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PLA and PP for injection machine in Barcelona.

This topic contains 4 replies, has 4 voices, and was last updated by  Esferica 3 years ago.

Esferica talleresferica

PLA and PP for injection machine in Barcelona.

21/01/2016 at 12:05

Hi there!

As we posted in the welcome section, at TallerEsfèrica we built an injection machine.
We now have some information about working with plastics and these machines that might be useful for someone.

So far we’ve tried HDPE, PLA and PP, having amazing results with both PP and PLA. We have to redo the tests with HDPE. When we made them, we didn’t fully control all the parameters to properly run the injection machine.

Our fist choice was to work with PLA since it is not from fossil resources but vegetal ones, which is amazing as it is renewable.
Its melting temperature is low (from around 170ºC up depending on the composition) and the fluency is amazing. When around 190ºC is becomes quite liquid and it flows great. We think it could even fill up a mold with 0.5mm walls with our machine.

The problems we found to discard this option for now were a few. First, it is a highly hygroscopic material, meaning it has the capacity to absorbe water from the environment. When this happens, the material becomes brittle and cracks very easily, rendering it useless due to its new low mechanical properties (for our application). Before using this material for injection it needs to be cured with low (below 55ºC) temperatures to make the moist absorbed leave the material. We did it a few times leaving it for the night on a heater (less than 55ºC probably) and it worked fine. The difference is huge. Basically, if you don’t do it and the material has water in it, you won’t be able to have proper injected parts, as they will be very fragile.

Another factor that makes PLA brittle is the thermal shock. When the mold is cold at the time of injecting the parts crack very fast due to sudden contractions. These contractions aren’t bearable by the material as it becomes more brittle when having these thermal shocks. If the mold is hot (around 60ºC) the shock is lower, bringing less internal tensions and making it less brittle and capable of supporting the contractions without cracking.

It isn’t as much fluent as PLA so the force needed to inject is higher, but the properties of this plastic are more interesting for our application. We inject it at about 200ºC and heat the mold at about 40ºC to help the flowing of the material. We are trying to find a way not to heat the mold, but we are not sure if it is possible yet in our particular case.

Hope this helps someone!
Marc and Aniol from TallerEsfèrica.

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24/01/2016 at 16:30

Thanks for sharing,
I am inspired.
Oh, FYI google translate makes the pictures on your site dissappear.

13/04/2016 at 14:40

So, you need to cool the mold, because PP is semi crystalline.
What you need is higher pressure on the injection.

20/04/2016 at 19:31

hola chicos, vivo en andalucia y estoy muy interesada en este proyecto pero aun no ecuentro a nadie que me ayude con las maquinas. quisiera saber que tanto habeis avanzado y si las estais vendiendo, el precio.
gracias de antemano.

06/06/2016 at 12:51

Hi Joana!

I don’t think we are the ones to sell these machines, as we would feel it wouldn’t be fair. We used them as a starting point for our project. We can, nevertheless, collaborate with you and help you develop them for your needs.

If you give us an contact method we can discuss it.

Hola Joana!
No creemos que debamos de vender estas máquinas. Creemos que no sería correcto. Nosotros las usamos como punto de partida para nuestro proyecto. No obstante, podemos colaborar con vosotros y ayudaros a desarrollar lo que necesitéis.

Si nos pasáis un contacto podemos hablarlo.

Hasta pronto!

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