Three dimensional (3D) printers have revolutionized our ability to create something out of nothing. If you can visualize it (and translate your vision into a detailed computer schematic) you can print it. Unlike traditional printers, though, 3D printers pose layers of complexity. Inner layers, to be specific. You have to imagine your end product inside and out to pick an infill pattern.
The best pattern offers as much strength as you need while minimizing the print time and material used. Display models that only need a simple line or rectangle pattern (if any). Triangle and hexagon patterns offer more strength, while concentric or wiggle patterns offer flexibility.
On one end of the spectrum, a figure could have no infill pattern and be completely hollow. On the other end, a figure could be completely filled with plastic. The former offers no structural integrity while the latter uses a lot of material and takes a very long time to print. Infill patterns are designed to provide the support required using the least material possible.
Choose the Best Infill Pattern for the Job
Asking what is the best 3D printing infill pattern is like asking what is the best tool. It really depends on the job. Are you trying to hang a picture? Try a hammer and nail. Digging a hole? Try a shovel. The power’s out? Call an electrician. Likewise, the best infill pattern will depend on how you want the final product to perform.
If time and money were no objects, you might as well make everything you print completely solid. This would ensure that they can handle as much weight and wear and tear as possible. Here in the real world, however, this isn’t practical because the materials used in 3D printing can be very expensive, and the process can take many, many hours. You’ll want to minimize both.
There is a balance. The more structure you add to the figure’s interior, the sturdier it will be. This will, however, take its toll in the form of:
- Material costs
- Production time
- Weight of the final product
Often these factors are ultimately more important than how much weight the figure can hold.
By selecting an appropriate 3D printing infill pattern, you can get the results you need with as little cost as possible. You first need to know the requirements of your final product.
Low Strength Infill Patterns
Perhaps it’s because 3D printing is still in its infancy, but it seems that a large percentage of things 3D printed are either models designed to show clients what a potential product could look like, or an unlicensed reproduction of some character or other type of intellectual property associated with some piece of media popular among “nerds.”
These Frodo figurines and Millenium Falcon tchotchkes may participate in the occasional puppetry battle but will spend the majority of their time just looking pretty on a shelf. As such, they do not need to withstand a lot of pressure or trauma. They can, therefore, be printed with very basic infill patterns that offer enough support to hold the top layer, but not much else.
The infill patterns that are best for these types of prints are those that minimize the amount of material used in (and the time spent printing) the model.
- No Infill: There’s no rule that you have to have any infill pattern at all. In some cases, you can print a 3D model with no infill at all. In this event, the base layer, sides (shell), and top layer would make up the entirety of the model.
The biggest concern in a model with no infill pattern is that the top layer sagging. No infill is when the top layer is printed, there is nothing in the middle to support the weight of the material. It can be like trying to create a bridge with just a single sheet of paper. If the material is strong and the shell is thick enough, however, this may be all that’s needed.
- Lines: The simplest infill pattern is simple lines. By passing through the hollow cavity of the figure in evenly spaced, parallel lines, this infill pattern offers not only the lowest amount of material used (depending on the space between lines) but also the simplest movements for the 3D printer to accomplish.
Each time the printer has to stop and change directions represents time, energy, and material spent. By minimizing the frequency with which this happens, then, the line infill pattern minimizes expense.
- Rectangular Aligned: Lines are simple but only offer support in one direction. By alternating the direction of the lines 90 degrees on each layer, though, you can create a grid of perpendicular lines that creates a mesh that can handle stress from both directions.
This infill pattern preserves the simplicity of the line pattern while adding structural support in multiple directions. It’s a simple and effective way to add some structural integrity to your figure with minimal expense.
Medium Strength Infill Patterns
Some things that are 3D printed these days, however, are expected to have some function. Whether they were specially designed for some light function or you just want to be able to place your Mountain Dew Code Red on top of it, these models need to withstand a moderate amount of force.
For these types of figures, a two-dimensional infill pattern is usually sufficient. These patterns are relatively easy for the 3D printer to achieve and offer a rigid structure within the shell.
The default density of most 3D printers is often only 18 to 20 percent dense, meaning that about 80 percent of the inside of the figure is still empty space. This ratio keeps the figure light and doesn’t use a lot of material. This also equates to faster printing times.
- Triangles: Triangles are the strongest simple structures in nature. They have the fewest number of sides possible and can withstand pressing force from any direction (perpendicular to the surface’s face, that is). This is why triangles are commonly incorporated into structures like bridges.
One downside of the triangle infill pattern, however, is that it requires a lot of passes of the printer to achieve. This means that printing a triangular infill pattern takes a lot of time and uses a lot of material.
Another downside is that the triangle’s strength only exists on one 2 dimensional planes. This will be discussed in more detail later.
- Hexagons (Honeycomb): A more economical solution that offers a lot of (2 dimensional) structural support is a series of hexagons. Like triangles, hexagons are able to abut each other with no gaps, and disperse force evenly throughout their form. They have the added benefit of having shorter sides and thus use less material than triangles.
Hexagons can be found in nature in the honeycomb structure created by bees in their hive. Producing wax uses a lot of the bees’ resources, so they only want to make as much as is necessary. It turns out that the hexagon pattern is the most efficient use of space and material.
While this has been proven mathematically, the bees don’t create it consciously. They simply burrow round holes that their bodies can fit into. Using all of the space available, the thin walls of these round holes are pressed together, squishing into hexagons. You can also see hexagons form when round bubbles are similarly pushed close together.
Many 3D printer users use a hexagon infill pattern as their default because it offers such great support with (theoretically) the least material. Because 3D printers do not create hexagons in the same way as bees. The hexagon infill pattern requires the 3D printer to make a lot of turns and passes, which takes more time. Some programs also involve a lot of overlapping, which uses more material.
High Strength Infill Patterns
The infill patterns described in the previous section are based on 2-dimensional shapes. They offer a lot of structural support, but only perpendicular to their face. They are designed to take a lot of force applied to the sides (the shell) of the figure but are less supported when force is applied to the top and bottom layers. These only have a strength comparable to line infill patterns.
The patterns described so far simply lay on top of each other. For instance, the space inside the triangle is empty from the top down to the bottom layer. This is fine for many figures, especially those that are designed to only be used in a certain way. A drink coaster, for example, is meant to hold weight only on its 2 largest surfaces. It is not designed to hold weight on its edges.
Many objects being 3D printed, however, need to be equally structurally sound in all directions. The 3D printing infill patterns that achieve this best are those that form 3 dimensional shapes in the infill, so there is never a hollow cavity all the way through the figure.
- Cubic: This infill pattern creates a series of stacked cubes formed by the negative space between filaments.
- Octet: Similarly, this infill pattern forms a stack of pyramid shapes.
Flexible Infill Patterns
Usually, 3D printing uses rigid plastic materials like polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS). The goal is typically to create a figure that is as solid as possible (while also using as little material as possible to reduce cost, weight, and amount of time it takes to print).
You may, on the other hand, want to create a figure that can compress or twist or is in some other way flexible. In such a case, you would want to use thermoplastic polyurethane (TUP), which is a flexible plastic, and use a 3D printing infill pattern that allows movement.
The most flexible infill patterns are those that employ parallel instead of perpendicular lines. Because the parallel lines are not held at a certain distance apart by connecting perpendicular lines, they are able to stretch or compress further or closer together inside the figure, resulting in the corresponding movement of the figure.
- Concentric lines: This infill pattern works by creating smaller and smaller versions of the figure’s shape within itself. It is as if you were to start with a room, then build another set of walls a foot from the current walls, and then another set of walls another foot within those walls.
While it can get more complicated the more intricate the shape of the figure is, the result would be a series of smaller and smaller rooms, with none of the different sets of walls ever touching. It also resembles the ripples formed by dropping a pebble in a still pond.
- Wiggle (gyroid): This pattern is a series of parallel wavy lines across the cavity of the figure. In addition to offering flexibility, it is also one of the fastest patterns to print because each layer requires only a few turns and passes by the printer head.
- Cross: This 3-dimensional infill pattern creates pockets that can compress from any direction. Setting the printer to rotate slightly between every layer can result in a little more rigidity.
Printing a 3D figure that is flexible in the way you need it to require a lot of trial and error. Each pattern allows movement in different ways and directions, and you can further fine-tune the result by adjusting factors like infill percentage and line density.
Vanity Infill Patterns
So far, we have been talking about which 3D printing infill pattern is best based on the requirements of the final product. It could be, however, that you’re more interested in the process than the final product. If that’s the case, a vanity infill print might be best.
People love watching “satisfying” videos, and one of the most satisfying things to watch is a time-lapse video of a 3D printer at work. You get to see a figure coming into existence one layer at a time in a minute or two instead of the many hours that it takes in real-time. It’s like erosion in reverse, and at warp speed.
If the goal is making a video like this, some of the patterns might be a little boring to watch. Luckily, because the printer can follow any pattern one can imagine (and encode), elaborate, intricate patterns have been developed that are a lot of fun to watch at high speed.
These vanity patterns are typically just as effective as the other patterns in that they can produce moderate to high strength prints. Because the printer head has to make so many movements, they usually take a lot longer to print, and use more material than they need to. This inefficiency makes them less suited for most production, but fun to watch.
Other Factors to Consider
When adjusting your 3D printer settings, choosing the best infill pattern is only one of several decisions you’ll have to make. Take time to consider these other, related settings.
Infill percentage describes how much infill there is between the shell (sides), top, and bottom layers. 0 percent infill would result in a completely hollow figure, and 100 percent infill would result in a completely solid figure. Most printers’ default infill percentage is 18 to 20 percent, which works well for most applications.
As a general rule, the higher the infill percentage, the sturdier the final product will be. The increase, though has diminishing returns. For example, while increasing the infill percentage from 25 to 50 percent will result in a figure that is 25 percent stronger, increasing the infill percentage from 50 to 75 percent will only increase the strength by 10 percent.
If you are printing a piece that will be drilled into, you want to ensure there is enough infill for the screw to hold a firm grip on the material.
The gradual infill setting adjusts the infill percentage within the figure’s cavity such that it is thinner in the middle to reduce the amount of material used, but thicker on the edges where it is needed to provide a solid scaffolding for the top layer to adhere to.
Infill Line Direction
Adjusting the direction of the infill pattern can significantly alter the resulting figure’s strength. Typically, the default setting is 45 degrees from the sides so that the motors that move the printer head along the x and y axis work equally in tandem to infill at maximum speed. Depending on the shape of your figure, however, it may be beneficial to adjust the angle.
Adaptive Makerbot Infill Patterns
As you can see, there is a lot to consider when choosing the best 3D printing infill pattern. Many factors affect the final product, and small changes to any variable can have profound impacts. With 3D printing technology still in its early days, there is a lot of guessing and even more trial and error to find what infill pattern is best. Soon, however, you may not have to think too hard.
Automation is coming to take all the guesswork out of the equation. Makerbot has developed an algorithm called MinFill which analyzes the figure you’re about to print and determines the amount of support each section requires and develops a pattern to create it.
Not only does this ensure that each section has the best infill, it also prints 45 percent faster and uses 45 percent less material. Surely more companies will create more and more innovative algorithms.
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