Know Your Fits And Tolerances

February 25, 2019 by 12 Comments

When designing parts on a screen, it’s very easy to type in a bunch of nice round numbers and watch everything slot together in perfect harmony. Unfortunately, the real world is not so kind. A 10mm shaft will not readily fit in a 10mm hole, and producing parts to perfect dimensions simply isn’t possible. This is where fits and tolerances come in, and [tarkka] have created a practical demonstration of this on Youtube.

Tighter tolerances require more care and thus increase production costs significantly.

Hole and shaft tolerances are important to ensure parts mate correctly and as intended. If a shaft is to fit into a hole easily and the dimensions aren’t critical, a clearance fit is called for. If assembly should be easy but the part is required to locate accurately, a running fit is called for. Alternatively, if the parts are intended to be pressed together permanently, an interference or force fit should be used.

The video covers the basics of fits and tolerances in an easy to understand way, with visual examples. The fits discussed are based in Imperial measurements, but the metric standard of hole and shaft tolerances (ISO 286-2) is also noted.

Getting your tolerances right is key to making good parts – we’ve covered common issues such as tolerance stacking before. Video after the break.

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Casting The Bed Of A CNC Machine In Granite

February 25, 2019 by 22 Comments

If you’re looking at CNC machines, or machine tools in general, heavier is better. That old drill press or mill made of a few hundred pounds of cast iron isn’t just better because it’s stood the test of time for a hundred years — greater mass equals less vibration. Thanks to modern epoxy resins, we now have a replacement for tons and tons of iron. Epoxy granite, or chips of granite bound together with epoxy resin, is a viable and very good base for CNC machines, mills, and other tools that are served well with a ton of mass. [Joerg Beigang] is building his own CNC router, and he’s building the base out of epoxy granite. Here’s how he’s doing it.

Before you pour epoxy into a mold, you’ll need to figure out how you’re going to attach your ways, linear rails, and ball screws. [Joreg] is bolting these parts to pieces of aluminum he cut on his home made panel saw before carefully drilling and tapping them to accept the linear rails. These aluminum plates were then mounted to the bottom panel of the mold, in this case melamine-coated plywood.

As you would expect, the most intricate part of this build isn’t globbing up a mold with epoxy resin. No, the real trick here is making sure the rails of the CNC are aligned perfectly before the epoxy goes in. This was done by bolting the linear rails to the mold box and checking everything with a dial indicator. Once that was done it was time to pour.

The bed itself is made of 18kg of epoxy granite, with the entire pour done in four batches. The best way to settle a big pour of epoxy granite is through vibration, just like concrete, but it looks as though [Joreg] is getting some good results by tamping it down with a few sticks. You can check out the first part of this build series below.

If we’ve captured your interest, it’s worth reminding you that this isn’t the first epoxy granite CNC machine we’ve featured.

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E-Ink Price Tags Fall Off Store Shelves Onto Your Workbench

February 25, 2019 by 38 Comments

There’s always a magic moment for our community in the lifecycle of any piece of technology: the point at which it first becomes available for pennies on the surplus market. Something which could previously be had only at a price is rendered down to mere pennies, and we are free to hack to our heart’s content.

Such a moment came for [Aaron Christophel] when he bought a quantity of used e-ink price tags (German, Google Translate link) that had formerly graced the shelves of a supermarket. A pile of readily hackable e-ink displays lay before him, so he set to work.

Cracking them open he found the display itself as well as a PCB with its own microcontroller, but he soon identified it as compatible with a WaveShare module for which he had data. Since its interface was thus identified as SPI he could desolder the unknown CPU and break out the pins for an Arduino or other board. The display itself turned out to be a custom model with a few quirks for price tags, it had a black border that could be enabled, and for some reason it appeared as a two-colour red-and-black model in which its black pixels responded as though they were the red channel. He has a quick overview video that we’ve placed below the break.

These displays have started appearing in our community, not least in electronic conference badges. This source of cheap components from the surplus market makes them ever more accessible, and we look forward to the projects that will come from them.

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Would You Like To Play A Game? WOPR Summit Is This Weekend

February 25, 2019 by 6 Comments

During the summer months it might be known as “America’s Playground”, but around this time of year, Atlantic City is generally the destination of choice for bus loads of seniors looking to burn up some of that fixed income. Of course, that was before the WOPR Summit came to town. From March 1st to the 3rd, it promises to transform Bally’s Hotel and Casino on the famous Atlantic City Boardwalk into a high-tech oasis in a sea of oxygen tanks and walkers. There might not be any fun in the sun to be had at this time of year, but a full schedule of talks and workshops covering everything from penetration testing to ham radio is more our speed anyway.

There’s still a couple days to register for WOPR online at a discount, but naturally they’ll be happy to take your money at the door if you miss the cutoff. As of this writing, there’s even still rooms left at Bally’s for the special WOPR rate, which you’ll probably want to take advantage of as the schedule has events running until well past our normal bedtime.

WOPR looks like it will be a nice mix between hardware and software, with a generous sprinkling of InfoSec. Presentations such as “Strategies for your projects: Concept to Prototype” and “Being Q. — Designing Hacking Gadgets” sound like classic Hackaday fare. But even if you aren’t normally into the security scene, talks such as “Ham Hacks: Breaking into Software Defined Radio” and “An Introduction to IoT Penetration Testing” seem like they’ll be an excellent way to cross the divide. In between the talks, they promise to have a hackerspace up and running for you to check out, complete with soldering classes and contests.

It’s not often that you get to witness the birth of a new hacking conference, especially one on the East Coast, so Hackaday will be shaking off the last bits of our long winters nap as I catch the next bus out of the Senior Center that’s headed towards the Boardwalk. Track me down and you might even be able to take some of our Jolly Wrencher stickers home along with your slot machine winnings. But even if you can’t make it to America’s rather chilled and blustery playground this weekend, I’ll be sure to report on all the highlights so you can live vicariously through the comforting flicker of your favorite screen.

Stethoscopes, Electronics, And Artificial Intelligence

February 25, 2019 by 20 Comments

For all the advances in medical diagnostics made over the last two centuries of modern medicine, from the ability to peer deep inside the body with the help of superconducting magnets to harnessing the power of molecular biology, it seems strange that the enduring symbol of the medical profession is something as simple as the stethoscope. Hardly a medical examination goes by without the frigid kiss of a stethoscope against one’s chest, while we search the practitioner’s face for a telltale frown revealing something wrong from deep inside us.

The stethoscope has changed little since its invention and yet remains a valuable if problematic diagnostic tool. Efforts have been made to solve these problems over the years, but only with relatively recent advances in digital signal processing (DSP), microelectromechanical systems (MEMS), and artificial intelligence has any real progress been made. This leaves so-called smart stethoscopes poised to make a real difference in diagnostics, especially in the developing world and under austere or emergency situations.

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All Things Enigma Hack Chat

February 25, 2019 by 2 Comments

Join us Wednesday at noon Pacific time for the All Things Enigma Hack Chat!

This week’s Hack Chat is a bit of a departure for us because our host, Simon Jansen, has tackled so many interesting projects that it’s hard to settle on one topic. Simon is a multidisciplinary hacker whose interests run the gamut from building an ammo-can Apple ][ to a literal steampunk Rickroller. How about a Bender Brewer? Or a MAME in a TARDIS? Or perhaps making an old phone play music to restore a car by? Oh, and remember that awesome ASCII animation of Star Wars: Episode IV? That was Simon.

So, a little hard to choose a topic, but we asked Simon to talk a bit about his recent Enigma watches. He has managed to put an electronic emulation of the Enigma cypher machine from World War II into both a wristwatch and, more recently, a pocket watch. They’re both gorgeous builds that required a raft of skills to complete. We’ll start there and see where the conversation takes us!

Please join us for this Hack Chat, where we’ll discuss:

  • Where the fascination with Enigma came from;
  • Tools, techniques, and shop setup;
  • Melding multiple, disparate skill sets; and
  • What sorts of new projects might we see soon?

You are, of course, encouraged to add your own questions to the discussion. You can do that by leaving a comment on the All Things Enigma Hack Chat and we’ll put that in the queue for the Hack Chat discussion.

join-hack-chatOur Hack Chats are live community events on the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, February 27, at noon, Pacific time. If time zones have got you down, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io. You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.

Glowtie Is Perfect For Those Fancy Dress Raves

February 25, 2019 by 3 Comments

Are you bored of your traditional bow tie? Do you wish it had RGB LEDs, WiFi, and a web interface that you could access from your smartphone? If you’re like us at Hackaday…maybe not. But that hasn’t stopped [Stephen Hawes] from creating the Glowtie, an admittedly very slick piece of open source electronic neckwear that you can build yourself or even purchase as an assembled unit. Truly we’re living in the future.

Evolution of the Glowtie

While we’re hardly experts on fashion around these parts (please see the “About” page for evidence), we can absolutely appreciate the amount of time and effort [Stephen] has put into its design. Especially considering his decision to release the hardware and software as open source while still putting the device up on Kickstarter. We seen far too many Kickstarters promising to open the source up after they get the money, so we’re always glad to see a project that’s willing to put everything out there from the start.

For the hardware, [Stephen] has gone with the ever popular ESP8266 module and an array of WS2812B LEDs around the edge of the PCB. There’s also a tiny power switch on the bottom, and a USB port for charging the two 1S 300mAh lipo batteries on the backside of the Glowtie. The 3D printed rear panel gives the board some support, and features an integrated bracket that allows it to clip onto the top button of your shirt. For those that aren’t necessarily a fan of the bare PCB look or blinding people with exposed LEDs, there’s a cloth panel that covers the front of the Glowtie to not only diffuse the light but make it look a bit more like a real tie.

To control the Glowtie, the user just needs to connect their smartphone to the device’s WiFi access point and use the web-based interface. The user can change the color and brightness of the LEDs, as well as select from different pre-loaded flashing and fading patterns. The end result, especially with the cloth diffuser, really does look gorgeous. Even if this isn’t the kind of thing you’d wear on a daily basis, we have no doubt that you’ll be getting plenty of attention every time you clip it on.

It should be said that [Stephen] is no stranger to wearable technology. We’ve previously covered his mildly terrifying wrist mounted flamethrower, so if he managed to build that without blowing himself up, we imagine building a light up tie should be a piece of cake in comparison.

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