Using 100% infill is one of those things that is typically not advised. It is said to use a lot of material and takes too much time to print. On the other hand, it is often claimed that using 100% infill gives you the strongest prints. Are these claims true or are they merely assumptions?
In this article, we will reveal what the current research says about the strengths of prints made using 100% infill. We will also show you what a print made using 100% infill looks like, give you an idea of how much extra material is used when printing at this infill density, and more.
Realistically, you will rarely ever need to use 100% infill when 3D printing, but if the need arises, it will help to have some idea of what to expect. Read on to unlock some of the mysteries of 3D printing using 100% infill.
Are Prints With 100% Infill Stronger?
Tests have shown that the tensile and compressive strength of a printed part will increase with the infill density, maxing out at 100% density. However, there are other types of strengths that you may need to be considered for a 3D-printed part.
In another test that focused on the impact strength of 3D printed parts, the impact strength of the printed parts was highest at 85% infill density. Perhaps more surprising was that the impact strength of some parts at 100% infill density was lower than at 50% infill density.
According to the study’s authors, because the greater infill density made the part more homogenous it may have made it easier for a crack to propagate through it once it started.
There are other studies that are still being carried out to understand the strength of 3D-printed parts at different infill densities. However, the present research suggests it’s too early to assume more infill will always equal more strength.
What does 100% Infill Look Like?
At 100% infill, anything that wasn’t designed to be a hole will be filled with plastic. These will be parts of the design that are supposed to look and feel solid but are typically not printed as such to save time and material.
To demonstrate the effect of 100% infill density, the common print-in-place octopus above was partially printed at 100% infill and at 0% infill. The space around the hole in the middle is solid in the design.
At 100% infill density, this space is completely filled with material. At 0% infill density, this space is left completely hollow. In most cases, users will go for something between these two extremes.
It should be noted that these differences are easy to see because these were partial prints. If both prints ran to the end, the visual differences would probably be less obvious.
How Much Material is Used at 100% Infill Density?
One of the most common arguments you’ll hear against using 100% infill density is the amount of extra material it consumes. However, this argument isn’t so black and white.
For the octopus print above, Prusa slicer gives the following estimates for material consumption at the indicated infill densities:
| Infill Density Percentage | Mass (g) |
|---|---|
|
|
16.44 |
|
20 |
21.8 |
|
100 |
34.09 |
The amount of material used at 100% infill, if the part was fully printed, would be 107% greater than at 0%. Realistically, this type of item would be printed at around 15 – 20% infill. This means printing at 100% infill would require closer to 56% more material.
However, these numbers are coming from just one print and there is an infinite number of items that can be 3D printed.
In a sample of 10 parts, the prints required between 5% and 1043% more material when printed at 100% infill. This was in comparison to the infill percentage that the items were likely to be actually printed at. These values ranged between 0% and 80%, per my judgement.
Note: The charts below were filtered to enhance the visibility of the results, i.e., one outlier was hidden. Find details on how you can access the unfiltered data at the end of the article.
As seen in the charts, using 100% infill usually results in the use of more material. This effect can be extreme or quite muted. The extra material used is easy to notice for many prints, but those that lack features that can be filled such as those with relatively thin sections will use very little extra material when printed at 100% infill.
Depending on factors such as number of shells, shell thickness and the thickness of different sections, it is easy to have designs with no difference in mass regardless of infill density.
Which Infill Patterns Can Print at 100%?
One of the quirks of using 100% infill density is that it cannot always be done even if you have a good reason for doing this. One of the factors that can prevent you from using 100% infill density is the infill pattern you choose.
In PrusaSlicer Version 2.6.1, the only infill patterns that allow 100% density are:
- Rectilinear
- Aligned Rectilinear
- Concentric
- Hilbert Curve
- Archimedean Chords
- Octagram Spiral
This means that many popular infill patterns such as gyroid, grid, and honeycomb are incompatible with this setting. However, since all the available infill space will be ‘packed with material, the infill pattern selected at 100% density may have less of an effect on part parameters such as strength.
In one study, it was found that the compressive strength of four specimens printed with four different infill patterns at 100% infill, did not vary significantly.
What Are the Drawbacks of Printing at 100% Infill Density?
The main disadvantages of printing at 100% infill density are:
- It uses more material than you probably need
- It requires more printing time
- It may result in a functionally weaker product
When to Use 100% Infill
Despite the disadvantages noted above, there are some situations when using 100% infill still makes sense. These are:
- Where you need the maximum tensile or compressive strength. Current research still indicates that tensile and compressive strength is, on average, highest at 100% infill density.
- Where you need the extra mass.
Conclusion
At 100% infill density, any closed space in the printed part that wasn’t in the design is filled with the material resulting in a more solid and homogeneous structure. This may improve tensile and compressive strength, but it may compromise impact strength and other things.
Printing at 100% infill density almost always requires more material and adds hours to the printing time. You are also limited to specific infill patterns but this may not matter as much at this infill density. In a fully printed part, there may be no visual difference between a part with 100% infill and one with no infill at all.
Printing at 100% infill density may be interesting from an experimental point of view, but it is rarely practical or even necessary. The same can’t be said about printing at 0% infill.
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