Who needs a case? The 3D Printed Mil-Plastic is here | Hacker News Reader

Who needs a case? The 3D Printed Mil-Plastic is here

back7.co

100 pointslvturner73 comments

I absolutely hate it when a blog doesn't have a date or has incomplete dates. When was this posted?

Someone else here posted a link to a related post (https://back7.co/home/raspberry-pi-recovery-kit). A "related article" has the title "Project Retrospective: Raspberry Pi Field Unit from 2015". No idea which year this was posted either.

Too much whitespace and too much scrolling.

>I absolutely hate it when a blog doesn't have a date or has incomplete dates. When was this posted?

Depending on the CMS authoring tool used, sometimes the raw HTML ("View Source") has meta info of the timestamp. In this particular case, the raw html has this:

  <meta itemprop="datePublished" content="2020-08-25T18:00:00-0700"/>

Obviously, any meta timestamp is self-reported so you have to judge if it's a legitimate date (e.g. possibly cross-reference with archive on Wayback Machine, etc.).

The web landing page also shows "Aug 25" in light gray underneath this story's photo: https://back7.co/

Also it features a Pi 4 so it can't be older than June 2019.

(but yes, I do share your frustration and sometimes spend more time looking for ANY date than reading an article...)

I agree with you in general.

In this case, though, the article talks about "a few months over the quarantine" and "including a 3 month break due to life and COVID impacts". That makes it pretty easy to date!

But it won't in four years.

Are we going to get another COVID?

Another outbreak is possible, possibly meaning more quarantine.

That doesn't make it easier for me to date at all.

For one, I probably don't live where this guy lives - the quarantine timeframe has been different everywhere.

One common thing I've noticed from working in web publishing for the past couple of decades is that design is often created to serve the frequent homepage reader who is familiar with your publication, not the first-time entrant who came in via an individual page. The unstated assumption is that you will start on the homepage, and navigate from there to the article you want to read. Leaving the year off of the article isn't an anti-pattern to them because it should be clear that it's recent from the fact that you found it on their homepage.

Never mind that this rarely matches with reality. Even with pretty comprehensive web analytics to show actual usage patterns, it's common for site developers, designers, and publishers to make decisions based on this unconscious bias.

For something like this, which does not include time-sensitive material, why does a date matter? This is as close to timeless content as you’re like to find WRT a Raspberry Pi case project.

Here's a great feature for a browser add-on - perhaps something that takes a look at the Wayback Machine, or google cache, or something, and gives you a little hint in one of the page corners that tells you when was the last time this page has been updated, or when it was created in the first place.

It says "Aug 25" in grayish letters under the image.

This is good feedback, thank you. I'll add the date at the top of the article in the article text from now on, and should be able to go back and update old articles. As for whitespace, it's the CMS and template. I am able to create projects like these because I can leverage a CMS (Squarespace here). My projects usually get picked up/noticed when they are live, no one usually looks at my older stuff. Cheers!

Many research papers are undated too. It’s aggravating, but I can see why authors do it (especially for any blogs with ad revenue attached).

Does the author of this blog, anywhere, detail which 3d printer was used for these parts ?

Unrelated:

Very happy and satisfied to see Macmaster-Carr store links for several of the parts in the materials list. MC is the best.

EDIT:

In this post[1] the author mentions the Pruse MK3S[2] but I am not sure if that is what is used for all of the projects on the site ...

[1] https://back7.co/home/learning-to-scale-small-manufacturing-...

[2] https://shop.prusa3d.com/en/51-original-prusa-i3-mk3s

McMaster Carr is pretty great if you're American.

For the rest of us, there's Misumi!

They're both great! Mcmaster is the greatest website of all time. Sometimes the premium is 200% above other sources, but nobody cares because they can save so much time using Mcmaster. Misumi's configurable products that are machined to order are also a gamechanger, particularly on the Japanese site which has a lot wider variety. And they are hiring robotics engineers which should give interesting results.

MC could really use a shipping estimator. I remember ordering a $10 thing and getting charged $40 after shipping, which I didn’t m or would happen until after it shipped. Other than that I agree.

To add to the “greatest website of all time” aspect, they provide STEP files of a ton of those parts (maybe all of them?). When you’re drawing up a project like the OP’s in CAD, you can import the STEP file of the parts from McMaster and verify fit right there. If you’re using Fusion 360, there’s a button right in the app to browse McMaster and download the model!

And... if you need a part with a particular shape but not necessarily the strength of metal... shhhh... you can just 3D print it yourself from the STEP file.

It's a good website. It looks like they finally support tabbed browsing, but a less rigidly-enforced product hierarchy and better support of metric measurements would make it a lot better.

For example when I'm buying a sheet of steel, this list ordering isn't as easy to work with as it could be: 3/32", 0.095", 0.1", 1/8", 0.134"..., 1 mm, 2 mm, 3 mm...

Not really though because Misumi only sell to companies. McMaster Carr sell to anyone.

I think that's backward. Misumi let me create an account and buy whatever I want as a private individual, even in Canada. McMaster refused to ship to anyone here except for "trusted institutions" like verified companies and universities.

Not in the UK. I need to provide a VAT number.

Yes, the quality of the prints stood out for me and I also wanted to know on which printer this was done.

The author made a casing for a Prusa MK3/MK3S. So I assume this was used.

Based on his instagram stories, he's been using a couple of Prusa i3 MK3/S printers.

”This is part sculpture”

Hear hear. Ten out of ten for functional and appealing aesthetics. Industrial design is the best kind of design.

Exit, to go hug a Mellor traffic light

This is really excellent. I was recently introduced to ApolloX filament and I'm looking forward to doing some parts for my engine bay.

Tangential, but I have a really hard time finding projects like this to print, Thingiverse is really difficult to filter through the misc bits and bobs to find cool projects.

Does anyone have any recommendations on how to discover truly interesting projects to 3D print?

As a tradesperson working in metal fabrication and driving a 4kW laser cutter as my primary role at work where I have the ability to cut up to 20mm carbon steels, 20mm stainless, and 8mm aluminium, and 10mm copper & copper alloys. Our other workshop can cut much thicker carbon steels with CNC oxy and up to about 50mm stainless with a CNC plasma cutter.

All these tools are pretty much just glorified files and coping saws.

Kinda need something you actually want to build in order for them to be of any use. They tie in nicely to creativity in general.

My advice would be to pick up some other hobbies, wouldn't really matter what it is you'll soon start seeing things you could replicate or do better with customer design.

This is really good advice for basically any creative endeavor. If you want to learn, then by all means do tutorials and popular projects, but when you want to get inspiration for new projects, there's nothing better in my experience than having other hobbies and joining other communities.

This is somewhat related - I am working on https://makely.me - if you have a 3D printer you can earn money printing people's custom orders. Could serve as inspiration I guess.

What am I looking at? A 3D-Printed Raspberry Pi case?

I had the same problem with the article. The article gives me vibes like a shady Indiegogo campaign:

- Very professional looking photos, full with filters. Still hard to figure out how it exactly looks. For example how big is it? 10cm? 20cm? The studio setting with nothing else in the background makes it hard to guess.

- strange-non existing buzzwords like "Mil-Plastic"

Fantastic aesthetic for all their projects. Mil-industrial-retro-future.

Nice. It'd be fun to have a military connector: https://en.wikipedia.org/wiki/U.S._Military_connector_specif...

In case you didn't see the previous version of this: https://back7.co/home/raspberry-pi-recovery-kit

The devil always lurks in the details.

1. Choosing 5015 spec: as if this deprecated standard's threaded mating interface isn't super annoying to handle, you'll likely only encounter select insertion patterns of this circular interconnect spec on well-designed modern systems for high power interfacing, whereas this toy uses it for...low voltage GPIO.

2. Choosing AlCd olive drab finish: likely for no other reason than it looks "mil spec". Cd is a heavy metal useful as a sacrificial corrosion inhibitor that allows the interconnect to satisfy a 500 hr salt spray performance requirement...but Cd is toxic and can be absorbed through the skin via contact. You won't be seeing much of this once preferred finish on new designs these days.

3. Choosing front side receptacle mount: makes disassembly and servicing more difficult than it needs to be, especially given solder cup termination...made even more difficult to access by a seemingly nonfunctional spacer plate.

4. Interconnect spacing: clearly unfamiliar with 1472 human engineering requirements...I'm liable to suspect the designer has never actually attempted to mate both plugs simultaneously...may be in for a surprise, and if they happen to clear, it'd be by a gnat's ass and a significant encumberance to do so.

All good points. Reach out to me on social media and I’ll send you a few stickers!

This is awesome! I prototyped a similar device for my (now-zombie) startup targeted at the military market, but I only used regular ABS plastic to print the case. This makes me want to revisit that project....

I wonder if the PETG case is as strong as a pelican. They are well proven pieces of equipment with good market, bring able to 3d print something of equal strength is a game changer.

PETG is slightly less strong than PLA - PETG has a bit of flex. I use PETG for raspberry pi cases because they get quite hot. Though having said that, PETG is fast becoming my favourite thing to print with.

PETG isn’t that great tends to deform less and shatter more, ASA is better if you need temperature resistance and is only slightly more expensive than PETG these days and it’s also much more machineable.

PLA these days also has quite decent temperature resistance in filaments that were designed for that, but even the most generic stuff should be ok for most electronic applications there shouldn’t be a spot that goes over 45c her alone 60-70 where you really begin to see issue.

For a portable device like this I would be worried about leaving it in the car if it's PLA. You can easily see 70c inside a car on a hot sunny day.

That said, you can heat treat standard PLA to make it resistant to temperature.

I wouldn’t leave a raspberry pi in a car that gets to 70c due to a very likely risk of damaging the BGA SoC and other soldered components.

The SoC doesn't thermal throttle until 85C. It is not going to desolder from being inside a hot car.

Doesn't PLA get dimensionally unstable with heat treating?

It usually is yeah, but you can sometimes get good results. I think it depends a lot on the heat level against the specific print you are doing.

PETG shatters more? Are you guys using colored PETG? Pure (transparent) PETG will buckle before it shatters, and is much stronger than PLA for me.

Even coloured PETG has been amazingly shatter resistant for me? I took a bad print and stuck it in a bench vice. It was long and skinny (maybe 3-4mm thick before the print failed), and it literally bent itself in half and did not snap.

It depends, pigment changes its properties. White Spektrum PETG tended to shatter a bit too easily for me (though still not more easily than PLA, I think).

Huh! Good to know! This was D3D in green. The only thing that's managed to break it so far is a drone clipping the ground with its landing gear at 40km/h, and the 3D printed piece was the perfect "weak link" to prevent a more catastrophic failure :)

Oh yes, engineering intentional weak links is an art of its own, when you don't want the more expensive components to break.

The joke in engineering school was: "You may choose to design a specific weak link into your design; if you do not do so, one will be provided for you."

My favorite PETG property is its sandability. You can sand down PETG way easier than PLA and it's not really any harder to print.

Almost forgot to mention my second-favorite property, or more like a lack of a property: PLA tends to break over time. If you print a coat hook out of PLA it will fail sooner or later. Fractures just build up over time until it gives out. No such thing with PETG, it's either deforming or it isn't. none of this slowly deforming over time nonsense.

And while I'm at it, my third favorite property: It's fairly bendy and springy! Even though it's less strong than PLA it's way less likely to break because of it.

All in all my favorite 3d printing material so far.

Isn't PETG much more durable than than PLA? PETG is less strong in the sense that is can flex, but it is much more impact resistant and less brittle than PLA I thoguht. Also, in something like a case with screw holes, even slightly too big screw will crack the case, while PETG will usually be okay. I could be wrong–I'm pretty new to 3D printing.

PETG isn't as hard as PLA and is less fragile, with minor flex. It's main downside is that it's a pain to glue without special glues as the usual suspects (cyanoacrylate, epoxy, etc) don't usually like to stick to it.

Ya. Strength usually refers to static tensile strength, of which PLA scores pretty damn high.

There's a YouTube channel called CNC Kitchen which does regular testing of filaments. He measures various kinds of strengths (tensile, compressive, impact, young's modulus etc). I highly recommend it.

But when people say strength they usually mean static tensile strength.

Yeah, I built a solar tracker that sits out in the sun. I originally printed with black PLA plastic. After a few hours of direct sunlight it melted! Now I print with PETG and that stuff is solid.

I can't really tell the material properties differences between PLA and PETG (in terms of strength).

Ouch. I found PLA to have less flex. PETG has a lot more flex.

Also, what is the point of a solar tracker? We can all tell where the sun is...

I point a camera at the sun for long periods to take multiple exposures (goal is to watch a sunspot moving across the sun). People also use solar trackers to keep solar panels aligned with the sun.

I thought PETG has a higher elastic modulus than PLA, but I haven't really tried it. I generally size my pieces to not flex, since that introduces error in the tracker.

Not even close even glass fiber / cf nylon won’t be as strong as modern injected plastic where you can do fiber flow simulations before molding it.

Also almost all current fiber filament is well meh the fibers are way too short for them to matter in fact they might result in weaker prints.

There are commercial 3D printers that impregnate the fiber at printing which allow you to lay very long and even do single continuous fiber prints but these aren’t available for hobby use.

what is a pelican in this context?

Pelican is a manufacturer of rugged cases, often used to transport expensive/fragile equipment.

Forgive my ignorance, what is mil-plastic?

It probably means military since the way it looks does make you think of military equipment and he mentions pelican cases as well. I don't think he means military spec though, to be clear.

Marketing term. Real ruggedized items use terms such as "IP68" or "MIL-STD 810G".[1]

[1] https://www.milesdata.com/blog/ruggedness-defined-understand...

In this case, olive color and ribs.

Sidebar: If you scroll down on Android the address bar disappears as expected (which can cause lots of problems for height measurement and other effects but that's another sidebar), however if you click on the hamburger menu and scroll it doesn't, anyone know why?

This is dope. Might make one for myself...

Wonder why separate each fins? Outer frame looks like it can be printed in one go. To allow sanding after print?

They mentioned they didn't want any supports, so presumably it means single fins?

My understanding (not having used a new one) is that current RaspberryPis get pretty hot.

I’m sure it’s not as hot as a printer head (~200c) but I’d worry it might be enough on the inside of an enclosure made of lower-temp thermoplastic to cause warping.

"Yes, this is closer to a desk toy than a field computer."

That's disappointing. The boating crowd can't use this.

It's not that hard to get watertight USB connectors.

A person in the world makes a thing, shows you the thing, and even nice enough to give you enough info so you can also make the thing if you want.

Turns out the thing is not useful for something you picked out of thin air and that makes you feel disappointed? Where is this entitlement coming from? Why would it need to be useful for the boating crowd? I know a person who builds grandfather clocks. Absolutely useless on a boat. The cabinetry would warp in no time. Does that too disappoint you?

Furthermore, the nice person who shared this design now, also shared previously a real watertight design. Your boating crowd can still use that. It wasn't removed or invalidated by this newer thing at all.

> "It's not that hard to get watertight USB connectors."

I really don't understand what you are saying. Are you saying that the author should have used watertight USB connections because someone might read their post later and that someone might have a boat?

Please tell me that I'm misunderstanding what you wrote.

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