frogfall

warrior

18/07/2019 at 21:43

Hi @ckerstan,
Have a look at Rotomolding (rotational moulding).

ckerstan

new

19/07/2019 at 15:38

Hi @frogfall,

awesome, thanks for the tip! Have just looked at a few videos – doesn’t look all that easy… ! Have you or anyone else done this with the precious plastic machine before?

best,

Carla

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 🙂

ckerstan

new

20/07/2019 at 04:59

Hi @plastichub,

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.

s2019

warrior

23/07/2019 at 22:09

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.

ckerstan

new

24/07/2019 at 04:19

Hi @s2019

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?

Best,
Carla

s2019

warrior

24/07/2019 at 17:23

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.

bdurack

starter

24/07/2019 at 17:29

You can get rotomould laser cut kits which are often used for thermosetting plastics. If you have a metal mould (assuming you can heat it correctly) you might be able to retrofit the mould to a kit like this:

https://www.instructables.com/id/Rotomoldeadora/

ckerstan

new

25/07/2019 at 02:27

Hi @s2019
i don’t see a link posted by @andyn ?

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.

– Carla

s2019

warrior

25/07/2019 at 02:33

Sorry, I forgot to paste the link. http://onearmy.world/community/forums/topic/v4-beyondplastic-process-heatable-mould/

ckerstan

new

25/07/2019 at 03:44

Awesome @s2019 ! Can definitely do a cone shaped buoy ! Thanks for the link .

bennyflyplastic

new

29/10/2019 at 02:54

Hi @ckerstan,
I am a roto molder from China, this buoy mould can be manufactured by us easily.
Here is my website and email:
https://flyplastic.com
[email protected]