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Hey guys,

I've had a little search but haven't been able to come up with an answer.

I'm running the standard power supply set up as per the manual and on 230VAC. My heated bed takes about 25 minutes to get to 80 degrees C and will not go higher than 84. I guess this is not normal? What do you think I could check to speed it back up?

Any help would be great.

Thanks,

First check that the wires going to the heated bed are not heating up too much. Or that your boards connections are not heating up.

Secondly if you have a voltage meter check the psu voltage. It could not be delivering enough current. (You should ideally chec psu output, rambo input, rambo bed output, and the bed itself).

Thanks mate will give that a go.

teoman wrote:First check that the wires going to the heated bed are not heating up too much. Or that your boards connections are not heating up.

Secondly if you have a voltage meter check the psu voltage. It could not be delivering enough current. (You should ideally chec psu output, rambo input, rambo bed output, and the bed itself).

What would you consider to be an acceptable voltage while heating? I'm seeing 11.4V which I believe is lower than it should be...

VAXHeadroom wrote:

teoman wrote:First check that the wires going to the heated bed are not heating up too much. Or that your boards connections are not heating up.

Secondly if you have a voltage meter check the psu voltage. It could not be delivering enough current. (You should ideally chec psu output, rambo input, rambo bed output, and the bed itself).

What would you consider to be an acceptable voltage while heating? I'm seeing 11.4V which I believe is lower than it should be...

Anything below 12 volts will slow your heating considerably, maybe even limit top temperature.
Did you measure psu output without bed heating? I would bet it is over 12 volt... but drops under load. Those inexpensive computer psu's do that.
I find putting a load resistor across one of the 5 volt outputs makes the 12 volt put out higher voltage AND not drop so much under load.
Auto parts stores often have them for LED turn signals.
Like this http://www.amazon.com/Resistors-Signal- ... sistor+kit
It will get warm, so fasten it to the grate on psu so air blows over it.

You may want to consider installing a higher quality psu.
Total wattage is not the most important, the amps available on +12 volt rail is what is important.
I have a SeeMeCNC supplied 450 watt Viotek psu +12v is 22A
I run a Silverstone #SST-ST45SF-G 450 watt psu, it's +12 volt is 37A
It is a bit pricey, partly since it is small form factor and modular wiring. They make full size non modular for a bit less money.

Putting a folded towel over bed helps it heat quicker. Just remember to remove it before print starts!

The reason why i stress over the wires and connectors heating up is that if you have made a poor connection, that adds another resistance. And just like the bed it starts heating up so you can melt some of the connectors there.

bvandiepenbos wrote:

VAXHeadroom wrote:

teoman wrote:First check that the wires going to the heated bed are not heating up too much. Or that your boards connections are not heating up.

Secondly if you have a voltage meter check the psu voltage. It could not be delivering enough current. (You should ideally chec psu output, rambo input, rambo bed output, and the bed itself).

What would you consider to be an acceptable voltage while heating? I'm seeing 11.4V which I believe is lower than it should be...

Anything below 12 volts will slow your heating considerably, maybe even limit top temperature.
Did you measure psu output without bed heating? I would bet it is over 12 volt... but drops under load. Those inexpensive computer psu's do that.
I find putting a load resistor across one of the 5 volt outputs makes the 12 volt put out higher voltage AND not drop so much under load.
Auto parts stores often have them for LED turn signals.
Like this http://www.amazon.com/Resistors-Signal- ... sistor+kit
It will get warm, so fasten it to the grate on psu so air blows over it.

You may want to consider installing a higher quality psu.
Total wattage is not the most important, the amps available on +12 volt rail is what is important.
I have a SeeMeCNC supplied 450 watt Viotek psu +12v is 22A
I run a Silverstone #SST-ST45SF-G 450 watt psu, it's +12 volt is 37A
It is a bit pricey, partly since it is small form factor and modular wiring. They make full size non modular for a bit less money.

Putting a folded towel over bed helps it heat quicker. Just remember to remove it before print starts!

I posted my voltages in the thread I started describing the PSU shutting off while heating (as low as 11.3V while both heaters are on full):

http://forum.seemecnc.com/viewtopic.php?f=77&t=8625

Power supply is junk, save yourself a bunch of headaches and replace it.

Also like others said make sure wires are making good connections.

Resistance... wiring...
I remember reading somewhere that the hotend wires shouldn't be soldered, but can't recall why.
Could someone explain this please?

I'm using XT60, and they need to be soldered.

You should not solder the wires to the resistors of the hotend because they get hot and melt the solder.


You should not solder the ends of your wires to make them nice and tidy (the parts that screw in to the connectors of the rambo) because then they do not crush at all. The crushing of multiple strands of copper compared to one single solder covered strand increases the surface are for electrical contact lowering the resistance (so it heats up less). And when you have more contact any heat that is generated is transferred through the wire away from the connector.

The XT60 connectors won't get hot enough to melt the solder, so you're fine there.

g.

bvandiepenbos wrote:Power supply is junk, save yourself a bunch of headaches and replace it.

Also like others said make sure wires are making good connections.

How's this look? (12v 50A switching supply)

http://pages.ebay.com/link/?nav=item.vi ... 98&alt=web

Thanks guys.

VAXHeadroom wrote:

bvandiepenbos wrote:Power supply is junk, save yourself a bunch of headaches and replace it.

Also like others said make sure wires are making good connections.

How's this look? (12v 50A switching supply)

http://pages.ebay.com/link/?nav=item.vi ... 98&alt=web

VAX, but your actual PSU is shutting down right? The stock viotek shouldn't do that. Take more time, yes; but not shut down.
You have another problem there. I don't think a more powerful PSU will fix your issue.

Tincho85 wrote:Thanks guys.

VAXHeadroom wrote:

bvandiepenbos wrote:Power supply is junk, save yourself a bunch of headaches and replace it.

Also like others said make sure wires are making good connections.

How's this look? (12v 50A switching supply)

http://pages.ebay.com/link/?nav=item.vi ... 98&alt=web

VAX, but your actual PSU is shutting down right? The stock viotek shouldn't do that. Take more time, yes; but not shut down.
You have another problem there. I don't think a more powerful PSU will fix your issue.

Sorry for the slow reply.
SeeMeCNC (through Matterhackers where I bought the V2) replaced the PS and I'm running again.
I think the key is to remove the back panels - there's a hole in the bottom place, presumably for air intake to the PS, but the PS has the fan on the top! I think they changed power supplies and the shell design didn't change. Since the fan is now on the top, it will pull in hot air from under the heated bed unless the outside 2 hard back covers are removed (which mine now are!)

The fan has always been located on the top of the ATX power supply. AFAIK, they're ALL like that. (Standards'll do that to you...)

g.

geneb wrote:The fan has always been located on the top of the ATX power supply. AFAIK, they're ALL like that. (Standards'll do that to you...)

g.

OK I buy that ... but then why the big square hole in the bottom plate? Sure looks like it would fit the fan...

Engineered to replace the power supply without dismantling the entire base.

KAS wrote:Engineered to replace the power supply without dismantling the entire base.

Bingo.

g.

Assuming it's just he PSU, I was in a similar position and I was able to replace the stock PSU with a larger one (1300W EVGA, that doesn't drop below 12V under load) and that resulted in a 2x speedup in getting to 90C. It also let me get the bed to much higher temps, since 90C was about as high as it would go, and now 110C is easily achievable. I had to remove the bottom plate to get the much larger PSU installed, but that was the only piece that needed to be removed.

Interestingly, a dish towel covering the build plate offered just about the same speedup. (post with graphs) So if you're satisfied with the max temp, and all you want is faster heating times, a cotton towel is as good as a PSU upgrade!

To speed heating, I did the towel-on-build plate method for a bit, then realized that I had a bunch of scrap blue foam insulation panels in the garage. I cut a 12" square chunk, put it in place of the towel, and got just about as good speed-up with the added bonus that the blue panel rests on top of the binder clips, not directly on the build plate, so it doesn't leave any schmutz in the hair sprayed surface the way the towel did.

Putting a 12 v 50w light bulb in the 5v rail made a big difference for me- about half a volt increase on the 12 rail, which decreased heating times hugely- I was struggling to get to 90 beforehand, now I can get to 110

This isn't a printing question, but I'm curious... what about the 12v 50w bulb increases the voltage on a different rail?

hubrigant wrote:This isn't a printing question, but I'm curious... what about the 12v 50w bulb increases the voltage on a different rail?

I believe it has to do with a safety mechanism built into ATX power supplies. If there's no load on the 5v rail, some of them will limit the voltage on the 12v rail.