How Much Infill Do I Need For 3D Printing?

Infill is one of the key settings when 3D printing, but I wondered how much infill you actually need when making a print. I’ve done some research to find out some good infill percentages which I’ll explain in this article.

The amount of infill you need will depend on what object you are creating. If you are creating an object for looks and not strength, 10-20% infill should be enough. On the other hand, if you need strength, durability and functionality, 50-80% is a good amount of infill.

The rest of this article will go into depth about what factors affect how much infill you need for your 3D prints and other tips you can use.

What is Infill?

When you are printing a 3D model, one thing that doesn’t need any precision or attention is how you print the interior. For this reason you don’t need to make a completely solid interior for the model. This is why you can use a different approach to print the interior in a more effective and efficient way.

Infill is the three dimensional structure that is printed inside the model to hold the walls or perimeter of your model together. Infill is used to give strength to the printed model with the use of a little amount of material. It can be a repeating pattern that can make the printing easy.

One of the main advantages of infill is that the interior can be printed in varying degrees of hollowness. This factor can be represented in another term called infill density.

If the infill density is 0% it means the printed model is completely hollow and 100% means that the model is completely solid inside. Apart from holding the structure, infill determines the strength of the structure too.

How much infill is required for a 3D printed model solely depends on the type and the functionality of the print. We will discuss different infill and the different patterns used for different purpose.

Different Infill Densities for Different Purpose

Usage as a Model or Decorative Piece

For building a model for representation or exhibition, you don’t require the model to be strong to handle a lot of stress. Due to this reason you don’t need an infill that is too strong to hold the structure together.

The infill density used for this purpose can be made around 10-20%. This way you can save material as well as do the required purpose without giving you issues.

The best pattern to be used in this scenario would be lines or zig-zag. These patterns hold the structure together by providing the strength that is required for this purpose. As these are very simple patterns, it can be printed easily and it decreases the overall print times.

Standard 3D Models

These are the printed models that are used after printing other than exhibition. These prints require more strength compared to the previous one and should be able to handle a moderate amount of stress. This means the infill density should be increased to a value around 15-50%.

Patterns like tri-hexagons, grid or triangles are the suitable ones for this purpose. These patterns are a bit more complex than lines and zig-zag. Hence these patterns would require more time to print. In fact it would take these patterns 25% more time compared to the previous ones.

You can split and study the property of each pattern as they too have minor differences among themselves. The grid structure is the simplest and the weakest of all three. Being a simple grid it can be printed quickly compared to the rest.

The huge advantage of the triangles pattern is its ability to bear load when it is applied perpendicularly on the walls. The triangular pattern can be used in areas of the model with small rectangular features as this pattern makes more connection with the walls compared to grid under this condition.

The tri-hexagon is the strongest of all three and it has a combination of both triangles and hexagons. Including hexagon in the mesh makes it much stronger. This is evident from the fact that honeycombs use the same polygon for its mesh.

Another advantage of a tri-hexagon mesh is that it undergoes less structural damage compared to others due to poor cooling. This is because all the edges in this pattern are short compared to rest, which leaves a small length for bending and deformation.

Functional 3D Models

These are the printed models that are made to serve a purpose. It can be used as support models or replacement parts.

The functional 3D models are subjected to high amounts of strength and must possess good load bearing capacity. This means it should contain an infill to fulfil these requirements. For this purpose the infill density should be around 50-80%.

The best infill patterns that showcase these amounts of load bearing capacity are octect, cubic, cubic subdivision, gyroid etc. The octet pattern is of repeating tetrahedral structure which delivers strength uniformly to walls in most of the directions.

The best pattern to handle stress from any direction is gyroid. It has a three dimensional wave like structure which is symmetric in all direction. This is the reason this pattern exhibits strength in all the directions.

The gyroid structure shows exceptional strength at low density. This is a naturally occurring structure that is found in the wings of butterflies and within the membranes of some cells.

Flexible Models

The material for printing the infill must be considered to get flexibility. The best solution here would be to use PLA for this purpose.

The infill density for this purpose can be anywhere around 0-100% depending upon how much flexibility you need. The different patterns available for this purpose are concentric, cross, cross3D etc.

Concentric is an infill pattern that would be a ripple like pattern of the outline. This would be concentric copies of the outline that make up the infill. Another pattern for the purpose is cross. This is a 2D grid which lets space in-between twisting and bending.

The concentric and 2D patterns are very flexible, but if you want something that is a little rigid too then the best option will be to use a pattern called cross 3D. This infill has an inclination through the z axis, but remains the same in a layer of 2D plane.

Advantages of Infill

Increases Printing Speed

As the infill is a repeating three dimensional pattern it easy to print. The 3D printer prints in layers and each layer consists of 2 main parts; the infill and the outline. The outline is the perimeter of the layer that becomes the outer shell or the walls of the print model.

While printing a layer the outline needs a lot of precision to print as it defines the shape of the object. Meanwhile, the infill being a repeating pattern can be print without the level of precision used before. This means it can be printed quickly in a to and fro motion.

Low Material Consumption

The material used for printing a model will the highest when it is printed as pure solid inside. This is called an infill with 100% infill density. We can reduce the use of material for printing a 3D model by using a suitable infill. We can choose the infill density according to our needs.

Different Patterns to Choose

There are a lot of patterns to choose for the infill, this gives us options to choose from according to our need. Different patterns hold different properties and we can use them accordingly. The pattern is often selected by considering the following factors-

  • The shape of the model – You can choose any pattern for an object. The optimal solution here would be to pick the one that gives the maximum strength with the least amount of material for that particular shape of the model. If you are making a round or cylindrical solution the best patter to hold it together would be to choose a concentric pattern like archi or octa.
  • Flexibility – if you are not behind strength or rigidity; then you need to choose an infill pattern that allows flexibility like concentric patters, cross or cross 3D. There are patterns for overall flexibility and ones that are dedicated for flexibility in a particular dimension.
  • Strength of the model – patterns play a huge role in setting the strength of a model. Some patterns like gyroid, cubic or octect are pretty strong. These patterns can give more strength to a model than other patterns at the same infill density.
  • Material use – Regardless of infill density, some patterns are designed in such a way that it is packed tightly whereas some are loosely bond giving a lot of free space.

Efficient use of Infill

Angle of Infill Printing

There are different things to consider while printing an infill. One such thing is the angle at which the infill is printed.

If you notice, in most of the prints the angle of the print is always 45 degrees. This is because at an angle of 45 degrees, both the X and the Y motors work at equal speeds. This increases the speed of completing the infill.

Sometime you will be in a situation where changing the angle of the infill can hold some weak parts stronger. But changing the angle would decrease the speed. The best solution to avoid this problem will be to position the model in the right alignment with the infill in the slicing software itself.

Infill Overlap

You can achieve a stronger bond of infill with the wall by increasing the value of infill overlap. Infill overlap is a parameter which when increased increases the intersection of the infill with the inner wall of the outline.

Gradient and Gradual Infill

If you want your infill to hold stronger towards the walls of the 3D print, then the best way to do this is by using gradient infill. The gradient infill has the infill density changing through the XY plane. The infill density becomes higher as we approach the outline of the model.

This is one if the most efficient way of adding more strength to the model. The only downside of this approach is that it takes more printing time.

There is a similar type of printing called gradual infill in which the infill density changes through the Z axis.

Thickness of Infill

Use thick infill to get more strength and rigidity. Printing very thin infill will make the structure prone to damage under stress.

Multiple Infill Densities

Some of the new 3D printing software comes with powerful tools to change the infill density multiple times in a single model.

One of the main advantages of this method is the intelligent use of material in places that needs strength in a model. Here you don’t have to use a high infill density through the entire model to hold just one portion of the print strongly.

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