1 Topic by autoxer

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Topic: Free PSU upgrade (for computer nerds)

So my setup has always been slow, never quite figured out what it was, but the power supply always struggled too.

The provided one appeared to be under heavy load and the motor current would spike when heater shut off for a second.  Always annoyed me with it spiking around, so I pulled out an old computer PSU.  For those of us with old PCs sitting around, this is a simple upgrade.  I cut out the original 12 V supplied wires and spliced them into a yellow 12V line on a computer power pass thru cable.  The green line had to be shorted so the PSU turns on.  Really simple if you have good solder skills, but for me it took a bit.  Probably could get away with crimp connectors too.  Figured this would be common, but I didn't see too many others post it.

My basic now 12 year old PSU does 17A on the 12V line, which is plenty of current.

http://i2.photobucket.com/albums/y29/viars3/Solidoodle/PSU_connected.jpg~original
http://i2.photobucket.com/albums/y29/viars3/Solidoodle/PSU_splice_in.jpg~original
http://i2.photobucket.com/albums/y29/viars3/Solidoodle/PSU_shorted_on.jpg~original

Cooling fan would have been a lot easier to hook up if I started this way.  Might cool to make optional connectors for PSUs in the kit over taking the laptop style power supply.

2 Reply by elmoret

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Re: Free PSU upgrade (for computer nerds)

This is not such a great idea actually, as most of the wiring in the kit is 18AWG, which will happily set itself on fire at much over 16A. The included power supply shuts down at around 6.5A. Hope you added a fuse at 8A or less. This is why the ATX connector has multiple wires for +12v and ground in order to spread the current, but you're using a molex connector with a single wire for each. You should not push more than 8A through these wires, even in the event of a direct short... which means you need protection on the supply side.

Not to mention the fact that most ATX PSUs don't like unloaded 5v/3.3v rails.

EDIT: Why is there a block under the barrel? It is supposed to remain unconstrained by design.

EDIT 2: There's bare spots in your power wires! Those need to be cut and resoldered, or crimped if you aren't good at soldering.

This is another example of people not knowing their limitations and not asking for help. sad

Filastruder - the robust, inexpensive filament extruder
E3Dv6 All Metal Hotend - the premier 3D printing hotend

3 Reply by autoxer

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Re: Free PSU upgrade (for computer nerds)

elmoret wrote:

The included power supply shuts down at around 6.5A.

Shuts down or just lowers the voltage?  Most of those power supplies are very basic.

The computer PSU has some surge protections built in.  Between the surge protector strip and the PSU a short is not going to be a problem.  As far as the system, I fail to see how it could draw more current other than a short.  The heater is resistor and not likely to change, the motor may draw more current but its not like its going to drastically draw 18A.  Its already a risk melting plastic, so not sure how this changes anything.

I did this and supported the barrel because the filament was coming out wavy.  The motor was not constant because the included power supply didn't react well to the heater turning on and off.  It cause the barrel to jump, and the barrel just moved around a lot in general.  I've been thinking about mounting vertically so it doesn't matter, but I have to set something up to do that.  Most of my filament has been made this way.

4 Reply by elmoret

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Re: Free PSU upgrade (for computer nerds)

Shuts down. It has internal protection, I can film a video if you like.

A surge protector does NOT protect against a short. Furthermore, it will happily pump 15A at 120V into the load, or more if it is not equipped with a circuit breaker.

If the motor were to fail internally, it certainly could draw in excess of 18A. Electrically, what you're doing would not be deemed safe practices, but if you understand the risks, then ok.

The power supply voltage typically drops a few percent when the heater comes on. This is very audible as our ears are very sensitive to pitch, but it does not make a significant difference in RPM. If the power supply voltage is dropping more than 5%, I'd be happy to exchange it.

The barrel should not move more than a few mm in normal operation. I have made 120kg of filament, none of it wavy. Constraining the barrel will create additional wear on the auger/screw. If the barrel is moving more than a few mm, then probably the 4 bolts were not tightened enough or something else is wrong. It is also possible the filament guide is not set up properly, if wavy filament is an issue. Your block under the barrel may be hiding this by moving the nozzle relative to the filament guide.

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5 Reply by autoxer

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Re: Free PSU upgrade (for computer nerds)

elmoret wrote:

Shuts down. It has internal protection, I can film a video if you like.

A surge protector does NOT protect against a short. Furthermore, it will happily pump 15A at 120V into the load, or more if it is not equipped with a circuit breaker.

Well I'm pretty sure between the circuit breaker, surge protector, GFCI, and internal power supply protections, something will stop a short.  I don't exactly want to test it.  It could draw more current, but drastic failures would probably be a surge or a short.


elmoret wrote:

The barrel should not move more than a few mm in normal operation. I have made 120kg of filament, none of it wavy. Constraining the barrel will create additional wear on the auger/screw. If the barrel is moving more than a few mm, then probably the 4 bolts were not tightened enough or something else is wrong. It is also possible the filament guide is not set up properly, if wavy filament is an issue. Your block under the barrel may be hiding this by moving the nozzle relative to the filament guide.

Mine was moving a good 1/4" or more under load.  I took the thing apart a few times and put it back together trying to figure it out and it only seemed to occur once it was loaded up.  The bolts are very tight.  There was plenty of clearance and it spun fine with nothing.  I tried supporting it similar to this:
http://www.thingiverse.com/thing:298429

Nothing worked so I took the braces like that off and supported the barrel.  Now the board the thrust thing is attached to moves a tiny amount and the barrel is still.  Since it started making good filament I stopped messing with it.