Trouble with the heated bed

[TekNick]

Hello fellow Printers!

For the most part my printer has been behaving quite nicely, except I'm having some issues with the heated bed. It's always had trouble getting above 82 C (as in it doesn't get that high, and eventually just stops heating and leaves a "Killed" message on the LCD).

Today, however, I was playing with the bed (checked the solder connections, cleaned the glass to try ABS slurry) and now it won't heat up past 50. Instead of getting a "Killed" message it literally shuts down the whole machine. I tried heating just the nozzle and that behaves just fine, it only kills the machine if I try heating the bed past 50 (as in if I turn the knob past the 50 degree point). Before I go digging through all the physical electronics, is this a firmware problem, a common loose connection, or will I probably need a replacement part?

Thank you in advance!

[mhackney]

The stock power supply really has a hard time with the Onyx. You might be heating too fast which is drawing too much current and then shutting it down. Try getting up to temp in steps manually before starting the print. So, if you wanted to reach 80° start with a heat up to 40° then go in 10° increments until you get there.

[TekNick]

That is starting to make sense, unfortunately the problem keeps getting worse. Now I can't even select the "Change Temp" option without it turning itself off...

Correction: I just took the glass off and left the Onyx bed sitting loose, it seems to be letting me get through the LCD steps alright... I'll post again if I find anything.

[Earthbound]

There are a bunch of lousy power supplies out there that can't deliver the goods to heat an Onyx bed. You might have one that is failing. But the fact that moving the glass changed the behavior, I wonder if you have a pinched wire, chafed insulation, or other issue with the power wiring going to the Onyx. The stock build wiring is barely adequate, and it is easily pinched between the base, insulator "star", and the Oynx itself. Might be worth pulling up the Onyx bed and looking underneath for signs of trouble.

[TekNick]

I'm starting to suspect this most recent problem was a pinched wire. I hadn't pulled the wire all the way back through when I reassembled it, and after doing so it appears to be functioning.

That being said, would you recommend upgrading the power supply to better handle the Onyx bed? I'm currently using the stock 600W ATX.

[Mac The Knife]

Double check the screws on the connector at the Rambo board,,, If they loosen up, they'll cause longer heat up times, and cause the connector to overheat instead.

[jram]

I'm starting to suspect this most recent problem was a pinched wire. I hadn't pulled the wire all the way back through when I reassembled it, and after doing so it appears to be functioning.

That being said, would you recommend upgrading the power supply to better handle the Onyx bed? I'm currently using the stock 600W ATX.

I highly recommend an upgraded PSU,I went with a 650 EVGA and all of my bed heating problems are gone,my Diablotek went out the first day.I've seen that others are going the 24v route.

[nitewatchman]

I just went to a 24VDC/12VDC system over the holidays. It was simple, easy and not terribly expensive. Bed runs on 24VDC and everything else still runs at 12VDC (Rambo, Fans, Hot End, LEDs etc.)

Meanwell 24VDC 480 Watt Power Supply (SP500-24) - $36.36 eBay Ship Free
Cyrdom SSR - $9.90 eBay Ship Free
24VDC/12VDC 20A Converter - $1.04 eBay Steal +$5.00 S/H
IEC Socket and Switch - $4.33 Amazon Prime
10A Fuses (5) - $5.99 Amazon Prime
1/2" Aluminum Plate 4-1/2" x 7-1/4" - Scrap Box
Hand full of M3 and 8-32 Screws
Terminals and wire

I machined the 1/2" plate for a heat sink and attached it to the side of the P/S to mount the SSR and Converter in the same fashion as rpress (http://forum.seemecnc.com/viewtopic.php ... 9&start=25). I machined mine because I can and have a Tormach CNC Machine, you don't have to do it this way but you must have a heat sink for the SSR although mine does not even get warm to the touch during operation.

I attached the P/S to the base with Silicone Sealer and two try wraps, you could also use carpet tape for example.

Bed now heats from room temp to 105C in less than 5 minutes. 0 to 60 in 1-1/2 minutes. This also includes heating the thermal mass of my 1/8" copper heat spreader.

This worked for me YMMV.

nitewatchman