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Heat bed Mk3

Posted by Meph 
Heat bed Mk3
October 11, 2017 06:26PM
hi one question i got a heatbed MK3 im having a hard time achiving temperatures of 90 degrees, i was looking into connections of bed and all this time i had only 1 circuit enable it was connected 1 to positive and 2 to negative, i was searching and i see that this bed is plugged 1 to positive 2 and 3 to negetive to enable the 2 circuits
i have wired all and now and i notice that the ramps 1.4 Mosfet is getting to hot and that when red led is blinking it does click noises non stop and i measure amps and i read 15 Amps,,bed seems to heat way faster, is this normal?
if so do i need to replace fuse with one bigger like 20 A maybe and replace the mosfet with a better one?
what about the litle clicks i hear from the led blinking cause of PID?

Edited 1 time(s). Last edit at 10/11/2017 06:42PM by Meph.
Re: Heat bed Mk3
October 12, 2017 12:41AM
90C is about the best you get with a 12v supply ...I wouldn't use PID with the bed with a RAMPS at 12V too many horror stories with burnt connectors and blown fets. grab one of these mosfet boards its simple to install and protects the main board from thermal damage.
Re: Heat bed Mk3
October 12, 2017 03:21PM
that Mosfet Board might be a good option
was wondering if odify the system for 24v if a 16.8 Amps power supply would be ebought for all system
right now i have a 12V 30 Amps power supply
Re: Heat bed Mk3
October 12, 2017 03:34PM
My 1st 3D Printer came with a 12V at 30 Amps power supply, don't get me wrong but it works for what I print but Could use a little push..
My 2nd 3D Printer came stock with a 24V at 20Amps 480Watts supply, and it appear to be just right.
Re: Heat bed Mk3
October 13, 2017 09:24AM
I have a 12v Mk3 heatbed on my Prusa i3 - it will make 100C if I wait long enough (20+ minutes). It struggles to maintain it if the room is cold though.

To achieve this I had to put insulation on the bottom of the heater - 2 layers of 2mm cork, with a 1.2mm aluminium plate to hold the cork on. I used the screw holes in the heatbed to hold everything together, using nuts and washers to get the correct spacing.

I also find that a piece of corrugated cardboard sitting on top will speed up the heating.

I should add that my CoreXY printer also had a Mk3 heat bed up until recently, but has been replaced by a 200W stick-on heater at 24v - got to 120C in about 8 minutes! It did put a heavy load on the power supply, so currently I'm modifying it (again) to a 230v 200W heater. Obviously this is not trivial as there are so many safety issues to be dealt with, but it does mean that I can use a far smaller power supply (120W, I believe) for everything apart from the heat bed.

Edited 1 time(s). Last edit at 10/13/2017 09:28AM by David J.
Re: Heat bed Mk3
October 13, 2017 12:44PM
Many (perhaps most) PCB bed heaters are under-powered for printing ABS. You can get more power out of them by turning up the power supply voltage, if your power supply is the usual LED/CCTV sort that has a voltage adjustment potentiometer AND it has spare power capacity. For example, turning up a 12V supply to 14V will give you 36% more heating power.

However, if you are running Arduino/RAMPS with a graphical LCD attached, then the voltage regulator on your Arduino may be overheating already, and turning up the voltage will make it even hotter unless you provide 5V power to the Arduino a different way.


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: Heat bed Mk3
October 14, 2017 02:40AM
i guess i would need to modify my ramps 1.4 i see many videos in how to do it from what i understand it needs to remove a diode that powers arduino ,then use a buck converter to step down voltage to power arduino, change the poly fuses, most like needs to also change the fans i would say to higer voltage
Re: Heat bed Mk3
October 14, 2017 02:59AM
If you increase the PSU voltage to just 14V, you don't need to change the polyfuses. You can put a couple of silicon diodes in series with each fan to being the voltage back to about 12V; although I know of people who run 12V fans form 14V with no apparent problems.


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: Heat bed Mk3
October 14, 2017 01:26PM
just got my 3rd MK3(think the pads are a little different) mainly because when used with the openbuilds buildplate it makes a nice simple sandwich.

...but havent wired any up yet sad smiley though Soon i'll have one done ) and might not need the other 2
as I plan to be able to move working bed between machines.
I got the MKS Mosfet with Red Heatsink, I got my 12AWG Silicon wires(and yes they are a little thick me thinks)
I probably dont have a good enough solder iron to do the job might put the bed on the stove.
I also have some 18 awg but I'm guessing I need something inbetween to solder to bed.
I have some thermistors on the way, but not the ones I wanted,
I couldnt find what I really need for the Pads on the MK3 Led's & resistor or NTC therm block?

I'm thinking of sandwiching a Silicon Trivet under the bed

these are cheap in Home Bargains, but wouldnt mind one of these honeycomb ones in Black

(with laser cut perspex) to keep the heat up/even, (maybe one ontop during warm up)
but doubt i'll be going above 60 for a while. still contemplating XT60's or something for quick change...of relay/mosfet to other machines. not sure what wires/connectors i'll use for the signal, i have some JST connectors so probably them.

It would be good if some sort of Clip/Guard/shield/clamp could attach to the bed where the wires go too
but probably not a great idea using PLA.

I found this pic on a site and the wiring for the bed doesnt look like how I intended to do it. Maybe for different relay setup & mainboard


Edited 2 time(s). Last edit at 10/15/2017 03:42AM by MechaBits.
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