Ender 5 Pro stuck on E Heating

I have an Ender 5 Pro running Marlin bugfix v. 2.0.something. (I meant to check but I forgot. The printer is off and running right now, and the folders on my computer just say 2.0.x.) There is a BLTouch involved and my prints are set to level the bed before each print.

Frequently - and increasingly so - after starting a print, the printer gets stuck at “E Heating.” Watching the info screen, the temperature oscilates about 3 degrees above and below the target temperature. It will do this for at least 20 minutes; I’ve never had it actually settle down once this behaviour starts.

By luck - I was planning to shut it down - I discovered that if I go into the Temperature menu and select “cooldown” the printer will start the bed leveling process. I can then frantically set the temperature by hand and the print will complete.

After doing this a few times to confirm it’s reliable behaviour, I tried using the “Preheat PLA” option instead. A fan then kicks on - I’m not sure if this was the part cooling fan or if the hotend fan isn’t running during the preheat - and the displayed temperature drops by about 10 degrees. The printer then heats the hotend back up to printing temp, and the print proceeds normall.

This suggests that the printer is unable to achieve a stable hot-end temperature during the initial warmup, but the fact that the printer starts if I set the target temp to 0 is… odd. If this was a 2d printer I’d say there was junk PCL stuck in the pipe. Cycling the power and using a different SD card don’t seem to impact this.

I do tend to load a lot of files on the SD card, and have not yet tested the effect of having less information on the card.

Because I have a workaround, this is more aggravating than anything else, but I worry that it’s a symptom of a deeper issue. I’m not sure what my next step should be, and welcome suggestions!

there are 2 kinds of fans the cooling fan, meant to cool the hot end, and the part colling fan thas means to blow on the part. If it’s only varying by 3 degrees I wonder if doing a PID tune might help it?

The fan should be on as while the hot end is heating but this shouldn’t affect the part cooling fans as they are called for only during the print from the gcode

The hot-end cooling fan directs air over the radiator fins on the heat sink. The part cooling fan directs air past the nozzle, which is embedded in the heater block. The thermistor is also embedded in the heater block. So it seems obvious to me that if the part cooling fan kicks on, the thermistor will register a lower temperature.

The hot-end fan is usually on if the printer is on. I’m not sure if there’s any way for an Ender-5 to turn that fan off, actually. So I’m 90% confident that the fan I hear kick on when I select “Preheat PLA” from the menu is the part cooling fan.

Actually, that makes some sense, now that I’m spelling it out. If one is printing PLA, one will presumably have the part cooling fan running, so the printer will need to compensate for that to maintain nozzle temperature. Thus, turning that fan on before heating up the nozzle has value.

To be clear, I only thought this through when considering your suggestion - my instinct was that it was the part cooling fan, but I hadn’t worked all that out. Identifying the things I hadn’t thought about was the goal of this post, so that was helpful.

Trying a PID tune is a good suggestion! Thank you for helping brainstorm!

Great let us know how you ake out

As a fellow Ender 5Pro owner, I can empathise. Every once in a blue moon mine behaves the same way.

First try the PID tuning:

I’ll admin I only skimmed this thread because I have an appointment in 40 minutes and I’ll have to read it in more detail later, but for now, I’d like to point out that of the three methods of moving heat (radiation, conduction, convection), conduction is by far the most efficient, particularly through metals. That’s why the hot end has a big cooling fan on the front, blowing through the read heat sink at the back; the upper part of the hot end is necessarily physically connected to the heater block and will suck heat up vertically which will melt filament prematurely, so it’s essential that the upper end stay cool. That’s why the front end cooling fan comes on whenever the printer is active. The cooling fan on the side is for cooling the filament after it has been extruded to prevent the liquid plastic from drooping. That isn’t necessary on the first few layers since you’re right next to a hot plate anyway and so the fan doesn’t usually come on until about layer 3. I wanted to point out, in my long-winded way, that the part fan doesn’t play a part at all early on and when it does come on, it’s aimed slightly downward and not directly on the heater block. Also, the heater block is covered in the black silicon sock so the air never touches it anyway and all that’s left exposed is the last 2mm or so of the tip. It’s not enough to cause the 3C temperature swings you and I experience.

I just wanted to stop you from going down the wrong path as you seemed to be focusing on the part cooling fan as a culprit.

So, make sure the black silicon “sock” is still on the printer. Mind you, even without it, the printer should still be able to hold a stable temperature, but it’s presence helps.

I don’t have a definitive solution to this. I used to have to turn my printer off and then on again to start a print. Generally, I would say it has to do with the thermistor not resting directly against the heater block. A bit of plastic or an air gap will introduce a time delay in the theristor’s reaction time. Just keep in mind that thermistors are notoriously fragile devices, being encapsulated in a drop of glass, so handle carefully and be sure you have a spare.

Off to my appointment. I’ll re-join this thread later.

I would check the resistance on the thermistor to make sure it’s 100K +/- 2.

Ensure the thermistor is seated properly in the block but past physical issue PID tune should take care of it.

Good to know that other printers sometime have this issue!

To be clear, no, I don’t think the part cooling fan is causing the issue. The issue is clearly that the nozzle overshoots the target temperature, the printer stops heating it so it can cool off, it then undershoots the target temp, so it starts heating again, and then overshoots, repeat ad nauseum.

My comments on the part cooling fan were merely me logicing through my conviction that the part cooling fan kicks on when one selects “preheat PLA end” from the Temperature menu. (Which I can now confirm it does.)

The amount of cooling this causes does reinforce the notion that the thermistor is not operating properly, but I will point out that the open end of the silicon sock, where the heater cartridge and the thermistor cabling come out of the heat block, faces the part cooling fan. It’s not surprising at all to me that this has an impact on the temperature of the heat block.

I forgot to note that I have a microswiss all-metal hotend, because sometimes I print ABS. Perhaps I’ve installed my heater block backwards? I’m also missing a screw for the part cooling fan shroud, so it’s not pointed exactly where it should be. However, the printer works fine once I get the print to actually start, and taking all of that apart is such a pain in the butt, so I’m going to leave it be.

I do find it absolutely fascinating that using one of the Temperature menu commands causes the printer to break out of the cycle and them start the print. It’s just going “oh, I guess it’s all fine now.” I intend to experiment with other Temperature menu commands, just to see what happens.

The PID Tune certainly seems like the best bet. Right at the moment I don’t have an easy way to do that - getting GCode onto an SD Card is a nuisance and I don’t have a computer I can take over to the printer, nor is it easy to take the printer to a computer. That should change in a few days, though, so I will try the PID tune as soon as practicable.

Otherwise - as noted, it’s annoying but doesn’t actually prevent me from printing, so I’ll just carry on as I have been until I can make the PID tune happen.

Thanks to everyone!

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You might want to give some thought to installing an OctoPi. That will give the printer network access so you don’t have to take it anywhere to work on it.

Unfortunately, I have a budget of about 100$ a month for ALL my projects. I can squeeze it up to 150$ if I don’t spend on entertainment items like books or movies.

February’s budget is going to a new desk. March’s is probably going to a 12v 10Ah Li-Ion battery. April’s will probably be needed for new filament. Et cetera. So far, the money and learning costs of getting a Pi and installing Octopi have very much exceeded the available resources; and 90% of the time I don’t need to have a computer talking to the printer anyway.