Onyx R3 "SuperBed" Build

Check out how others are building and modding their own heated beds
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Jimustanguitar
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Onyx R3 "SuperBed" Build

Postby Jimustanguitar » Wed Nov 12, 2014 1:30 am

For some background, check out this thread for a description of the heated bed versions:
viewtopic.php?f=54&t=6758&p=52767&hilit=onyx#p52767



The majority of us have the R2 bed. It is a great design, but there are 2 things that I don't like about it.

1. The heating traces are spiraled with an even spacing which makes them less concentrated the further you spiral out towards the perimeter. R3 and beyond fixed this problem by varying the spacing of the spiral to cover the whole bed more evenly.

2. The thermistor hole is in the dead center of the bed which isn't the most accurate spot to put it. It's also where every single piece is going to print over, and it tends to give you false readings that throw off the bed temp for that critical first layer. Later versions improved this as well.



The R3 bed fixes the heat consistency issue, and it can easily be drilled off center for a better thermisor location. And best of all IT'S ON CLEARANCE because its resistance is a tad high. For me, the resistance is a non-issue because I've either been printing low temps for PLA or I've been plugging in 24v for higher than usual ABS temps. So, for my purposes, an R3 bed with a modified thermistor hole is every bit as good as an R7 for half of the price.



Here's my build.

First I marked out the furthest location from center that my thermistor leads would reach without hitting a trace and drilled a new thermistor hole. I used a 5/32" drill bit which is a much tighter hole for the thermistors I had. My theory is that the smaller the hole, the closer the temp reading would be to the actual bed material. (note, I drilled 2 holes in my bed... I found a thermistor with slightly longer leads that allowed me to reach further)

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Next I put a piece of tape over the top of the holes to keep silicone from oozing through, stuffed the hole with silicone using a toothpick, and inserted the thermistor as far as it would go (lightly). I also taped down the leads to hold them in place while drying (not pictured) and squeezed a glob over the top to make sure the thermistor was really secured in there. After it dried, I soldered the leads to the pads.

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Make sure you get a piece of dog hair in there. It helps :)

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I wanted to make the main power leads on my bed disconnectable. To do this, I flattened the crimp sleeve from a male spade connector into a tab that I could solder to the pads on the bed.

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For my resistor, I used a 1Kohm 1W. It's a higher resistance and wattage than the "stock" resistor because I do run 24v occasionally. I bent the leads to hold it off of the surface of the bed in case it would warm up and cause a hot spot. Then I soldered it on, and put a bed of silicone under it. I put silicone around all of the components on my bed after they were soldered on. The idea was to "shock proof" everything since I move my printer and throw it in the car so often.

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I mocked up my LED and bent the leads just right so that the LED would be flush with the top of the hole in the bed and still contact the solder pads evenly.

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Also soldered leads the the thermistor pads that terminate at a JST connector, to make the thermistor disconnectable as well. Covered everything exposed with a glob of silicone to shock proof it, and let it all dry. Then fitted up the snowflake to make sure that everything cleared.

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It all fit, so I put her together. Printing again, yay! One more note, if you're using a heat spreader that covers up the heat indicator LED (I've got Brian's Trick Laser heat spreader prototype on mine) you can still see the glow of the heater light from below (my LED was leftover from a variety pack from Radio Shack, so it may be brighter than stock).

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Anyway though, I'm up and printing again. I like the new bed quite a bit. Nice upgrade for an evening's time and not a lot of money.

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Flateric
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Re: Onyx R3 "SuperBed" Build

Postby Flateric » Wed Nov 12, 2014 7:01 am

Nice writeup and good info.
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Re: Onyx R3 "SuperBed" Build

Postby geneb » Wed Nov 12, 2014 10:26 am

Please be careful with those spade lugs. If you apply too much force to them, you run the risk of pulling the copper pads off the board. Excellent hack otherwise!

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Re: Onyx R3 "SuperBed" Build

Postby 0110-m-p » Wed Nov 12, 2014 11:21 am

Very cool mod. I've been considering one of three options, upgrade to dedicated 24V psu for my R2 bed, upgrade to 24V psu and a R3 bed, or keep 12V through the RAMBo and get an R7 bed. Guess I need to add a 4th option...24V R3 with your thermistor location mod.
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Re: Onyx R3 "SuperBed" Build

Postby Jimustanguitar » Wed Nov 12, 2014 12:03 pm

Whatever option you choose, If you do an R3 at all go ahead and drill a hole. There's no good reason not to.

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Re: Onyx R3 "SuperBed" Build

Postby 0110-m-p » Wed Nov 12, 2014 12:48 pm

So are you running a dedicated 24V psu for the heated bed or still through the RAMBo?

What kind of temperatures are you hitting and how fast?
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Re: Onyx R3 "SuperBed" Build

Postby Jimustanguitar » Wed Nov 12, 2014 1:57 pm

0110-m-p wrote:So are you running a dedicated 24V psu for the heated bed or still through the RAMBo?

What kind of temperatures are you hitting and how fast?


I've got the bed on an SSR that is fed by a relay. When there's no 24v present everything runs on 12v from the ATX supply (NC state of the relay is 12v). When I plug in 24v to a molex connector that I've added, the relay clicks over and feeds 24 volts to the SSR (NO state of relay). So I can switch back and forth just by plugging in my 24v supply.

Haven't timed it yet. That's next.

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Re: Onyx R3 "SuperBed" Build

Postby nitewatchman » Wed Nov 12, 2014 2:40 pm

Jimustanguitar wrote:
0110-m-p wrote:So are you running a dedicated 24V psu for the heated bed or still through the RAMBo?

What kind of temperatures are you hitting and how fast?


I've got the bed on an SSR that is fed by a relay. When there's no 24v present everything runs on 12v from the ATX supply (NC state of the relay is 12v). When I plug in 24v to a molex connector that I've added, the relay clicks over and feeds 24 volts to the SSR (NO state of relay). So I can switch back and forth just by plugging in my 24v supply.

Haven't timed it yet. That's next.

Would you be willing to post a bar napkin drawing of the circuit you describe above? I really like the concept of being able to plug-in the 24VDC power supply when the higher temps are required while maintaining the normal base circuit of the Rambo.

Very Clever!

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Re: Onyx R3 "SuperBed" Build

Postby 0110-m-p » Wed Nov 12, 2014 2:43 pm

Wiring that to a switch would be awesome too.
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Re: Onyx R3 "SuperBed" Build

Postby Jimustanguitar » Wed Nov 12, 2014 3:37 pm

NapkinCad 2.0

Image



I have a DPDT relay, so for simplicity this diagram only shows the positive flow... Negative is about the same, it just doesn't go through the SSR after the mechanical relay.
When I plug in 24v it throws the relay and feeds the heat circuit, and when I unplug it it just uses 12v from the ATX supply.

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Re: Onyx R3 "SuperBed" Build

Postby nitewatchman » Wed Nov 12, 2014 5:21 pm

Perfect!!

Some of the best things our industry start on the back of an envelop or a bar napkin!

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Re: Onyx R3 "SuperBed" Build

Postby 0110-m-p » Wed Nov 12, 2014 6:06 pm

Why not just run a single 24V psu and a 24V-12V converter to get 12V to the Rambo?
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Re: Onyx R3 "SuperBed" Build

Postby Mac The Knife » Wed Nov 12, 2014 7:26 pm

0110-m-p wrote:Why not just run a single 24V psu and a 24V-12V converter to get 12V to the Rambo?

I can't think of a reason, other then the fans and leds, why you couldn't.
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Re: Onyx R3 "SuperBed" Build

Postby bdjohns1 » Wed Nov 12, 2014 10:23 pm

0110-m-p wrote:Why not just run a single 24V psu and a 24V-12V converter to get 12V to the Rambo?


This is what I'm doing over on my Smoothieboard. The board itself including the steppers actually do off 24V. I have a stepdown converter for the hotend and fans. A single 100W-rated converter is more than enough.

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Re: Onyx R3 "SuperBed" Build

Postby Jimustanguitar » Thu Nov 13, 2014 8:13 am

0110-m-p wrote:Why not just run a single 24V psu and a 24V-12V converter to get 12V to the Rambo?


You definitely could do that. I've been thinking about it too.

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Re: Onyx R3 "SuperBed" Build

Postby Eaglezsoar » Thu Nov 13, 2014 12:43 pm

Here is a nice one that can handle up to 20 amps.
http://www.amazon.com/HOSSEN%C2%AE-Conv ... +converter

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Re: Onyx R3 "SuperBed" Build

Postby teoman » Thu Nov 13, 2014 3:10 pm

How many amps would be needed?
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Re: Onyx R3 "SuperBed" Build

Postby Jimustanguitar » Thu Nov 13, 2014 4:03 pm

The bed draws the most. On a stock 12v setup, they can pull upwards of 14 amps, so at 24v you'd double it...

The Rambo itself, hot-end, stepper motors, etc aren't that much so a 20A converter would easily do the trick if you ran them at 12v.

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Re: Onyx R3 "SuperBed" Build

Postby 0110-m-p » Sun Jan 18, 2015 12:37 am

Print took a piece out of my glass tonight so I need to order another so I'm thinking about going ahead and picking up the R3 bed while I'm at it. Ever get any numbers for performance on your 24V R3 setup (time to 100C, max temp, etc)?
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