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Our new machine to sort plastics

This topic contains 44 replies, has 19 voices, and was last updated by  Milan Thottathil 6 months ago.

Matoha matoha

Our new machine to sort plastics

27/02/2018 at 16:07

Hi guys,

We are a group of students and we have created a low-cost machine for immediately identifying plastics using infrared rays – see our video here https://www.youtube.com/watch?v=aEFnh86olhg

And we would like to ask for your help! We are interested in how you currently sort plastics and if you have any good hacks for it. Additionally, if you would like to be one of the first people to test our machine, please do let us know!

The best way to get in touch with us is to go to https://matoha.com/pp/.

Be sure to check out our Facebook and Twitter page as well!

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31/12/2018 at 05:39

i need one of this!!! 🙁

16/05/2018 at 13:11

Hi @copypastestd ,

We had a look at the samples you sent us (thank you!) and acquired the spectra. A detailed write-up with the spectra is here. In short, we found that the black composite is composed of one layer of pure HDPE and one layer of HDPE+additive/different polymer. The POM/acetal sample gave us some nice spectra!

Thanks again for sending the samples!
Martin / Matoha Ultrascience

30/04/2018 at 05:30

This is a wonderful invention! :-). On what operating system does it run, Mac, PC? Also, are the results audible, so that someone who cannot see well sort plastic? I use a lighted magnifier to read the recycle markings on plastic. And even that proves very difficult at times. This would definitely speed up the sorting process. I would love to be a beta tester. 🙂

24/03/2018 at 18:43

I would love to build one to help you out with testing, we work on recycling plastics at user point. I see it still in development, but if we could work with you to improve it ready to release opensource then that would be great! Drop me a message if you want.

23/03/2018 at 10:36

And like solid pieces.

If you see, that sheet consist of 3 layers (black/gray/black).

I tried to melt it in coca-cola can, and that rod do not float like regular HDPE.

23/03/2018 at 10:33


sorry in advance for many pictures below:

In our lab we use PE sheets for CNC milling.

To produce frames for other CNC machines.

We buy such HDPE sheets here: https://www.fdplast.ru/list-pnd/

So after milling we have a lot of waste.
Which could look like ships.

19/03/2018 at 19:56

i did not know it the markings are factory made

some just lied to sell abs as abs-pc i guess

19/03/2018 at 19:18

@imuh thank you! So one of the samples was marked ABS by the manufacturer, the other one ABS-PC by basman. So yes, his marking might be inaccurate. Or maybe it was a very clever way to see if we can actually distinguish things – if we said they are from different materials even though they are same that would be quite embarrassing 😀

No worries, we are making plans how to release it open-source 😉 At the moment it’s somewhat a mess, so I don’t think anyone has spare couple of hundreds euros lying around to build something that doesn’t fully work (yet!).

@basman – how did you know which one is ABS-PC?

19/03/2018 at 18:21

@matoha (btw thank you so much for all the work you are doing on the plastic analyzer machine !)

I’m sorry but you got me lost in your last linked youtube video. Your “big machine” as you say so shows there is no presnece of polycarbonate.

I know you are not an all-seeing-&-knowing god, but what happened there?
Was the monitor piece marked (by constructor) ABS PC? Or was just a supposition from @basman ?

I’m sorry to bother asking this but if the error comes from constructor; it might be verry missleading for DIY activists (until you release your baby open source hehe :p)

Anyways, thanks again for all your commitment to this project !


10/03/2018 at 16:32

@basman We have received your samples, thank you! Have a look here what we found out about them using our machine 😉 https://www.youtube.com/watch?v=2DortfmrGgM

05/03/2018 at 12:06

@andyn Our near-infrared source is a special alloy of tungsten, contained in a quartz envelope. Additionally, it is filled with a mixture of iodine and bromine vapours for optimal performance. Also known as a £1 halogen bulb 😃 (usually the simplest solutions are the best 😉).

The reflected light then goes through a monochromator which scans across the wavelengths of interest and the monochromated signal is measured by a photodiode.

For now, we are quite lazy to release the blueprints since it’s not ready yet with many bugs in there. E.g. even if someone built it, it wouldn’t be very useful. (Dave Hakkens does the same thing, releasing stuff only when it’s ready.)

05/03/2018 at 11:08

@plastikfantastik Thank you! At the moment, the acquisition of a single spectrum is ~ 100 ms, though because of certain bugs on our PCB (which we’ll fix in the next revision) we have to employ heavy averaging (~10x) to get a decent signal-to-noise ratio. The machine learning classification afterwards is fairly quick, < 10 ms.

The signal intensities we are working with are like 1 nA spectrum peak size, which is obviously very tricky to get working – that means we need ~ 10 pA (10^-11 A) resolution with similarly low noise.

05/03/2018 at 03:03

I wonder if clear plastics don’t pose a major issue. With light there’s less reflection and different refractory properties which would vary with the shape and thickness of the analysed plastics.

Is this a problem with IR sensors ?
Or do you instead use both clear and opaque plastic samples for the training process to capture different spectrum of the same plastic type/color ?

23/03/2018 at 10:43

After that I noticed thatmaterial from black layer floats, and gray layer sinks.

I tried to call on factory which produced them, and they said that whole sheet made of HDPE.

But I do not understand why gray material sinks.

Could you analize it on your machine, I will send you examples?!

Also I could send you pieces of Polyoxymethylene (POM).

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