PCB Heatbed
Release status: working
Description | PCB Heatbed
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License | unknown
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Author | |
Contributors | |
Based-on | |
Categories | |
CAD Models | [[1]]
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External Link |
Contents
WARNING
"WARNING!!! Be aware from where you buying the PCB heatbeds!! There is one critical thing, the heatbed must be etched directly from 35um copper clad! ASK YOUR SELLER!!! If the board is plated, as it's normally done, no manufacturer can guarantee the final thickness of copper or even how even the copper is around the board. Which means that the final power wont be evenly distributed around the board or the board wont have high enough output generally.
Main warning sign are plated holes! Plating of holes requires copper plating.
About
PCB Heatbed MK1 is developed by Josef Průša
I was working on this idea for nearly six months, inspired by neufeld.newton.ks.us/electronics/?p=864 .
Where to get it
The .brd file is available here: [[2]]
(Please note that I dont get any provision from these :-)) Manufactured PCBs can be found here:
EU
RepRapSource (Germany) http://www.reprapsource.com/en/shop/show/6403
Cubic Print (Germany) http://www.cubic-print.com/PCB-heated-bed
LHPPortugal(Portugal) http://www.lhpportugal.com/loja/index.php?route=product/product&product_id=193
USA
Printing
Cover the bed with kapton tape. Degrease it and print.
ABS temp: 110°C PLA temp: 50-60°C
MAKE SURE YOUR PSU HAS 10 MORE AMPS SPARE!!!
Mounting
Known working solution, I (prusajr) use is Glass sheet (3mm) with glued on cork standoffs and on top of that is glued the heatbed. http://www.flickr.com/photos/prusajr/5410919911/ http://www.flickr.com/photos/prusajr/5410919707/
When mounted only using the four corners, the inherent warp of the pcb can be a problem, hence it is better to use the cork mounting system above (as the piece of cork in the centre helps to keep the pcb flat).
Magnets can be used in replace of the cork, this makes the bed removable. However, I (mooneyj) have only tried this on a darwin type printer (where the build platform only moves in z). During fast printing, the darwin vibrates and it seems the heatbed magnets slide over each other slightly. The acceleration of the y axis on a mendel may cause the magnets to slide also. Perhaps a hybrid of magnet and bolt mounting would work well?.
The current standard, however, is to simply place the glass on top of the heatbed, and affix it on the four sides with bulldog clips. The clips will not melt under pressure, and sufficiently hold the glass to the bed. This makes removal more easily for cleaning as well.
Note: According to the Eagle file posted on Thingiverse, the M3 holes are spaced 209 mm
Sides
PCB Bed has two sides, one with the traces (bottom side) and one with silkscreen (top).
Printing on top side is safer, works great.
Printing on bottom is more effective and heats up quicker. (Though the LED, resistor and wire connections are liable to collision with the print head. Also the tracks could be damaged if the print head collides. Make sure your z-bed-springs are not too strong to prevent damage during a collision).
Connection
Optional LEDs
The LEDs are optional, but if you choose to use the LEDs you MUST install the resistor.
'Parts'
2 x Surface Mount LEDs
1 x 1K ohm Surface Mount Resistor
Mount the LEDs in different directions (polarity) so that one of the LEDs will light up regardless of the board's polarity. You can use a single LED if you are certain of the polarity.
Electronics
RAMPS
See RAMPS1.4, RAMPS1.3, or RAMPS1.2 depending on your version.
Sanguinolou The MK2 PCB heatbed heats up to 110C when powered through the heated bed connection on Sanguinolou, your power supply should be 300W and ensure your wires from your power supply to the Sanguinololu should be capable of handling the total draw of 20A+. Using a 300W ATX power supply with the 4wire ATX dual 12V connector is working well for me.
N.B. It is recommended that you use a heatsink on your heated bed mosfet, it will get hot!
Testing
Its now in working state, Printed load of kits on it, working great.
Main Idea is to use resistance of pcb traces as heating element.
The following video shows a PCB heatbed MK2 being heated to 60 degrees as seen by an infrared camera: <videoflash>QE90bDUaAno</videoflash>
FORKS (not done by Prusa)
MK2
(It's not successor of MK1 even with it's name. It's concurrent design. - Josef Prusa)
About
MK2 Heatbed - Minor changes by Tony Lock
I liked Josef's original design but wanted to be able to use through hole components, have the thermistor poke through the middle and for it to look good on the 'back' with the silkscreen that Josef designed on that side as well.
Where to get it
The MK2 .brd file is available here: File:PCB heatedbed Mk2.brd
Manufactured MK2 PCBs can be found here:
Printing
MK2
Although you can print directly to the bed covered in polyimide tape, no PCB is perfectly flat. It is recommended that you follow the directions in mounting, below, for better results.
Mounting
MK2
The MK2 board can be mounted either side up and is designed to be mounted as Josef describes:
http://josefprusa.cz/pcb-heatbed-final-mounting-and-wiring-solutio
The holes in the 4 corners to attach the heated bed MK2 to the top print plate are not suitable for M3 bolts though! Use M2.5 instead.
The glass protects the tracks from a head crash and is easily swapped out.
The board dimensions are identical to the MK1 design.
Insulation between the board and the thick plate should improve heat-up times and reduce energy consumption. An example is here:
http://reprap.org/wiki/Mendel_heated_bed#Thermal_Insulation
Caution, I have not tried this with the temperatures that the PCB bed can reach!
Sides
MK2
The PCB still has a side with the traces on and a side without but now the silkscreen is on both the top and bottom, this makes it look good even when 'upside down' under a layer of glass. The LED, resistor and power wires can be mounted on either side of the board, with either surface mount or through hole components. If you are using through hole be careful when soldering to not have overhang on the other side of the board that could interfere with the glass and introduce a gap between the glass and the PCB.
There is a central hole in the board (similar to this one http://wiki.makerbot.com/cchb1). It is sized so a small thermistor (for example the EPCOS one: http://uk.farnell.com/jsp/search/productdetail.jsp?CMP=i-ddd7-00001003&sku=3878697 ) will fit though it allowing contact directly with the glass. todo: test efficacy of using heat sink compound to better thermally couple the thermistor to the glass
Connection
Polarity doesn't affect the PCB, however the LEDs have a polarity.
MK2
There are pads and un-plated through holes for connecting the power wires. Ensure that the wire you use is thick enough for 10A, and solder it to the pads on the track side of the PCB. It is a good idea to think about strain relief so your moving build platform does not flex the joint, this can lead to failure of the joint over time. I recommend routing the wire from the heated bed to strain relief on the thick sheet before routing it to your controller/power supply. todo: get pictures of strain relief
Optional LEDs
MK2
The LEDs are optional, but if you choose to use the LEDs you MUST install the resistor. Solder the components to the pads on the track side of the PCB. With the MK2, conventional wired parts can be substituted for the surface mount parts.
'Parts'
2 x surface mount or conventional through-hole LEDs. Install with opposite polarity so one or the other will light up regardless of the polarity of the power supply to the board.
1 x 1K ohm surface mount or through-hole resistor