New take on the 'compression machine'


It seems to me that the compression machine using a domestic oven is quite an inefficient way to make things. In the first world, old ovens are cheap, plentiful and there is no problem running them on a domestic power supply, but in developing countries, if there is a power grid at all, it can’t cope with the 4kW+ that most ovens use. And when recycling plastic it’s important to consider the source of the energy used to do it, and the environmental impact, or you could be doing more harm than good.


I have developed this machine to be as energy efficient as possible and to work even in areas with no power, it can run directly off a single PV panel. The machine in the video is a prototype but I would like to build a full sized one approx 4x bigger that can produce larger pots, bowls etc. using interchangeable moulds. I have a crowdfunder set up here: (please share!)


The small flower pot made in the video uses 74 Watt-hours of electricity. That’s approx. one twentieth of what it takes to warm up a domestic oven to operating temperature, before you even put the plastic (and moulds) in. You also don’t need a shredder as quite large pieces (whole caps etc.) can be put in the mould and the heat and pressure fuses them solid with almost no voids or air bubbles.



Thanks for the input! Will be looking at working with this design.

Thanks for the reply. I am still experimenting with different ratios of sand and plastic, that is not my biggest problem. I need help to connect and apply the heat to the mold and also the milling of the mould. Can you help me with that? Or do you know where i can read and learn how to connect the electrical components? Or if i make a drawing of the mould i have in mind, can you make me a quotation of the costs. That is only if you have interest and fascility! I dont know your circumstances and dont want to force myself on you! If you cannot, then please tell me and i will accept unconditionally! Would appreciate an honest answer.     Thanks again,



Yes, I don’t see why this wouldn’t be possible. I don’t have experience myself mixing sand and plastic, but I know others have done this with some success. I think the challenges will be getting a thorough and consistent mix of sand and plastic, and the sand is likely to cause a lot more wear on the mould so you probably want to use something tougher than aluminium.

Hi Andy,
You seems to be online. Wanted to write you earlier, but did not have my thoughts arranged. Firstly congrats on your Swaziland project!! I am also from the south (now in Germany) so it lies close to my heart! Also on other vids from you, it looks like you have access to nice machinery, milling etc. I am interested in a flat mould, two plates pressed together, which are then heated to specific form. But the product to be pressed must be a pre-mixed mass of molted plastic and sand. This has to be prepared seperately. I am thinking of a silinder and press method.     (lets say 90x100mm). The plastic heated and pressed out, mixed with sand and pressed thru the silinder again and then this mass moulded in the flat press. With your expertise and knowledge, do you think such is possible? I hope i mak sense and will appreciate if you are prepared to give it a thought and let me know.    Wish you a nice day!

The heating element (cartridge heater) looks like this: These are actually bigger ones I plan to use for the next machine running on solar PV. It goes into a hole drilled horizontally in the bottom of the mould and as it’s totally enclosed by the mould the heat is transferred much more efficiently than band heaters which radiate heat outwards from their external surface. For the small machine I was able to put the heaters only in the bottom half of the mould and as it is well insulated the heat travels all the way through.

Hey that’s awesome! Yes, I’m also looking for ways to reduce the power consumption. Back to the heating element, you attached it to the bottom of the mould right? Is it a heating ring, coil or other elements, and how do you ensure efficient heat transfer to the mould? Thanks

It’s not just the efficiency but also the low power consumption. Most of the PP machines need at least 1kW, and if you’re using a domestic oven for the compression machine these use around 4kW. That’s not a problem in any developed country, but 3rd world power grids (if they exist at all) can’t cope with such a demand. The prototype machine uses only 240W max. and once up to temperature will tick over on just a few tens of Watts. I can reduce the max power to 120W but it takes longer to heat up.


The machine is quite simple, basically two mould halves and a temperature controller. I didn’t do any drawings or take any photos of the construction, but I will do this for the full sized machine (this one is only an experimental prototype). I might also add more features such as having it stop automatically when finished which could be done with a sensor on the moving part, or even a simple timer. This would save power from heating for too long and the machine could run unattended and shut down at the end of the cycle.


Hey, its a great idea to make it energy efficient because that’s the ultimate goal. Could you share some resources and pictures you used while building this? Thank you!

The prototype machine uses 2x 120w cartridge heaters. It can run on low power on just one which means it could run directly from a single solar panel (I’ve not actually run it on PV, it’s running off the mains). The larger machine will need more power (probably 480W) but could still run on a battery bank charged by a single solar panel, or from a larger bank of solar panels, or in areas where there is a poor mains power supply (not capable of running a domestic oven)

Great concept, especially if you can work it on a pv panel. May i have details of the heating components, would like to experiment on a hollw brick form. I think in Africa bricks are more needed than flower pots.