every USB power supply cube by [Ken Shirriff]. It’s surprising how little has changed in four years with these supplies, and his analysis goes into how the circuits behind these supplies work, identifying each component and its purpose.
We also covered a Sparkfun teardown of some power supplies with similar conclusions, and a Fail of the Week in which a faulty USB power adapter was the likely cause of a fire.
When Jeffrey Brian “JB” Straubel built his first electric car in 2000, a modified 1984 Porsche 944, powered by two beefy DC motors, he did it mostly for fun and out of his own curiosity for power electronics. At that time, “EV” was already a hype among tinkerers and makers, but Straubel certainly pushed the concept to the limit. He designed his own charger, motor controller, and cooling system, capable of an estimated 288 kW (368 hp) peak power output. 20 lead-acid batteries were connected in series to power the 240 V drive train. With a 30-40 mile range the build was not only road capable but also set a world record for EV drag racing.
The project was never meant to change the world, but with Tesla Motors, which Straubel co-founded only a few years later, the old Porsche 944 may have mattered way more than originally intended. The explosive growth between 2000 and 2010 in the laptop computer market has brought forth performance and affordable energy storage technology and made it available to other applications, such as traction batteries. However, why did energy storage have to take the detour through a bazillion laptop computers until it arrived at electro mobility?
You certainly won’t find that grail of engineering by just trying hard. Rather than feverishly hunting down the next big thing or that fix for the world’s big problems, we sometimes need to remind ourselves that even a small improvement, a new approach or just a fun build may be just the right ‘next step’. We may eventually build all the things and solve all the problems, but looking at the past, we tend to not do so by force. We are much better at evolving our ideas continuously over time. And each step on the way still matters. Let’s dig a bit deeper into this concept and see where it takes us.
Continue reading “Evolving Our Ideas To Build Something That Matters”
Long ago, when I wanted a plywood sheet, I would go to the local big box hardware store and buy whatever was at the center of the optimization curve for cheapest and nicest looking. I would inevitably suffer with ultra-thin veneers on the top, ugly cores, unfinishable edges, warping, voids, and other maladies of the common plywood. One day I said enough is enough and bothered the salesman at my local lumber supply until he showed me one that wasn’t awful.
Baltic birch differs from other plywoods in a few ways. Regular plywood is usually made locally from the cheapest possible core wood in alternating grain layers laminated together with a hardwood veneer on the top. There are interior and exterior grades. The exterior grades are usually made with a different glue, but don’t necessarily denote a higher quality or stability. Some of the glues used can be toxic. Wear a respirator. In normal plywood, the ATSM or BB standards only apply to the face veneers used to finish the product. The core can be of whatever quality is convenient for the manufacturer.
True Baltic Birch is made in the Baltic Region with the biggest producers being Russia and Finland. Outside of the US it is sometimes called Finnish Birch or Russian Birch plywood for this reason. It is made from only top quality birch veneers laminated together with no filler wood. It is also unique in the care taken to make sure each layer of the wood is patched so there are no voids. All Baltic Birch is made with exterior grade glue, and when properly sealed will work for outdoor applications. There are grades of Baltic birch for marine applications and exceptionally void free aircraft grade plywood at a much higher cost.
The easiest way to spot Baltic Birch if you’re American is its form factor. Baltic birch comes in 1525 x 1525 mm squares, which approximates to 5 ft x 5 ft. Some people have said that manufacturers have started to produce 4 ft x 8 ft sheets specifically for the North American market, but this information comes with a caveat that these are usually lower grades made locally or in China parading under the name. The metric form factor extends to the thicknesses of the sheets. In America they will be sold as inch, but fit pretty closely to a metric form.
There are some really nice practical features of Baltic Birch. One of my favorites is the absolute uniformity of the layers. This means that two pieces of birch can be laminated together and the seam between the two becomes indistinguishable. I’ve used this to make cases by CNC routing out the inside of a sheet of Baltic birch, drilling some holes for alignment pins, and then laminating the whole assembly together. We’ve covered a few readers who have had similar ideas. Since the layers are uniform you can also do interesting things when combined with a CNC router. For example, carefully milling away the layers you can get a topographic map of the object.
Baltic Birch is also significantly flatter and more stable than other plywood options. It is commonly the material used for fences on expensive tables saws. It moves less during temperature swings and changes in ambient moisture. This is one of the reasons it’s popular with fine furniture builders. This also makes Baltic birch a good option for home CNC builds, certainly better than MDF . Due to the higher quality wood and better manufacturing it is quite strong as well. It is a great structural wood.
Baltic birch is more expensive than the regular grade stuff. So a sheet of ¾” thick Oak veneer plywood with a pine core, interior grade, from Lowes is about 35 US dollars where a similar sheet of 18mm Baltic Birch will run around 65 dollars.
I’ll still occasionally purchase a cheaper sheet of plywood when I have a non-critical application (like garage shelving), but when I am doing something precise or nice I’ll spend the extra on the birch plywood. While I love this material, I am by no means a wood worker. Have any of you had experience with this plywood? Is there an even better plywood out there?
I’ve left my sources below for further reading. [3] Ultimate Guide to Baltic Birch is very good.
[1] Dan’s Hobbies. (2016). A baltic birch plywood primer | Dan’s Hobbies. [online] Available at: http://www.dans-hobbies.com/2010/01/09/a-baltic-birch-plywood-primer/ [Accessed 19 Apr. 2016].
[2]Wikipedia. (2016). Plywood. [online] Available at: https://en.wikipedia.org/wiki/Plywood [Accessed 19 Apr. 2016].
[3] Stephens, (2014). Ultimate Guide to Baltic Birch Plywood: Why It’s Better, When to Use It |. [online] Woodworkerssource.com. Available at: http://www.woodworkerssource.com/blog/tips-tricks/your-ultimate-guide-to-baltic-birch-plywood-why-its-better-when-to-use-it/ [Accessed 19 Apr. 2016].
