Hey guys,

I am looking for a heatbed that can reach high temperatures without fail, ideally up to 150 deg-C or 200 deg-C if possible with good good dimensions (about 200x200mm or more). I plan to run some tests on such a high temperature heatbed, with the potential of connecting three or four of said beds together to cover a larger build area.

Share thy wisdom with me!!!

Thanks in advance!

The Noob (still)

One option for you is to make a custom bed out of aluminium plate and attach one or more silicone heaters to the bottom. This supplier [alirubber.en.alibaba.com] carries a range of sizes and will also make one up to your size, voltage and power specifications.

What plastic will you be printing that needs such a hot bed?

Edited 1 time(s). Last edit at 03/10/2015 07:31AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks a lot dc42. Those heatbeds are perfect. Now, another question. Do you know how I can connect, say, 2 of these silicone beds together? Just in parallel? Because surely to get the average temperature from one thermistor, the thermistor must be 100k total resistance. I hope that made sense.

Please help

The Noob

If you connect two identical 100K thermistors in parallel, you will get in effect a 50K thermistor and the temperature reading will be weighted in favour of the hotter one. If you connect them in series, then you will get in effect a 200K thermistor with the temperature reading weighted in favour of the cooler one.

Any modern 32-bit controller firmware should allow you to enter the thermistor resistance in a configuration file, so you can use 50K or 100K as appropriate. For firmware intended for 8-bit electronics, you will have to construct a new thermistor table, by halving or doubling the resistance values in the table for a single 100K thermistor of that type.

You can connect the heating elements of two identical heated beds in parallel (so that the combination takes twice the current) or in series (so that the combination needs twice the voltage).

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Are you planning on printing cookies and baking them as they print?

Thanks dc42, that was really helpful! I may need to connect 6 or 8 beds in total in the near future... the printer is going to be quite large. The connections won't be so easy :/

When the thermistor favours either the cooler one or hotter one, what kind of difference in temperature are we talking about? A few degrees?

I hope to wire the circuit onto an Arduino Mega 2560 board. I am not sure yet whether it would be able to handle the power. If I connect the beds in parallel (so twice the current required), do you think that would destroy the board?

the_digital_dentist, that's actually not a bad idea, two birds with one stone. I need the temperature to reach that high because of testing reasons, I want to observe the effects of the heating beds on a glass build plate to see if it can withstand the high temperatures

The Noob

I recently replaced a ceramic/glass cooktop in my kitchen and did a little research on the material. It's called Ceran, made by Schott in Germany. It has a near zero CTE. I attempted to liberate the old glass top from the electronics assembly that is glued to the bottom of the plate, but was unable to do it without breaking it. Maybe that material can be purchased for reasonable price in smaller pieces. I think it would make a good bed material because it definitely won't warp with the little bit of heat we apply when printing.

Yes! Glass-ceramics. It is not easy to find it cheap though... It might be too expensive for the budget of my project. However, I will definitely keep it in mind. Thank you

I will start assembling the multiple heatbed circuit once I have the beds. I will be here again soon because I know I am going to have a hard time doing this.

The Noob

For really large heated beds, mains power controlled by an SSR is a practical solution. But of course this raises additional safety concerns, especially if the bed is moving, and shouldn't be done without input from an electrician to advice on protective grounding, fusing, and other electrical safety issues.

Edited 1 time(s). Last edit at 03/10/2015 11:00AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

dc42

Yes, most likely I will have to use an SSR. At the moment I don't know which SSR to use or if I even need one yet, but I will know for sure once I get the beds. Fortunately, there is a professional electrician at my university.

Thanks a lot!

The Noob

So you need to choose mains-voltage bed heaters and use a zero-crossing SSR. If the bed will be moving, then to connect the power I suggest the type of extra-flexible high-voltage cable that is used for multimeter test leads, and provide strain relief at both ends.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Considering the size of the build plate, I think it would be best to have the build plate stationary with the head moving in the xyz directions. The silicone mats you sent me can run on mains supply so in case I need it then I would just have to get a zero-crossing SSR. Can you explain to me what the SSR does exactly? And why it's necessary in this application?

My knowledge of electrical components is not so great. Sorry.

The Noob

An SSR is a Solid State Relay. Using a zero-crossing SSR (the most common type) is the easiest way of switching AC mains power to heating elements. There are cheap Chinese SSRs available (e.g. SSR-25DA which is widely available on eBay) and more expensive Western brand ones.

They need only a few milliamps at 3 to 32V (usually) to switch them, so they can be drive direct from an Arduino pin.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

dc42

Thank you for that clear explanation. I have looked at the Chinese SSRs and no kiddin that is damn cheap. I have looked online how to connect the heated bed to the relay and relay to Arduino, and as it is called, it's a relay so it makes perfect sense. I am purchasing two silicone beds today and the SSR and hopefully they will arrive soon ready to try out.

Thanks a bunch dude!

The Noob

An SSR is simpler to connect to an Arduino than a mechanical relay, because it needs much less current. All you need to do is connect the + input terminal of the SSR to an Arduino output, and the - input terminal of the SSR to ground.

Do not try to PWM the Arduino output pin unless it is very slow PWM, e.g. one cycle every second or every two seconds.

I suggest you choose an SSR which has a plastic cover to fit over the terminals after the wiring is done.

Note that if you want to run one of these cheap Chinese SSRs at anywhere near its maximum rating, then it will need a heatsink. So I suggest you get an SSR with a much higher current rating than your heaters will take, that way that you can probably avoid the need for a heatsink.

Edited 1 time(s). Last edit at 03/11/2015 07:40AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

dc42

Pulse Width Modulation? What reason would I need to "PWM" the Arduino output pin?

Okay I will check the current required for the beds and will decide which SSR to purchase.

Thank you

The Noob

PWM is generally used to control the power to the extruder heater, and sometimes the heated bed power as well.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Ah yes, I understand. The voltage input can be varied like an analog input but it's really DC.

Thanks buddy

The Noob