4 ms·

IIRC it's around 120W printing something like PLA. Obviously higher when heating (pretty much maxes out the PSU), and higher steady state when printing other po

IIRC it's around 120W printing something like PLA. Obviously higher when heating (pretty much maxes out the PSU), and higher steady state when printing other polymers.

justinclift 6y ago
Is that a measured amount, or a guess based upon the heating element? Asking because if it's a guess, then the electronics + stepper motors need to be factored in too. :)
- sgtnoodle 6y ago
  Can't you just look at the power supply ratings? For example, 20A*12V would be 240W. Assume 80% efficiency, so 300W on the 120V side. Seems reasonable for an UPS designed to power a desktop.
  - walrus01 6y ago
    You can if you want an absolute maximum of what the thing can draw as a load, it'll be labeled, but very often the real world use of a thing with an AC to DC power supply is a very different wattage figure from what the power supply is theoretically capable of. Such as having an ATX midtower size 'gaming' desktop PC with an 850W power supply, that might be measured at 350W at the wall under full CPU+GPU benchmark load.
    - sgtnoodle 6y ago
      Right, so if your max rated load is below your UPS's capability, it should work with plenty of margin and you can stop worrying about it. If your max rated load is higher than your UPS's capability, then you can either analyze the actual load more to see if it still works, or just buy a beefier UPS.
  - abstract_put 6y ago
    There's a dramatic difference between max draw and how much energy it takes to keep everything at a given temperature. Particularly so if heating the bed to a high temperature for ABS or PC or whatever. Looking at the power supply rating you could easily be 2-3 times the average real power consumption, which is a big deal if you're trying to use battery back up.
    - sgtnoodle 6y ago
      Yes I agree with you? You need to size your battery supply to meet both peak power and overall energy needs. Generally when folk express concern about running random equipment on an UPS, they are concerned about peak power rather than energy capacity. I'll also make the claim that most hobby grade 3D printers come with power supplies that are barely adequately rated for the printer's peak power, so using the supply's rating is probably in the right ballpark. Edit: ah, I interpreted the thread a bit differently. Ignoring the UPS rating aspect, yeah the average power draw will likely be a fraction of the peak. My guess would be around 100W total for most Prusa style printers printing PLA. The stepper motor draw would be highly dependent on the speed of the print and the shape of the part, since power draw will be highest when accelerating at higher speeds.
      - walrus01 6y ago
        For a UPS you want to know both the max wattage of the load, as what % of the total output that the UPS's inverter can put out at any given time, and also the nominal steady-state watts so that you can calculate the Watt-hours, which is what will determine runtime on a given battery size. If you have a UPS with, for example, 4 x 12V 8Ah AGM batteries, it has a certain amount of Wh you can realistically use before you deep-discharge the batteries into severe damage.
        sgtnoodle 6y ago
        Indeed. Depending on the intended use of the UPS though, the energy capacity might not matter all that much. For a 3D printer, it seems like an UPS would be in place to weather the occasional hiccup in utility power. Utility power interruptions seem inherently bimodal. Either it glitches out for a few seconds and comes back, or it's out for hours. Pretty much any UPS will have enough energy to run a 3D printer for a few seconds or minutes, but very few UPSes exist that would run one for hours on end. Taking that use case to the extreme, maybe someone lives in an area with very unreliable utility power. They might absolutely need to have enough energy stored to run their 3D printer for an entire print. Maybe they solve that with lots of batteries, but in many places with unreliable utility power, it's more likely they're just going to fire up a gas powered generator whenever the power goes out. Once again, the UPS only needs to last long enough for someone to notice and fire up the generator. Folk certainly might have more exotic use cases. Maybe someone lives completely off-grid and powers their 3D printer off of solar panels, and a generator isn't a sustainable option. They'll definitely be more interested in energy capacity. The power capacity seems important no matter what, since exceeding it will either result in a voltage brownout, tripping of a protection circuit, or melting something.
- abstract_put 6y ago
  It was a measured amount at the outlet with a Kill a Watt style device, so including electronics, stepper motors, and PSU inefficiency. That said, I did it a year ago so I could easily be misremembering. I'm pretty confident it was < 150W printing PLA ~215°C with a 60°C bed.
  - a254613e 6y ago
    Yup, that's pretty consistent with my measurements. 210/60 temperatures: https://i.imgur.com/i1L5rwo.png https://i.imgur.com/i1L5rwo.png Prusa MK3S, with enclosure.
  - justinclift 6y ago
    Cool, that's good info then. :)

IIRC it's around 120W printing something like PLA. Obviously higher when heating (pretty much maxes out the PSU), and higher steady state when printing other polymers.

justinclift 6y ago

Is that a measured amount, or a guess based upon the heating element? Asking because if it's a guess, then the electronics + stepper motors need to be factored in too. :)

sgtnoodle 6y ago
Can't you just look at the power supply ratings? For example, 20A*12V would be 240W. Assume 80% efficiency, so 300W on the 120V side. Seems reasonable for an UPS designed to power a desktop.
- walrus01 6y ago
  You can if you want an absolute maximum of what the thing can draw as a load, it'll be labeled, but very often the real world use of a thing with an AC to DC power supply is a very different wattage figure from what the power supply is theoretically capable of. Such as having an ATX midtower size 'gaming' desktop PC with an 850W power supply, that might be measured at 350W at the wall under full CPU+GPU benchmark load.
  - sgtnoodle 6y ago
    Right, so if your max rated load is below your UPS's capability, it should work with plenty of margin and you can stop worrying about it. If your max rated load is higher than your UPS's capability, then you can either analyze the actual load more to see if it still works, or just buy a beefier UPS.
- abstract_put 6y ago
  There's a dramatic difference between max draw and how much energy it takes to keep everything at a given temperature. Particularly so if heating the bed to a high temperature for ABS or PC or whatever. Looking at the power supply rating you could easily be 2-3 times the average real power consumption, which is a big deal if you're trying to use battery back up.
  - sgtnoodle 6y ago
    Yes I agree with you? You need to size your battery supply to meet both peak power and overall energy needs. Generally when folk express concern about running random equipment on an UPS, they are concerned about peak power rather than energy capacity. I'll also make the claim that most hobby grade 3D printers come with power supplies that are barely adequately rated for the printer's peak power, so using the supply's rating is probably in the right ballpark. Edit: ah, I interpreted the thread a bit differently. Ignoring the UPS rating aspect, yeah the average power draw will likely be a fraction of the peak. My guess would be around 100W total for most Prusa style printers printing PLA. The stepper motor draw would be highly dependent on the speed of the print and the shape of the part, since power draw will be highest when accelerating at higher speeds.
    - walrus01 6y ago
      For a UPS you want to know both the max wattage of the load, as what % of the total output that the UPS's inverter can put out at any given time, and also the nominal steady-state watts so that you can calculate the Watt-hours, which is what will determine runtime on a given battery size. If you have a UPS with, for example, 4 x 12V 8Ah AGM batteries, it has a certain amount of Wh you can realistically use before you deep-discharge the batteries into severe damage.
      - sgtnoodle 6y ago
        Indeed. Depending on the intended use of the UPS though, the energy capacity might not matter all that much. For a 3D printer, it seems like an UPS would be in place to weather the occasional hiccup in utility power. Utility power interruptions seem inherently bimodal. Either it glitches out for a few seconds and comes back, or it's out for hours. Pretty much any UPS will have enough energy to run a 3D printer for a few seconds or minutes, but very few UPSes exist that would run one for hours on end. Taking that use case to the extreme, maybe someone lives in an area with very unreliable utility power. They might absolutely need to have enough energy stored to run their 3D printer for an entire print. Maybe they solve that with lots of batteries, but in many places with unreliable utility power, it's more likely they're just going to fire up a gas powered generator whenever the power goes out. Once again, the UPS only needs to last long enough for someone to notice and fire up the generator. Folk certainly might have more exotic use cases. Maybe someone lives completely off-grid and powers their 3D printer off of solar panels, and a generator isn't a sustainable option. They'll definitely be more interested in energy capacity. The power capacity seems important no matter what, since exceeding it will either result in a voltage brownout, tripping of a protection circuit, or melting something.
abstract_put 6y ago
It was a measured amount at the outlet with a Kill a Watt style device, so including electronics, stepper motors, and PSU inefficiency. That said, I did it a year ago so I could easily be misremembering. I'm pretty confident it was < 150W printing PLA ~215°C with a 60°C bed.
- a254613e 6y ago
  Yup, that's pretty consistent with my measurements. 210/60 temperatures: https://i.imgur.com/i1L5rwo.png https://i.imgur.com/i1L5rwo.png Prusa MK3S, with enclosure.
- justinclift 6y ago
  Cool, that's good info then. :)