Very bad Onyx heating (max 80°C)

[cambo3d]

Did you combine three or more of the 12 volt wires for the heat bed and its still not giving you enough juice?.

Yes, I did. The voltage drop in the wires is negligible. The problem is, that you will never get more power out of this bed, if you work only with 12V.

The reason why hackneys heats up quicker, is that his power supply holds a consistent voltage under load which helps maintain the amount of current flow needed to get the bed up to temp.

Not really the reason. The most im portant thing is, that his supply can be adjusted to deliver 15V.

ATX spec allows a drop down to 11.40V, but that's it, what this standard supply could drop, until it has to shut down.


use a different power supply! A drop in voltage ,even though looks small; effects effects how much current will flow through the onyx. 12v power supplies are actually 13.5-13.8 volts.
ATX power supplies are not the best choice for this type of application.

[aehM_Key]

Please review your post and quote properly.
I think you can not generalize on the output voltage of power supplies.

Has I wrote earlier in this thread, have I already ordered a 24V supply.

[cambo3d]

Please review your post and quote properly.
I think you can not generalize on the output voltage of power supplies.

Has I wrote earlier in this thread, have I already ordered a 24V supply.

that's a fact buddy.

[aehM_Key]

Well, if every

12v power supplies are actually 13.5-13.8 volts.

a fact for you is, than you're probably an expert in this field and I should listen to you

[cambo3d]

well you dont have to listen to me, that's your choice you can look this information up yourself.

[aehM_Key]

Ok, I'll immediately start investigating the user manuals and data sheets of all 12V power supplies on planet earth

Problem solved, back to topic.

[cambo3d]

lol.. have fun ok I'm just trying to help.

[aehM_Key]

I'm just trying to help.

Me too. I'm trying to explain to you, that there are several 12V power supplies on the market which do not have 13.5..13.8V output.
Maybe you haven't had such ones, but this doesn't mean, that there are none on the market.

[cambo3d]

ok I understand that, I never said that there were none out there. I said atx power supplies aren't the best choice for this application.

another thing too, if you switch to 24v for your heatbed, your going to need 20amps alone just to operate the heatbed. the led on the heatbed is also another thing to look at. Your going to obviously burn it out at 24v when it was designed for 12v.

[mhackney]

Let me start with the backstory, when I first installed the Onyx it was heating up very quickly - sub 2 minutes to 90°C. Then I removed it, resoldered the power leads so they "bend back" the opposite direction to route nicer through the slot in the base. I noticed that it took a little longer to heat - maybe 3 - 4 minutes but didn't really think anything of it. Then this thread got started as well as other Onyx discussions and I measured my voltage, etc. But I was perplexed why it was taking longer than original. I went back and looked at a screen shot of the heat curve and sure enough it was heating nearly twice as fast back then.

So, tonight I removed the Onyx and what do you think I found? Well, actually nothing - I like suspense. However, I decided to solder a third wire to each of the leads. So now I have three 18 gauge wires running from (+) and three from (-). I also made sure the connection at the connector was nice and tight. Then, for grins, I tuned my power supply down to 12.0 volts to see what would happen. The results are astonishing! I just took a screenshot with my clock/calendar overlaying the temperature curve display so you can see there are no shenanigans...

I am getting heat up to 90°C in 2 minutes and 15 seconds with my 12 volt 30 amp supply!

and as if that isn't enough, I kicked it up to 110°C to see what would happen.

As you can see, about another minute and a half and I reached 110°C.

Now I am not suggesting your results with the stock supply will be similar BUT I would highly recommend trying three 18 gauge wires to each terminal to make sure you are getting full current!

[cambo3d]

that's a good point to bring up also,

make sure the gauge of the wire going from the rambo to the heatbed is enough to handle the current your running. If you have a thicker gauge wire it definitely would not hurt.

If your worrying about being able to keep your bed level. I suggest use silicone wire vs regular hook up wire. It is more flexible and will conform better in tight spaces. example here http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXKX17

[mhackney]

In fact, I had learned long ago that 18 gauge wire was good to carry 16 amps. However, a quick google turned up this:

http://www.powerstream.com/Wire_Size.htm

scroll down to the chart. 16 amps for chassis wiring - 2.3 amps for power transmission. So some calculations:

Onyx: 1.3Ω
Supply: 12 volts

I = V/R = 12/1.3 = 9.23 amps

So, two 18 gauge wires are probably not enough. Three are better but still below maximum current requirements. I have not noticed any heating in these wires in operation so I presume the 2.3 amps is probably very conservative.

[Polygonhell]

I have not noticed any heating in these wires in operation so I presume the 2.3 amps is probably very conservative.

The 2.3Amps is for power transmission which is really LONG runs of wire, not something inside a box.
As I mention in your build thread having said that it does make a difference.

[theverant]

Now I am not suggesting your results with the stock supply will be similar BUT I would highly recommend trying three 18 gauge wires to each terminal to make sure you are getting full current!

I have two 14 gauge wires and get nowhere handy to that performance. While my heating times seem slightly better than some others posting on here, they are still pretty darn slow compared to yours and and this point I would definitely like to upgrade my power supply. What are you using for a switch on yours? Also, how are you hooking things up to it? I believe the one you posted here previously was similar to this one:

[img]http://www.jewelrywhsle.com/hkesupplier ... etal-2.jpg[/img]

12v / 30A
What are the -V, N, and L connections for? Do you use just a regular light switch to control power in?

[mhackney]

theverant, if you don't know what -V, N and L are, I strongly suggest you do some research and reading before mucking with electricity. No offense, but this can be dangerous if you are unsure of what you are doing.

The ground symbol, N and L are for the AC connection to mains. You ABSOLUTELY MUST UNDERSTAND what these mean and how to connect them. Google it, you'll find what you need.

The +V is positive and -V is negative for the 12volt output. Since the RAMBo has three 12 volt input connectors along its side, I used one of each of the three 12 volt pairs (+ and -) to each RAMBo connector.

You certainly could use a standard AC light switch. I have a lighted AC double pole switch to disconnect both the N and L lines when off. These are standard fair at electronics suppliers. But, PLEASE make sure you know what you are doing. If you only switch one line (single pole) and don't do the correct one, you can get zapped/electrocuted even when the switch is "off".

The +V ADJ dial at the left is where you can crank up the output volts. Also, DO CHECK the AC Input switch - usually on the side - tpo make sure it is set to your local mains (NA is 120VAC).

Cheers and please be careful!

[theverant]

Cheers and please be careful!

Hey no offense taken, we're all looking out for each other here. I have no intention on plugging anything into mains until I have a firm grasp on the workings. I will definitely read up, but thanks for the info to get me started.

[theverant]

I was salvaging a fan off an old IDE enclosure and saw the plug/switch... looks like a good combo for that 12v/30A power supply, eh? The switch is rated up to 12A, and that power supply draws only <7A.

Also, for other curious about setting up this power supply - Youtube to the rescue. (this is not my video)
http://www.youtube.com/watch?v=x-m1jsqIOPs

[joshccna]

Hey folks, I measured the output on my 12 V 30 amp supply and it is actually putting out 15volts - there is an adjustment to tune output and this one was set to it's max out of the box. The other 4 were not. This one also was set to 230VAC out of the box whereas the others were set to 120V.

So some thoughts - I am actually getting a possible 173 Watts output to the heated bed. That's about 56% more power. The other thing is, are you sure you are getting 9.2 AMPS/12V to your heated bed?

I have ordered a 24V 14.6Amp supply which should give me about 277 Watts to try out on the MAX. It should be here the first week of March and I'll report back.

cheers,
Michael

Where is the adjustment?

[mhackney]

Not all supplies will have this. Mine is on the back plane to the far left.

[computerguru]

After just having assembled my Rostock Max and having issues getting the heating bed past 80 degrees Celsius, I found this thread.

Being the kind of person that goes overkill, I disassembled the hot plate assembly and (very carefully) soldered 12 awg solid core wire I had left over from some electrical work on my house. With the 18 awg...it would take about 20 minutes to heat up to 55 degrees. With the 12 awg wire, it was at 80 degrees within 20 minutes, and after 35 minutes it's now at 94.6 degrees and climbing (slowly.)

I wouldn't recommend using solid core (very hard to work with in the narrow confines of the Rostock), but I can attest that higher gauge/multiple wires definitely helps.

[aehM_Key]

I'm running mine now at 125°C (real 110°C), so this was not really an option for me. But it's a good advice for those, who don't need such high temperatures.

[Eaglezsoar]

I'm running mine now at 125°C (real 110°C), so this was not really an option for me. But it's a good advice for those, who don't need such high temperatures.

You are running yours on 24v, is that correct?

[aehM_Key]

23V actually

Have a look at my upgrades: http://forum.seemecnc.com/viewtopic.php ... 289&p=7094

[dbarrans]

OK, I just got mine cranked up last night with a new 12v 30a power supply. The short answer is it still takes a long time to heat up the bed, so it must not be the supply, unless it's the voltage.

Here are the details:
14 gauge stranded wire from the inlet to the power supply.
12 gauge stranded wire from the power supply to the heated bed pins on the RAMBo.
12 gauge stranded wire from the RAMBo to the Onyx.
1/8" aluminum plate and 1/8" borosilicate glass on top of the Onyx.
12.4 volts measured at the power supply, and at the Onyx.

With all this, it still took 15 minutes to get the bed from 17 degrees C up to 60 degrees C.

The only things left I can think of to try are cranking the voltage up to 15v, or try different firmware. Any other ideas, short of going to 24v?

On a positive note, the aluminum plate does a great job of evening out the temp. When the center was at 60, the edges were about 58.

- dan

[aehM_Key]

The short answer is it still takes a long time to heat up the bed, so it must not be the supply, unless it's the voltage.

Well, this is what I posted in the 3d post of this thread.

Yes, go for 15V, it will speed up. Firmware will not help at all.