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Joined 1 year ago
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Cake day: June 17th, 2023

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  • This looks great! I’m super happy with my MK4, and have never had to do anything with it after the initial kit build and re-seating the LCD cable to fix some early screen-blanking issues.

    I’ll probably skip this for my own printer since it seems like most (but not all) of the speed up comes from layer height, but $99 is not terrible for anyone who gets value from it. And anyone buying a new printer gets this stuff with no price increase, which is nice and makes the MK4/MK4S even easier to recommend.

    I didn’t know how much more dimensionally accurate Prusa’s prints are compared to the competition, but it makes sense now why there are so many calibration models online if that just isn’t the way every printer works. I’ve designed some parts that need an 0.1mm first layer because I’ve never had any failures with that, but I guess if I share the STLs other people might have trouble.


  • I do think it’s important to be unassailable, because it’d be easy to say “the libs are making misleading claims” and then people not paying lots of attention will think there’s a “both sides” situation going on. I’m sure we all assumed it was literally on display as an exhibit; I was mislead. If you stick to transparent, honest language, the “both sides” stuff falls apart.

    The MAGAs are unreachable, but the poorly-informed are out there too, and making them easier to confuse (by actually also spewing misleading-but-technically-true things) is not a good strategy.




  • They definitely don’t know what they’re doing. They featured this one, which is a death trap. It has a disclaimer that it might not be safe above 120V, but it’s absolutely unsafe and a code violation in the US, where we use 120V (and are very litigious). The disclaimer says they’re trying to get it approved which implies they believe it could be and that the design is sound, but fundamentally it cannot meet code in the US for mains voltage use.

    Even if the design were sound, there are material requirements, and having seen the quality of prints some people find acceptable, there’s no chance allowing random people online to print their own boxes is safe.

    I think they basically run the contests and feature things based on “ooh this is neat” and “this will excite people to use 3d printers”. It’s a marketing thing, and I guess I accept it because I have low expectations of even pretty-good businesses. But if it’s illegal…someone should probably let them know.


  • I haven’t bought used myself, but based on my own experiences with my printer (MK4; I love it) I don’t think there’s a ton to worry about buying a used quality printer. I would not buy a used low-end printer because the odds are much higher that the seller found it frustrating.

    A used Prusa MK3S is probably an excellent choice if a Prusa MK4 kit is out of your budget and a Bambu printer is out of your budget or doesn’t meet your other requirements. The seller probably either realized they don’t actually print often, or upgraded to a MK4 (or XL if they had the budget). While you can upgrade a MK3S to MK4 with Prusa’s upgrade kit, the cost of the kit is so close to just buying an MK4 that it’s not worth doing (and Prusa admits this; they only offer it because of the flak they got for not doing such a kit in the past). The MK3.5 or 3.9 upgrade kits could make sense for some people…but in many cases someone looking to upgrade would likely leave the MK3S untouched and just buy an MK4.


  • Do you want the printer to be a tool, or a hobby (i.e. you don’t mind fiddling with the printer itself to improve the results, you don’t mind spending more to upgrade components, etc)?

    If the printer itself is a hobby you can go cheap, but if you want something reliable you don’t have to mess with or upgrade, I’d suggest getting something as nice as you can afford, maybe a Prusa mini or Bambu A1 mini if you don’t care about open source. Also consider something like a used Prusa Mk3.x.


  • You’re affecting the hardness of the metals if you’re heating them to glowing point, because you’re heat treating them. The actual consequence is probably minimal, but you could potentially be softening the brass tip which could affect the rate of wear. From skimming a few random online sources, brass is only work-hardened, so if the nozzle was previously hardened, you’re un-hardening it (apparently quenching from high heat only hardens ferrous metals like iron and steel?).






  • Are the test models ones that come with the printer, or models you’ve found online? If they’re from online, does the printer ship with any you could try? Something sliced by the manufacturer is most likely to work. If those fail, I’d contact customer support.

    I have no experience with resin, but is the resin coin stuck to the screen or the build plate? Are you angling the chess piece or trying to print it straight / vertical? My understanding is that resin prints need to be carefully aligned so they’ll peel of the screen, and big flat surfaces like the bottom of a chess piece won’t.



  • It’s because of the “lift to drag ratio”. Airplanes in level flight at ordinary speeds generate about 15x as much lift as drag meaning if the engine spends 1 unit of work moving the plan forward, the wings give 15 units of work* upwards. So flying level needs about 1/15th the engine power of going straight up. (I’m using “work” very sloppily here, not in a precise physics sense.)

    You can see this in sailboats too, which can travel faster than the wind when they’re sailing at an angle to the wind. Efficient boats travel faster when they’re going almost perpendicular to the wind, not straight downwind! This is because the “lift” of the sail pulling the boat forward even more strongly than the push of the wind in the downwind direction.

    While I can’t give an intuitive explanation for why this is, there’s a very easy demonstration that it’s true: kites. If a kite had a lift-to-drag ratio of 1, then it would fly at 45° up. It would fly 50 meters downwind of you when it’s 50 meters up. But any decent kite can fly at a much steeper angle than that; sometimes they look like they’re right over your head! That’s because with a lift to drag ratio of e.g. 10, the 1 unit of drag gives 10 units of lift; if it’s 10 meters downwind it will be 100 meters high.





  • Realistically, I usually stop if I see a car even if I have right of way, because I’m the one who gets hurt if they roll through. Modern cars’ A-pillars are thick and I know I’m hard to see. I only exercise my right when there aren’t cars near the intersection, or I made eye contact with the driver and they waved me through.

    But why would a driver have to know I’d treat it as yield? If they arrive first, I have to stop—same as if it were a stop sign—and if I arrive first, they have to stop: same as if it were a stop sign.

    The only difference a driver will see happens if I arrive first and don’t stop, and then they’ll either know the law and appreciate me getting out of the way faster, or not know the law and think I’m one of those aloof cyclists. But they still had to stop.