the hotbed wont go past 70c / gcode qurk

ive got a anet A8-b prusa i3 ben working on it for months just barley go it to print 2 ABS cubes.

the hotbed wont go past 70c and taks 4ever to git thar with out help.

so im thinking of gitting bigger power box.

but i alredy went from 20A to 25A wold 30A blowup my bord?

or do i neede anew hotbed?

also got some gcode problems my printer is pretty persnickety about wanting the line starting with m140 in-sted of m190 i always have to maunly chage this is thar a way to make cura do this automatically?

Edited 2 time(s). Last edit at 09/09/2016 03:46AM by BigC.

you need to check a few things with your bed.

Most of this presumes you have a ramps type board,,,

Firstly you need to insulate under your bed, or your just trying to heat the room.
secondly check the voltage on the heated bed, it has to be 12, any less and you need to find out why, were the loss is, loss is bad it will be causing a hot spot which leads to fire.
check the bed wire are not heating up at all
check the bed terminals are screwed down hard and also cold.

The bed on its own uses 11amps it wont pull any more than that, but a lot of power supplies cannot provide the listed current,

If your power supply is adjustable up the voltage to about 13v, but no more the mega can't take it.

If your running a ramps, its also a good idea to replace the crappy mosfet (STP55NF06L) with a better one. IRLB 8743 is a good replacement

Lastly the polyfuse, replace it with a real fuse, make sure its not cutting out (putting a fan on it and see if ithe bed gets hotter as a test)

Edited 1 time(s). Last edit at 09/09/2016 05:18AM by Dust.

iv unplugged the hotbed set it to 110c, checked the output from the ANET V1.0 Ramps 1.4 only got 9.82V and 8.31A.
on the bottom of the hotbed it says it can take 12V or 24V depending on wire configuring.
its currently configured for 12V.

its a pcb MK2B dual power GPLv2 by reprapdiscont.

my swiching supply is 12V 25A only. it includes a fan built-in.

Edited 7 time(s). Last edit at 09/09/2016 05:46PM by BigC.

9.82V and 8.31A. is really low... should be 12v 11amp

check your bed cables, if in doubt double them up so you have twice as much copper. (this includes both gnd wires on the bed since its a 12/24 bed.)
and test again

Also check you bed resistance should be 1.1 ohm (nb a lot of meter cannot read this accurate)
measure the bed, then measure the probes shorted and subtract that from bed measurements

i tested the beds resistance several times with my harbor-frate multimeter ( wich i usd for tesing amp's n volage) and got 2.9 -1.7=1.2 ,3.1-1.7=1.4 ,3.4-2.3=1.2 ,4.6-3.4=1.2 ,4.8-3.6=1.2

with the haetbed on only i tested the temperature distribution which yielded at 75 set 74 current temp ,74 center ,72 side ,71 corner ,at 71 set 70 current temp ,71 center ,70 side ,69 corner.

iv ben thinking ether my mutimeter is wack (which it mite be) or that somethings wrong with the temp protocol in the fermwair ,if so is their a way to tweak it without completely recompiling it.

Edited 1 time(s). Last edit at 09/16/2016 03:24AM by BigC.

Bump

Low resistances are very difficult to measure. There's probably not anything wrong with your multimeter. I'm actually surprised your bed is doing as well as it is on such low voltages. You should just need a power supply that will deliver closer to the rated voltage under load. Industrial power supplies are simpler to configure and generally more stable than ATX if that's what you're currently using.

I had a similar problem, and the solution has been mentioned above, insulate under the bed, I have a slab of 6mm cork under the bed to help stop the heat getting away, without this the bed never gets past 80c

On my printer, I was able adjust the output voltage of the power supply. My power supply has a screw on it to adjust the voltage. It is near the output terminals of the supply.

And The answer to all my problems was...
...gluestick and cork :-| @ X} - XD
Oh well thanks for all the help √π

;p

Edited 3 time(s). Last edit at 10/05/2016 01:56AM by BigC.

if you are not printing with ABS why bother with heated bed never use mine so many posts on people with heat bed problems all electric heaters draw lots of current save the juice for the hotend heater.