So the evolution of home-made heated bed controller began:

Warning: long article ahead!

So I began the work. I discovered the program called Fritzing.
Which is an amazing program if you are prototyping.
Is exactly what I needed, so I quickly digitalized my breadboard design:

The program also capable to transform the breadboard design to schematic and pcb. So I thought it is he most simple way to manufacture the board. But turned out the ratsnest is completely unusable and the pcb manipulation is extremely slow:

Fritzing is supporting breadboard, schematic and pcb editing,
and autoupdate each of them, while you are editing one of it.

This feature turned out to be the real dealbreaker, as it messes up the original breadboard design. And also couple of other smaller bugs, like you cant connect multiple wires to a single device, you always need to put a breadboard which ruines the cleaniness, and makes the breadboard view overcomplicated:

So at the end I spent 3 days working on this simple pcb, and finally I decided to redo it in KiCad when the final etched board contained miswirings (because of the constant redrawing):

I would also like to note, the developers were really helpful and responsive,
so I will definietly keep an eye on this project.
It has a real potential, and for breadboard drawings it is already useful, like for article drawings!

Traditional Toner transfer method

I would also like to show you, how I created pcbs in the past.
I used the toner transfer method, which is really popular.
The method itself is really simple.

1. Search a suitable size raw pcb:

2. Cut off the right size from it:

3. Clean it throughfully:

4. Print your pcb design on a "etiquette paper", and using a hot iron, stick the paper to the hot pcb:

5. Put into water, and wait until the paper cames off the pcb:

6. You can help the paper gently. Now it came off:

7. Using the corrector on the above picture correct the pcb, where the melted toner powder is missing:

8. Put the pcb into your favorite etching solvant. Here is my chemie "arzenal":

(dont look at the pcb, it is made using the below detailed laser etching method)

There are mainly two options:
- FeCl water solution (I bought a ready made solution. Its under my hand, you can only see the bottom half of the flacon)
- Hidrochloric acid (HCL) and Hydrogenperoxide (H2O2) solution (10:1)
(more dangerous, because Cl2 gas develops during the etching process)

9. Clean the toner painting off of the pcb using aceton or nail cleaner:

10. Using tin solution, protect the copper from oxidasation:

11. The final board:

As you can see it is ugly and the process is slow and error prone, especially the ironing part.

The more sad part, that it could not fitted on the arduino board;-\

About a millimeter its smaller then it should be.

So I stand back, and thought a bit. I had 4 buyers, who had trouble to assemble the
heated bed controller shield themselve. The above method is simply
too slow. Also I decided to redo the circuit in Kicad, to be able to professionally
get manufactured the boards.

I just met accidentally with a guy who recently bought a laser cutter. And I had the
crazy idea, why not do the pcb using laser cutter after all?

I talked with him, and he agreed, that I can try out his laser cutter, and do several experiments.

Evolving of the laser etching process

I had an idea of covering the pcb with Kapton tape, and burning off the tape using the laser cutter.
Also Chris wanted to use the Kapton for solder mask.

I had really high hopes, when I travelled to another Town to the guy.
For test I used Chris' extruder controller board, because it is complicated enough and use many small traces.

Here is the laser cutter working:

Here is the top and the bottom side of the board done:
top:

bottom:

And also some closup photos, where you can see, that the Kapton itself is burned nicely
away, but the glue, which is under it stayed and gathered all the smoke:

The another closeup:

I etched them. Top:

Bottom:

Two closup pictures to show you the problematic areas:

Trace completely disappeared:

So this experiment was a complete failure. I also tried out Chris' idea, of using the
Kapton tape as solder mask. It is not working either. The burned glue prevent
soldering, if you try to clean it off, you clean also under the remaining Kapton tape too:

Try 2:

Try 3:

I even tried with some resin/flux which helps soldering :

So this idea was not working either.

The final process

We simply painting the boards with regular black paints, and tried out.
Here is a picture during etching (using hydrogenperoxide and hidrochloride acid):

The result was astonishing! Here is after etching (black paints still not removed).
Top:

Bottom:

I cleaned up the board using nail cleaner:
Top:

Bottom:

And tined the board:

The final result is almost perfect. There is only one problem left to be solved. And it is the
offset of the bottom and top layer:

For this I will manufacture a tool, so no offset between the top and bottom layer.
(the raw pcb is not exactly square)

Finally I changed the design to not need that many copper to be etched off.
So here is the final pcb, etched, tinned:

And also working in his all glories:

(Im really sorry for the noisy picture. Had not enough light in the room. And I gave away all my present heated bed controllers (mine included), so I cant update the picture before the end of September)

Finally I think it worth the hassle. Especially for me, as I had very few buyers in the past, so
cant really charge people the cost of manufacturing that few pcbs.

Also for prototyping this method works awesome. Even for this simple circuit I etched 4 different version.

Also a big warning for my buyers:
DON'T disconnect the heated bed shield while the arduino is powered up!
It will kill the output leg of the arduino. I killed already two legs of mine.
Dunno exactly why it happens. (maybe this is the fault of the SSR relay).

Next article will be a little heated bed news. (Im already at version 1.7)

Everybody who is using a heated bed ended to build a controller for it. Why is that?
Because the bed without a controller can only have one temperature,
which depends on the ambient temperature, also
has a very slow warming up time (the final temperature is reached after 20-30 minutes), and
really pain in the ass to build one to the exact right temperature.

So I ended up building my own version. The heated bed kit already
comes with a 200K value thermistor. It is the same, what Rapman is using for his hot-ends.
The specification of the thermistor:

Also special thanks goes to Francois, because my controller is based on his solution.

So I used an SSR relay, to switch the heating on and off. Chris suggested in one of his articles to use a varistor between the SSR relay legs, which may (or not) prevent accidental overvoltage.
I keep that in mind, and maybe I'll add it later.
An another nice idea to have a "thermal cut-out", or even better a "thermal fuse" on the heated bed. Also a simple fuse wont hurt either. I'll keep adding them to my safety list;-)

Adjusting the circuit to the 200K thermistor

Chris' articles comes to rescue again.

He mentioned in his article, choosing the right value improves the linearity.
Also he mentioned in his article, that Rs should be the resistance of the thermistor at the middle of the
temperature range, he choosed 470Ohm, which is the right value at 130C for his 10K thermistor.

So I choosed mine to be 4.7KOhm:

When I was tinkering with the bed, figured out, that
the AD readings change a little when warming.
So I double-checked his article, and also figured out, that my middle temperature should be around 50C.
I could simply calculate the temperature putting different Rs value to this formula:

But this time I have not stopped there. I wanted to see how it improves the AD reading.
So I dusted off my limited drawing skills, and installed jsxgraph extension on this blog.

And here is a graph displaying connected parallel to :

As you can see, the overall resistance is a lot more linear:

(Vertical axis: equivalent resistance in kOhm,
horizontal axis: Temperature in Celsius)

The real circuit is like this:

(picture is stolen shamelessly from Chris' article.)

So I "quickly" draw an another graph, where the x axis is temperature, and the y axis is the AD reading (how the uC will read the circuit). So it is between 0-1023.
Here is the math:







also

The Internal reference voltage(Vfsd) is 1.1V (page 251 in atmega manual).

Here is the graph:

(Vertical: temperature reading by ADC [0-1023],
horizontal: temperature in Celsius)

Adjusting the temperature table
When we display the temperature on the LCD we need to convert back the A/D reading (0-1023) into Celsius degrees.
For this we build a lookup table. There is a script for it in the reprap svn.
It has a small bug, vadc is 5.0V, while in our case it is 1.1V.
So I modified the line 92, and corrected it (notice the t.vcc/t.vadc). Here is the modified sourcecode.
max_adc = int(1023 * t.vcc / t.vadc *r1 / (r1 + r2));

Also here is the generated table:

// .createTemperatureLookup.py --r0=200000 --t0=25 --beta=4338 --r1=26700 --r2=100000
// r0: 200000
// t0: 25
// r1: 26700
// r2: 100000
// beta: 4338
// max adc: 979
#define NUMTEMPS 20
short temptable[NUMTEMPS][2] = {
{1, 528},
{52, 187},
{103, 153},
{154, 135},
{205, 122},
{256, 112},
{307, 103},
{358, 96},
{409, 89},
{460, 83},
{511, 77},
{562, 71},
{613, 65},
{664, 59},
{715, 53},
{766, 46},
{817, 38},
{868, 29},
{919, 16},
{970, -14}
};


Checklist
So I'm going to use 100kOhm resistor, and 26.7kOhm resistance built from two resistors (22+4.7), and one 10uF tantalum capacitor for noise filtering:

Also I switch on and off the transformator using an SSR relay:

The SSR relay can be directly driven from an uC output pin (arduino in our case).

Then I display the temperature, and other useful informations (like button pressed or not) using a 2x16 chars LCD display:

This LCDs has a common interface, so they driving them from arduino is a child play. There is a premade library called LiquidCrystal for it.

Although the pinout can be different. The datasheet of what Im using can be found here.
Here is the bottom side of the LCD:

Building the thermistor circuit (voltage divider)

Warning: the tantalum capacitors has polarity, and its marked on it. Here is a closeup picture:

So here is how I put it together.
First I soldered the tantalum capacitor's '-' leg, two wires and the 22kOhm resistor together:

Then I soldered the 22kOhm to the 4.7kOhm one, also I soldered the tantalum capacitor positive leg to the 100kOhm resistor:

Finally I also soldered two wires and the 4.7kOhm resistor to the 100kOhm resistor leg. Also one single wire to the other leg of the 100kOhm resistor:

Here is built in all his glory:

SSR relay

I wanted some kind of universal solution, so instead of destroying the toroid transformator's plug, I modified an extension cord:

So instead I sacrified an extension cord;-) Also it has a lamp builtin, which is extremely useful.
Also when the SSR realy is switched on, they still conduit some uA current, enough to turn this
light on. (also the 230V still can bite you).

Here is a closeup picture:

Run the controller autonomously

All I needed a plug for the arduino:

I connected the arduino (using this plug) to Rapmans controller pcb fan output. (watch out the polarity!)
Viewing from the top, the left is the + and the right is the - (GND).

How is it working

When you turn it on, it displays the Bed temperature, the target temperature (105C by default), and the A/D reading and also the button states. (for buttons I use simply a 10kOhm resistors connected to 5V and one of the inputs, when I push the button it connects to the ground. So it is inverted, when I push the button, the reading is LOW).

When heating the bed, in total of 4 light source indicating when the bed is heating:

The led13 of the arduino itself, the SSR relay, the extension board and also on the LCD there is a small star when heating.

Also here is the modified sketch file for arduino.

I also will upload the schematic, it is almost the same what Francois draw.

Hope you liked the article. I also may will improve a little in the future.

The initial test shows, the bed's temperature can go up to 164.3C, which is pretty hot:-)

(on the picture it only shows 148.7C, but it is because I already disconnected the transformers from
mains, so it already cooled for about 3-5mins.)

I thought a lot about heated bed insulating, as my previous one
was made of MDF sheet, which smelled a lot and burned:

Also it left an unremovable stain:

My primary concern was, the bed was not hot enough. So I decided to improve on the insulating, and I bought stone wool, which can withstand this temperature easily:

I bought stone wool covered on one side with aluminium foil (it has a fancy "thermal mirror" name;-), which makes the fixation more easy, and also helps to keep the fibers inside.

I also modified the aluminium sheet again. I added four additional threaded blind hole, to easily fix the stone wool:

(It is the bottom of the finished heated bed, but please keep reading;-)

This version of the aluminium sheets also contains some more bugfixes,
like rotated power resistor's holes (aesthetically better),
was misplaced one hole of the 9 resistors,
I also made sure about the magnets placement (it turned out pretty important).

I also decided to put 9 resistors at the bottom of the bed. But I also wanted to arrange them
into two group. My girlfriend came to the rescue, and proposed this resistors arrangement:

The 5 red resistors are 15Ohm values, all connected parallel, giving a total resistance of 15/5 = 3Ohm.
The 4 blue resistors (at the two edges) are 10 Ohm values, connected parallel, giving a 10/4 = 2.5Ohm total resistance.

I also discovered the last time, that the total resistance varied with the heated bed temperature. At room temperature it was about 3Ohm, while when hot, it was 6.2Ohm!
It could be because of bad joints. So this time I additionally soldered everything together too.

Here are the resistors placed on the vanilla aluminium sheet:

Five 15 Ohm values and four 10Ohm ones.

I forgot to mention this is also a walkthrough tutorial, if you are crazy enough to buy a heated bed kit from me.
(but I hope it is equally useful for your tinkering fellas too!)

Step 1: Cover the bottom of the bed with Polyimide (Kapton) tape

Cover it, also the top of the bed should be covered around the edges (lets say 2-3 cm).

Step 2: Cut out the power resistors

Once you covered the bed, you should place the power resistors on it, and mark them around:

And also cut it with a retractable blade. Here is it half done:

Also one finished:

You should also cut out all the magnetic holes too.

Step 3: Metal bar

This steps needs a bit more explanation I think.

I was always worried about the lifetime of my magnets, so I consulted with a magnetic expert, and incorporated in the design what I gathered during the short conversation.

First, the neodymium magnets are usually stable until 80C. But the temperature which it can withstand vary on many factors, like the size of the magnets, its shape, the exact alloy and manufacturing (it can be manufactured for up to 140C). And also it depends a lot from the magnetic fields and how the magnetic forces travels around the magnets.

A magnet operating in a "closed circuit" is more stable at higher temperature, and also it has more magnetic force directing upwards.
For better explaining I draw two explanatory diagrams (sorry for my limited drawing skills).

Open circuit:

Closed circuit:

Directing magnetic forces is possible via irons (and other magnetic metals).
Determining the width of the metal bar, I have done with trial and error.
Here is the little experiment setup:

The bottle cap is (obviously) attached to the magnet. Putting a width enough metal bar between
the cap and the magnet, catch all the magnetic force:

So I decided this L-shaped metal is width enough and I cut 4 bars:
- 3 pieces 190x10x4
- 1 piece 120x10x4

Here is a photo of one of the long ones:

So I decided to put the magnets on the table just like a chess board, one is reversed compared to the other.
So one magnet up, one magnet down. Putting all magnets upwards, would be worse then doing nothing at all.
So I put together all the 14 magnets, and drawed the direction with a marker on all the magnets:

That way I can make sure I put it right on the table. I also wrote neath all the magnet holes its direction (up or down):

Step 4: Placing the magnets

For "gluing" in the magnets into the holes, I decided to wrap around each magnets with Kapton tape.
So I can hardly push in the magnets. Here is a photo of two magnets wrapped around (and also the short metal bar):

For double-checking if they are attached to the aluminium sheet, I placed the sheet in the air, and watched if one of the metal bar (with magnets) are falling down:

Step 5: Wiring

I also covered all the metal bars with Kapton tape, for insulating (and also for additionally fixing them).

I wired the middle Z shape:

Here is a perspective photo:

I bit more advanced stage (also with the "schematic"):

Here is finished:

Once I finished all the wires, I soldered each joints (remember the explanation from the beginning of the article):

I covered everything with Kapton tape. Everything.

Step 6: Thermistor

I drilled a little the table, and put the 200k thermistor in it. I also soldered a piece of wire on each thermistor legs, and covered them with Kapton tape:

Also the magnets are trying to grab the thermistor, so I placed near the terminal:

Step 7: Insulating

I covered the table with stone wool, also note the bolts, which fix the insulating to the table.

Bottom side:

On the top I put the metal sheet on it, and cut around with the blade, so it has a nice finish:

Also here is a little demonstration how strong are the table magnetically:

Maybe on the photo it is not obvious, but in reality it is incredibly strong. I cant slide the metal
sheet on it...

Also one more time the temperature proof:

Note: it reached 164.3C, just I disconnected the table, and it cooled down a little while I was grabing a camera.

Also here is an explanation what are the 6 wires coming out of the bed:

I hope you enjoyed the article.

László's Heated Bed Installation

I ordered László's heated bed and received it -very well packaged, into a big banana's carton. Here is a short description of the installation I made, not always following László's howto...

The bed is very well machined, very flat (more flat than BfB acrylic bed), with locations allowing to quicly set the magnets.

I decided to connect (serial connection) 9 resistors, 5 x 22 ohms and 4 x 18 ohm, directly to 220 volts. We get more or less 265 W of heating power like that: 220*220/182.

Direct plug into 220 volt can be very dangerous, so it is not advised to do that without good electrical skills. Using a transformer is a non dangerous alternative.

This picture shows the resistors installation:

I used thermal grease between resistors and plate. Wires between resistors are soldered, and insulated with glass-fibre braided sleeving. On resistors, the two 220 volts arrivals are insulated with kapton tape, the other resistors weldings are not isolated because the tension here is only 24 volts more or less (voltage divider: 220/9).

The plate is plugged to the ground, which I verified, and there is a ground fault circuit interrupter into my electrical installation, that I verified too... So, normal precautions are taken against 220 volts dangerousness.

In the picture you can see the wires going to the thermistor: I am using an Arduino based temperature control system, the thermistor is inserted into a little hole I made into the plate and fixed with kapton tape.

A picture of the first test:

My Arduino's system (RBBB) is into a CD box. I zipped the schematic and .pde sketch here.

And the heated bed installed:

After some days of utilization, I found that László's z-switch holder was not strong enouth and didn't guarantee a constant z home position, so I made a little hack:

I cutted the bed a little and placed the z-switch into the same x & y positions as with acrylic bed. The z-switch is firmly fixed with wood. There is an error hole that you can see in the picture ))

And now the heat isolation. I screwed some wood under the plate on 3 sides:

and added removable wood sheets (so one can reach the magnets):

and finally, removable wood parts on the plate, that I arrange during the beginning of the print:

This is not a perfect insulation...

For the utilization, it is very important to note that the bed expands with heat, decreasing its distance to the printing head. The head level must be set accordingly!

In conclusion: very good heated bed! I am just beginning to print with it…

Update:
I somehow forgot to include the schematic. Here we go:

(clicking on the image gets you to the .pdf file)

Also here it is the arduino .pde sketch file.

I designed a filament holder for my Mendel.

Dunno, if Im really that megalomaniac, or simply too lazy to wind off an 5kg filament spool...

For my Rapman the standard filament holder never worked. Cant imagine how it could ever work...
So I quickly made one from two filament holders and put on the shelf above the machine:

(again I dont know how could I be so stupid to buy 3 of it...)

With this modification, it works rather good. The only problem, that it can only hold 1kg of filament, and
usually the filaments comes either in 2.5kg form or 5kg form, like this one:

Winding off an 5kg filament like this one to the above filament holder is not much fun, especially, if you are alone.
Also the filament holder must be attached to something (in my case it is attached to the shelf):

If not, the machine can pull the whole thing to himself. For me it broke off the fan from the extruder once.

So I decided for my Mendel I make a better filament holder.
Here is my Wanted list:

• can hold the 5kg filament spool without problem
• turn easily, even the 5kg turn easily
• be above the machine
• compact
• somehow attached to the machine, to be self contained (ie. I can move the whole machine freely anywhere)

So the design was born. It is huge.I mean really, the filament holder is about 60cm diameter, and bigger than the machine itself. The whole thing is about 1 meter height. Here is a photo:

It can turn freely, I use two 608 bearings for it. Maybe you can see better from this angle:

Also the two disks are about two times bigger (in diameter) then the filament itself:

The reason is simple. The previous filament holder had a tendency to make a knot from the filament, ruining the whole print as the machine could not take any more filament. So it prevents to wind off from the holder.

Ingredients:

• 6+6 M4x16 hex bolts
• 12+12 M4 washer
• 6+6 M4 nylock nut
• 2 608 bearings
• some leftover M8 threaded rod pieces: 5 ~30cm long ones
  also 2-4 more as saltire/Saint Andrew's cross to make it more rigid. (you can see 2 on the pictures)
• some rp parts: 4 disk, 2 bearing holder, 4 mendel attachement
  (see the first picture)
• 8+16 M8 nut
• 4+16 M8 washer
• 4 M8 mudguard washer (normal washer is fine too, if you haven't any)
• cardbox

Here is the deal:
If there are more then ten people requesting the RP part design files (.stl) within a week, I will upload
them to thingiverse. If not, I dont brother to do it.

Also one more photo at the end;-)

Hope you find inspiring this brainstorming article.

Update:
I also somehow forgot to mention where the idea came from. I saw thing:1550. The credit for the cardbox idea goes to Charles Pax of course.

z-switch-holder - thing:3134

When I made my last modifications to the heated bed, my previously designed z limit switch holder was not working anymore.

So I decided to rethink the design, and made this thing:

I also uploaded all design files to thingiverse, as thing:3134.

It has many advantages over the stock one:

• does not require mounting holes on the bed
  (useful if you are replacing the stock bed, with something like a heated bed)
• has wide tolerance
• saves two M5 hex nuts and bolts.
• reprappable;-)

Here are some photos how are mounted on an actual machine:

A side photo:

One from behind:

It works really nicely. Download it, print it, enjoy!

Big foot - thing:3135

If you are using the previous z limit switch holder, maybe you need this one too:

Having your own bed results some offset. Your long M5 bolt, which pushes all of the limit switches has real difficulties to push all of them easily.

Even my previously designed big foot was too small. So this new design was born.

I uploaded to thingiverse, as thing:3135.

Here are some photos from real life.
The first one prove, how big is it, and just have the maximum size possible.
(note it almost touch the acrylic part when X home'd):

A side photo:

And one from perspective:

Counter nut holder for the extruder - thing:3136

Ok, this thing is really simple. Actually I successfully designed and printed it at the first try!:-D

The stock acrylic plastic, where you are supposed to push the hot M3 nuts is really a bad thing.
Sooner or later the bolt comes out of the plastic, it is a nightmare to change the plastic in your extruder.

So I designed this thing, and was on the machine within a half an hour:-)
I also replaced the M3 bolt with longer ones (M3x50), so I never really need to completely take off the filament pusher when I change plastic.
Here is a photo while mounted:

Also an another photo, where you can see the longer bolts:

Extruder stanchion - thing:3138

This thing is really simple too:

It is basically a cube, which helps to make the extruder more rigid. The extruder does not shake as much as normally would do when it makes short fast moves.

Here is it mounted:

Also this design is available too on thingiverse, as thing:3138.

I hope you enjoyed this little article. The upcoming article will be about some test prints.

It's time to update my version too;-)

Im recently developing some bigger things, like an enclosure case
for Openmoko phone and some circuitry.
Here is a failed print about the first prototype:

The final case will be 200x140x80mm, so it is pretty big. (however, I will redesign it to make a bit
smaller, so only about 160x140x80;-)

All in all, I needed to develop a bit further my heated bed.
I always assumed it is operating a bit too low temperature.

Some days ago I was in Ikea store, and there were some leftover items, what you can buy at a reduced price,
and I found a 100cmx40cm MDF sheet for ~1.2EUR, it was an "instant get";-)

The rest of the story is obvious, I went to home, and three days later,
I had my improved heated bed:

I covered the aluminium bed with MDF sheet even at the top:

I also added one more power resistors at the bottom (6 in total), and borrowed a
wool coat from my mom as an additional insulator. I have seen on Nophead's blog, that wool is perfect insulator:

Im a bit worried though, I think the whole thing will catch fire sooner or later ...

The power resistors are at 170C, and the MDF sheet are smelling like it were burning.
So the machine has a really unpleasant smell right now. I have not really liked the ABS
fume, but burning wood is way stronger smell...

Anyway small price for the final result...
Im thinking of covering the bed with Polyimide tape first, and after with the MDF sheets.

z-switch-holder

When I assembled the whole bed, noticed, that my z_switch_holder are no longer working.
So I designed a new one, along with the "big_foot":

I dont know about you guys, but for me nothing works at the first time. Everything
what I design have at least 4-5 iterations. Just like when I do programming,
which is mainly a trial-and-error process too.

Sunk magnets

With each aluminium plate machining I make a small improvement.
This time I made blind holes for the neodymium magnets:

Final thoughts

This heated bed became some kind of a monster. It is pretty complicated, has an
enormous size, which I dont think the machine will ever use...

I also made recently some test prints with some bigger objects (need to write a
blogpost about it though;-), to push a bit to the limit of this heated bed, and
the result were a bit ...

Step one: Pins
Mount the 5 pins. Also remove the protecting foil from the aluminium if you have any.
(precision plate usually has one).
On the below picture I highlighted the pins, but the foil is still on the aluminium (remove it!).

Step two: Terminals

Mount the terminals on the back of the bed (four in total):

Each terminal is mounted using an M3x35 bolt, 13 washers under the terminal, and one M3 nut.

The bed is pretty hot, so we need to leave some distance between the terminals and the bed, hence that many washers.

Step Three: Resistors

Prepare the resistors before mounting them.
(you may be able to skip this step if your kit arrived power resistors with wires already mounted)

For this step you need the two pliers. The leg of the power resistors can bend really easily, so you need to hold the leg with a plier while you are twisting the 1.5mm2 wire with the other pliers.
You cant avoid the use of two pliers, you risk to simply twist off the leg of the power resistor.

The use of the two pliers:

Usually 4-5 twist is enough, but make sure, the wire is not moving
(if it is not tight enough, then twist more).

Cut off the remaining wire:

And here is the final result:

Do this for all of the resistors, so 10 legs in total (5 resistors). It should take less then 10 minutes.

Step five: Resistors mounting

Mount all the five resistors using the shipped M3x6 hex bolts, dont overtighten it!.
The aluminium threads are not strong.

Should look like on this photo:

Also notice, that the wires are longer then they are needed to get to the terminals. Its on purpose, see next step.

Step six: Connect the resistors

I made in all wires an "S"-form when connecting to the terminals.
It has two goals:

• easier connecting to the terminals
• thermal stress/expansions does not loose the terminals' screws

Here is a picture of it:

It does not look beauty, but who cares?;-)

Here is a picture of the final wiring. All the resistors are connected parallel.

Step seven: Magnets

Caution: These are really strong magnets.
You need to handle them with extra caution. If you wear pacemaker, then ask somebody else to mount this bed.
Also you can easily injure yourself if your finger is pinched between two magnets.

Put some polyimide tape on the magnet:

And place all the 12 at the bottom of the bed, in a way that 3 at each edge of the steel sheet, and four in the middle.
Make sure none of the wires are touching them. Also may be a good idea to put one layer of polyimide tape between the magnet and the bed.

Here is one magnet mounted on the bed:

Step eight: Power supply

The power supply is a 200W 230/23.5V toroid transformers with integrated heat protection:

Clean off about 200mm from the end of the power supply's wire.
Cut into the wire watchfully to not cut into the inner insulations:

Here is cleaned off:

You should connect the power supply just like on this photo:

Step nine: Polyimide tape

Prepare the steel sheet with polyimide tape. The best way to cover it diagonally just like on this picture:

Step ten: Replace the bed

We are done. You only need to put this bed into the machine.

ps: This article may be updated in the future, as I want to keep it an up-to-date assembly instruction.

If you are interested buying one, drop me an email to

Hope you enjoyed this article.

JAGS was kind enough to send me a sample before I order more from the factory.
Also I decided to do a detailed article for future reference.

Positives
It has the best cross-section what I have seen so far. It is perfect circle.
Here is what Teddy bear measures:

And the 90 degree turn:

So it is really top-notch quality.
You can check the roundness without any measurement instrument,
by twisting the filament between your two fingers. You feel it when it is not round.

Negatives

I was pretty happy with the filament until I have tried out.
It is really hard to wind it to the filament holder.
I broke off about 5meter of the filament, and two people required to wind it. It is really springy,
so winding to a smaller diameter requires at least three hands;-\

Here it is a photo winded to the holder (when I took photo, a third hand hold the filament to not wind off from the holder):

Im printing ABS at 244C, this filament at this temperature embeds many small air bubbles:

And also at this temperature it has no strength, looks like Im extruding some kind of plasticine:

So it would be best to extrude at 240C for me. Here is a comparison photo:

From left to right: printed with white ABS at 244C(see worst filament ever blog), the gray filament at 244, and 242 at the right side.

Also this plastic sticks far less to the polyimide tape. I needed to set the temperature at the first two layer to 250C, because it tend to not stick to the heated bed at all.
I never needed to hand-adjust the temperature during the print before.

Maybe if I would raise the temperature of my heated bed, i would not needed to change the filament temperature.

Here are some closeup photos of the comparison:

Also the worst part:
The filament has some kind of contamination, some other material then the plastic.

Also I cleaned a bit more the filament:

And it occured to me what never occured before. Something blocked the nozzle, because the filament contained something, which could not pushed out at the 0.5mm nozzle hole.
(Ok, maybe Im not the right person to decide.
I only tried out 3 different ABS suppliers, and only extruded 7kg so far. So other persons may have different experiences...)

So it ruined the print about its half. I printed 12 x-vert-drive-side-plate-180-end at once,
and I was not at home, so I only noticed when I got home at evening.

It pushed two minuscule filament out of the nozzle, if I helped with my hand pushing the filament into the extruder.
Enough talk, some photos:

I tried to pull out the filament two times, but it was not helping.
I needed to absolutely dissassemble the nozzle, and take off any remaining plastic when the nozzle was at 250C. It is really time consuming process, and also working with something in your hand which is at 250C is a bit risky.
I used a capacitor, and its leg to clean up the nozzle. I basically pushed in the extruder, and pulled out (it always sticks some plastic to it).
Here is a closup photo:

The round stuff is what stuck at once to the capacitor's leg.

Also here is a closeup photo, what came out of the extruder nozzle:

Also the ABS has a pretty bad fume, but this one is even worse. It has really the worst smelling ever.

So I dont know what to do. The manufacturing quality is perfect, but the material has some real problems.

Maybe natural ABS (without any additional thing) is a safer choice. I will contact JAGS for details and infos.

Also I fixed my worst filament ever by pulling it through a 3mm hole. Also doing this, the plastic loose its springyness, so was a lot easier to wind it to the holder.

So Im prefering this filament for now. (it push the extruder to its limit, even after the fix, but anyway)

Also what I like in this gray colour, that it really emphasizes the imperfection of my skeinforge settings;-)

So Im a bit hesitating...

Update:
When I was writing this article I also ran a pretty big print (like 6 hours print), I printed the first two layers at 250 degree Celsius. Everything seemed right, when I noticed one of the x-vert-drive-side-plate-180-end part came off the table during the print:

So there were pretty big warping:

The bottom of a part:

You can clearly see where it is detached from the heated bed.
I kept printing, and another issue arrived. The nozzle got blocked, again.
I cleaned the nozzle with a capacitor's leg, and continued printing, then
I tried to clean more then 5 times, and I dissassembled the nozzle absolutely
during the print.
I could not save the print, and also an another part got detached from the bed:

The extruder blocked about 10 times. So I think there is something really in the
extruder's nozzle. A 0.5mm diameter pebble/stone is really hard to notice.
Im not sure if I can clean it off completely.
I will cut off the cables from the extruder, so I can see it more clearly what is
inside. Maybe I need to buy pure acetone at Monday.

I will switch back to my white filament, and print using that filament.
Maybe in a week or so, I will try to use up again this gray filament.

I dont know if there is a single grain of sand, which I cant clean off,
or the filament has multiple contamination.
That is the main reason, why I want to switch back to my white filament.

Update 2:

I switched back to my white filament, and I had no blockage since.
(I have printed 4 object so far).

What is interesting, that this gray filament contains some kind of lubrification.
The first two object could not stick too well to the heated bed:

Also to be more clean I have placed on a flat surface and numbered them:

(The number 1, is the first print after the gray filament, number 4 is the last print)

Update 3:

I do believe, it contains some lubrificant/oil, because it is more slippery compared to other printed parts (for example compared to the white parts).

Also I think, the glossy finish what the filament has, and the printed objects comes from this added oil/lubrificant.

I had many problems lately with my extruder.
First I broke its PTFE tube because I printed with extruder nozzle too close to the bed.

When I replaced the PTFE tube, I have been supposed to prepare the PTFE tube like this:

I drilled with 4.5mm drill bit too much. with my new filament the extruder is very unreliable.

I think with this filament the extruder is operating beyond its limit.
I bought 50kg of it in 5kg coil form, like this:

Here it's a comparison photo between my old (blue) and new(white) filament:

I called my teddy bear to help measuring it:-)

The micrometer precision is 0.002 mm by the datasheet.

The cross-section of the new filament:

Looks like it has more an egg form then an ellipse:-(

Here is what Teddy bear measured on the old filament:

And a 90 degrees turn of the filament:

Its is pretty round in my opinion.

And now the new filament:

And the 90 degrees turn:

Yeah, I could not believe in my eyes either. The difference between 3.5 and 2.7mm diameter is a huge.
Working with this filament is not easy, I do believe i need a more reliable extruder then the stock Rapman's extruder.

I need to crack this nut, because I have 50kg of this filament...