The point I was making is the Zero has a tachometer signal for the heat break fan. Otherwise, it couldn’t detect the stopped heat break fan and shut down the printer to hopefully avoid a bad heat break clog from heat creep as I had, probably because I was printing PETG with a 60 C chamber which reduced the heat break fan cooling capacity.
It definitely does sound like I was referring to the heat break fan because that was mentioned in my first sentence, but after that I was intending to speak generally about other PWM fans that have tachometers. I switched from specifically the heat break fan to PWM fans generally and should have made that clear.
I don’t recall ever hearing the heat break fan increase speed. I assume it has PWM capability but Klipper runs it at 0% or 100%. I have heard other PWM fans speed up momentarily after being temporarily stalled, but that shouldn’t happen if the fan is already running at 100% speed. I suppose that could happen if 100% speed is mapped to the RPM normally produced by 80% PWM to allow the fan the capability to run at the desired speed after wear and/or contamination adds friction that slows the fan.
I just tested it and Fabio is right. After I stopped the heat break fan with my finger for a couple of seconds and then allowed it to spin, it started slower (no half second kick start) but then revved to a higher RPM for maybe a second. When I paid more attention with the extruder cover off when using Mainsail to heat the extruder to indirectly turn on the heat break fan, it started faster (kick start enabled) and seemed to rev slightly higher before settling to 100% speed but not as much overshoot in speed as when recovering from a stall. I’m not sure what’s happening but I’m too lazy to connect the digital storage oscilloscope. DC fans running at 100% don’t usually overshoot in RPM. They ramp up to speed without overshoot.
@Fabio originally noticed the overshoot and was asking how to make it always run at the increased speed. I just wanted to be clear it’s already at 100%.
I’m gobsmacked that a fan like that has onboard PID. What will they think of next.
I doubt the heat break fan has an onboard PID controller but the fact that it over speeds slightly when Klipper turns it on and it over speeds a bit more when recovering from an induced stall tells me that I don’t understand exactly how it’s controlled.
A three pin fan typically has +V, GND and TACH, with the +V pulsed for PWM speed control and the TACH used to close the loop to control the speed and to determine if the fan has failed, although there are some 3 pin fans that have a fan failure signal instead of the TACH.
An online search didn’t solve this mystery and I hate not understanding something like this once I start looking into it. I’m almost curious enough to put the TekScope on the GND and +V pins.
I hadn’t bothered installing the magnetic exhaust vent cover until a couple of days ago. I found it and installed it, but it was after the bad clog in the heat break. I set the chamber temperature in Mainsail to prevent the noisy exhaust fan from running but I should probably remove the vent cover and leave the chamber temperature set at 50 C when printing PLA and PETG and prevent the exhaust fan from running by removing the glass top, and if necessary, opening the front door.
Some notes I’ve made regarding temperatures:
With the door open and lid removed, printing PLA at 210C / 65C and the aux fan at 70-100%, the chamber temperature was around 38-40C during a 9 hour print. With PETG at 240C / 85C and the aux fan at 20% with the door still open and without lid, the chamber temperature was 44-46C.
The chamber fan isn’t going to make much difference if the door is open since the aux fan will anyway be pushing any warm air directly out of the chamber far more directly than the chamber fan can.
The chamber fan however does make a diffference when printing with the door and lid closed especially when printing ASA at 260C / 110C. The chamber temperatue stabilized around 56-58C with the chamber fan running at 40% (vent cover plugged).
It seems that if I try to 3D print at 0.10 layer height (with a 0.4mm nozzle) I get worse results and, often, also a bad jam… of the heat creep type. With PETG I could still unload the filament, with PLA I had to disassemble the extruder, as the filament broke between the gears and the heat break.
I’ve clogged my zero with ASA guessing it is of the heat creep failure and bad enough that gentle 1st steps of heating, tugging and wire poking have not yet worked. I previously went through a fairly painful series of clogs on my Creality K1 which resulted in my damaging the hot end and later the extruder. I’m hesitant to repeat a similar learning experience here as I have not yet ordered any spare parts for the zero and fear a possibly long shipping time to receive them.
My K1’s Creality replacement parts were better than the originals and now it is significantly more clog resistant than before but I have no idea yet about what are the best options for replacement parts for the zero either sticking with Sovol or from anywhere else.
I’ve read through this entire thread and have yet to decide on what my next steps should be. Anyone willing to take a stab at a step by step guide for this?
Unfortunately there is no one best method as each clog is a little different. I hope everyone will add their tips and tricks.
Many choices depend on the tools and supplies on hand. For example I’m NEVER without long cotton swabs with wooden handles. Many times the handle is more useful than the tip.
I would proceed as follows:
Heat to printing temperature and remove the nozzle. Remove the filament tension screw and spring. Lay the lever down. Is there enough filament to grab with tweezers?
YES:
With the heater still at print temperature unmount the fan from the heatsink and put a piece of cardboard between the fan and heat sink. Grab the filament with the tweezers and using the tension roller as a fulcrum pull up on the filament. Keep tugging until enough heat soaks into the heat sink to loosen the filament STOP as soon as it moves, cut the filament flush with the extruder body and push the filament DOWN and out the bottom with a swab handle. Shut off heater.
NO:
Heat to print temperature and remove the nozzle and silicone sock. Turn off heat. Unplug the heater and temp sensor from the MCU board. Remove 2 screws holding the heater to the heatsink. Separate the heater assembly from the printer and mount in a vice (or vicegrip plyers) by one of the mounting ears. Protect the plastic electrical connectors by wrapping them with several layers of paper towel topped with aluminum foil. Starting with the nozzle end heat the assembly with a heat gun. Once the plastic starts to melt start heating at the middle of the block and start trying the push the filament through from the “top” with a swab handle. Avoid applying heat to the thin tube, you do NOT want to liquify the filament only get it warm enough to unstick.
BOTH:
Put everything together (except the nozzle) and heat to print temperature. Clean the internal threads with a swab. Using a socket wrench, to avoid burnt fingers, carefully screw the nozzle into the heater. Wait a few seconds for the nozzle to heat then tighten the nozzle.
The YES method can be modified for “medium bad” clogs as follows:
Leave the nozzle in place
Once filament moves shut down the heater and wait until EVERYTHING is below 40 °C
Just realized I didn’t post a follow up on this thread and I wanted to say the clog clearing instructions have worked well for me and made the process straight forward so far. My only deviation is instead of blocking the fan with paper I’ve been suspending it with a solid core wire through one of the fan’s mounting holes and hanging it from the extruder cable such that it doesn’t blow anywhere near the heat sink.
Since clearing my first bad clog by pushing it through I’ve had one more minor clog which easily pulled out the top. I think I’ve got my parameters dialed in for the ASA filament I’ve been using and hopefully won’t be getting more clogs wiith it. In my case running the exhaust fan at 30%, was off when I got the bad clog, and lowering the hot end temp by 5C has been sufficient so far. I think I’m ready to start experimenting with other higher temperature filaments.
In cardoc’s instructions it says to unmount the fan from the heat sink and put a piece of cardboard between them. I perhaps incorrectly remembered the instructions as using paper instead of cardboard.
