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[Solved] Help with temperature swings?  

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Emmes
(@emmes)
Active Member
Help with temperature swings?

I got my mk3s up and running again with some assistance.  I've tried using a different nozzle temperature for "other layers", and frequently get a print failure (usually detachment from the bed) a couple of layers in.  I would occasionally tune manually mid-print to a lower temperature in order to reduce stringing, which would also frequently fail if I do several degrees of change at once.  Eventually I hooked up octoprint, and I'm fairly sure these temperature readings are accurate:

So, in this print, I've set the 1st layer to 215, other layers to 210, and I get a spike as low as 205.1 during the 2nd layer, usually causing failure.  If I manually tune the nozzle down one degree at a time, it never seems to dip more than 1 degree below the setting.

Is there a good way to export gcode by default that gradually drops my temp from 215 to 210, perhaps 1 degree every few layers after the 2nd layer?  I know how to add custom gcode M104 214 by hand to a layer, but it's a pain to try to select 9 different layers and enter 9 custom gcodes.  But is there a way to add them to every one of my new projects either by default when I create a new project, or importing them all at once somehow?

Best Answer by Neophyl:

Is your fan set to start at layer 2 perchance ?  It is VERY common for the part fan blowback to cool the extruder down when it starts up close to the bed.  You can also get the same effect higher if your printers have larger flat areas, the fan that cools the part gets blown upwards.

Its one of the primary benefits of running a silicone sock on the heater block.  It insulates it from the part fan.  You can also set the Full Fan Speed at layer value to make it cut in more gradually at the initial layers, but nothing beats a sock.

This topic was modified 4 months ago 2 times by Emmes
Posted : 27/01/2024 2:02 am
Emmes
(@emmes)
Active Member
Topic starter answered:
RE: Help with temperature swings?

I just started one where "Other Layers" only goes down by 1 degree, and I'm seeing a 6 degree swing.  Maybe changing in gcode is different than the live adjustment?  It looks like it's just an M104.

  Attached: 3mf

Posted : 27/01/2024 2:41 am
Emmes
(@emmes)
Active Member
Topic starter answered:
RE:

On further investigation, it's happening even with no temperature change.  After watching a couple of prints more closely they seem to line up with printing the 2nd layer of my skirt.  I see a smaller dip on the 3rd layer of my skirt.

1) That 5 degree dip only seems to happen on the second layer of the skirt.  The 3rd layer is a smaller dip.  Why?  I assume that it's tied to the print speed of the 2nd layer of the skirt, but I'm surprised that the 3rd and final layer is treated differently.

2) I don't see a "skirt" setting in "speed for print moves", and I can see that my skirt does print fairly quickly.  But why wouldn't something like infill also cause a temperature dip?  I haven't touched speed for print moves, and infill is 40mm/s which is as high as any other value.

3) I'd really like to use the "other layers" setting in filament settings/temperature, but it's challenging when the skirt causes a temperature dip.  Can this be done in a way to avoid my temperature swing?

a) Ideally I'd like to print 3 layers at the "first layer" temperature, and then the rest at the "other layers" temperature, so that I avoid the skirt temperature dip.

b) I guess I could lower the speed at which the skirt is printed, but I'd hate to lower other non-skirt speeds.  Which setting is the skirt speed?

c) It would be greatly appreciated if this wasn't something I have to customize in every prusaslicer project.

 

This post was modified 4 months ago by Emmes
Posted : 02/02/2024 5:54 pm
Neophyl
(@neophyl)
Illustrious Member
RE: Help with temperature swings?

Is your fan set to start at layer 2 perchance ?  It is VERY common for the part fan blowback to cool the extruder down when it starts up close to the bed.  You can also get the same effect higher if your printers have larger flat areas, the fan that cools the part gets blown upwards.

Its one of the primary benefits of running a silicone sock on the heater block.  It insulates it from the part fan.  You can also set the Full Fan Speed at layer value to make it cut in more gradually at the initial layers, but nothing beats a sock.

Posted : 02/02/2024 8:10 pm
Emmes liked
Emmes
(@emmes)
Active Member
Topic starter answered:
RE:

Sorry for the delay, had some downtime.

All my prints started failing after a cleaning, and I had to adjust my live z significantly.  Back on track, and my problems are definitely a combination of first layer adhesion and the fan turning on.

Silicone sock is on my todo list, but I need to properly clean my heater block and want to swap my nozzle first.  Both of those are a bit intimidating and I haven't been forced to do either of those maintenance steps yet.

This post was modified 3 months ago by Emmes
Posted : 14/02/2024 11:25 am
Emmes
(@emmes)
Active Member
Topic starter answered:
RE:

One more followup:  This turned out to be related to my build plate, and possibly 2 loose screws causing occasional runaway heatbed M112s.  I laid down some painter's tape as a last resort, and immediately had the opposite problem and struggled to remove my print from the plate.

Replacing painter's tape every print is naturally a big hassle, so I ordered a new $12USD off-brand plate and no longer need the painter's tape.  It might be time to take some acetone to my original plates, as I've both applied 70% isopropyl alcohol to both of them many times, applied iso to a 60 degree celsius plate, and glue stick to my 1st off brand plate, all of which have probably left some residue.  I also cleared the plate many times with a credit card, which may have been made of a hard enough plastic to damage the plate.

This post was modified 1 month ago 2 times by Emmes
Posted : 13/04/2024 3:43 am
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