You just spent a few paychecks on a fused deposition modelling (FDM) type 3D printer. Desktop printers use plastic filament as the source materials to 3D print an object on these printers. How do you keep your printer from turning into a boat anchor due to bad filament?
Just like inkjet printers, there are good and bad brands of filament. There are also other factors to consider when you order filament. Here is my list of things I found out the hard way to look for when it comes to getting good filament.
What are you 3D printing?
This may seem like a dumb point, but it really should be your first consideration. Are you printing a car part that will require nylon/Kevlar, or a simple toy that can use PLA?
Something that all printers are guilty of is buying filament for the WOW factor alone. We see blogs that report on a new filament made of beer or carbon fiber, and we quickly buy it online before considering what we will even want to print with it. After dropping serious cash on exotic filaments, I’ve seen many printers print items that were just fine printed in PLA. They also are stuck with a spool of expensive filament that they become gun shy about using. The end result is a spool of exotic filament that sits on a shelf, becoming brittle and difficult to run through their 3D printer.
What is the printing material?
This is another consideration that printers forget when they are looking at different materials. Not all 3D printers can handle the temperatures for every filament. Other 3d printers may say they can, but in reality can’t cope with the viscosity of certain materials. For this you will have to do research for your 3D printer. Look on Facebook or other forums to see what people have experienced with different materials and your 3D printer. Never trust the reviews you see on Amazon. Printers have already tried running every filament through their printers, so you might as well learn from their mistakes.
For this point you have to think about how much you use your 3D printer. If you use your 3D printer occasionally, storing filament between prints becomes a concern.
PLA filament is the main offender in this category. PLA has to be stored in a cool, dry place when not in use; otherwise it turns into stiff brittle plastic bits in a few months. I’ve had spools of PLA go bad in as little as 3 months. If you 3D print daily, you can use up PLA before it goes brittle.
Other filaments have a better shelf life, but should be likewise stored in a cool, dry place. You will have to check with the manufacture and online for their recommendations.
How the filament is rolled on the spool makes a world of difference. I have experienced more heartache from bad spooling than anything else in 3D printing. At the factory, warm filament is wrapped around the spool. As the filament cools, it tightens and forms to the radius of the spool core. This results in the filament coming off the spool in an arch. If the core is too small, the filament will snap instead of feed smoothly into the hot end.
I hit a problem with off-brand filament spools. The diameter of the core affects how the filament feeds as it reaches the end of the spool. What I found is that the filament at the end of the spool tends to have a tighter radius and be a bit more brittle. When you run a long print, that may result in a print dying after 6-8 hrs.
Off brand filaments can come on spools with a core 30 mm OD. While this makes for a smaller spool, it turns the filament on the end into a brittle spring instead of proper filament.
The worst I found for this was Bee Supply filament. A client gave me 4 0.2 kg spools of their PLA, and every one turned into shards because they were wound around the tight spool radius.
When you get the spool, look at the filament on it. Is it wound so tight it has started fusing to itself? Is it so loose it falls off the spool?
Is it uniform and lying flat? Are their loops sticking out and bumps in the filament? Badly spooled filament will tangle as it rotates. This tangle will prevent feeding, which will clog the printer head and burn out the motor.
How to test your filament
a. Cut a section about 100 mm long.
b. Look at it closely, and under a magnifying lens if possible. Do you see any bubbles or hairline cracks? Bubbles come from bad extrusion, and are weak points that the filament can snap at. Check other parts of the filament to see if there are any bubbles. If there are a lot of bubbles, your filament may turn into shards.
Hairline cracks can be from stress or bad mixing at the factory. If there are a lot of cracks, run a test print at a slow feed rate to make sure the filament does not turn into bits.
c. Roll the sample straight in your hands like a clay snake. Does it straighten out, or does it fight you? If the filament is not flexible, consider running this at a slower feed rate.
d. Bend the sample around. Is it flexible enough to bend into a tight loop, or does it snap instead? Good filament will bend and kink before breaking, while brittle filament will snap like dry spaghetti.
e. If there is any doubt after this, run a test print. Many printers have test files built in, or you can find them online.
What is good filament?
Good filament should come cleanly off the spool. It should be flexible enough to bend around the feed tube into the printer head. Filament should be continuous enough that it flows uninterrupted through the hot end. It should print at the temperature listed for the material.
If you want to try new brands and filament materials, look around at forums for 3D printing to see how they perform.