Designing 3D Printable Objects for Chickens
Software for 3D-Modeling
There is a lot you can do with 3D printers just using the ever-growing collection of 3D models available in various places on the web. However, 3D printers become an even more powerful tool when you start designing your own things. The first step in designing your own 3D-printable models is learning a 3D-modeling tool.
There are two general categories of programs for producing 3D-printable models: digital sculpting and computer-aided-design (CAD). Sculpting tools include programs like Blender and Nomad Sculpt. They are ideal for producing models for appearance purposes, like characters for video games and printable figurines. A sculpting tool like Blender can also produce functional parts; in fact, all of the projects in this article were created with Blender since that is the software the author is most familiar with. However, there are certain things that more sculpting-based tools do quite poorly even though they can technically "do" the tasks. For example, setting tolerances that can be scaled correctly with multiple objects. More traditional CAD tools include AutoCAD, Fusion 360, Sketchup, and FreeCAD.
I wish I could say there was one or more of these tools that was extremely easy to pick up, but, unfortunately, that isn’t the case. If you have no prior 3D-modeling experience with any similar programs, it is a decently large learning curve to get into any of the tools listed in the previous paragraph. It is also not entirely easy to move from a sculpting tool to a CAD tool and visa versa; there will still be a learning curve. Fortunately, you don't necessarily need to sign up for a class to get started with a new tool - there are many video tutorials available on the web for commonly used sculpting and CAD tools.
Once you have designed a model, whether in a sculpting or CAD tool, you will want to export it in .stl format. Then, you can import it into your slicer. Sometimes this goes smoothly and you are ready to print! However, it's also possible that the slicer can find problems with the stl file. Some tools are prone to this; Blender is one of them if you perform a lot of mirroring or shape-inverting operations when designing your model. One of the more common issues from Blender in particular is the presence of faces where the normals are incorrect (normals being what define the notion of inside vs outside for a model). These kinds of issues can cause the slicer to misinterpret how it needs to print walls and infill, and so they will need to be corrected in your 3D-modeling software and the file re-exported before it can print correctly. If you see areas printing fully hollow that should contain infill, you very likely have an issue with normals to sort out in your stl file.
Design Considerations for Chicken Safety
When designing 3D-printable objects for use for and around chickens, one consideration should be first and foremost: chicken safety!
Smoothness / Rough Edges
Although FDM printers work by extruding a continuous, smooth line of filament, they are still capable of making strangely sharp edges and corners sometimes. Prints can also have imperfections that can snag combs and wattles. This is especially true of anything where a chicken needs to reach into a container, like with a port feeder. If a chicken needs to put its head into a design, make sure there is plenty of clearance for its comb and that wattles can safely drape over the leading lower edge.
The smoothness requirement means that safe designs are likely to require two levels of bevel/chamfer on edges that are exposed to chickens: one level to get a general rounding of any hard corners and another over all edges to create a very small rounding effect. Edges that a chicken has no way to contact don’t matter for this, but be absolutely sure the chicken can’t contact them. Simply being at the back of the design against the HWC is not a sufficient safeguard; a chicken may try to force its face back there if the object can wiggle at all.
Below is an example of increasing levels of smoothness in a design: no bevel, a coarse bevel on the vertical edges, and a finer bevel on all edges. The rightmost design is the best one for chickens.
Even smooth designs can end up with some odd bumps and sharp bits from stray filament left as the print head moves between different parts of the model. Once printed, run you hand along all of the outer edges. If you feel any snagging of your skin at all, that’s an area that needs some attention from something like a deburring tool, hobby knife, or file/sander.
Supports (Best Avoided when Possible)
Supports are extra 3D printed material to help with overhanging structures in a print, and they are intended to be removed post-print. This removal process often isn’t entirely clean. Parts of the support nearest the model may be left intact and require filing to remove, or worse a support can be too well-attached and end up tearing a hole in the model on removal. Supports can also be extremely difficult to remove if they occur on the interior of a model with a cavity where they are hard to reach. Because of these potential drawbacks, support-free designs are always preferable when possible.
My method for creating support-free designs is to first sketch out a minimalist version of what I have in mind, then figure out what face still need to sit on the build plate to maximize how much else of the model is self-supporting while trying to visualize the way the filament will be laid down in each layer. I then look for overhangs that would be problematic (more on this in the next section), and try to rework each problematic area of the design.
Don't Rely on Glue for Multi-Part Designs
This is a design principle I had to learn the hard way when I first started designing. Unfortunately, food-safe glues and PLA/PETG don't mix very well...literally. No actual welding takes place between the surfaces with cyanoacrylate-based glues (CA or superglue) which are the most readily available glues that are safe once cured. This means that very large and rough surfaces can sometimes stick well enough, but it is likely to fail on thinner joins. Those glues that do weld the materials are both potentially hard to get and not food-safe. Alternatives to glue include:
- Friction-fit designs. Layer lines can work to your advantage for push-fit joints held in place by friction.
- Snap-fit designs where thinner areas of material can flex just enough to let the parts slide together.
- Bolts to hold surfaces together.
Below is an example of a push-fit design where parts are held in place by friction. A small gap allows the halves of a dovetail joint insert to be squeezed downwards into a hole. Once in place, the layer lines on the parts create a lot of friction and make the parts very difficult to disassemble.
Center of Gravity, Stability, and Strength
Chickens jump on things. To some extent the need for a tip-proof design depends on the nature of the chickens its around. I have some fully 3D printed feeders that are just fine in with birds that are well-behaved around them. If I were to move those same feeders to another flock, they would be tipped within minutes and likely eventually smashed to bits from abuse. One way that you can avoid tipping is to hang the object or otherwise anchor it to a wall. If hanging from hardware cloth, use multiple loops to distribute which wires are taking the force and to stop the object from rotating.
3D-Printed objects also need to take punishment chicken beaks. While chickens may not be very strong, what force they can apply gets focused on a very small point at the end of their beak. Don't make your walls paper-thin! Although strength can be controlled to a degree within the slicer settings (add more wall layers, denser infill, etc.), if your walls are too thin then those settings will have limited effect. For larger designs, err on the side of thicker walls to allow those extra slicer settings for strength to actually have an effect.
Holes and Overhangs
Holes in feeders in particular need some care. If it's big enough for a chicken to even think about shoving its head in, it needs to be big enough for the chicken to do that safely and have comb clearance. If it's not meant for a chicken head, don't make it big enough for a chicken to get more than the end of its beak inside. My personal experience has been that hens are more keen on shoving their heads into small spaces than rooster are. Because of this, I strongly recommend against feeder designs that try to limit how much of a hen's head can come in contact with the feed. If the feed level gets low and the hens are hungry, they will try to shove more of their face in than fits safely and will damage the front of their nares or comb, or even potentially damage their beaks.
With a few exceptions, most consumer-grade FDM printers can only print very small overhangs reliably. This means that a large, horizontal surface hanging in the air is likely to fail due to sagging filament. There are test designs available on the web that you can print to determine what kinds of overhangs your printer can handle. One reason to be careful with overhangs even if your print doesn't completely fail on them is that sagging, poorly adhered strands of filament are a dirt trap and will be very hard to clean without damaging the model. This is obviously something to avoid for a model intended to hold feed.
Overhangs at roughly 45-degree angles out from horizontal are usually printable without issue. Some printers can manage significantly lower angles. However, the closer you get to a pure vertical wall (90 degrees from the build plate), the more universally safe that wall is.
Circular holes through vertical walls and arches may seem like they should print just fine – and they usually do when small. Larger holes and arches may struggle. For holes, the bottom half should always be fine; it's the top curve that is problematic. Failure in mild cases will show drooping bits of filament along the underside of the arch, but the print may otherwise be fine. Larger arches can cause a more serious print failure if the initial bridge across the middle of the top collapses, leaving nothing for the next layer to adhere to. One way around this problem is to make holes diamond shaped, with points at the top and bottom.
Below is an example of a gravity-based, fully-3D-printed feeder design of mine that, although not ready for public usage, demonstrates substitution of 45-degree angles for the more traditional, unsupported, horizontal overhangs that are used in this type of port-like feeder. Feed is intended to flow in through the back into a chicken-accessible space; it can do this through a rectangular hole as is the norm, but it can also to the same thing through a 45-degree triangular hole! Although it looks strange, that aspect of the design actually works quite well (what doesn't work as well is the lack of anchoring points for stability as per the section above on center of gravity).
Prototype, Prototype, Prototype
Never assume that your first print of a new design will be ready for immediate use out with your flock. For large designs that will consume a lot of filament, you can minimize prototyping waste for testing mechanisms that you’re not confident in by printing just the mechanisms in question by themselves (like just printing a hinge by itself) or by printing at smaller scales.
Once you know your design will print and any snap-fit, hinge, etc. mechanisms will work as intended, test your design with your chickens in a supervised setting. If you have curious but calm chickens, those should be your beta testers. You should always try to anticipate as much of their interactions as possible (trying to jump on things, sticking their head in holes, etc.), but they may still find problems or interesting new ways of interacting with your design that require going back to the drawing board to make it more compatible with your flock.
Example of one of my more gregarious roosters helping me test the comb clearance of a design:
- Previous page: 3D Printable Projects for Chickens
Last edited:
