Heated bed doesn't get hotter than 75 Celsius

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mrvb217
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Joined: Tue Jul 31, 2012 10:21 am

Heated bed doesn't get hotter than 75 Celsius

Post by mrvb217 »

Hi,

is it a common issue that with everything assembled like in the manual
one can only reach about 75-78 degrees Celsius?
I've got 12V at the power suplly input for the heated bed on the RAMPS
which drops to 11.5V when the heated bed is turned on.
At the heated bed itself I only have about 10.5V left with 1.5 total R.
I've used the provided cables and PSU.
I've also tried connecting the cable that's normally at D8 +
directly to the RAMPS 11A power supply + with similar results.
Any ideas for getting the heated bed up to 110?
PLA is no option for the stuff I want to print and I just can't
get the ABS to stick to the bed.

Thanks in advance,

Martin

Kjetilei
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Post by Kjetilei »

I was only able to reach 75 degrees Celsius.

I don't know much about hotbeds, but if you have another 12v PSU available it might be able to increase the temperature more? Or maybe more resistors are needed?

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gfeliksdal
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Post by gfeliksdal »

Hi Martin,

The heated bed is not able to reach 110 degrees C in the current setup. The electronics are a limiting factor in combination with the large size of the plate. The electronics can simply not handle more power to heat the bed. We are currently researching for a way to heat a plate this size up to 120 DegC or other ways to get the ABS to stick to the bed. If the tests are not ok, we will offer a smaller exchangeable heated bed which is able to reach at least 110degC if ABS prints are a must.

Tried solution by other print enthusiasts which I've found on the web is to print on an Acrylic plate. ABS sticks very well to this surface, sometimes so well it is extremely hard to get it off.
Another way to get ABS to stick to kapton is to use ABS glue. Let a piece of ABS solve in acetone to form glue. Put that on the table and print. These solutions seemed to work, but only for smaller parts. Big parts will still have enough warp forces to peel themselves off the print bed.

We don't have a convenient solution for ABS as PLA is printing at the moment, but we are working on it and hope to provide it in the near future.

Kind regards,

Guillaume.

mrvb217
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Joined: Tue Jul 31, 2012 10:21 am

Post by mrvb217 »

Thanks for the quick answer, I'm relieved that it's not supposed to reach higher temperatures.
Been thinking about using an additional 24V 20A PSU for the heated bed, with a relay switched by D8. I'm not fully sure if I have to use a diode somewhere to protect the electronics, so I won't follow this approach until I know what I'm doing. Maybe something bad could happen because a relay would operate much slower than the mosfet, and I just don't know enough about electronics to figure this part out by myself.
In the meantime, I'll try out the ABS+acetone solution approach. It seems to produce reasonable results for many people even at lower heated bed temperatures.

Lioric
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Joined: Wed Aug 15, 2012 1:13 am

Post by Lioric »

Of course you will need a protection diode if you are using a relay, when the relay is deactivated it will be act as an inductor and the diode is needed to forward bias the current back to VCC

But I don't think a 24V PSU is needed, I haven't received yet the printer, but from what I have seen on other posts and from the assembly manual, the limiting is because the heat elements are handled directly by the RAMPS (and are limited to the amount of power the Arduino Mega can handle), so that connecting a heat bed directly and switching it with a relay (as you mentioned) will do it (In this case a more power PSU can handle whatever you need)

As this Silicone heat bed below, they claim to reach 120C Degrees in 1 minute, with included thermistor and 200mm x 200mm bed size. They even mention that RAMPS can handle it directly, but I don't think so. A relay and a direct connection to the PSU (400w?) and you are ready for ABS

http://store.qu-bd.com/product.php?id_product=30
because a relay would operate much slower than the mosfet
Don't worry about that, just use a SSR (mainly to avoid the clicking noise), the thermal mass of the printing bed makes this a moot point



Another thing, probably higher temps can be obtained with the current setup if the bed is insulated from below, that way the downward radiated heat is avoided and the bed will draw more heat

mrvb217
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Joined: Tue Jul 31, 2012 10:21 am

Post by mrvb217 »

Thanks for the advise! Just to let you know: ABS glue did the magic trick for me, the results are very good so far. Just in case someone else wants to give ABS a first try: I've set the extruder temp to 230, heatbed to 70 and used the 'normal' SFACT profile with an extrusion height reduced by 0.02. Seems to handle even bridges well. Guess I won't try to raise the heat anytime soon.

HLA
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Location: Vienna, Austria

Post by HLA »

Nice. Thanks for trying it out. It's great to see progress being made with ABS!

Could you post some images of the final ABS prints? - that would be fantastic.

HLA

mrvb217
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Joined: Tue Jul 31, 2012 10:21 am

Post by mrvb217 »

Of course, I'll send some tomorrow.
Grüße ins schöne Wien!

HLA
Posts: 73
Joined: Sat May 05, 2012 11:35 pm
Location: Vienna, Austria

Post by HLA »

Perfect, thanks. Will order some ABS myself to dare the next big step on Felix.

Schöne Grüße zurück :)

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