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Does Filament Quality Really Matter?

If you’re new to 3D Printing, you may wonder what all the specs listed with 3D filament are and why they matter. Well, each spec is there for a reason. And they are important. Let’s talk about a few of them now.

Filament Diameter

Diameter is the distance from one side of the filament to the other in a cross section. If you sliced a piece of filament into a tiny, thin slice, then measured it, you could get the diameter of that section. Most 3D printer filament comes in one of two standard diameter sizes: 1.75mm or 2.85mm (often referred to as 3.0mm). The size you use depends on the printer you use. Most printers use either one or the other. Once you’ve determined the size you use, you can go to the next level to see if the filament you’re buying is actually going to be that size. 

Diameter Tolerance

When filament is described, you will usually find the tolerance level of the filament listed right along with it. It will be something like 1.75mm ±0.05mm.  This last part, the Plus or Minus part, tell you how closely the manufacturer adheres to the size when they are making the product. ±0.05mm is pretty much an acceptable level and is generally considered the industry minimum for quality of the diameter of filament. Many manufacturers (Like 3DomFuel) will work toward making higher quality and tighter standards with their filament. In fact, our standard is closer to ±0.02mm. So, what does this mean? Well, if your filament has a tolerance level of 0.05mm, then that means the filament can vary as much as 0.05mm in either direction. Or to put it simply, the filament may be anywhere between 1.70mm and 1.80mm in size. 

That doesn’t sound like much, does it? But in reality, that translates to a 5-6% difference in size. I know, that doesn’t sound like much either. But the reason it is important has to do with math. Yeah, yeah, you thought you’d never need math again… but 3D Printers use it constantly. 

Why does this matter?

When a program (called a “slicer”) calculates how to print your item, it makes all the calculations based on a few assumptions. These assumptions are given to it by you in the settings. One of the numbers you give the slicer is the diameter of the filament you’re going to be using. It then uses that number to figure out how much, how fast, over how much area, and at what thickness to push filament out of the extruder nozzle. If the filament you’re using is not the same diameter as what the slicer is expecting, your print will not look as good as it should. In fact, it can lead to small holes, missing sections, too much filament in places, and other issues. So, it is important that the filament is as close to the spec as possible.  If you tell your slicer it is 1.75mm, it needs to be as close to that as it can be.


The other consideration for size in filament is the Ovality of the filament. In other words, does the filament look like a circle at every point? Or is it “squeezed” so that it is oval in shape? In the drawing above, you can see that the blue encircled area is not round, it’s oval. So, the ovality is off unless you have filament that is round like the outer black circle. 

Ovality is important for more than one reason. First, the physics of the shape will tell you that a filament that is oval may have a hard time being pushed or pulled through your printer. Each printer has a motor that assists with pushing the filament through the nozzle. The motor is controlled by the instructions it gets from the software (the slicer). If it is oval, and the software says “Push”, but it can’t get a good grip on it. Then nothing happens. This can cause more inconsistencies in your print. 

Additionally, ovality is also another indicator of poor diameter. The diameter could be off in both directions. Causing more issues with your print. 

Most 3D manufacturers omit ovality in their specs. They just ignore it, or just don’t report it. 3D-Fuel not only reports it, we actually print the specs right on the box. Each spool is measured as it is produced. Hundreds of times a second we’re measuring the diameter and ovality of the filament as it passes through. These recordings are saved, then printed on a graph so that you can see the actual results of the spool you purchased. You get a report showing the diameter as the filament passed through, an average diameter, and the average or “mean” ovality. 

At 3D-Fuel, we are in a “continuous improvement mode” with all our production, all the time. We have continued to improve our results and feel we now produce the best filament available anywhere. Our filament now averages below ±0.02mm in diameter tolerance, and less than ±0.01 in ovality. Filament that is the right size prints better. Period.

Watch out!

When you’re selecting filament, it is easy to get caught up in pricing. Looking for the cheapest filament is normal. Most of us have gone through that, or are still doing it. But in the long run, it is the best filament that saves you money.  Cheap filament can cause problems from bad prints to clogged equipment. Costing you time and money in lost prints and repair time or expenses. 

And when you see a spec on a 3D filament, how can you know it is correct? Filament made in the Far East is sold to people who sell it as their own brand and they never know if it actually meets the specs they have been told it does. Also, look how they quote the specs. Here are two specification listings:

Diameter Tolerance ±0.03

Diameter Tolerance averages ±0.02

Which is better? At first, you’d say the second one. But look closely. The first states that it is within 0.03mm all the time. The second says that they AVERAGE that. An average could include any size above or below that number as long as the average 0.02mm. So, it could be 0.15 to 0.001. The best way to know, is for the manufacturer to actually measure it and put it right on the box. That’s the best way to know you have high quality filament. 


Example of a 3D-Fuel box with printed actual specs

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Peter de Villiers - July 25, 2023

A useful article for me thanks, I had issues with a roll of PETG with diameters ranging between 1.6 to 2.0mm this caused the filament to get jammed in the Bowden tube. It took me a few days to figure it out as I couldn’t successfully print anything. I am still trying to get a replacement roll from the supplier, no luck so far. In the mean time I have ordered some rolls from a different supplier.

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