How Do PETG “Blobs Of Death” Happen?
The blob of death is a common manifestation of any number of problems that could occur with your 3D printer. Appearing, quite literally, as a blob of PETG filament that encompasses your 3D printer’s extruder nozzle. Obviously, this clogs up and blocks your extruder from printing anymore and can be a huge inconvenience for anyone wanting to continue producing new prints.
This can happen for any number of reasons. However, the most likely issue is the nozzle simply isn’t screwed on tightly enough. If this is the case, the gap between the nozzle and the heat break will be big enough for the molten PETG filament to leak out and form a blob of death around your hot end.
Though these blobs of death are some of the most common causes of printer breakdowns, there is no need to panic and buy another extruder right away. This isn’t an uncommon occurrence, and there are plenty of simple ways to get your nozzle back to being clean as a whistle once again.
Preventing Blobs Of Death With Proper Hot Tightening
Hot tightening can be one of the trickiest parts of preparing your 3D printer to print. If not enough torque is applied to the nozzle, there will be a gap big enough for molten PETG to leak out. However, heating the nozzle up to the highest temperature setting and applying too much torque can cause the nozzle to break. This is a slippery slope and the prospect of a broken nozzle is often enough to scare people away from applying sufficient torque.
Figuring out just the right amount of torque to apply may require experimentation but it’s all a part of the learning process and once mastered, blobs of death will no longer be much of a problem for you.
How Can You Clean PETG From Your Nozzle?
If your prevention techniques didn’t work as planned, there is no need to worry. As mentioned before, there are many ways that you can clean PETG from your 3D printer's nozzle. These include heating your nozzle, using PETG dissolving chemicals, and using tools to scrape your nozzle clean.
Heat The Nozzle
By far the simplest and easiest way to clean PETG from your nozzle is to simply heat it up again. You can heat the nozzle while it is still attached to the printer using the printer itself, or you can remove your nozzle from the printer and heat it with a torch.
No matter what you do, the important thing is to heat the nozzle to a temperature around 20 to 30 degrees celsius higher than the temperature you used during the printing process. If you don’t heat it up enough, you may not be able to scrape off the PETG, and if you heat it too much, you may risk damaging your nozzle. A solid 10 to 30 degrees Celsius above the printing temperature should be perfect for the removal of the PETG blob.
Once heated, the PETG will start to melt off the nozzle, and any particularly big or stubborn pieces of PETG can be scraped off with a knife or removed with pliers. Most of the time, this is all you’ll need to do to remove all of the PETG from the nozzle.
Use A Wire Brush
If there are still small pieces of molten PETG stuck on your nozzle, using a wire brush is the next step. Some of the smallest specs of PETG stuck to the nozzle can be the hardest to remove at or above melting temperature.
The key here is to lower the heat to around the glass transition temperature of PETG, fat below the melting point. I suggest heating the nozzle to anywhere from 90 to 130 degrees celsius. At this temperature, the PETG will be flexible and bendy but won’t become a liquid allowing the wire brush to peel off pieces stuck in the smallest crevices of your nozzle.
Using a wire brush without heating the nozzle can work well at removing any extra PETG stuck to your nozzle, but heating it just past the glass transition point can give you the extra advantage in removing those last bits of PETG.
Using Chemicals To Dissolve PETG
If all else fails, there are some chemicals that can aid in the removal of PETG from your nozzle. PETG is quite durable and chemical resistant, you can’t just use any chemical to clean PETG from your nozzle but, the chemicals that do work are very effective.
Acetone, methyl ethyl ketone (MEK), toluene, cyclohexanone, and dichloromethane are all chemicals that can be effective at dissolving the PETG stuck to your nozzle, however, some of these chemicals are easier to come by than others, and all can be harmful if handled incorrectly.
Some of these chemicals are very strictly regulated because of their harmful natures and the potential for misuse. Dichloromethane is a known carcinogen that can easily vaporize into the air around it and toluene is heavily regulated as it has the potential to be used in the making of explosives. Cyclohexanone and MEK are also heavily regulated and hard to find because they can be used to make illegal narcotics.
The easiest to find PETG dissolving chemical is acetone. Though still harmful if used incorrectly, acetone can be found in most hardware stores, often under the brand name Goof Off. Placing your nozzle in an acetone bath and letting it sit for anywhere from an hour to overnight will dissolve most of the PETG and make whatever small amount remains much easier to remove.
In absolute worst-case scenarios, this process can be repeated so that even the most stubborn pieces of PETG stuck inside the nozzle can be dissolved and removed. As long as you are persistent and thorough, the PETG doesn’t stand a chance of clinging to your nozzle any longer, allowing your 3D printer to continue producing quality prints like it was just shipped from the factory.