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Heated print bed unable to reach desired temparature

Posted by cheddy 
Heated print bed unable to reach desired temparature
July 29, 2017 07:43AM
I have an Flsun i3 Prusa clone from 3DPrinterCreator that has a heated print bed. The bed heating works fine for PLA printing (I run it at 60C for PLA, otherwise the models won't stick to the bed.) My problem comes when trying to print ABS, which requires a much hotter print bed (110-120C.) My printer in incapable of heating the bed much above 93C, at which point the heat is dissipating faster than the heater can supply it and it never gets any hotter. I have tried the trick of putting some insulation on top of the bed while it heats, and that works to get it up to the desired temperature, but as soon as I remove it when the printing starts the bed temperature starts to drop and the print model comes loose.

Are there any simple solutions to this problem? Do I need to get a better print-bed, or will a more powerful PSU give it some more umph? (e.g. a 360W PSU instead of the 240W one that came with the printer.)

I have read on other posts about flickering led lights on the RAMPS controller board (a BT7272A integrated RAMPS 1.4 board) and the implication was that the flickering is due to power consumption exceeding the capacity of the PSU. However, in my case the LED lights always flicker whenever the board is in heat-up mode, either heating the bed or the extruder, so I have always considered that to be normal operation. Am I wrong? Should the LED lights flicker while heating or is my PSU deficient?

P.S. I realize that these Chinese printer kits are cheap knock-offs and a more expensive brand name one would do a better job, but I was hoping that this kit would give me some experience with 3D printing before I shell out big bucks for a better unit. So far PLA printing is going pretty well, and if I can get the ABS printing to work I'll be a happy camper.
Re: Heated print bed unable to reach desired temparature
July 29, 2017 07:50AM
This is a common problem when using PCB bed heaters with ATX power supplies. Measure the voltage across the RAMPS bed heater power input terminals, the bed heater output terminals, and on the bed itself to see where the voltage is being lost. Ideally all three measurements will be very close to 12V.


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]

Full disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet.
Re: Heated print bed unable to reach desired temparature
July 29, 2017 01:35PM
Make sure that the wire going the the controller is at least 12AWG 20A wiring, My printer came with this tiny wire that needed replaced.

Check to see if the wiring to the hotbed is 14-16 AWG 10-15amp

Edited 1 time(s). Last edit at 07/29/2017 06:26PM by Roberts_Clif.
Re: Heated print bed unable to reach desired temparature
July 30, 2017 02:46AM
The silicone-covered cable used in electric RC models is very suitable for this job - it's flexible, the insulation will withstand the elevated temperatures, and its current-carrying capacity is high. It's designed for electric motors that run at tens of Amps, so it's more than capable of supplying the heatbed.

Have you tried putting insulation under the print bed? I have a PCB heater on both of my printers (the aluminium version) and I made a sandwich - PCB on top, 2 layers of thin cork sheet, then another metal plate on the bottom. This, plus a bit of corrugated card on top while heating up, allows it to get up to 100C in a reasonable amount of time. A cold room, or draughts, may prevent it reaching the target temp though. The chances of getting to 110C or 120C are very slim - I'd have to change the heatbed to something more powerful to get to those temps - though 100C is OK for ABS, in my experience.
Re: Heated print bed unable to reach desired temparature
July 30, 2017 05:49AM
Quote
cheddy

P.S. I realize that these Chinese printer kits are cheap knock-offs and a more expensive brand name one would do a better job, but I was hoping that this kit would give me some experience with 3D printing before I shell out big bucks for a better unit. So far PLA printing is going pretty well, and if I can get the ABS printing to work I'll be a happy camper.

I Have 2 Cheap Chinese Aluminum Frame knockoffs, and with proper wiring, new linear bearings additional heat-sinks they print as well as the best of them in a 220x270x190 Print Area.
Be careful the Chinese knockoffs usually have exposed 110/220 power leads that can lead to electrical shock, your first print should be a cover for these exposed wires and terminal leads.
Include a power Switch as pulling the power cord to turn off your 3D Printer is for the Birds.




Edited 5 time(s). Last edit at 07/30/2017 09:10AM by Roberts_Clif.
Re: Heated print bed unable to reach desired temparature
July 30, 2017 10:42AM
Great minds... that was one of the first design/print jobs I did...
Attachments:
open | download - IMG_2293.JPG (93.3 KB)
Re: Heated print bed unable to reach desired temparature
August 10, 2017 12:55PM
I am needing to reach a temperature of 150C+ for research and am investing in an independent 24V power supply with plenty of amps to run it. I just am wondering if the MK2 heated bed can handle it and how high of a temperature it can reach? Are there other print beds that can reach higher temperatures? If so, which ones? Thanks for the help in advance!
Re: Heated print bed unable to reach desired temparature
August 10, 2017 02:14PM
I advise against using any type of PCB heater to reach that temperature. Use a flat aluminum plate (preferably cast aluminium tooling plate) with a silicone heater slightly smaller in size attached to the underside. A power density of 0.5W per sq cm should be plenty. If it's a large bed, consider using an AC mains voltage heater controlled via a SSR instead of a 24V heater.


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]

Full disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet.
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