Making a buoy mould
Hi, can someone advise me on how to make a mould for a mini buoy? Would it need to be two separate moulds that then need gluing together or is it possible to make it from one mould? (needs to have air inside/float) see pic for ref!
thanks so much!
actually it is simple but it depends on your application :
– salt water ?
– how long does it has to stay on water ?
– how big ?
– where ? do you need to pass regulations ? …
– what kind of plastic you wanna use …
and possibly 10 more questions but I leave this as nice homework for you; evtl. you can use compression molding, yes 🙂
thanks for your response!
I watched that vid – but its a massive operation! Im a non-engineer, marine science student and have 0 experience with building such things but if it comes down to it i’m sure i will manage to organise a small rotational moulding construction 🙂
– yes its for saltwater and needs to be weather hardy as it will be in the ocean 24/7 (sun, rain, wind, salt etc.)
– small: size of a fist
– No regulations
– Type of plastic: unsure, depends what plastic is feasible for such a hardy buoy. Unfortunately most the waste here is soft packaging (LDPE and other) and i doubt that is possible to be used for this purpose? So we might have to filter through the waste here to find more HDPE and MDPE stuff is that works too… not sure, what plastics would you say are feasible to be used for such sea water buoys?
The goal is to use waste plastic found on an island in Eastern Indonesia to repurpose into mini buoys that the local seaweed farmers can use to hang their ropes for their seaweed farms on, replacing their current use of old plastic bottles as buoys which often end up washed up on the beaches and floating around the ocean as ropes break or they degrade.
Maybe if you make the mold so there is a flange at the seam. You may be able to heat weld it. Perhaps put some styrofoam inside in case you get leak. I would try LDPE if you have a lot of it or mix it with HDPE. You didn’t say what machine you have available for this.
There would need to be some plan (deposit? buy-back? trade-in?) for recycling these as they degrade so they don’t end up breaking down in the water.
thanks for your reply. Yes, i had thought about making it with two pieces and then melting them together. Making the mould for this would be easier than a rotational mould, but a two step process/extra labour.
Regarding the type of plastic – yes a mix of both LDPE (majority) and HDPE (minority) would be ideal and feasible. I don’t have a machine yet at all – i want to try to make a prototype first by some one else’s machine, but i will need to make my own mould. Once i can be sure that the product is possible to make, then i will invest in my own machine for the project.
About degradation in seawater – do you say this because its out of LDPE? Or would it degrade even if it was made out of full HDPE?
Take a look at the video @andyn posted in this thread. If you combine that with the buoy not needing to be a sphere (box or cone shaped molds should be much easier/cheaper). You may be able to create prototypes fairly easily without building a PP machine.
I think you need to research UV degradation for your materials. Clearly they can be made to last (kayaks, 55 gallon drums, etc.) but it needs to be thought through.
Yep good point about UV degradation – will have a look into that!
Thanks @bdurack for that link ! Super helpful, even for building my own rotational mold kit!
Thanks to everyone for their tips and feedback. Will keep you guys posted about my progress.
Sorry, I forgot to paste the link. https://davehakkens.nl/community/forums/topic/v4-beyondplastic-process-heatable-mould/
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