Cold pull.
Some info I found about the cold pull. Perhaps it is useful.
Cold pullA "cold pull" (also known as the "atomic method") on your 3D printer is a technique used to clean your hotend and nozzle. It's necessary in the following situations:
1. Partial Clog
This is the most common reason. If you notice your printer isn't extruding filament consistently, the printed lines are thinner than usual, or the extruded filament curls and sticks to the nozzle, you likely have a partial clog. This can be caused by:
* Dirt or burnt filament residue: Over time, small particles of dust, filament debris, or even burnt filament can accumulate in the nozzle or heatbreak.
* Switching between filaments with different temperature requirements: If you switch from a filament that requires a higher temperature (e.g., PETG) to one that requires a lower temperature (e.g., PLA) without properly purging the hotend, remnants of the higher-temperature filament can get stuck and obstruct the flow of the lower-temperature filament.
* Filament staying hot for too long: If filament remains in a hot hotend for an extended period without extruding, it can degrade and become sticky, making it harder to pass through the nozzle.
* Poor quality filament: Low-quality or old filament can contain impurities that lead to clogs.
2. General Maintenance
Even if you don't see clear symptoms of a clog, a cold pull can be part of your regular maintenance routine to keep the nozzle and hotend clean and prevent potential problems. Some users, for example, perform this every 20-30 print hours, especially if they frequently change filaments.
How does a cold pull work?
A cold pull involves heating the filament to a specific temperature (usually around 90-120°C for PLA), making it just soft enough to adhere to any clogs in the hotend and nozzle, yet still firm enough to be pulled out in one piece. When the filament is extracted, it removes any impurities that were stuck.
It's important to note that a cold pull is generally used for partial clogs. For a complete clog where no filament comes out of the nozzle at all, a more intensive approach is often needed, such as disassembling the hotend or replacing the nozzle.
Since firmware 6.0.0 on the MK4/S and MK3.9/S, Prusa printers can also perform the cold pull automatically, making the process even simpler.
Regards, Ron
RE: Cold pull.
I've had good success performing cold pulls both manually and with the firmware cold pull on my MK4S (previously MK3 then MK3S then MK3S+ then MK4) using eSun cleaning filament. (I purchased a 0.1kg coil from US Amazon in Feb 2019 and am still using it.) At least with non HF nozzles. Often this cleaning filament comes out as a perfect cast of the inside of my nozzle. When cleaning for maintenance or changing filament types I keep cold pulling until I get a cold pull without any observable specs of dirt or the previous filament. Usually takes two cold pulls (second cold pull comes out clean, so the first cold pull did all the work and the second was just verification).
See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs
RE: Cold pull.
Ron
Thanks for posting, interesting.
I have been using the filament SMART FIL / GEETECH for a FEW years and agree with the PULL principal.
I copied this from the filament makers how to use.
"230°C extrusion temperature, push the cleaning filament through until it comes out clean/clear. Then turn off the heater and watch the temperature drop passively until it is between 85°C and 110°C. Then carefully but decisively pull out the cleaning filament."
I do not have the onboard pre settings for COLD PULL on my 3D machines.
When I am running long time wise that is, and as I normally print jobs through the night, it can be disappointing and costly when you find by sods law in the morning the last layers are messed up because of a blocked nozzle. As I am not that very disciplined remembering this regular maintenance schedule versus the 3 printers run time. I connected up small digital clocks into the boards and they start to record accumulated time on start up and turn off when printers are powered down through
the custom end g codes.
After COLD PULL cleaning and or nozzle changes I reset the digital clocks back to zero.
John
RE: Cold pull.
I print almost exclusively standard filaments (without cf or glitter) and never have clogs and also never do preventative cold pulls.
The only time in the past years that I had a 'real' clog (not due to heatcreep) was when committing the stupidity of not paying attention and putting a glitter filament through a 0.15 mm Revo nozzle. The cold pulls were not working. I tried all kinds of filament: cleaning filament (PP), PA, PLA, PLA+. In all cases the filament would break somewhere right below the heat break and leave about 2 cm of filament in the nozzle. Each time I had to take the nozzle out, heat it up with a heat gun and poke it with a 1.8 mm stainless steel rod to get all the filament remains out. And using a 0.14 mm acupuncture needle to free the orifice. I lost count of how many repetitions of that procedure I needed to finally clear it from all the glitters. Somewhere between 5 and 10.
What maybe helps is that I religiously keep *all* my filament in a drybox, which has the double function of keeping it free from dust and debris. I cringe when I see people on YT having rows and rows of filament rolls gathering dust and water on open shelves or stacked on the floor... I feed filament into my mk3.5s directly from a drybox through a ptfe tube that goes all the way to the print head. So there is very little chance of any contamination entering my print head. That maybe helps reducing clogs.
RE:
I print almost exclusively standard filaments (without cf or glitter) and never have clogs and also never do preventative cold pulls.
The only time in the past years that I had a 'real' clog (not due to heatcreep) was when committing the stupidity of not paying attention and putting a glitter filament through a 0.15 mm Revo nozzle. The cold pulls were not working. I tried all kinds of filament: cleaning filament (PP), PA, PLA, PLA+. In all cases the filament would break somewhere right below the heat break and leave about 2 cm of filament in the nozzle. Each time I had to take the nozzle out, heat it up with a heat gun and poke it with a 1.8 mm stainless steel rod to get all the filament remains out. And using a 0.14 mm acupuncture needle to free the orifice. I lost count of how many repetitions of that procedure I needed to finally clear it from all the glitters. Somewhere between 5 and 10.
Ouch. That hurts just reading about. Glad you were eventually able to save that nozzle. The smallest nozzle that I've printed with was a 0.25mm nextruder nozzle, and yes, I was silly enough to print with a black fleck "stone like" filament. I kept getting jam notifications, but a cycle through the automated filament change cleared it up for 15-60 minutes. I was able to cold pull that nozzle clean.
What maybe helps is that I religiously keep *all* my filament in a drybox, which has the double function of keeping it free from dust and debris. I cringe when I see people on YT having rows and rows of filament rolls gathering dust and water on open shelves or stacked on the floor... I feed filament into my mk3.5s directly from a drybox through a ptfe tube that goes all the way to the print head. So there is very little chance of any contamination entering my print head. That maybe helps reducing clogs.
I also try to keep my filaments inside bags and boxes, but before my MK4 series I was printing on an unenclosed MK3 series. My printing space is in the basement, so dust is *constantly* dropping from the ceiling. Back when filament oilers were the big rage (glad we as a community finally outgrew that messiness), I found a model to hold a sponge that the filament would pass through. (Specifically this model, I used FilamentPM silver (came with my MK3) and got that nifty pattern on the bottom with Hilbert Curve bottom fill.) I never applied oil, but used it to wipe any dust/dirt off the filament right before it went into the extruder. I can't say that is the reason why, but I almost never got a clogged nozzle when printing with my spool exposed to the constant rain of dust from my basement ceiling. I still use the dust wipers on my enclosed MK4 series, but mostly out of habit. I have noticed that the sponge doesn't get as dirty on my enclosed MK4 as it did with my exposed MK3.
See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs
RE: Cold pull.
My five cents about cold pulls ( YMMV )
- If you’re using standard PLA for the cold pull, don’t heat the nozzle above 85C or you’ll risk breaking the filament when it’s pulled out. Nothing serious, but you’ll have to repeat the procedure.
- I found out the hard way that it’s a very wise policy to perform a cold pull before printing TPU, regardless if the former print was TPU or any other type of filament. Otherwise. if there’re small residues left inside the tip of the nozzle, TPU tends to accumulate slowly around those small particles until it ends up in a clog. That’s specially important with 0.4 nozzles ( I wouldn’t recommend at all using nozzles smaller than that with TPU or CF/GF filled filaments ).