Heated Bed

Now that I have printed a few success items with my mendel, I realize that to print many things at once requires a heated bed. I purchased a heated bed PCB heat bed mk2 and now that I have received it, may seem like a silly question but how and or what do I power this with ? I am using gen 3 electronics on a mendel. Could the heatbed plug into my extruder board ? An equally interesting question is if I mount a thermistor to the heatbed how is this temperature monitored.

Not being familiar with Gen3, I can't say whether or not temperature monitoring is supported for the HBP, but I believe the Gen3 uses thermocouples, not thermistors.

The MK2 can be connected to a 12VDC source (you can go higher), even the same one that powers the rest of the electronics, provided it can supply around 7-9 amps. You do not need to solder LEDs to the board, as they are optional.

RAMPS electronics have a dedicated connector for the HBP, and the thermistor that goes with it. I think Sanguinololu does too. Other GenX type boards also support HPBs. Sorry I can't be more help.

Not sure on Gen3 but Gen6 cannot run a heated bed but Sanguino can. I have my heated bed with Gen 6 but the heated bed is run from a universal laptop charger and to control the temp I adjust the voltage

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Experimenting in 3D in New Zealand

What do you use to adjust the voltage ? That's kind of what I was thinking of doing. Thanks for the input Jcabrer, I might be able to just use one of the leads from my current power supply, I'll have to check out the amp output.

You could try using a thermal fuse to control temperature. Attach it directly to the bed.

My gen3 remix does have spare heater outputs, and there's plenty of free pins on the extruder controller to add another thermistor.

If you mange to work out the firmware side of it that is...

A better and simpler option could be gen3+ [koti.kapsi.fi] [www.lulzbot.com]


On my sells mendel I just hooked my custom nichrome bed directly up to a 12v 4a brick supply, and it never went above 50C, so worked out fine for PLA.

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-Nudel
Blog with RepRap Comic

Universal laptop chargers have small pins that slide in and each one is for a different voltage, they come with a decent range of pins, I use a 60W one with 12V and it seems to be the right combination

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Experimenting in 3D in New Zealand

A lot to consider here, Thanks everyone. I'll let you know how it goes

How about one more suggestion? For our printer we have Gen 6 electronics so can't support the heat control from that. We're working on setting up an arduino board with a thermocouple to control the heat. Don't have it fully assembled yet so we can't say how it will work.
Some people like to change teh heat after a few rows, so this won't do it (at least not as far as we can figure out so far). But as we're starting with PLA and we've just started getting usable prints, we will worry about that later.

I have an arduino with a LCD screen controlling my bed temperature for my gen6. I copied the controller from Arcol's blog and modified it to suit my needs (and match my LCD). Like here: [blog.arcol.hu]


Mine looks like this: [www.flickr.com] It has no ambient temp sensor so that is why the "Amb" temp is wrong.

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grog Wrote:
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> We're working on setting up an
> arduino board with a thermocouple to control the
> heat.

That would work, just run two instances of pronterface, or hardcode the arduino to keep the temp at a said value when on. You could even add a potmeter to control the temperature precisely.

> Some people like to change teh heat after a few
> rows, so this won't do it (at least not as far as
> we can figure out so far). But as we're starting
> with PLA and we've just started getting usable
> prints, we will worry about that later.

I have the bed temperature stable for the whole build, and can't see any good reasons for changing it with PLA. I use 50-55C for big parts, and 55-60C for several small parts, to make sure they stay put.

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-Nudel
Blog with RepRap Comic

I built the Heated WolfBed (as described in German), but you can use the same idea with your PCB heated bed. Since the PCB heated bed uses a lot of power you might need a 2nd power supply to run it. In any case, I have the aluminum plate with the silicon heating pad glued to the bottom. Instead you would just use your PCB heated bed. I use a 12v / 240v relay to control the power to the silicon heating pad, you would instead use a 12v / 12v relay to control the power to the PCB heated bed.

You will need a Temperature Sensor V2.0 Kit (from MakerBot or somewhere else), or breadboard it yourself. Important is where to attach the temperature sensor to the extruder controller.



A+ & A- is where you connect the control lines for the 12v / 12v relay.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

your out of luck on gen6 for another adc to be available directly.
here is the circuit diagram i referenced. i think this board has several revisions.

[reprap.org]

however a desperate solution may be to use the opto to y pin as an adc pin as that pin can be programmed to be analog A6,
and have the ic2 header sda or scl pins replace the opto pin as a digital i/o pin. use the other ic2 pin to be a digital out to whatever you want it to go thru such as a transistor then a relay , keep in mind that relay have back emf that needs to be counted for, and the relay must have a contact current of greater than 8amps to be safe, there is some debate over the life of a relay so if you use that option get a socketed relay that can be replaced if needed.

again the arduino can sink or source 50ma per pin100ma per port, so relay must be powered by a transistor or a MOSFET driver.also keep emf under control by using a diode to short the back emf.

the gen 6 does seem to support rs485 so it should work with the maker-bot controller mentioned above. however you will need relays setup as the heater bed will blow the on-board MOSFET drivers.

Well after all that was said, I took the easy route (at least for now) and acquired a small laptop power supply which I have hooked directly to my hot bed. The unit is rated at 4.7 amps and keeps the bed at an average of 50-60 degrees. I have noticed that changes in temp affect the temp and will still replace this eventually with something I can regulate, but for now I think it's only to other questions.

Thanks everyone

Hi to all on the thread,

HereIgoAgain - i'm in a similar position regarding my heated bed.

I'm working with Gen3 Electronics and have been testing laptop power supplies with my heated bed since changing my print bed to dibond. Would you be able to let me know what power supply you used to get a temperature of 50-60 degrees? I have tried a laptop power supply with 15V and 4 amps and got no increase in temperature at all.

I think this may be due to the wrong combination of voltage and current as I connected the heated bed to my 12v power supply for the electronics and it heated up very quickly, however it went above 80 degrees which is more than my dibond print bed can handle. Even if it stayed below 80 deg, I can't use it as my PSU has a maximum of 10 amps which isn't enough for both the electronics and heated bed.

I'm guessing a power supply of about 12v and with 5 or 6 amps may do the trick but if otherwise, let me know.

Regards to all on the forum,

Raj

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The MK2 can be connected to a 12VDC source (you can go higher), even the same one that powers the rest of the electronics, provided it can supply around 7-9 amps

I have seen people quoting 7-9 amps, I have just bought a new 30A PSU and the ammeter on it shows my MK2 Heated Bed is drawing a steady 16amps @ 13.8volts!
No wonder my previous 20 amp PSU gave up the fight!

Andy

Edited 1 time(s). Last edit at 02/01/2012 02:54PM by Normsthename.

That is a lot more than my MK1 draws. It takes 10A @ 12V when cold. Might explain why some people can get it hot enough for ABS and some can't.

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[www.hydraraptor.blogspot.com]

Ok i hope this makes sense as I have had a drink or two.

Well I have gen 6 and as I wanted to print in ABS I needed 110c. The first thing i have to say is that PLA parts are no good for this as they melt. Well become soft and distort so if your thinking of using ABS you need ABS parts.

Second I couldn't get a laptop supple that could take the power so I got a variable bench power supply up to 15V of ebat and connect all the hater blocks in parallel. I got more powerful ones from RS. The supply was about £100. This lets me just set the voltage so in the end it gets to the correct temperature and stays there. Simple really. Good for other projects too.

If someone comes up with a electronic regulator kit or something than I can just plug in then that's great but till then I'm sticking with the simple approach.

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Make your Mendel twice as accurate.
[www.thingiverse.com]

Just to give people a heads up. The PCB based heaters can vary CONSIDERABLY in resistance. I've heard of them drawing everything from 5-20A, depending on how and when they were manufactured. It seems to be down to slight differences in copper thickness and track widths, since even a small change causes a big change in current draw.

I'm in fact working on an improved design right now. Until then though, assume it will draw about 20A until proven otherwise. This will give you the required leeway.

Hello folks.
I am working on a PCB heated bed platform.
I am also looking for suggestions for improvements and idea.

My two current changes to the standard (prusa) PCB bed are
(1) Connectorize the Bed.
This is to allow easier cable management, improve appearance...

(2) An i2c interface and an on board micro and thermistor to control the
temperature right on the board itself.
This will allow each board to be calibrated and also free the arduino.

Please let me know what you think of these and suggest more features.

My heatbed is not always drawing current and I was wondering if there might be a way to take advantage of this off time to reduce worst case current requirements. I'd like to see a tiled heatbed that switches the current between tiles. The idea would be to trade increased preheat time for a reduction in worse case current consumption. Additionally the tiling would distribute the energy more evenly which also may reduce current requirements.

I don't know how well this would work in practice, but it's on my todo experiment list.

If it is a moving bed machine then it is better to heat the whole bed because otherwise the object moves through cooler air.

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[www.hydraraptor.blogspot.com]

Regarding tiling the heated bed,
I am not sure if the complexity tradeoff is worth much there, especially considering what nophead wrote.

Would you guys like to see any other additions to the bed.