Learning Through Educational Tools: Infill Percentage

Infill percentage controls the plastic to air ratio inside of a print. For instance, 0% infill means that there is 100% air inside of a print. While, 100% means that the part is solid plastic. Anything in-between varies the amount of plastic inside the print. Generally I like to use somewhere between 10-25% infill. Though, sometimes I use higher infill percentages for increased strength, or for small objects.

Strength wise, anything less than 20% isn't likely to make much of a difference. Though, I like using 20% when the surface finish is important. Since 20% infill doesn't have wide gaps to bridge. Using 5-10% infill can work well for objects that have curved sides, and not much of a flat surface. They also don't use much filament, so it helps you save money for objects that don't need much strength (i.e. Statues, figures, etc.).

An article written by Clifford Smyth provides some empirical evidence of how much infill can have an effect on the strength of a print. He tested items with 25%, up to 75% infill. He discovered that infill greater than 50% has diminishing returns on strength vs. filament used. An interesting discovery he made was that lower percentages of infill allowed parts to be more flexible, while increasing the chances of the parts breaking.

While looking for articles on infill styles, I also discovered an article that showed the relationship of infill percentage to layer height. I would recommend taking a look at the results, since they are provided on some very nice charts. Summarized, the writers discovered that infill is a determining factor in part strength.

Just like Clifford, they suggested that infill should be considered when setting up a print. Since the purpose of a part is directly related to the amount of infill required. For instance, a fidget spinner would need strength, so higher infill would be important. On the other hand, a statue that is just going to sit there really doesn't need much infill. You can save money if you use less infill, since infill is material that you buy.

Ultimately it is up to you what infill percentage you use. My preferred percentages come from personal experience, and the information that I have garnered from various sources. The one thing that I can tell you, is that it is an extremely important part of a successful print. Don't freak out about deciding the correct values, usually the designers or someone that printed the object provides a good suggestion.

When in doubt, around 20% is a very safe infill percentage for most prints. You will be fine, just take your time, and learn what infill settings work best for each print. You will gain a sense for it over time. Happy printing!

External Sources

https://rigid.ink/blogs/news/optimum-infill

http://my3dmatter.com/influence-infill-layer-height-pattern/

https://ultimaker.com/en/resources/16528-infill

http://3dprintingforbeginners.com/infill-strength/