Wish power supply?!

Hi

I wanted to make a prusa mini i3 style printer with 3x nema 14 e 1x nema 17 with just one extruder and without a heated bed, but i wanted to use the smallest power supply i could. Considering using 12v wish would it be the minimun current i would need? Can anyone help me please?

Thank you in advance
Filipe

The smallest power supply you probably *should* use is a 12V 8A supply. The smallest you *could* use is in the 4A range. A lot depends on the exact current ratings on your motors, your hot end, and how hot you plan to run your hot end. A 40W 12V heater cartridge on your hot end will pull 3 1/3 A full on. For a 3.5A supply setup you probably don't want a hot end with a 40W heater. Motor size and motor current are two different things. You can find NEMW 17's that want anything from 0.4A through 2.5A per winding. You can indeed run motors at below their rated current, that's not what I would plan on when picking the supply.

What ever you pick, make sure that it is well regulated. If you are trying to run right at the limits of the supply, any "sag" in the voltage could make things very difficult.

Given that power supplies are cheap and the rest of this stuff is quite expensive - why the small supply? I'm not saying it's a bad idea, I'm just wondering what you are trying to do. There may be some other solutions.

I wanted to use a power supply as small as possible without sacrifing power so that it doesnt take much space. The nema 14 would use max 0.8A and the nema 17 1.2A, about the heater i'd probably use 40w 12v heater cartridge and probably a couple of fans as well. I tough that maybe a power supply of 12V 8.33A 100W would be enough. Also, it wouldnt consume so much energy wish is allways good...

Yep, that sound good, but remember, the power supply needs to supply at least 8.33As.

If you have a power supply that is rated to supply 500W and one that is rated to supply 200W, they both will pull exactly the same amount of power when they put out 8 amps at 12V. That assumes they both are equally efficient. In reality, the higher power supply probably is more efficient, so it actually uses slightly less power.

Size wise, you can get some *very* small supplies if you are willing to pay a bit more for them. Something that's smaller than your little motors is not all that crazy if you have the money.

The amperage (or wattage) of a power supply represents it capacity. It does not always supply all of that power - it only supplies what is consumed - but you better not consume more that it's rated for or things will begin to overheat and fuses will start to pop. If you spec your printer out to a total consumption of 8.33 Amps, obviously you need at least that much out of your power supply. I would opt for a bit of room as a safety margin; I wouldn't think it a good thing to operate your power supply at 100% 100% of the time. In this scenario, I would choose a power supply of at least 12 Amps.

By and large, the power supply does not determine the amount of energy consumed - the motors and heaters do. And they will consume the same amount of energy regardless of the power supply chosen.

If you are trying to come up with a very light weight / compact printer that's something else. A printer that's going to be carried around a lot has a number of things to worry about on it. One of them is the power supply, but it interacts with a bunch of other stuff in the design.

Thank you all for the replies, it really did not ocorred to me that what mattered where the power consuption of the parts and not the power supply itself.

I really am trying to make a more portable/compact printer and obviosly trying to save as many space i can that's way i wanted the smallest power supply i could find. But after searching for the ideal power supply that could fit into the design i am now thinking that maybe is best to get a power supply like one from xbox or something portable like that.

Once again thank you everybody and sorry for some misspells from my english.

Something like an Xbox supply is nice for carry around, since it's pretty much designed from scratch for that kind of service. It should be a 200W supply. It should work for a build without a heated bed.

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Changing things around completely - Are you *sure* you don't want a heated bed? They add very little to the size or weight of the printer. They do add 150 W to the power supply. They are *very* useful. I'm not saying that you are making the wrong decision. All I'm asking is weather you are sure or not before you buy the power supply.

Of course you *could* put a second Xbox supply just on the heated bed and only use it when you needed to. There are *many* choices.

I'm using a 450W ATX and it does struggle due to it being on the limit of amperage needed. I don't however have a load on the 5v rail, which is recommended to reduce issues.

If you can, go for a dedicated 12v supply.

Personally I'd also say go for a heated bed. You'll never be able to successfully print ABS without it (PLA on the otherhand will be ok for the most part). They are easy to set up and dont add any bulk. Soldering wise it's a case of just attaching 2 wires to a nice big hole - some people dont even bother solidering them, and instead use crocodile clips.

There's also the $20 to $30 cost of the heated bed pc board. That's not a whole lot on a full build. I've spent a lot of money based on "that next step isn't much" .....

I have been printing for some time and now i wanted to do something diferent. What i wanted was just to print pla and there for i wasn't including a heated bed to my power supply needs.

Ok, as long as you understand the choice you are making - go for it. My fear in many of these things is that people are not fully informed on all the little details. That can make coming to the right decision difficult.

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FSilvestre
I have been printing for some time and now i wanted to do something diferent. What i wanted was just to print pla and there for i wasn't including a heated bed to my power supply needs.

Can I make a suggestion? Whatever power supply you go with, make sure its got a minimum of 16A - that way if you do ever change your mind you wont need a new power supply. It wont cost you any more, and you'll probably find whichever one you pick is capable of at least 16A anyway.

Also, there may be times when PLA isn't the right material. I print 99.9% of the time with PLA, but it's not the best choice for an X carriage or for an extruder. I'm not saying you can't make it work, but based on my experiences, I'll never print an extruder or X carriage out of PLA again.

I think the OP already has a printer with a heated bed for printing a variety of things. What he is trying to do is make a compact / light weight / highly portable PLA only printer. More or less - a printer to take with you when you go visit friends.

If this is true, the big feature I would want to put on it is auto bed leveling.

That's it uncle_bob, never the less, thank you everyone for your oppinions.

About the auto bed leveling, i haven't tought about it yet but it could be a great addition to the printer, i have to recearch about it and see what i can make, thanks once again.

The auto leveling adds a few printed parts, a dirt cheap servo from your local hobby shop (or the big pile in your basement) and a microswitch. Cost, weight, and size wise it's not much at all. It's *much* nicer when you set the thing down in a new location and can print right away.