An Experiment in Water Cooled 3D Printing Extrusion

Scrapheap Challenge: The world’s worst syringe pump.

Or, three hours enjoyably lost to a visit from the bad idea fairy.

My PhD advisor and I were chatting in the lab today and had an idea that it would be interesting to try to drip/jet a bit of water onto just-extruded filament, ideally in small enough quantity that it phase changed and flashed off with all the excess energy, in order to allow printing unreasonable unsupported structures.

It unfortunately doesn’t look like it will be practical, but we got a PoC-grade implementation in a few hours and it seemed worth a quick write-up to document our experiment for the interwebz.

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Bladekey Refresh

I’ve been carrying a series of slightly-customized 3D printed bolt-type bladekeys since 2014. Despite being printed PLA, I’ve only had to print a new one once every several years – I wasn’t keeping good records but I think this is my third plastic body, second #8-32 “Chicago Binding Post,” and I upgraded the type of pocket clip at some point. I’m yet to have a catastrophic failure. The setup essentially eliminates key jingle, poking, or wear on pocket facings, while still being easy to tap check and use. The only slight downside to this setup is that when I attach a car key and put it in the vehicle, the blade-key dangles at knee height and occasionally grabs a leg hair – if I drove more I’d probably tweak how I attach the car key to fix that.

Pictures from the first one I carried in 2014, and the most recent swap out, induced by it “getting loose” and letting the stack of keys flip forward in my pocket – which turned out to be the result of several cracks in the plastic body. Plus, flexing that the bitting and labels are both obscured when closed, which I suppose is a minor security feature, especially when posting pictures on the Internet.

At this point I’d buy one of the fancy ones just to support the designer, but my desired size falls in between the models they do commercially (I use 15mm W x 58 L, closest sizes are 12mm W and 19mm W). Maybe sometime I’ll get ambitious and cut one in a different material on the router.

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Server Updated

The server that hosts this page was updated from Debian Jessie (8) through Stretch (9) and onto Buster (10) over the course of a few hours today. It involved surprisingly little suffering and should not affect functionality, please let me know if you find anything left in a broken state.

I didn’t realize how long it had been since I did any manual maintenance here, apt unattended upgrades, certbot, and a few scripts for user-installed package upgrades and backup had done such a good job maintaining things just visibly enough to know it was being taken care of that I’d let it get past-due. Most of my other individually-installed boxes are Arch rolling-release machines that require a few minutes of attention every month or two, so they don’t have the periodic major breaking maintenance issue to the same degree.

Now I can let it take care of itself again until 2022 or thereabouts.
A few notes that may be useful to others under the fold.
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Aneng AN8009 DMM with Hacks

Aneng AN8009 DMM

I just picked up an Aneng AN8009 DMM as an upgrade to the cheap, cheap (but surprisingly OK) Circuit Specialists branded MY-68 I’ve had as my home on-desk approxometer for ages. It’s a nice meter for $30ish, and can be readily hacked to improve its performance. I tend to point people to mid-range Uni-T DMMs when they asked for decent hobby meters, but now I might switch to one of these plus one of those little $10 Atmega328 based component testers cloned everywhere for ~$10 as basic electronics lab instruments.

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A Bit of 3D Printer Maintenance

We were doing a bit of beginning-of-summer lab maintenance and one of the projects was to figure out why the MakerGear M2 (Which has been heavily modified over the years, Azteeg x5 mini motherboard, E3D hotend, etc.) was behaving so strangely.
Well… there’s your problem.
Fresh 0.35mm nozzle next to the bored out, abraded down corpse of a nozzle that we’ve, in retrospect, been running for something like 3 years. Turns out printers work much better when the nozzle aperture is roughly the size it’s supposed to be.
Still seeing some odd temperature fluctuation, but … look at that thing.

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Masters in Electrical Engineering (Finally) Collected

That MSEE that I was going to finish in 2011, 2013, and 2015? I blew a couple months in the last year to get all the ducks in a row and actually collected it before the credits expired.  Huge thanks to Dr. Aaron Cramer, the current DGS for UK’s ECE department who went to great lengths to deal with the bureaucratic issues my lackadaisical attitude about credentials created.

Thesis is “A Compiler Target Model for Line Associative Registers” document and defense slides with notes linked.

The LARs design is fundamentally interesting, but the compilation work the MS is based on is not my favorite work I’ve done.  The core initial assumption (that LAR allocation and register allocation were more-or-less the same problem) turned out to be very, very wrong, and the implications of that wrong assumption turned out to be far reaching, turning a 2-year MS into a decade-long ramble. It’s not as depressing as I thought it would be when I tried to finish in 2015 (and was blocked by bureaucratic fuckery) because I did eventually determine that LARs aren’t subject to the “you can’t statically schedule around dynamic memory behavior” thing that doomed VLIWs, and in fact LAR allocation can be done greedily in ways that register allocation cannot.

The thesis is more or less assembled from three false starts plus the final effort; my initial research start with the wrong assumptions, my “oh, we’re wrong, but it’s OK” pass, and my “oh shit, we’re screwed, this won’t work and there his historical evidence to show it” pass, plus the final “I’ve figured out how this is tractable and possibly even desirable, but I’m out of time and fucks, so here’s the rough solution” pass.

I formatted the thesis in LaTeX (of course), using the ukthesis.cls class I found on the UK Math site that Eric Stokes, a former student, made a decade and change ago since UK is too chickenshit to provide a valid one of their own.  I did have to hack it a little bit, turn off some features, tweak the front matter, etc. to make it acceptable to the graduate school, and update a few things (eg. adjusted to use biber for references).  There are a few things in the document that should be in the class, and things in the class that should be in the document, but the easy-to-fix stuff is fixed.  Minimal example pulled from the accepted version with makefile and such here to save future students the extra annoyance.

The presentation is in beamer using the Owl theme, which was a delightful recent discovery – someone has made a beamer color scheme with a dark background and colors that actually look good on a projector. I (much to one of my committee member’s disappointment) went with the bullets-to-keep-me-on-track-while-I-talk style slides instead of my usual “amusing semi-relevant pictures to key off of” scheme.

It’s nice to be done and only have one, significantly less depressing, long-term academic project people are grumpy about my progress on.

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Self-Hosting News Sharing and Discussion

Back in 2013 when google killed Reader I mused about self-hosting my communal news shit-talking.  With the imminent death of G+, which I moved to despite knowing better, I’m looking into it again.  This process might (will) cause some spurious content to appear in the main feed while I try things. I’m still on (and pretty committed to) tt-rss on the news-consumption side, I’m poking around ways of rigging the published feed from that into a comment-able format.  Hopefully with a minimum of work and maintenance overhead on my part, and without hooking myself to yet another platform that won’t monetize well and will thus die.

Success!: The news tab in the nav-bar now takes you to a page that shows the things I publish from my Tiny Tiny RSS instance, complete with a place to yell at me for my hot takes, or share your own thoughts. It’s rigged up with FeedWordPress and a little bit of theme hacking, and can itself be subscribed as an RSS feed. There is a little bit of jank with nested feeds, but at least it’s in house.
A less lazy me would probably do this with a static site generator, a comment system (like isso or something) and some scripts, but I all sorts of don’t have time for that.

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E7250


I picked up a refurbished Dell Latitude E7250 (Dell’s “Premium” 12.5″ laptop, just over a generation out of date) because the little loaner Inspiron 11-3000 I’d been using as my carryin’ around laptop had become unacceptably shitty at essentially all the things I wanted to use it for. The E7250 is Superb, with notes:
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SC17 Notes

I’m back from SC’17, and to complete annual tradition, some thoughts:

  1. Chinese manufacturing is winning the day: The Nov’17 Top500 shows three of the top 5 and roughly 60% of the total compute power on the list are Chinese machines. Especially domestic-design Chinese machines (The ShenWei SW26010 in #1 are pretty thin on public details, but smell a lot like a better implementation of the Cell idea). Last time this kind of trend started (in Japan) the US spent a boatload of money on development, but I don’t think there is the political will for that sort of thing right now.
  2. Linux all the things: 100% Of the Top500 are now running some sort of Linux. Linux is a nice thing, but the mono-culture is sort of alarming.
  3. Singularity: Greg has a long history of solving real problems in the ecosystem (Warewulf, CentOS, etc.) in very pragmatic, very open ways. About 18mo ago he posed about a prototype container scheme suitable for HPC apps he’d been playing with. It’s now everywhere and running on everything because it solves compatibility problems, portability problems, reproducibility problems, archiving problems, workflow problems, verifiability problems, administration problems, and, unlike most containerization schemes, isn’t made of inefficient ill-conceived web-hipster bullshit. They’ve formed a little company to support it, which was second only to Nvidia in terms of brand presence. It has moved considerably up my list of things I need to learn.
  4. Fidget Spinners: So many fidget spinners on the show floor. With LEDs. And branded metal bits. Chinese mass production has also overtaken the swag in the industry.

Also, a pile of pictures from the show floor.

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Ruideng Adjustable Bench Power Supply

I built myself a little adjustable bench power supply from Chinese modules, partly because I thought it would be handy to have one, and mostly because I wanted a small, straightforward project to do for my own sanity.

I set up a slightly different configuration than is typical, and am documenting it for funsies and/or to ease clones if anyone is so inclined. The whole project was about $60 all-in, for an (approximately) 0-34V, 0-5A adjustable bench power supply.
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