Bed Heating issue

[kharrisma]

First attempt at printing with ABS.  Hot end at 245, bed at 105.  No enclosure, no print-cooling fan.  Never got as far as actually printing though:

Never encountered this particular error before.  However, also never set the bed temp this high, either.  "Verify_heater" just says set for 50 and watch the graph rise to confirm, which I've done.  Odd, since the bed is one of the few things I haven't altered in any way, and is probably the one thing that until now hasn't given me any trouble at all.  Base machine is an Ender 3, so the bed is still stock.  Max bed temp is supposed to max at 110, so it ought to be capable of reaching 105.  Read about using AC to heat the bed; benefits re rapid heating, and reduced load on the power supply... but it has to be done properly for safety's sake.  Anybody have any experience with AC bed heaters, or am I looking at an overkill solution?

 

What kinds of things should I be looking for?  Wiring's original, so voltage drop across too-small gauge wire isn't the issue.  Same for length - - stock.  

 

[PFarm]

I'd suggest raising the bed max temp to 120°c, then PID the bed at your goal temperature, 105 °c and save the config. If the error persists, then I suspect a bad thermistor. Printing ABS without an enclosure usually leads to warping. My first attempt at printing ABS was with my Artillery X1 inside a cardboard box. Getting the enclosure to a minimum of 40 °c will get you good results. Go cooling fan for the first layer, then fan on at 25-35% from the second layer on and overhangs at 60-75%.

Edited April 21 by PFarm

[ChicagoKeri]

What kind of printer are you using?    An AC bed heater is great for larger beds such as a 250, 300 or 350mm Voron.  

A smaller bed like a Voron 0 or a Switchwire should be able to achieve 105C without issue on 24v.

You might have one of two problems:

 One, the bed is heating OK but the thermistor is not registering correctly. This could be caused by the thermistor coming loose from the bed or incorrect configuration in printer.cfg.

Two, the thermistor is correctly reporting an inadequately heated bed.  This is often caused by poor electrical contact or undersized wiring.  An inadequate power supply could also cause this.   If the bed is not heating at all, a blow fuse or power MOSFET could be the culprit.

Good luck!

[Repman]

Does the temperature raise if you heat-up the bed? Or does this error come immediatly after starting the heat process?

Normally this error comes if your heater tries to heat the bed but it gets not warmer as fast as expected (as the error says). This happens also if you switch on a fan during heatup (e.g. the nevermore).

You should try a pid autotune at 100 °C:

- Set the part cooling fans to 25% (M106 S64)

- Then PID_CALIBRATE HEATER=heater_bed TARGET=100

- Save the PID Values into your firmware.(SAVE_CONFIG)

Then try again heating up.

Regards

BTW: As your headbed is low voltage the current is relatively high and you are at maximum of the power supply. A small airflow from an open window can cause that issue then too, because the heater is near his limits.

Edited April 21 by Repman

[kharrisma]

It's an Ender 3 platform; a lot has been modded, but the bed is as original, at 235 x 235, stock thin aluminum bedplate, magnetic spring PEI print surface, adhesive-backed blanket-type heater with integral thermistor.  Stock wiring, so gauge and length can be ruled out.  

The bed *does* heat (uncomfortably warm to touch), but I don't yet know what temp it's at when shutdown occurs.  I was puttering around with other things and keeping one eye on the printer, and saw it wasn't printing after awhile, and found the shutdown message.

It does have a higher-wattage heater in the hot end (V6), but it's been printing successfully in the HeroMe printhead (which I've replaced with the Stealthburner.)  No additional loads on the power supply.

For now, I'm going with the printer config max_temp and PID settings.  I'll try what's been suggested and report back.  Much appreciated!

[Mac_A_Million96]

It sounds like its a misconfigured safety parameter, basically it is timing how quick the bed temperature can change and over what period of time, the hotter you try and make your bed the longer it will take to get there, for example getting from 30 to 40 degrees will be much faster than getting from 90 to 100, however if you firmware is set to expect a change of 2c every 60 seconds and it takes longer than 60 seconds to change by at least 2c then you will get this error, go to your "verify_heater" settings and have a look at what is there, you can either increase the "check_gain_time" which will give the bed more time to heat up or you can decrease the "heating_gain" which will look for a smaller increase,

 

The purpose of this section is to make sure the heater and thermistor work, if either stops working and the printer puts power into them and the temperature does not change then it produces an error for safety reasons, you don't want a heater to be permanently powered if the thermistor stops working

[kharrisma]

Wow, thanks for that... I knew Klipper watched temp/time variations, but wasn't aware those were changeable parameters.   Default bed 'max_temp' is already at 130. I ran PID_CALIBRATE for both heaters, (110 for the bed and 250 for the extruder) with results signicantly different from default, and entered them. No issues during the calibrations.  I'll be trying another print later today.  If I'm still getting 'temp/timeout' errors, I'll try changing those 'verify_temp' settings (after *adding* a 'verify_temp' section, of course.)  SO much to learn....  Looks like I'll have to come up with some sort of enclosure, and I'm wondering if adding an insulation layer under the bed might help with the bed heating (and if it will cut down on current consumption, and maybe ease the load on the PS a bit.)  Still liking the idea of an AC bed heater for fast heat-up time!

[Mac_A_Million96]

your welcome, personally I think that an AC bed is definitely worth it, much faster heat up times and can be safer if the wiring is done well as your not relying on a 24v PSU and running rather high currents through the cables, but if you have to choose I would go with an enclosure first, once the bed heats up it should be able to hold it but even at that temperature larger ABS and ASA prints can be difficult, mine still gives me problems from time to time with large prints and I'm running a Voron V2.4 with bed temperatures as high as 125c