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Heatbed taking hours to heat up

Posted by djlapan 
Heatbed taking hours to heat up
March 04, 2017 08:27AM
Hi all,

From everything that I have read and watched on line, is that a heat bed should take between 5 - 15 minutes to reach 100 C. I am to to the 3d printed world and my heat bed is taking hours to heat up to only 50 C. Is there something in the firmware that I am missing.
Some information that might help.

Heat bed: SainSmart RepRap MK2B 3D printers Dual Power PCB HeatBed Heat Bed 12/24V Updated Version of MK2A
Thermistor: Anycubic NTC 3950 100K Thermistor with 1 Meter Wiring and Female Pin Head for RepRap 3D Printer Heatbed or Hot End

which both are connected to a 5mm thick aluminium plate.

What do I need to do to increase the heat levels on the heat bed.

Any advice would be great.
Re: Heatbed taking hours to heat up
March 04, 2017 09:03AM
That's a 12/24V heater. Are you using it with a 12V supply and connecting it as if the supply were 24V?

Assuming your connections are OK, if it takes too long to heat up it means the heater is underpowered. You can play games with insulating the bottom side and maybe speed things up a little, but in the end if it's taking much more than 5 minutes to heat up it's taking too long and you need more power. PCB heaters are always underpowered, especially if you have a 5 mm aluminum plate. Look for a heater that has a power rating of 0.4-0.5W /cm^2 (or more). That will get you up to temperature in much more reasonable time. As a point of reference, my printer has a 317 x 305 x 6.35 mm aluminum plate bed and a 450W heater. It gets to 105C in 5-6 minutes, depending on ambient temperature.

Increasing the bed heater power using a DC heater will probably require a higher current power supply, and maybe an external SSR to switch power to the heater. I've given up on DC powered heaters and decided future projects will have line powered heaters. That eliminates the power supply issues and only requires a cheap AC SSR to switch the power. You can get some really high powered heaters that are line powered. My newest project has a 300 x 300 x 8 mm aluminum bed and I went with a 750W line powered heater. You do, of course, have to be careful with the wiring if you use a line powered heater, but you have to be pretty careful with DC wiring if you use a high powered heater, too.


Son of MegaMax 3D printer: [www.instructables.com]
Re: Heatbed taking hours to heat up
March 04, 2017 05:32PM
Have you checked the voltage output of your PSU?? Mine was underpowered and was taking ages to heat up. Then I noticed a little adjustment screw beside the connectors in the PSU. I turned it up and it increased the power. It worked perfectly. Check your output smiling smiley
Re: Heatbed taking hours to heat up
March 04, 2017 07:38PM
You need about 10 to 12 amps of power just for the heatbed, and another 5 to 10 amps for everything else, I would suggest a 30a power supply, that gives you a little extra power and also a lot of cheap power supplies are over rated.

If you are using a SSR, "Solid State Relay" and its running real hot you might have got a bad one and its using up all your power, you might try a better SSR, or even a Mosfet heatbed expansion board, like this

[www.amazon.com]

or this

[www.amazon.com]

Also you need a heaver gauge of wire for you heatbed, you can use this to help you find what wire size to use

[www.calculator.net]

or

[www.powerstream.com]

or

[bulkwire.com]

It also helps to insulate you heatbed, I use a cork sheet glued to the underside of my heatbed, I use the cork tiles found here:

[smile.amazon.com]

and this silicone as glue to keep the cork sheet and thermistor attached to my heatbed:

[smile.amazon.com]

Edited 1 time(s). Last edit at 03/04/2017 07:40PM by will1384.

-----------------------------------------------------------------------------------------------------
3D Printer = ORD bot ---- [reprap.org]
Controller = Re-ARM with RAMPS ---- [panucattdevices.freshdesk.com]
LCD = RepRapDiscount Full Graphic Smart Controller ---- [reprap.org]
Stepper Drivers = DRV8825 ---- [reprap.org]
Stepper Motors = KL17H248-15-4A ---- [www.automationtechnologiesinc.com]
Extruder = Bowden type 00str00der ---- [reprap.org]
HotEnd = E3D v6 ---- [wiki.e3d-online.com]
Nozzle and Block = E3D v6 Volcano with 0.6mm nozzle ---- [wiki.e3d-online.com]
Heatbed = MK2b PCB Heatbed ---- [reprap.org]
Heatbed Insulation = 1/4-Inch thick cork tile ---- [www.quartet.com]
Heatbed Insulation Adhesive = Silicone RTV 6500 ---- [www.silco-inc.com]
Print Surface = Gizmo Dorks PEI Sheet ---- [gizmodorks.com]
Print Surface Adhesive = Gizmo Dorks 3M 468MP Sheets 8" x 8" ---- [gizmodorks.com]
-----------------------------------------------------------------------------------------------------
Re: Heatbed taking hours to heat up
March 05, 2017 03:51PM
djalapan,

as the digital dentist has already said, check how you have the heater power connected to the bed. It sounds as though you are running it off 12V and have the connections wrong. The Mk2a 12/24V bed has two seperate heating tracks, these are wired in parallel for 12V operation and in series for 24V, so the connections are different for the two operating voltages.

Follow the table printed on the bed and connect the 12V positive feed to pad 1. NOTE that BOTH pads 2 and 3 require connecting to the 12V negative feed. If you only connect one of these, then you will only be running the bed at half power. If you try to run it wired for 24V off of a 12V feed then it will only run at 1/4 power.
Re: Heatbed taking hours to heat up
March 06, 2017 03:31PM
So I tested my output to the heat bed. I am getting 9.96 Volts and the resistance is around 1.8 to 2 ohms. I've double checked to make sure that I have wired the heat bed correctly through the wiki, which I have wired correctly. Both power leads coming into the RAMPS 1.4 are reading 12.01` Volts and 11.97 Volts. I did tin the wire ends that are coming from the head bed to the RAMPS. Do I need a solid state relay. My Power supply is a 400 watt with one positive +12V and one negative -12V (blue wire(which I am not using)).

What could be the issue?
Re: Heatbed taking hours to heat up
March 06, 2017 04:08PM
djlapan,

I suggest that you check the connections at the pads on the bed itself again !!! There are two heater tracks on the dual voltage Mk2a beds, and both must be connected correctly to get the full output of the bed. The resistance that you are reading at the bed suggests that you only have one of the two tracks connected which will halve the heat output.

You say that you are running the bed off 12V. The +12V from the ramps hotbed connection needs to be connected to Pad 1 on the bed. The other wire from the hotbed connection needs to go to BOTH Pad 2 AND Pad 3 on the bed, so that both tracks are connected.
Re: Heatbed taking hours to heat up
March 06, 2017 04:53PM
Agreed. Pins 2-3 have to be bridged together for 12v. You leave them apart for 24v operation.
See my picture. This is for 12v
Attachments:
open | download - 123.jpg (558.7 KB)
Re: Heatbed taking hours to heat up
March 07, 2017 02:11PM
Quote
djlapan
So I tested my output to the heat bed. I am getting 9.96 Volts and the resistance is around 1.8 to 2 ohms. I've double checked to make sure that I have wired the heat bed correctly through the wiki, which I have wired correctly. Both power leads coming into the RAMPS 1.4 are reading 12.01` Volts and 11.97 Volts. I did tin the wire ends that are coming from the head bed to the RAMPS. Do I need a solid state relay. My Power supply is a 400 watt with one positive +12V and one negative -12V (blue wire(which I am not using)).

What could be the issue?

Cut the tinned wires off. Re-make the connection into the terminal blocks using bare, un-tinned wires and securely tighten the connection screws. If the 9.96V is the voltage supplied to the bed when it is switched on it is too low. The PSU is 400 watts but how much of that can be supplied via the 12volt output? It sounds like it might be a converted PC PSU which are notoriously 'voltage agile' under load, you can sometimes tweak the output voltage up a bit via an internal adjustment pot..aim for at least 11.5V under load.
Re: Heatbed taking hours to heat up
March 10, 2017 04:39AM
Hi dart16,

I remade the connections to the terminal blocks using bare ends as you suggested. It is heating up a little fasted. I am get 12.01 volts before I put a load on the PSU. However after I put the heatbed on the voltage drops to 10.18v. I am using a PC PSU. Are there any tutorials that you can point me too, to adjust the internal adjustment pot that you suggested.
Re: Heatbed taking hours to heat up
March 10, 2017 08:39PM
Just get a new PSU. The PC ones are for PCs not printers.
They are like 20 bucks on amazon.
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