PTFE Gaps are a somewhat common issue when dissecting and working on desktop 3D printers. It is a gap between the white/blue Bowden Tube and the end of the nozzle.
If you have taken apart your hot end to remove a clog, it's possible that is was not reinstalled correctly. 3D printers are easy to take apart but difficult to put back together correctly!
The two most common ways that you will know you could have a PTFE gap:
1. You are experiencing leakage of filament from anywhere on the hot end that is not the tip of the nozzle. Melted filament should only come out of the nozzle tip!
2. Your printer is under-extruding
*Drew's Note: Under extrusion is when the filament is not exiting the end of the nozzle in a solid, thick line. Under-extrusion can also be caused by incorrect slicer settings or issues with your extruder gearing (such as incorrect tension on the lever, a loose extruder motor connection, or that the filament gear is loose from the extruder motor shaft). Check these issues first before dis-assembling your hot end!*
Mk-8 Bowden Style Hot End Overview
Here is a great diagram of the inside of a hot end from Creality Experts. MakerMade, NWA3D, and many other 3D printer manufactures use the same Mk-8 Bowden Style hot end:
Here is what a PTFE gap looks like in this system:
Notice how the filament fills up the gap between the nozzle and the tube. That's not good!
I've found that there are two best practices to remove the gap: Basic and Full
Basic PTFE Repair Method
Most stubborn clogs and PTFE issues can be solved using what I call the Basic PTFE Repair Method.
1. Start by heating your hot end to 220C and let it sit for 10 minutes. This should soften the filament inside the nozzle.
*Drew's Note: These temperatures are for PLA removal, if using another material you will have to adjust the melting and glass temperatures for your material. A quick Google search will give you the correct temperature answers you seek.*
2. Remove the filament manually, by squeezing the lever, pushing it in toward the nozzle a little bit, and pulling it all the way out in one fluid motion.
*Drew's Note: We push the filament in a tiny bit before we pull it out to melt the end and make it easier to remove. This is called purging the nozzle.*
3. Load another color of PLA into the printer until you see the new color coming out of the hot end. If you can't push the filament out of the nozzle, you will need to jump to the Full PTFE Repair Method.
*Drew's Note: We use another color of filament because then we can see when all the old filament is removed from the gap! If you only have one color of filament, you can still do this method, but you won't be able to tell when you got all of the excess filament removed.*
4. Change the hot end temperature to 100C. The printer hot end will cool to 100C and when it does, we will squeeze the lever and remove the filament again, in one fluid motion. This is called a "Soft Pull" because you are removing the filament at the temperature at which PLA turns from a solid to a liquid (known as the glass transition temperature). This helps to pull out stubborn bits of melted filament. If the filament won't come out, move to the Full Repair Method.
*Drew's Note: YOU MUST PULL THE FILAMENT ALL OF THE WAY OUT OF THE TUBE QUICKLY! If you don't soft pull the filament all the way out in a quick motion, it will harden inside of the Bowden tube. If it hardens in the tube, you will probably have to replace the tube with a new one - contact us for assistance.*
5. Inspect the end of the filament. You will probably see a different color of filament melted to the end. Repeat steps 1-4 until you only see one color of filament. I recommend at least three times.
6. After you have removed all of the stuck filament, heat the hot end to at least 220C. Use the wrench or some pliers to loosen the nozzle clockwise by one turn.
7. From the top of the hot end, push the Bowden Tube down, so it is pressed up against the loosened nozzle. It will only move a tiny bit, so pushing hard for a few seconds should do it.
*Drew's Note: The "teeth" in the hot end coupler are one-directional. The white grommet must be depressed for the tube to be pulled out and lock in place preventing the tube from moving. You may have to remove the blue clip and depress the grommet to push it down.*
8. Re-tighten the nozzle. You should see the white grommet on the coupler move up a tiny bit. That is verification that the gap has been removed!
*Drew's Note: Be careful the nozzle is HOT!*
9. Load filament into the printer until you see it coming out of the nozzle. Kick off a print that worked in the past and it should print solid. If so, you removed the gap. Nice work!
Full PTFE Repair Method
The Full PTFE Repair Method is more involved and is better described with these tutorials.
This great video will walk you through the steps of how to get rid of the gap on Mk-8 Style extruders. The hot end is the same, only the controls are different on MakerMade and NWA3D printers.
These article is all things hot-end. When you are ready to get into the nitty-gritty of repairs, this guide is for you.
3. Contact us! If these repairs seem to daunting, you can get an entirely new hot end to replace yours and hopefully solve your issue. We're here to help!