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.
I’ve been really happy with the MK4 kit I built months ago. While I haven’t seen a Bambu in person, I’m pretty satisfied with the print speed and picked up an 0.6 nozzle in case I really want to print something bigger, faster.
I had seriously considered building a Voron Trident, but have no regrets about my decision to go with Prusa. It’s nice having a machine that didn’t require a bunch of tweaking; it was fun to build the kit but now it’s an appliance I don’t have to mess with; it’s almost like my Brother laser. I hit print, it prints*. (Asterisk because I have to clean the bed sometimes, occasionally I make a poor choice slicing and don’t add a support I needed, etc, but these aren’t printer-specific issues).
As far as bed-slinger vs coreXY, even Bambu recently released a new bed slinger, so I suspect the tradeoff is more complex than just “coreXY is better”. The whole “model flings around” just isn’t a problem I’ve seen in practice; maaaaaybe if you’re building exceptionally tall, thin structures that can’t be oriented properly it could matter but realistically most people are going to mostly print relatively small things. Even fast printers are slow; as soon as you use a printer you’ll realize that huge build volumes are absurd because big prints just take soooooooo loooooong even on fast machines. And there’s either upcoming support or existing support for bed-axis input shaping, since the slicer does know the amount of filament it’s extruding and can tell the firmware how much more the bed weighs as the print proceeds.
I don’t think Bambu printers are an unreasonable choice for people, but I think if Prusa is affordable to someone, their products are still a good choice.
It’d be interesting to see what it looked like in the slicer, just in case it’s obvious there.
And yeah, each new FreeCAD project I do builds on what I’ve learned and it gets easier to get better results.
Did you print the foot switch upside down and then flip it? If so, how does its other side look?
I can’t tell how the surface quality is by the knobs.
Your “main” top surface looks like under-extrusion.
It’s interesting that previously you said bacteria and now you say plastic. You know a lot, so enlighten the rest of us. What’s the concern here? As others have pointed out, coffee hoppers are rarely cleaned by most people, and this never gets wet and mostly handles dry whole beans with a little bit of dry bean dust. PLA is theoretically food safe as a material itself (and used in plastic utensils and containers). What are we missing? Please explain thoroughly in a single long post, not a quip because too many of us aren’t understanding from short quips.
The 7333A is a linear regulator, which means it drops voltage by converting power to heat. Typically those make sense when the input voltage is close to the output voltage or the load is very small. If it’s getting too hot, the load is high enough that the efficiency will be very bad…whether or not this is a problem depends on your application.
Some random site claims 170mA and another claims up to 400mA. 170mA * 8.7V (12V in minus 3.3V out) = about 1.5 watts, which is too much for a TO-92 package.
Can you use a tiny buck converter instead? Or a larger package for the linear regulator that can add a small heat sink?
As for your actual circuit, the second transistor is an interesting idea (you’re using it to invert the state so you can have the GPIO pulled in the non-problematic direction?) and I don’t have enough experience to give further suggestions.
Brother laser printers are great.
Keep in mind that while the heat pump works at low temperatures, it produces less heat. Senville’s 36000BTU unit produces just 27000 BTU at 17f per AHRI. The drop in output is an important consideration when evaluating system sizing and backup/auxiliary heating.