Printing a boat made out of milk jugs

Today, groups from all over the Pacific Northwest will take up their oars and head over to Green Lake for the 42nd annual Seafair Milk Carton derby. The team who builds the fastest boat made out of milk cartons wins the regatta (and $10,000). This year, we’d put our money on the 3D printer group from the University of Washington; they printed a boat large enough to carry a person using crushed melted milk jugs.

After building a huge extruder to feed shredded HDPE plastic through a nozzle, the team repurposed an old plasma cutter to serve as an 8-foot-long 3D printer. There were a number of problems the team ran into – getting layers to fuse together, finding a suitable printing surface, and perfecting the art of squeezing melted milk jugs through a heated metal tube – but the final result is impressive, to say the least.

As far as how lake-worthy the UW team’s boat is, we have no idea. The milk jug regatta will be held later today, and if you have an update of how the team fared, send us a tip.

27 thoughts on “Printing a boat made out of milk jugs

  1. I think this is a great project, and shows the ingenuity, skill and perseverance of those involved. Good luck at the competition, and hopefully it will hold up!

    However, I find it a bit unfortunate that the end result (the boat), has a shape that doesn’t warrant using a 3D printer to create. Without complex surfaces, it could have been easily made from sheet material.

    Of course they had to keep it as simple as possible, being the first test of this machine at this scale. I hope they keep going, and in time work out the remaining flaws to make the actual printing less labor intensive. Next year, make a proper boat-shaped canoe!

    I’m also looking forward to updates, especially about how the printing of the walls went.

      1. It has a thin plastic coating right? So then if you get a very very large amount you could harvest enough of that I guess :)

    1. From the rules on the derby website “Only the following types of cartons may be used to provide flotation: one-half gallon, one gallon milk or juice cartons or one gallon plastic milk or juice jugs.” So pretty much any container used to hold milk counts…

    2. If you had bothered to spend 5 seconds checking the rules, as no doubt these fine folks have already POURED over, you would have seen this:

      A. Only the following types of cartons may be used to provide flotation: one-half gallon, one gallon milk or juice cartons or one gallon plastic milk or juice jugs.

      So, I think they will be just fine here.

    1. yes milk jugs are hdpe
      if you flatten a bunch out and solvent weld the sheets together you can use it with homemade vacumm formers

      1. which might have actually worked better than 3d printing it but kudos to them it looks better than i expected it to

    2. Whatnot said:
      “HDPE? Are you sure milk jugs are high density PE?”
      Even if the other replies to this were that HDPE wasn’t used; could always get a sponsor to foot the bill for printing out X number of milk jugs (partially filled with milk of course) in the desired type of plastic!

      1. I was just curious since I know milk jugs to be a type of plastic that is rather flexible and I thought high density usually also had the property to be more stiff.

        I never use the jug variety though so I have to guess or ask.

    3. HDPE accounts for most of the plastic, but every jug has at least two layers of different types of plastics. Some five. There are layers to prevent oxygen migration, layers of recycled filler, layers to block the recycled layer from interfacing with the milk, light blocking layers and pigments, etc.

      The yellow jugs are an attempt to reduce cost and improve recyclability while still preventing oxidation and vitamin breakdown due to UV light.

      PET milk bottles are a rising trend you will see soon.

      These layers are one reason milk jugs are not as suitable for 3D printer plastic filament.

    1. Our design team came up with a longboat for this, actually, but imagination outstripped capabilities and time, so it got shelved until next year.

  2. I foresee a change to the rules coming which bans altering the form of the milk jugs in such a fashion as shredding, melting and extruding.

    When was the last time you saw a waxed paper half gallon or gallon milk carton?

    Remember when the paper milk carton industry tried to convince the public that cartons were better than plastic jugs because they blocked light which supposedly harmed the milk? Someone did tests which showed little difference in light transmission and IIRC no deterioration of the milk from light exposure.

    1. Atleast here in Germany you get Milk normaly in 1 Liter cartons. And yes i would also think that they change the rules at some point.

  3. Wow – Some people are hard to please. How many 3D printed entries were there?

    Surely the point of this competition is to encourage as many different approaches as possible?

    Or should they penalise anyone not producing a horrible lashup held together with duct tape and hot melt glue?

  4. Folks, the WOOF 3DP team is composed of undergraduate students. In about ten weeks, they got a 10x5x3 foot printer running from a re-purposed plasma cutter. They went through 3 extruder designs including testing in this time. Early on, they contacted the rules committee for the event to ask if they were allowed under the rule — the answer was yes but the boat must be recycled milk jugs. Why the “simple design” – their extruder system was still not working 3 days before the event (anyone whose build a RepRap knows this pain). They produced a new first in the 3DP world. For that, I am excited for them.

    1. All i can say is turn it back! A large portion of recycled products are sent over seas creating jobs for others..turned into new products and sold to you. The HDPE used on the UW boat was obtained localy by the students and milled right here to be used here! If you go looking on the internet for HDPE flake …most of it is available from china…Invest localy save jobs ,environment and culture/industry. Personaly i am proud of opensource diy usa. My personal sacrifice to follow this resulted in being able to help process the UW’s HDPE into flake with equipment bought and created for this.

  5. Updates here and here.

    I’d say it is more likely Seafair adds a new category than that they ban 3d printed milk jug boats. Future 3dp jug boats will be, no doubt, more complex and fun to see race. For the first time through the process–getting a big printer to print, and getting a product in the water–this is a great first step.

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