Choosing the Right Infill Percentage for the Job


Infill Display

Choosing the right infill percentage for your prints will not only save you time, but it will save you money as well. You want to strike the right balance between strength, functionality, and cost. Leaning towards a lower infill density can significantly reduce the print time and material used, but it can also leave you with a print that isn’t functional. Unfortunately, the opposite also applies. If you choose a higher infill percentage than needed, you will end up wasting time and material to account for the difference between what you needed and what you actually printed.

So what infill percentage should you choose? Well, there will be some subjectivity here, but I can tell you what I do.

Print PurposeInfill Percentage
Model or Mini Figure Prints10 – 15%
Standard Prints20 – 30%
Functional Prints50 – 70%
Calibration PrintsVaries based on designer recommendation but typically 100%

In the rest of this article, I’m going to dive into more details around the time and material difference between infill percentage. I will also go into more about why these are my recommendations.

Print Time and Filament Usage

To use for reference in this article and the YouTub video I created on this topic, I printed this infill percentage display from Thingiverse. The cubes are 25mm x 25mm, with the top layers not printed. This table is based on the actual values that I gathered during and after the prints.

Infill PercentagePrint Weight (Grams)Print Time (Minutes)Estimated Cost
0%3.8634$0.10
5%4.8435$0.12
10%5.6236$0.14
15%6.4137$0.16
20%7.1938$0.17
25%7.8638$0.19
30%8.6139$0.20
35%9.3939$0.22
40%10.1841$0.24
50%11.7842$0.28
60%13.3645$0.31
70%14.9451$0.35
80%16.5955$0.39
90%18.0861$0.42
100%19.5473$0.46

The costs listed above are based on the following assumptions.

Power Cost$0.12 KWH
Material Cost0.022 per gram

If you are interested in learning more about how I calculated these, check out my “3D Printing Actual Costs with Examples” article.

As you can see from the table above, there is a substantial difference in time and material required between a print with no infill and a solid print. In this example, an extra 15.68 grams of filament was used, and the print took an additional 39 minutes to complete. This also resulted in the cost being over four times more.

Keep in mind that these numbers are based on little 25mm cubes. You can also check out the video I created on this below.

Recommended Infill Percentages

Model Prints

If you are printing mini-figures or models that will just be for a display, you can get away with using a lower infill percentage. I tend to print these at 10% but have occasionally gone up to 15% if I know it will get handled more, or by kids. These prints don’t need to be very strong, and 10-15% infill is more than enough. Don’t waste extra filament by trying to go higher here. It just doesn’t really buy you anything, and it’s not worth it.

Standard Prints

I define standard prints as prints that will be used frequently, or even daily, but won’t be used for anything load-bearing or structural. Some examples of prints that would fall into this category include birdhouses, masks, toy cars, most printer upgrade parts, toys that will get played with, etc. Most of the objects you print will fall into this category.

I will print objects that fall into this bucket with a 20-30% infill. Most of the time I am on the lower end of this range but will occasionally go up to 30% if I feel it’s needed for the item being printed. There is no right answer on the exact infill percentage to use, so go with what you think is right for the object you are printing.

Functional Prints

Some people may think this category is overkill, but if im printing something that is meant to be functional, I prefer to have it strong, especially if it’s going to be bearing any weight. I would rather risk wasting a little time and money than having the object fail when it’s being used. Some examples of objects that would fall into this category include custom replacement parts for tools/machines, tools, bookshelf arms, anything that will be continually holding weight, etc. I would say that probably only 10% of the things I print would fall into this category.

If the object being printed needs the strength and falls into this category most of the time I will just print with a higher infill. I tend to print objects in this category with a 50-70% infill, most of the time leaning towards the 70% side. I realize this increases the cost considerably, but sometimes it’s just needed.

Calibration prints

Calibration prints are prints that are used to calibrate your printer and typically have the infill percentage called out in the instructions.  These prints are meant to serve a particular purpose, so I tend to follow the recommendations provided by the designer when specified. If the infill percentage isn’t specified, I treat them as standard prints and use a 20-30% infill.

Here are some example calibration prints that I have used in the past.

Shell Thickness Tip

You can also increase the shell thickness from the standard two layers to four layers. Doing this will allow you to reduce the infill percentage without sacrificing strength, in many cases, it can actually make the print stronger. That said, this is not something you would want/need to do all the time, but if you are printing a larger model, it can save you some filament.

Here is an example. I took this Thanos model and reduced the scale to 30% to fit on Ender 3 Pro.

Infill PercentageWall ThicknessPrint TimeFilament Used
10%2 Layers30 Hr 18 Min295g
15%2 Layers38 Hr 5 Min400g
5%4 Layers30 Hr 24 Min254g
10%4 Layers38 Hr 4 Min355g
*Note: Infill pattern used was grad.

I this example, I would go with the wall thickness of 4 and the 5% infill. It adds about 6 minutes to the print time but will reduce the filament used by 41 grams. These savings can really add up if you do a lot of larger prints.

Recap

Understanding what infill percentage to use can save you a lot of time and money. You want to make sure that you strike the right balance between strength, functionality, and cost. Leaning towards a lower infill density can significantly reduce the print time and material used, but it can also leave you with a print that isn’t functional. Going with a higher infill percentage than needed will result in you wasting time and material to account for the difference between what you needed and what you printed.

Make sure you check out our YouTube channel, and if you would like any additional details or have any questions, please leave a comment below. If you liked this article and want to read others click here.

Rob

I'm Rob, the founder of 3dprintscape.com. I’m a Marine Corps vet with a master’s degree in Information Systems and have been working in the technology field for over a decade. I started working with 3D printers because I was fascinated by the technology and wanted a hobby that my kids and I can enjoy together.

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