Everyone who has ever 3D printed something has faced the same problem: How to make parts as strong as possible while consuming as little material as you can get away with?
3D printed objects are typically not 100% solid and are instead held together by a lattice structure that uses some amount less than that. Printing at higher infill densities will of course make your object stronger, but at the cost of more materials, longer printing times, and reduced effectiveness of the additional material used.
The specific infill pattern you use will have a huge effect on the strength of the finished part. As of right now I can choose from a total of 7 different infill patterns, only 3 of which are actually practical (Concentric, Honeycomb, and Rectilinear). There are other infill patterns available for people using Makerbot software (which allows you to make custom designs like ‘cat-fill’), but those patterns are a novelty more than anything else.
If you’ll notice, all patterns currently available simply repeat themselves every layer. The infill designs are all ‘Z-axis independent structures’. This causes finished parts to have a mechanical strength that differs depending on which axis is under load (an undesirable characteristic). Very soon this will no longer be the case.
A friend and I recognized the limits of current infill patterns and decided to design our own. Knowing that a hexagonal structure uses the least material to create a lattice of cells within a given volume, we let our design take inspiration from the way that bee’s nests intersect two opposing honeycomb layers into each other:
Here is the result of our work:
For a 3D view see: http://www.thingiverse.com/thing:714679
Cool huh? Unfortunately we designed this the hard way, by literally drawing a cube and subtracting out the honeycomb shapes to leave behind the appropriate wall thickness throughout, then printing the object as 100% solid. This object took 2 hours to slice, (a process that usually only takes moments) and 4 hours to print. It is definitely not optimal in that way, but it was only intended as a concept. The result actually feels very strong for its weight and I was able to stand on this thing without issue.
What we didn’t realize until later was that people have been working on and talking about designs like this for years. In fact, the good folk(s) at Slic3r were already hard at work adding a Z-dependent lattice structure into their slicing software!
The next official version of Slic3r hasn’t been released yet, but you can download the experimental version and try out their 3D Honeycomb design, which looks like this:
This new infill pattern should, in theory, provide maximum strength in all axes while using the least amount of material to do so. Obviously, I’m really looking forward to the next official release of Slic3r!
Final Note: I also didn’t realize until today that Slic3r is almost entirely a one man job! Made by Alessandro Ranellucci, a software designer from Italy. I love this free software so I decided to buy this man a beer via his donation page; you are welcome to do the same.
Slic3r recently released it’s new version 1.2.9 which has more capabilities than I currently know how to use! The most obvious one is the new 3D honeycomb infill, which looks fantastic! I printed out an example block with no exterior walls to provide a visual comparison to my infill design.
This little cube is only 20% infill and it feels super strong in my hands! But how scientifically quantifiable is that? Take a look at my mechanical test results here to see how this infill compares to the traditional options!