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?).

Lower cost products sometimes have more variability and maybe you got a good one from the factory.

This is an interesting suggestion. The unsupported overhangs at the transitions are part of why I don’t like using gyroid infill; I don’t need my infill to introduce new potential problems in a print. That said, reducing layer height would be disappointing in most cases because I also don’t need my infill to slow the print down (and with some filaments, it’s also pretty visible), so the other suggestions might be more difficult-but better-ideas. It’d be cool to try a patch someone submits.

Did they describe the types of user error that could cause this?

Or too thin (much less than one layer height)?

It’s not necessarily fluff; features do matter, but which ones matter and how much they matter is complicated. Do you want to tinker with a printer, or do you just want a tool that works?

If you want a tool, I recommend a Prusa or maybe a Bambu. My Prusa just does what I ask it to; I’ve done zero calibration, optimization, tweaking, etc. Cheaper printers often require understanding bed leveling, figuring out how to adjust them best, etc. or vary more copy-to-copy (so one Ender 3 might work great, while another might be a source of frustration) or require upgrades to really become enjoyable.

Do you have a budget? Or is it just about making sure you’re getting your money’s worth (so $2000 is fine if it’s 10x better than a $200 printer)?

Yup. My kid found the idea hilarious when I explained why I’d swiped a washable glue stick from the arts and crafts box.

It hangs on well, but also makes removal easier.

You could always try it…

I use PEI instead of glass and find that a thin layer of glue stick works great for helping sticky materials release.

Could you share some examples of what you’ve been able to create, and approximately how long they took?

Do I just connect thermal pads to the ground plane and call it a day?

Yup.

Wouldn’t that make the components hard to solder with hot air?

Sorry, I’ve never tried hot air assembly.

Do I make an isolated polygon that only acts as a thermal pad?

Ideally the copper area is big to spread out the heat. If you have an isolated polygon it can’t spread very far and buys you less cooling.

Wow, thanks for the incredibly broad write up! That’s a crazy number of tools to try.

FreeCAD:

giving up as soon as any two edges’ fillets touch

I haven’t quite had that issue with FreeCAD; an ordinary corner works fine. Where I’ve had that issue is when the fillet is large relative to the edge sizes though, so there are definitely failure cases.

not working well if you don’t learn its definition of good design

This is so incredibly true. I’ve had to restart projects because I didn’t realize how I’d need to approach them to get FreeCAD to allow me to do what I wanted to do. That’s probably the biggest issue I have with it: you really have to know how it wants things done, and often you won’t learn that til you’ve tried, failed, and watched a couple YouTube videos from more experienced users. Fortunately, after a few projects I’ve gotten to the point where I can usually get relatively simple designs right the first time…but I have no doubt I’ll still sometimes have to start over or take big steps backward to change my approach to a problem.

Others have mentioned OpenSCAD and that’s what I started with years ago; it’s fine for simple things (or fractals/programmatically specified forms) but when designing something with more complexity I find it very difficult to manage, compared to just directly drawing what I want and then constraining it appropriately.

You’re right, 50%@70f (let’s say Texas indoor conditions) is 19%@100f, so you’re right that just heating is probably perfectly good.

You’d need a very sensitive filament to bother doing more. That said, if you did have a peltier with the cold side at 32f, you’d get 25%@70f or 9%@100f…which actually isn’t amazing since you still need to warm it up to 100f to get that 9%! Peltiers are inexpensive and I might still experiment with it one day, but…it doesn’t seem like a huge win.

I see. You have a huge delta-T there, which is unnecessary for keeping a filament box dry.

A couple sources say PA6 (a random moisture-sensitive filament) should be stored below 20% , or at 15% relative humidity. In a 66f/19c room temperature, that 15% RH would be a dew point of 17f/-8c according to dpcalc.org. In a 74f/23c room, 15% is a dew point of 23f/-5c; as you warm up the temperature further the dew point to achieve a particular RH increases (which is why we heat air to dry things).

Huh? Running it backward as a thermoelectric generator is low efficiency (Carnot limit) but the efficiency pumping heat from e.g. freezing to room temperature isn’t that awful. Picking some completely random model from DigiKey, if the hot side was at 27c/80f, and you wanted the cold side at 0c, 2.4 amps at about 7V (16.8W input power) would let you remove about 15W from the cold side with a deltaT of 30c (i.e. the cold side at -3c/27f) per the graphs on page 5. That’s a COP of about 0.9 for cooling. You’d need to remove about 30W from the hot side.

In practice, cooling the hot side is difficult so you might instead use the Th=50c graph, at which point 2.4A @ 8v (19.2W input power) would give 3-4W cooling power with the cold side at 0c, for a COP of about 0.18. But nowhere near your numbers.

If you put some decent thermal mass on the hot side and operated intermittently, as long as you drained the condensation, you could get closer to the Th=27c performance.

I don’t think the efficiency is a big deal; you’d only have to run the peltier intermittently (e.g. each time you open the box) as long as you can drain the condensation somehow and it’s otherwise well-sealed. I’ve idly pondered OPs idea myself and I think it’s not a terrible way to dry a box. You avoid the consumables or need to recharge your dessicant materials.

One other thing that occurred to me is squish. Just like your first layer issues, the plastic on every layer needs something beneath it to squeeze against so it converts from a circular tube to a flat, wide oval. Maybe your slicing didn’t have enough support or infill in the main body as compare to the final top surface? You could try increasing the horizontal shells.

By the way, I assume you did not turn on ironing, because that could also affect the surfaces differently if one got ironed and the other didn’t for some reason.