I’ve been enjoying my Zero but haven’t printed that much with it. I was printing the sixth birdhouse that I designed, using the unaltered PETG profile (255 C nozzle) and noticed that it was air printing. I stopped the print and heated the nozzle to 255 C, let it heat soak for a couple of minutes and tried to pull out the filament. It broke at the extruder gears, where the filament had been chewed. I heated the nozzle to 320 C to try to soften the plastic so I could clear the jam. I was able to get the acupuncture needle up the nozzle all the way to the hilt, 50 mm, but was only able to get the cleaning rod down 30 mm from the top, just to the extruder gears.
There is no resistance when sliding the needle up from the bottom, so the nozzle and long heater block are empty. The clog is apparently in the heat break. This isn’t going to be easy to fix.
I understand why the Zero needs a long melt zone but I don’t do speed prints. I bought the Zero for the precision and motion system reliability provided by the small print volume with all steel linear rails, but I feel that motion system reliability is compromised by the extruder design. I’d much rather have a slower but more reliable extruder.
Foaming TPU-LW prints well on my SV08 and Neptune 4 Pro but I have spent a long time trying to get it to print on the Zero. I might be able to lower the nozzle temperature and make it work. I was going to try that today, before the catastrophic jam. However, I suspect the foaming TPU-LW is never going to work well in the long melt zone on the Zero.
Maybe I’ll upgrade the Zero extruder with the Bondtech INDX when it’s available?
Remove the filament tension screw and lay the arm flat. Clean up what you can then remove the nozzle. From the bottom it is a straight 2mm diameter “pipe” all the way to the gears. use the “push rod” the top, inserted from the bottom. Heat the rod by leaving it in the “hot zone” of the heater for a couple minutes if you can’t move the clog cold. Low powered soldering iron tip into the filament passage below the feed rollers might help too.
Thanks for the advice. I hadn’t even removed the cover from the extruder until today, and to my knowledge, Sovol hasn’t released Zero maintenance videos yet.
No luck on lowering the extruder idler gear and pushing up from the bottom. I heated the nozzle to 350 C and let it heat soak for a few minutes with the stainless push rod sticking up through the heater into the clog. Unfortunately, stainless is a poor thermal conductor, but every little bit helps. When that didn’t work, I disconnected the heat break fan and suspended it well away from the heat break heat sink with tape covering the fan to encourage some heat transfer up into the heat break where the clog needs to melt. No good. I could touch the outside of the heat sink for a second so it was probably 70-80 C. Then I heated my Hako soldering iron to 480 C and pressed the barrel of the heater against the heat sink while the nozzle was at 350 C. It smoked a bit and the clog at the base of the heat break was a bit softer when I pushed up hard against it. I was able to move the wire around the side of the clog some but it wasn’t yielding. That’s some clog.
If I had the replacement hot end and heat break, I’d replace it and keep the clogged heat break and hot end for the spare heater and thermistor.
I’m tired of messing with it tonight. Time to quit while I’m behind, before I make it worse. If I hadn’t gotten in a hurry earlier today and instead 350 C heat soaked the heat break, I possibly could have pulled the filament out the top instead of snapping it off in the extruder gears. I’ll try heating and poking up on the clog again tomorrow. If that doesn’t work, I’ll remove the hot end and heat break and…?
I gave it one more try and cleared the clog. The clog seemed to be at the bottom of the heat break, just above that long melt zone. I was never able to push up from the bottom despite a lot of poking and probing with the cleaning wire, which I abused so much that the finger loop at the end unwound despite the fact that most of my pushing and pulling was with needle nose pliers close to the nozzle opening.
What finally worked was to grab the little nub of filament that remained at the extruder gear with some good tweezers that I have. They have serrated tips that gripped enough that I was able to steadily tug upward which stretched the filament and reduced the diameter as the long strand of softened filament slowly wormed its way out of the heat break. I’ve generally had better luck pulling filament to clear a clog rather than pushing it.
Lesson For Next Time: Don’t get in a hurry and yank the filament so hard that it breaks in the extruder gears where it’s difficult to pull up or push down.
I also noticed that the nozzle wasn’t threaded in very securely when I removed it. There was evidence that some plastic was starting to seep into the threads. When reassembling, I screwed in the nozzle, heated it to 300 C, allowed it to heat soak for a minute then torqued it securely.
I restarted the failed job. The first layer looked good. I love that full bed mesh and Z offset before each print so I didn’t need to recalibrate anything manually after the nozzle swap. It’s on layer 18 now and looking good.
I had tried feeding the PETG through the PTFE tubing and it worked for 7 hours before the jam. I don’t know that was the problem but I removed the glass top and reverted to my usual of having the spool on a bearing hub spool holder three feet above the printer with the filament feeding directly into the top of the extruder with no reverse Bowden tube.
By the way, is there any way (a setting) to control the speed of the heat break fan?
I had a bad day with several prints failing because of heat creep, I had ironing enabled, then also without it: in the end it was PETG not liking the closed enclosure and 55C. But it makes the printer and thus the room much quieter, so I’d prefer to keep all closed, if there’s a way to avoid heat creep, that is.
PETG with the bed at 80 C resulted in the enclosed Zero chamber reaching 60 C. I’m now printing PETG with the door closed but the glass top removed and the chamber remains under 50 C, and the closed door helps block most of the high frequency fan and motor noise.
When printing PETG using the stock Zero PETG profile, monitoring in the Mainsail web browser interface, Fan 0 (the extruder part cooling fan) runs at 20% and blips up to 100% for overhangs. Fan 2 (the auxiliary part cooling blower at the rear of the printer) remains at 0%. Fan 3 (the chamber exhaust fan on the right side of the printer) remains at 0% because I set the chamber temperature to 60 C to prevent the noisy exhaust fan from running.
I think the heat break cooling fan runs whenever the hot end heater is active? That’s based on the sound when preheating the nozzle at the start of a print. I don’t see a display for that fan (Fan 1?) in Mainsail.
The heat break fan blows air from inside the enclosure on the heat sink. Combined with the fact the filament is being preheated as it travels to the tool head. Not much headroom for heat creep.
My first idea is print a muffler and put over the chamber fan outlet or duct it to the outside and set chamber temp around 30 °C
Other ideas:
Duct room air to the heat break fan
Install thermoelectric coolers on tool head
Water cool the heat brake
Nope, too noisy. I have though made one single print with the Aux fan on, and it made the print far worse. I guess it’s only for PLA and maybe TPU.
The extractor fan doesn’t lower chamber temperature much, whereas the huge noise. I prefer to open the top lid and/or the door, to lower the temperature.
Anyhow, I get very good prints until the jam, so if there was a way to increase heat break fan speed, I’d gladly try that too.
AIO CPU kit, extend the hoses, bond the pump to the heat sink with ?? Pump and fan want 12V not 24V. I’d go with a wall wart as the Zero doesn’t have a huge PS. Oh and the radiator fan will run full speed without a speed controller which should come from the PC motherboard. Is manual control okay or do you want to monitor water temp and have the fan speed self adjust.
Is there enough surface area on the heat sink? A custom copper solid one is doable, cad model is available for the stock one to lay out all the holes…
What about the top of the tool head? Gummy soft PETG at the feed rollers is gonna be a problem at some chamber temperature. Put another heat block on the extruder motor?
---------------> OR <-----------------
Turn on the enclosure fan and set at 35 °C for PETG
Klipper is monitoring the heat break fan speed. If you stop the fan with your finger briefly, Klipper will increase the pulse width modulation duty cycle to run the fan faster to achieve the desired average speed. If you stop the fan for a few seconds, Klipper will detect that the fan isn’t running and will generate a fatal error and shut down the printer.
Would be true for part fan, if like the Zero had a tach signal
Extruder fan pulse width is 100% or 0 shutting off below 45 °C for the nozzle.
It is possible the brushless fan has a PID controller built in with target speeds for different duty cycles in which case stopping the fan would increase the I gain for a time. A few years ago that would have been unlikely but we live in a world where a RP2040 on a circuit board (PI zero) can be purchased for less than $4 RETAIL.
It’s a one minute experiment you can do at home. Use Mainsail to set an extruder temperature of 222 C. You’ll hear the heat break fan kick on. Remove the extruder cover. Push your finger against the heat break fan to stop the spinning blades. In 15 seconds, I see the following error message in Mainsail:
The point I was trying to make is that Klipper can not increase the speed of the extruder fan. You could reduce it in the configuration but not increase it.
Yes Klipper watches the tach signal and will shut down if the fan stops.
BUT, any “overspeed” of the fan following being stopped has to come from the fan itself. There is no such thing as 110% PWM
