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The Top 6 Filament Mistakes That Cause 3D Printing Failures

Oct 28, 2023Oct 28, 2023

There’s more to 3D printing failures than poor slicer settings. We explain how bad filament handling practices can ruin your 3D prints.

It’s natural to question your slicer settings or bed tramming when a 3D print goes horribly wrong. After all, a single funny slicer parameter can result in a clogged nozzle and other 3D printing catastrophes.

But sometimes the problem exists at the filament level. Diagnosing such problems and knowing how to prevent them altogether is an essential 3D printing skill that is key to avoiding fruitless troubleshooting elsewhere.

If your 3D printing woes occur despite following good slicer and printer maintenance practices, familiarizing yourself with these filament handling mistakes might help you save the day.

An overwhelming majority of clogs reported by 3D printing beginners running affordable printers can be blamed on the use of filaments that are too hot for the stock extrusion setup. To reduce manufacturing costs, these printers allow the PTFE liner to touch the nozzle. While this saves money on expensive machined heat breaks, it also introduces the PTFE tube into the melt zone.

That’s a terrible idea because PTFE begins off-gassing chemicals that can cause brain damage when printing filaments, such as ABS, nylon, and polycarbonate that flow at temperatures beyond 250°C. Apart from the literal nerve agents being released, the rapid deterioration of the PTFE tube also leads to nozzle clogs.

The solution is simple. Just upgrade to an all-metal hot end, as explained in exhaustive detail in our Ender-3 upgrade guide. Doing so keeps the PTFE tube safely away from the melt zone, thereby eliminating the chance of nozzle clogs and toxic off-gassing. Most popular 3D printers even have drop-in heat breaks available that convert the stock hot end to the all-metal variety for a fraction of the cost.

Nozzle clogs in affordable printers aren’t restricted to overheating PFTE liners. Even flexible filaments, such as TPE and TPU, which print cooler, don’t play well with entry-level printers running Bowden extruders. Our direct drive extruder explainer delves in detail why that is the case, but in simple terms, it’s hard to push flexible filaments through long Bowden tubes. It’s like pushing a rope down a hose, which consequently requires comically high retractions.

A direct drive extruder is recommended for printing flexible filaments, especially if you prefer extra-soft ones with lower Shore hardness. The really flexible variety even requires specialized extruders with shortened filament paths. But if you insist on using a Bowden extruder, you have to stick to harder flexible filaments and significantly reduce printing speeds.

If you thought tangled earphone wires were bad, just wait until you encounter tangles in filament spools. Like the proverbial sword of Damocles, tangled spools are ticking time bombs just waiting to ruin long prints. These tangles aren’t even complicated given the relatively high rigidity of the filament. Therefore, they manifest as a single loop that eventually causes filament feed failure.

Preventing filament spools from tangling requires following one cardinal rule: never let the free end of the filament fly back into the spool. Once that happens, it invariably slips under a stray filament loop that loosens momentarily. The next time you fish out the loose end, it has already formed a loop that will eventually tighten up to cause a print-ruining filament feed failure.

That’s precisely why filament manufacturers take great pains to tape the loose filament end securely to the spool. Virtually all filament spools also incorporate provision to thread the loose end such that it is held securely. If your filament manufacturer hasn’t implemented this feature, a 3D printable filament spool clip is the next best solution.

Shedding the training wheel of PLA and graduating to PETG is a bittersweet experience for most 3D printing enthusiasts. While PETG is a lot less forgiving than PLA, what catches most beginners by surprise is the propensity of the material to absorb moisture compared to PLA.

A moist filament can cause everything from horrible print quality to total print failure, and the problem isn’t easily apparent unless you know what you are looking for. Almost all advanced 3D printing filaments tend to be fairly hygroscopic, with nylon and polycarbonate being practically impossible to print without proper filament drying equipment.

For starters, make it a point to store such filaments in vacuum sealed bags, along with fresh desiccant material such as silica gel beads to absorb extant moisture. This will prevent the filament from absorbing additional moisture in storage. However, this does nothing to extract moisture already absorbed into the filament.

For that purpose, you need a dedicated means for drying filament. The relatively cheap filament dryers built for consumer 3D printers work great as long as you select the right heater setting and use fresh silica gel beads to absorb moisture. Food dehydrators also work wonderfully.

However, nylon, PEEK, and polycarbonate to some extent require PID-controlled ovens to reliably dehydrate these filaments. Regular ovens are cheaper, but they lack the precise temperature control that makes the difference between a perfectly dry spool of nylon and a very expensive 3D printed replica of a nylon spool.

While we have a general idea on the temperature ranges commonly used for different filament types, never make the mistake of assuming the correct setting for your specific filament type. That’s important given the prevalence of specialized blends employed by different filament manufacturers.

Depending on whether the manufacturer intends to make a difficult filament print easier or improve its strength, the nozzle temperature and print speeds can vary wildly for the same filament type. Fortunately, these critical settings are specified in the data sheet. All you have to do is read it and use these settings as the basis to fine-tune your slicer parameters.

There are specialized filament blends, and then there are composite filaments. The latter involve enhancing engineering materials such as ABS, polycarbonate, and nylon with composite materials such as carbon fiber, glass fiber, and metal granules. Such composite filaments are a great way to improve the tensile strength, warping resistance, temperature tolerance, and printability of technical materials.

Unfortunately, such filaments are impregnated with as much as 30 percent of chopped glass/carbon fibers and metal particles. Not only are these additives extremely abrasive, but they can even clog standard 0.4mm nozzles. Such materials can render regular brass and stainless-steel nozzles useless within no time.

You need larger 0.6mm nozzles manufactured from abrasion resistant materials such as tungsten carbide, tool steel, ruby, and even diamond to print such filaments reliably. However, such filaments lack the thermal efficiency of brass and copper nozzles, so you will have to print at hotter-than-normal nozzle temperatures.

Now that you know how to prevent common filament handling mistakes, you are that much closer to a trouble-free 3D printing experience. Having said that, it also pays to pay a bit more for quality 3D printing filament. The improved quality assurance and consistent production quality of quality filaments is a worthwhile investment considering how the slightest deviation in filament composition can wildly affect the quality and reliability of your 3D prints.

Nachiket has covered diverse technology beats ranging from video games and PC hardware to smartphones and DIY over a career spanning 15 years. Some say that his DIY articles serve as an excuse to pass off his 3D printer, custom keyboard, and RC addiction as “business expenses” to the wife.