heat bed takes forever

Hey guys I have a issue with my heat bed I tried using search function so before I get the book threw at me
Im using mk 1 heat bed and it takes about a good 10 minutes to get up to temps and also when I need to use a fan to blow on my hot end It causes the bed too cool off and my prints unstick from the kapton tape.

I am printing with 3mm abs

The wire for my heat bed is pretty thin its 22G my thoughts is if I went to say a 16g wire or even 14g It would have less resistance and would be able to heat faster and hold the temps better?

Or is it something else im missing the bed was new and I don't see any problems with it other than the wire unless it could also be in my code?

10 minutes is not bad to get to 110C.

Yes you would have more current with thicker gage, and more voltage and current is more power so it will heat faster. Maybe even go down to 12 gauges? Make sure it is not solid wire but twisted wire so it will last a little longer. Also you can insolate your bed with wool. if you are using a heated pcb board, then remove any metal place above or beneath the plate, and instead raise it from the surface about 2-5m, and place wool beneath it.

If you are using a resistor or ni-chrome heater look at your layout and try to increase wire in parallel.


But if you must know, heating bed in 10 minutes is about normal. Cooling takes up to 30 min.

If possible, adjust your supply's output voltage to slightly above 12V. This will drastically decrease your heating time. The dedicated 12V supplies typically have an output voltage adjustment knob that can do +/- 10% which is more than enough to help with heating times.

A heat deflector under the heat bed made out of tin foil has helped me a lot

The heat reflector is an excellent tip!

I am currently REALLY looking at the heatbed on my Prusa Mendel and if you have any other tips I would love to hear them. For posterity, I'm capturing it all in a running article on my blog My Man the Maker, so the knowledge doesn't get lost in the stream. I'm also busy updating the RepRap wiki as I go along.

My plan is to implement a couple of different variations in search of a nice balance between difficulty of build / consistency of heat. My (inherited) RepRap actually had this strange sandwich of custom resistor wire + silicone sheeting + unwired MK1 that just looked *crazy*. I'm rolling back to MK 1 and building back up from there...so It's the perfect time for input!

For myself, I'm really open to input from everyone and I'm more than happy to implement a set of TIERED, progressively more complex approaches to the heated bed. Bad bed = bad print!

- NOOB: Cheap, cheerful, maybe not the best but up and running with a minimum of complexity:
(MK 1 PCB oriented, mostly)

- PROD: Solid, consistent, slightly more complex approaches that supplement the PCB approach:
(separate PSU, SSR, Reflectors, etc...)

- EDGE: New approaches, new materials. Throw convention out the window:
(Marble? Concrete? Carbon Fiber? Forced Air? Steam?)

So, anyone got suggestions for me or experiences to share?

Graham Leach

Edited 2 time(s). Last edit at 05/08/2013 06:02AM by GrahamLeach.

Buy yourself a volt meter first & learn about ohms law E=IR and P=EI. Then you can easily determine what the effect of making changes will be before spending time and money making them. While you are at it pick up a cheap dial indicator and a base. A 1" stroke indicator is good for these machines. Instead of guessing at what the mechanism is doing you can measure it, before making the wrong changes.

I also had a problem with my fan cooling the bed too much. It would drop from 120c down to 90c, and so any small prints would just plink right off during printing.

I put this insultaiton under the bed. It's basically aluminum foil bubble wrap. Afterwards it only drops a few degrees, maybe down to 115c, minimum.

Im using 14 g audio wire on my bed and it seems to work well. Make sure you solder what connections you can and most especially AVOID CRIMPS!!! I used one and it burnt up after a few prints. Insulation under the bed is a good idea too, just make sure that if you use anything with foil that it stays away from the terminals on the PCB. Im also using an old piece of sound deadening as insulation for the top for the initial heating and it usualy takes around 5 minutes to get up to temp for ABS.

Oh yeah, and if you are using Slic3r, there is a cooling tab that will allow you to change when the fan comes on. Mine currently comes on at layer #10.

Hope that helps!

Edited 1 time(s). Last edit at 05/13/2013 09:46PM by Crussell.

Switch the fan off for ABS unless the parts are tiny.

Crussell Wrote:
-------------------------------------------------------
> Im using 14 g audio wire on my bed and it seems to
> work well. Make sure you solder what connections
> you can and most especially AVOID CRIMPS!!! I used
> one and it burnt up after a few prints. Insulation
> under the bed is a good idea too, just make sure
> that if you use anything with foil that it stays
> away from the terminals on the PCB. Im also using
> an old piece of sound deadening as insulation for
> the top for the initial heating and it usualy
> takes around 5 minutes to get up to temp for ABS.
>
> Oh yeah, and if you are using Slic3r, there is a
> cooling tab that will allow you to change when the
> fan comes on. Mine currently comes on at layer
> #10.
>
> Hope that helps!


first, check to see if the connections to your wires are getting hot, if they are, you need to find a better way to connect the wires, more secure you know.

second if the wires are still hot, go up in gauge

third take a piece of cardboard a bit bigger than the bed. take some fluffy cloth staple it to the cardboard, then staple aluminum foil on top. if you are afraid of shorts cover the foil with a thin layer of tape.

now ive recently discovered a method for blowing the fan full blast on the print to increase precision of filament. after you have printed a few layers, take like some napkins or whatever you have and cover up the rest of the bed with the napkins. now the bed will keep hot, and use less energy, and you can blast your fan.

I plan on making a sort of cardboard camera iris to cover up the bed more easily, if you can cover up most of the bed you can just blast the fan and this would be much better than the napkins. ill post the link from instructable on how to make one, its kind of a cool thing to have too.

edit:[www.instructables.com]

Edited 1 time(s). Last edit at 05/14/2013 02:29AM by aduy.