upgrade heater bed power supply

[jestah]

Hi guys,

After installing my own heat spreader (6mm al. plate) I can not get it hot enough to print ABS. The heat tho is far more even and I want to keep it as it seems to be the best way to get even BIG prints.

Should I open the stock PSU and wire some heavy gauge wire directly to the 12v output or is it worth upgrading to a second PSU?

I see that 12v SMPS turned up to 15v work well an some people are running 24v SMPS. What is better as I have also read that the heater bed is not designed for 24v.

I measured my bed and it has 1-1.1 ohms resistance so with a 15v supply would a 15A give enough head room ? Can I run the Rambo on the same 15v supply?

If I go for a 24v supply and wind it back a little should 20A be enough (this was based on being able to wind it back to 21v which I am not sure is possible) ?

Can any one recommend a good seller on ebay for me to order a psu from?

Many thanks and can't wait to get printing without a 30min warm up!

[barnett]

I've got an aluminum plate on the onyx and I think it's 15-20 min to get to 80C (thermocouple measured).

I saw John & Steve at the Kansas City Maker Faire this weekend and John suggested running extra yellow/black wires from the stock PSU to the Rambo power input that supplies power for the heated bed. I think it was the pair closest to the corner of the Rambo.

I haven't tried it yet, but that was his advice.

[September]

I've been thinking the same... as in to upgrade the amount of amps to the hotbed to make it quicker.

Looking a the Onyx wiki it's draws around 10A, unfortunately I didn't read the power supply (the default one supplied with the Rostock MAX complete kit) to see what kind of AMPs are available to the 12VDC lines.

Following Genes assembly guide he recommends joining 4x12VDC lines together, which I have done, just not sure what each of them is rated for as to know whether it would help adding an extra line. If I was over drawing I would have blown the power supply, so I guess there must some to spare and I need to be more patient... Also it's Winter here which doesn't help.

Either way I think it will only draw a max 10A, so if it already has 10A available, no point adding more.

Perhaps someone with better Electrical knowledge can confirm.

[barnett]

ahh ok I didn't know gene had that tip in the manual. Several people have used a separate PSU for the heated bed.

[Jimustanguitar]

On the inside of the power supply, all of the yellow wires are connected to the same place. By increasing the number of wires going to the bed, you're reducing the resistance slightly by creating a larger gauge of wire. This doesn't magically unlock more electricity, it just matches the wire gauge to the current draw that you're putting on it and keeps the wires from being the weakest link in the chain. Wires that are too small will heat up, and when things heat up, their resistance usually increases...

Make sure that you use the same number of black ground wires as you do yellow power wires.

[jesse]

It's possible to make the heated bed hotter by using insulation while it's heating.

http://forum.seemecnc.com/viewtopic.php ... =10#p14809

[September]

Yeah he recommends it for the Onxy hotbeds, you'll find it on pg 95, of the PDF 2nd Ed, v1.07 18th June 2013, joining four blacks and yellows in parallel, this keeps the VDC at 12 while decreasing the resistance.


Some power supplies have multiple rails, half my PSU have two rails each with 12VDC@40A, although if your power supply is under 500W it's fairly safe to say it only has a single 12VDC rail.



Anyway personally I wouldn't try pushing it past it's ratings unless I was prepared to replace the parts and I wouldn't trust it unoccupied in case things started over heating to the point of a possible electrical fire.

[kbob]

Put a meter on the two big solder contacts on the Onyx while it's heating at 100%. See how close it is to 12V. Put a meter on two other 12V outputs far from the Onyx, see whether it's any more. There will be some voltage drop through the wiring and some voltage sag in the power supply (I don't know how much.)

If you're running quad 18awg wires from the power supply to the RAMBo and quad wires or 14awg wire from the RAMBo to the Onyx, I would expect there to be minimal voltage drop in the wires.

But measure it and know for sure. (Then tell all of us! )

[cambo3d]

12v isn't enough to make the onyx heat faster, adding a higher amp power supply wont help.

changing the voltage will, anything from 15-24v will see a dramatic improvement.

http://forum.seemecnc.com/viewtopic.php ... =150#p7627

http://forum.seemecnc.com/viewtopic.php ... =170#p7960

[jestah]

So the plan is defiantly to get a better PSU but can some one confirm if there is any advantages to 12v turned up to 15v or a 24v turned down as low as possible.

As I have found conflicting info as to the current draw for the above to configs what current rating PSU should I be looking for on Ebay? It seems for the 15v supply I should aim for 15A+ would be enough and for the 24v I should aim for at least 20A if not more?

Sorry to re-ask questions but I would like a bit of a solid answer before spending more cash to get this printer working.

[nayaanika]

Hi my computer's SMPS is a making sound at regular intervals, how can I rectify the same. And also the sound diminishes slowly.
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