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Heated bed help!

Posted by 3DPrintingNoob 
Heated bed help!
February 26, 2015 09:44AM
Hello everyone,

I am a complete beginner to 3D printing (but I have done lots of research!).

I have to create a 3D printer with a build area of 1200 x 700mm. Therefore, the build platform has to be even larger...and heated too. I would like to know how I can connect many heated beds in series or in parallel (whichever is best!) in order to heat the large build platform please. Also, what would be the best heated bed for this assembly?

Thank you in advance (Really!)

The Noob
Re: Heated bed help!
February 26, 2015 10:12AM
Parallel if you want to drive them at full power. I would experiament with a sheet of glass (I got mine from a scanner) a fiberglass cieling tile, and some nichrome wire (dead hairdryer) I found that 12v = ~40 feet of wire. Just attach it to the bottommin a zigzag pattern using pet tape or kapton tape wiring each section in parallel . Then buy a quality thermistor, and attach it to the underside of the bed. Put the fiberglass tile on the bottom, fiberglass up, and it heats up much faster. Make absolute certain that your power supply and ESPECIALLY THE DRIVER can take the current. Mine draws about 50 watts and it is a 175x150mm bed. As you have such a massive bed, I would buy 4 thermistors and put them in series/parallel configuration and spread them about the bed so a better average is measured, similar to this [sub.allaboutcircuits.com]
Best of luck on the build!
VDX
Re: Heated bed help!
February 26, 2015 10:22AM
... with this building sizes and objects in this dimensions you'll get warping even with heating bed or ambient chamber.

For a thermo-cured glue dispensing project we had to build a heated bed with similar size - here we used a 40mm thickt T-slot plate, drilled through-holes between every 3rd T-slot and inserted long heating rods to get enough heat into the aluminium.

The part-holders were solid aluminium plates, maybe 800x500x20mm, with an array of pan-holes for the parts, that had to be tempered to the end temperature ...


Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
Re: Heated bed help!
February 26, 2015 10:45AM
iamdarkyoshi

Thank you for that input! Yes, I will be conducting some tests on smaller-scale heated beds before moving to the large dimensions. How would I get a measurement from the thermistor? If there are 4 and I need one measurement then how would I do that? (Did I mention I was a noob?) Just to make sure, the RAMPS 1.4 board is a driver for the heated bed right?

Thank you for your help and advice!

The Noob


The (getting better) Noob

Zapadee zoopidee.
Re: Heated bed help!
February 26, 2015 10:55AM
Viktor

This project is a must for me and apparently it's doable. Furthermore, I plan to make the print inside a heated chamber (up to 130*C). Yes, I will have to look at aluminium part holders rather than 3D printed ones!

Thank you!

The Noob


The (getting better) Noob

Zapadee zoopidee.
Re: Heated bed help!
February 26, 2015 01:54PM
I posted an image of 4 resistors in a series/ parallel configuration. Take 2 thermistors and put them in parallel. Do this again. Then take each set and put them in series. Wire the whole lot to the thermistor input and configure as if it is one thermistor. If each thermistor is 100k nominal, wiring 2 thermistors in parallel results in a 50k nominal. Then take two of these sets, in series, and you get back to 100k nominal. The board will read this as one thermistor, because the nominal resistance is the same as one thermistor.

As for the driver, it needs to be able to drive whatever current the bed pulls. If the driver/ power supply is rated for, say something like 15 amps, and you connect a 20 amp load, it might go into protection, but more likely, it will release the magic blue smoke. Electronics all run on a magic blue smoke, and if it is released, they dont work anymore lol

I would just experiment, but dont forget to double check the wiring and a fire extringuisher!
It has been said that you arent an official member of the reprap comunity until you have nearly burned your house down...
Re: Heated bed help!
February 27, 2015 03:04AM
For a bed of that size, you will need to provide so much heating power that the only practical solution is a mains powered heated bed. It can be controlled easily using a zero-crossing SSR. But there are a number of safety considerations. You need to implement either double insulation or (more likely) protective grounding of metal parts. You need to use highly flexible cables with suitable voltage and current ratings to feed power to the moving bed (the type of cable used for multimeter tests leads should be good for this), with strain relief to protect the terminations against fracturing. I suggest you get help from a qualified electrician. The bed itself can be made from an aluminium plate with silicone heaters underneath, and a glass print surface on top.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Heated bed help!
February 27, 2015 05:41AM
iamdarkyoshi

Thank you for the detailed information, I will try that today if I can get some heated beds!!! As for the driver, what would you recommend for 2 heated beds to heat the print surface to 130*C?

Is there no other way to be an official without almost burning my house down? :p

Thank you!



dc42

Yes, I have been looking into using the mains power supply. I am not sure what an SSR does exactly, all I know is that it stands for Solid State Relay :/

Yes! I was considering using silicone heaters under an aluminium plate! Is it possible to just attach the heaters to the aluminium via kapton tape? Also, is it necessary to use a glass print surface? Wouldn't that just reduce the temperature on the print surface? I will be sure to add the safety features, I have contact with a professional electrician.

Thank you!

The Noob


The (getting better) Noob

Zapadee zoopidee.
Re: Heated bed help!
February 27, 2015 10:38AM
Yes SSR stands for solid state relay. It's a device to switch AC mains (in this case) reliably under the control of a low-voltage signal, with electrical isolation between the switching signal and the switched circuit. There are some very inexpensive Chinese ones such as SSR-25DA, and rather more expensive ones from leading Western brands such as Crydom.

I have no experience of attaching silicone pads to the aluminium plate, so I can't really advise you. I believe some silicone heater pads come with adhesive tape attached, but I don't know what temperature the adhesive is good for. I guess you could possibly clamp the heater to the aluminium with a sheet of MDF. You need to make sure that the heater makes good contact with the aluminium over the whole of the flat side, so just taping it at the edges would not suffice.

You can print directly on coated aluminium if it is flat and smooth enough. Using glass on top has some advantages:

- You get a really smooth and flat surface

- You can take the glass bed and print off and replace it with another glass bed, allowing you to start a new print immediately without waiting for the first one to cool enough to remove it

- If it gets badly scratched or otherwise damaged, you can easily replace it.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Heated bed help!
February 27, 2015 11:05AM
I really do not know what to recommend for the driver, but a solid state relay should do nicely. My bed only goes up to 60 degrees (until i raise the voltage on the supply) , but with a gluestick on glass, warping usually isnt an issue. My bed draws less than 50 watts, so that is why I am using the controller as a driver, as it takes nearly the same current as the hotend. But with a larger aplication, you would connect the output of the controller to the relay, and use the relay for the bed, because the controller (my printer is a 280$ twoup) usually isnt built for very high power dissapation.
Re: Heated bed help!
February 27, 2015 11:29AM
Be aware that possibly some SSRs that work for AC will not work for DC: they will switch on but not off (they latch on and only go off once the control voltage is removed and voltage across the switching element drops to a certain level, AC is fine because it's always passing through zero many times a second. ) So make sure they will work for your bed supply before purchase.

Cheers,
Robin.
Re: Heated bed help!
March 02, 2015 11:37AM
I really appreciate all the input everyone, thank you very much.

Below is the equipment for the test I plan to do, please add anything you think I need to add. For example, I know that the heated beds come with wires and thermistors (??).

Apparatus:
- 2 silicone or PCB heated beds
- Aluminium plate
- Solid-State Relay (SSR) e.g. SSR-25DA
- Kapton tape (ensure full contact of heated bed with aluminium plate)
- Glass plate (if aluminium plate is not smooth or coated)
- 2 thermistors

Once again, thank you everyone!

The Noob


The (getting better) Noob

Zapadee zoopidee.
Re: Heated bed help!
March 02, 2015 12:44PM
As Zedsquared says, you need to get the right kind of SSR. The SSR-25DA is good for switching AC mains. If you want to switch DC to the heated bed, then you need a DC SSR - although it's better to use mosfets instead, because if correctly chosen, they have much lower voltage drop than any DC SSR I know of.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Heated bed help!
March 02, 2015 07:30PM
A little off-topic, and I'm sorry for that, but did you realize that your nickname doesn't make any sense? Not now, and not in the future? Because you will (hopefully) not be a noob in the future after learning all the tricks on the reprap forums winking smiley

Keep in mind, this is not a warning, nor meant in a negative way. I just want people to be conscious about what they do, especially in cases like this smiling smiley A name is hopefully chosen with care, and a forum membership is of course also making you part of a community. You simply can't stay a noob forever winking smiley


http://www.marinusdebeer.nl/
Re: Heated bed help!
March 03, 2015 04:45AM
Thank you for the confirmation dc42!

Ohmarinus, you're right. However, relative to the users in this community, I am quite the noob winking smiley


The (getting better) Noob

Zapadee zoopidee.
Re: Heated bed help!
April 07, 2015 09:39AM
Hello again,

I plan to use FOUR 300x300 mm silicone heatbeds capable of reaching 150 deg-C, all beds controlled by the controller board (e.g. RAMPS-FD). I am pretty sure the board can't provide enough power to power the beds as the board is rated at 12-24 V. HOWEVER, what if I select the four beds to be at 12 or 24 V each and connect them in series/parallel to the controller board? Would that work?

I am super confused about this right now.

Please help!


The (getting better) Noob

Zapadee zoopidee.
Re: Heated bed help!
April 07, 2015 10:51AM
Quote
3DPrintingNoob
Hello again,

I plan to use FOUR 300x300 mm silicone heatbeds capable of reaching 150 deg-C, all beds controlled by the controller board (e.g. RAMPS-FD). I am pretty sure the board can't provide enough power to power the beds as the board is rated at 12-24 V. HOWEVER, what if I select the four beds to be at 12 or 24 V each and connect them in series/parallel to the controller board? Would that work?

I am super confused about this right now.

Please help!

I've been reading quite a few of your posts and honestly I think you need to slow down. From what I have read it appears you do not even own a printer or know the basics besides what you have read. You have been (and still are) asking very basic electronics questions that a little bit of Google and datasheet reading could solve and have a very ambitious print size for your printer. There is a reason that the most common printer has a print size roughly 8"x8"x8" and very few are any larger for hobby use let alone the 700-1000mm you have been talking about in other posts.

Just as an example here are some numbers

8mm steel rod, 1000mm long, supported at ends will sag ~.238mm in the center just from gravity

12mm steel rod, 1000mm long, supported at ends will sag ~.106mm in the center just from gravity

Adding a rough motor weight of .8 lbs to the center of the 12mm rod increases the sag in the center to ~.149mm

Those numbers only have 1 rod but the numbers for 2 rods typical of most repraps will be similar due to the weight of the rod itself not to mention the motor, hotend, bearings and whatever carriage system you have. I would strongly advise you to at least buy some form of printer kit, assemble it and get some real world experience with printing before sinking money into something so ambitious.


Please add your printer design to [reprap.org]
Re: Heated bed help!
April 07, 2015 11:07AM
Don't get me wrong! We do have a printer! We have an Imagine printer. However, we are obviously not using an SSR in this case since it's just one heated bed. It may not seem so complicated but just by increasing the size of the print area by three times, the complexity of the project can really increase. Furthermore, this project has a deadline at the end of May, however, the parts and components need to be ordered/manufactured before mid-May, which is quite soon relative to lead time.

Can you please help me with my post?

Thank you


The (getting better) Noob

Zapadee zoopidee.
Re: Heated bed help!
April 07, 2015 11:22AM
Quote
3DPrintingNoob
Don't get me wrong! We do have a printer! We have an Imagine printer. However, we are obviously not using an SSR in this case since it's just one heated bed. It may not seem so complicated but just by increasing the size of the print area by three times, the complexity of the project can really increase. Furthermore, this project has a deadline at the end of May, however, the parts and components need to be ordered/manufactured before mid-May, which is quite soon relative to lead time.

Can you please help me with my post?

Thank you

Perhaps some reading will help you - [physics.bu.edu]

Also, you need to know the resistance of the beds. Without that number you do not know the amperage required and can not spec any parts like the power supply or relays to do the job...

I do think you have rather large issues (bigger than wiring heated beds together) to take care of like the basic mechanical design if you want to have any change of completing this by the end of May.

Edited 1 time(s). Last edit at 04/07/2015 11:23AM by tjb1.


Please add your printer design to [reprap.org]
Re: Heated bed help!
April 07, 2015 11:33AM
I'm sorry, but my task is to work on the heated bed. I am in a team of 6 and each of us has something to do. The mechanical design has already been dealt with, the only issue now is how to power and control the heatbeds. I understand how basic electrical circuits work but what I am having trouble with is knowing how to implement the heatbeds together to work with the controller.

E.g. take a silicone bed rated at 12 V with a power of 270 W. Connect 4 together (series/parallel doesn't matter), now, tell me. Would I need an extra power supply, or does the controller provide enough power? I know I suck at this, but that's the whole point of asking for help. To learn.

Thank you


The (getting better) Noob

Zapadee zoopidee.
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