PROJECT: 3D Printed Compost Bucket

Experiments, Pellet Head Extruder -

PROJECT: 3D Printed Compost Bucket

Here at the MD lab, we find ourselves constantly returning to the question of how to best apply our technology in a meaningful way. Without delving too deeply into the philosophical quagmire of how to define “meaningful”, you could say we are focused on the “so what?” that is proposed by possessing the capability for large format printing. We have the technology, now what can we make with it? In the lab we are constantly using our printers to rapid prototype new designs for products, and sometimes the 3D printed parts remain in the final design, while other times they are replaced by other materials. What objects can we make that are designed with 3D printing in mind as the final mode of production? Even if the sky is the limit, perhaps we should start with something more mundane?

What we printed was a compost bucket! A container in which food waste turns into dirt- it ain’t much, but it's honest work. We are big proponents of composting here, and as a matter of fact Vermont just passed a law requiring everyone to compost their food scraps, so soon there ought to be a compost bucket in every home… and why not have it be 3D printed? As far as the design, it is fairly simple. The cylinder that makes up the container portion has a very slight taper as it grows, which aids in the release of the soil once you empty it. It also allows them to be stacked, for example if they were being employed by a compost collection company. The bottom of the container has an open honeycomb pattern which allows excess moisture to drain through (these are meant to be used outside) and helpful insects that aid in breaking down the food waste to enter the container. The lid is printed separately, with a slight lip to overlay on the rim of the container, and a similar honeycomb pattern to allow air and moisture to pass through- we need to do some further research on composting science and find out if this is actually desirable or not. As with any 3D print, the scalability means that you can easily alter the dimensions to your preference.

 For the particular print pictured in this post, the container was made using LX175 PLA while the lid is rPETG. Both pieces were printed using our MDPH2 extruder head. Using PLA offers us an opportunity to experiment in a real-world application with how quickly a print will break down due to the combination of UV damage and composting activity. LX175 is certified as compostable but whether that applies to scenarios outside of industrial composting is something we would like to better understand. Potentially, if the compost bucket degraded and composted alongside it’s contents it could actually be a desirable quality in certain situations, though for most applications something like PETG would be preferable for longevity sake. As usual, the LX175 printed without any difficulties, though the rPETG lid prints kept suffering from spotty underextrusion, a symptom eventually diagnosed to be caused by insufficient drying of the pellets. 

Only time will tell how long our first 3D printed compost bucket will last, but we are already thinking about how to improve the next- the first piece of feedback was to make future iterations opaque, so you don’t have to see what is happening on the inside! Beyond composting, we are continuing to look to the future and consider how we can use our large format printers to make useful objects widely available, whether simple or complex. We’d love to hear your thoughts on the subject, so don’t hesitate to reach out! 

 

Below are some photos from the experiments:

1. Compost bin and lid ajar

2. Clear might not have been the best choice!

3. Some extrusion problems with rPETG

4. Compost looks gross but is good!


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