Project: The next heated bed

Topics around mechanical design, controller and electronics. Mods & hacks welcome.
socke
Posts: 215
Joined: Mon Mar 21, 2016 2:55 pm

Project: The next heated bed

Postby socke » Sat Mar 25, 2017 6:12 pm

I made again a big modification of the heated bed in my KS N2. If you already read my earlier post of my first modification (http://forum.raise3d.com/viewtopic.php?f=4&t=1003), you may ask why? Well, here are my reasons:

  • The original aluminium plate was far away from being even. In the center of the bed there was an air gap of around 1mm between the aluminium and the glass plate – estimated at room temperature. In hot state it was much more. As air isn't the best heat conductor, it took a long time to get the glass plate on print temperature. If I was printing PC (bed set to 110°C) I had to wait at least half an hour – anoying!
  • A leveled bed at room temperature did not mean, the bed was still leveled at 90°C.
  • Leveling the bed was still improvable. It was much easier and faster than adjusting the original bed, but still took a few minutes.
To avoid these disadvantages, I decided to use a 8mm strong, casted aluminium plate as base. These are offered in custom dimensions, so no sawing is needed - only drilling a few holes.
The heater is an silicone heater glued on the bottom of the aluminium plate. There are versions for 12V, 24V, 110V and 220/230V supply available. Because of the bad performance of the original bed, I decided to increase the heating power – I have chosen a 220V, 750W version. If you are not familiar with installing components on mains voltage level, I strongly recommend to choose a 24V version (with the same power rating as the original bed)! It would also make the mod much easier, as the original power supply and wires are still usable.
In any case you should be prepared for modifying the printers firmware, as the built in thermistor is most likely of another type. At least that was the case here.
As I've chosen the high power variant, the heater is switched by an Solid State Relay which is controlled by the original heater output of the mainboard.
The springs I've used have the same dimensions as in my first mod, but are a little bit stronger. Maybe it's not really needed, but it helps stabilizing the bed as I'm using only 3 springs (and 3 thumb nuts) for the easiest possible handling.
I also designed a new set of stabilizers for the springs, these needed to be a bit smaller, as the bolts are mounted on the very edge of the aluminium plate.
At the beginning, my aim was also to have changeable bed surfaces by using some cheap window glass plates. But currently I think, I don't need this feature anymore because a colleague of me recommended to use a thin sheet (0.5...1mm) of Pertinax as print surface. After my first trials with this surface I'm really impressed. I was able to print immediately every filament I normally use (PLA, PETG, PC). My colleague is also printing ABS, TPU and others on it for years. The best is, this material is cheap and durable. If better sticking is needed, just do a light sanding (but do not breathe the dust!). The only disadvantages I know are: It takes some care on attaching and you shouldn't heat it above 120°C as it would produce toxic fumes. Also it smells a bit at the first few times of usage.
Overall there are a a lot of advantages and I wonder, why this material isn't recommended more often? Most likely I will stick a new Pertinax sheet directly on top of the aluminium plate later, I think I don't need any other print surface anymore.

Here is my shopping list:

3D data:
  • Aluminium plate:
    heated bed v17.zip
    (4.61 KiB) Downloaded 31 times

    Here is also an comparision of the original (red) and my new bed (green):
    comparison old - new bed.JPG
  • Option: 3D printed corners (2x) for fast aligning of the glass plate:
    corner.stl
    (19.22 KiB) Downloaded 19 times

Regarding the firmware, the most important thing is to select the right temperature sensor, in my case:

Code: Select all

#define TEMP_SENSOR_BED 11

Further, I found that there were relatively large fluctuations in the displayed bed temperature. This can be explained with the higher heating power. Even if this is more a cosmetic issue, it was easy to solve by decreasing the bed hysteresis and the control interval:

Code: Select all

#define BED_HYSTERESIS 1
#define BED_CHECK_INTERVAL 500

Below are some fotos from the build:

The heating pad arrived:
DSC_0590.JPG


to be continued...
Last edited by socke on Sat Apr 15, 2017 3:29 pm, edited 5 times in total.

socke
Posts: 215
Joined: Mon Mar 21, 2016 2:55 pm

Re: Project: The next heated bed

Postby socke » Sat Mar 25, 2017 6:12 pm

The prepared aluminium plate:
DSC_0595.JPG

The bottom of the aluminium plate with the silicone heater sticked on, please note the grounding wire:
DSC_0597.JPG

Mounted and connected the SSR in the printers bottom:
DSC_0613.JPG

Drilled 3 new holes into the printer, diameter should be 3.5mm:
DSC_0592.JPG

Placed the the new bed:
DSC_0599.JPG

to be continued....
Last edited by socke on Sat Mar 25, 2017 6:51 pm, edited 3 times in total.

socke
Posts: 215
Joined: Mon Mar 21, 2016 2:55 pm

Re: Project: The next heated bed

Postby socke » Sat Mar 25, 2017 6:13 pm

Also mounted the power socket cover from Raise3D at this opportunity:
DSC_0604.JPG

Front view with compression spring and printed corner:
DSC_0639.JPG

Finished and printing something:
DSC_0617.JPG

DSC_0624.JPG


Conclusion

I have achieved all my main goals with this modification. The new aluminium plate is precisely flat and more important it keeps flat in the tested temperature range. Also the heating performance has been improved: Heating the bed from 17°C to 100°C takes only 3 minutes.
Further, the leveling of the bed can't be easier or faster in my opinion with the 3 thumb nuts. Now it takes me only one minute...
At least I would recommend everyone to use the Pertinax build surface as it can be used also without the whole bed mod. It's cheap, lasts long and can be used for any common type of filament.
Last edited by socke on Sat Apr 15, 2017 3:30 pm, edited 4 times in total.

socke
Posts: 215
Joined: Mon Mar 21, 2016 2:55 pm

Re: Project: The next heated bed

Postby socke » Sat Mar 25, 2017 6:13 pm

Update 15.04.2017:
Currently I'm using 4 paper clamps for fixating the glass plate, which works very well:
DSC_0674.JPG

Also updated the shopping list.
Last edited by socke on Sat Apr 15, 2017 3:38 pm, edited 2 times in total.

socke
Posts: 215
Joined: Mon Mar 21, 2016 2:55 pm

Re: Project: The next heated bed

Postby socke » Sat Mar 25, 2017 6:13 pm

reserved

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walshlg
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Joined: Wed Mar 23, 2016 12:01 pm

Re: Project: The next heated bed

Postby walshlg » Sat Mar 25, 2017 10:17 pm

excellent mod. 3 point leveling is best but impossible unless you have such a strong plate, which needs a stronger heater! I also like how you extended the plate foreward, its a shame to waste that front 12 mm of printable area just to have clearance for plate clips. well done

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walshlg
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Re: Project: The next heated bed

Postby walshlg » Sat Mar 25, 2017 10:19 pm

where is the thermal probe?

socke
Posts: 215
Joined: Mon Mar 21, 2016 2:55 pm

Re: Project: The next heated bed

Postby socke » Sun Mar 26, 2017 7:22 am

walshlg wrote:where is the thermal probe?


It's at the bottom side of the heater pad, in the center at the end of the black wire.

socke
Posts: 215
Joined: Mon Mar 21, 2016 2:55 pm

Re: Project: The next heated bed

Postby socke » Sun Mar 26, 2017 7:37 am

walshlg wrote:excellent mod. 3 point leveling is best but impossible unless you have such a strong plate, which needs a stronger heater! I also like how you extended the plate foreward, its a shame to waste that front 12 mm of printable area just to have clearance for plate clips. well done


It's not extended forward, it's shortened backwards and on the right side. But yes, these areas originally just wasting power as they are not in the print space (space is needed for extruder head only). But on the front, the originally clips made some print space not usable.
With my mod, the bed is over sized by only 10mm at the left and right side for mounting.

lami3d
Posts: 220
Joined: Sat Oct 29, 2016 7:40 am
Location: Marseille - France

Re: Project: The next heated bed

Postby lami3d » Sun Mar 26, 2017 12:11 pm

Wow, tell me when you will produce your own printer !! i will buy it :D

Your first mod is already great and i never had a pb to be flat (even if it's hyperstatic,= because i put 13 points and it doesn't move an inch for 3 months and i removed the glass plate many times, and in any case it takes not too much time to adjust it) --> tx again !

I don't if i'm going into this mod but it seems a very good one.

To accelerate the heating of the chamber and plate (for PC for example), i blow with a hair dryer at the bottom of the printer during 5 minutes :lol:

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Vicky@Raise3D
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Joined: Fri Mar 25, 2016 3:54 am

Re: Project: The next heated bed

Postby Vicky@Raise3D » Thu Mar 30, 2017 6:31 am

A little curious whether our machine can afford a such high power part.
Please keep us updated. Want to know working life and whether it does any harm to other parts.

socke
Posts: 215
Joined: Mon Mar 21, 2016 2:55 pm

Re: Project: The next heated bed

Postby socke » Thu Mar 30, 2017 7:23 am

Vicky@Raise3D wrote:A little curious whether our machine can afford a such high power part.
Please keep us updated. Want to know working life and whether it does any harm to other parts.


Why shouldn't it afford the power? The heater is directly supplied by mains power, which causes an additional 3A current there in my case.

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Vicky@Raise3D
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Re: Project: The next heated bed

Postby Vicky@Raise3D » Fri Mar 31, 2017 3:37 am

Do you mean the main power supply unit in our printer or you connect the heated bed by other power supply way?

socke
Posts: 215
Joined: Mon Mar 21, 2016 2:55 pm

Re: Project: The next heated bed

Postby socke » Fri Mar 31, 2017 6:25 am

As written before, the heater is not connected to the 24V= line from the printers internal switched power supply, but directly to 230V~ mains power. So the limited power of the internal supply isn't an issue here.

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walshlg
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Joined: Wed Mar 23, 2016 12:01 pm

Re: Project: The next heated bed

Postby walshlg » Fri Mar 31, 2017 4:41 pm

I am getting nervous about a 220V connection , I hope it is well covered, I have dropped a few screws down into the base several times!!

socke
Posts: 215
Joined: Mon Mar 21, 2016 2:55 pm

Re: Project: The next heated bed

Postby socke » Fri Mar 31, 2017 6:15 pm

I can assure you, it is well covered.
At least much better than the original main switch in the KS printers without the newly published cover. ;)

ssommer79
Posts: 24
Joined: Sat Oct 29, 2016 6:07 pm

Re: Project: The next heated bed

Postby ssommer79 » Mon Apr 03, 2017 11:12 am

If i would like to change the current heated bed on my N2 to another 24V Versions, what is the Limit for the "Watt"?

24V/200W, 24V/300W, 24V/400W, 24V/480W?

socke
Posts: 215
Joined: Mon Mar 21, 2016 2:55 pm

Re: Project: The next heated bed

Postby socke » Mon Apr 03, 2017 12:27 pm

If you don't like to replace the original power supply, I think 24V/300W is a safe choice.
Maybe 24V/400W is working too, but I wouldn't take it if I wouldn't have measured the real power of the remaining system before.
But it could happen, that you will reach not much more than 100°C bed temperature with the 300W heater.

socke
Posts: 215
Joined: Mon Mar 21, 2016 2:55 pm

Re: Project: The next heated bed

Postby socke » Sat Apr 15, 2017 3:40 pm

Just added a minor update to the first posts, showing how to fix the glass plate...

lami3d
Posts: 220
Joined: Sat Oct 29, 2016 7:40 am
Location: Marseille - France

Re: Project: The next heated bed

Postby lami3d » Sat Apr 15, 2017 5:10 pm

I would love to perform this mod but it seems too much for today :oops:
I'm not even sure to understand everything well ! but it's very impressive :o


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