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In reply to: DIY Sheet press

warrior
22/06/2019 at 15:13
3

Update 06/2019:

I did some numerical approximations with the two-dimensional heat-equation and the results were somehow surprising to me (even though they are somewhat trivial).

Disclaimer: The following results are just qualitative approximations, do not rely on them. The values you can see in the pictures have no real meaning.

So basically I took a template for computing the 2D-heat equation in excel  and modified it to my needs. On the first picture I set the conductive parameter to 1 everywhere, also on the edges. Also I set the temperature on the edges fixed to 0, which approximates the ambient temperature, so the edges are cooled by the constant temperature of the surrounding air. I also added the 16 heat sources, spread out similar to the real design. Then I played around with some parameters and after 140 iterations: Boom: Pic1. This is about the temperature distribution that we could see with our tests. a big hot circle in the middle, too hot in the center core and too cold on the edges and especially in the corners.

So for Pic 2: (looks promising, doesn’t it?) I kept everything as it is, except for the conductivity of the edges, which I divided by 10. So basically I mathematically insulated the heatpress on the edges. After the same 140 Iterations, the results are amazing!

 

However, as written before, the results should not be taken too seriousely, at least not the quantitative results.

 

I will try to improve the approximation by punching in realistic numbers for temperatures, conductivities, lengths etc. if I find the time in the near future!

 

Until then,

all the best

Flo

 

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warrior
11/04/2019 at 17:12
0

@pporg
i’m a bit confused, you mean the normal precious plastic flag? You can find that in the download pack on https://preciousplastic.com/.
hope that helps,
all the best

Flo

warrior
11/04/2019 at 13:48
1

@javierrivera haha nice one!
Nice that such “old” ideas get revived! 😀

In reply to: DIY Sheet press

warrior
14/10/2018 at 20:11
1

@nickchomey @andyn @anne-barbier
Thanks a lot for all your input!
Wow I really forgot about putting them in series… now I feel stupid :’D Thanks A LOT for that hint. We will probably do a mixture: Wire all the edges parallel to pairs of center pieces and an extra PID for the corners.

anne-barbier, thanks for confirming. 🙂

Due to the uneven heating the redundant plastic doesn’t want to flow out, so after preheating for half an hour we press 1,5-2,5 hours and then let it cool inside the press. We have designed the press to be operated with swappable molds, however without clamping down, the surface won’t be flat in the end… So itm we let it cool overnight with pressure applied.

As for shrinkage we have about 2% shrinkage with pp (52->51cm)

All the best
Flo

In reply to: DIY Sheet press

warrior
14/10/2018 at 12:38
0

@nickchomey thanks, I forgot to upload the pic^^

In reply to: DIY Sheet press

warrior
14/10/2018 at 09:02
3

UPDATE 14.10.2018

Power consumption: Pressing a 11mm sheet PP we need approximately 1kWh per sheet.
That’s quite much. Reason is a major design issue with our machine, I’ll try to explain:

(See first picture) Below you can see our arrangement of the heating elements on the heating plate. (black circles) and they each heat the plate (obviousely). So I drew arrows to the nearest 4 corners of each heating element. Here you can see the main problem: The inner parts get heated by 4 adjacent heating elements each. On the edges there are only 2 adjacent elements, on the corners only ONE…
So we have a very unevenly spread temperature. The yellow spot is the location of our temperature sensor, so all heaters heat until that space has the right temperature, then all the heaters stop heating even though the edges are maybe only heated to half the temperature of the middle section… That leads to a situation, where we can choose to either have the mid-section inside the green circle perfect and the rest still granulate, or heat the middle too much and have a perfect outside. Ideally the outside should be at least as hot as the inside, so all redundant plastic can flow out. That is not the case with our machine, so we get 11-13mm sheets instead of perfectly flat 10-11mm ones.
Also, as mentioned in the post before this one, the 5 ton carjack is way too little pressure for this area.

Our workaround will be an additional Temperature PID for each plate and to connect the four edge heating elements together and have an additional Tempsensor on the edge, so that these heaters heat long enough.

Even with this workaround we will not be able to have an eavenly-spread temperature. So unfortunately, we cannot recommend building this exact version of a sheet press. 🙁
We will maybe go for a used pizza oven in the future, where we heat our plastic and then press it in a press that is just a press. Here in Austria, used pizza ovens cost from 400€, so totally doable. (We payed more than that for the heating parts of our machine)

I hope this experience helps you, if you have any other questions about this project, I am happy to help you!
All the best
Flo

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In reply to: Coffee Table

warrior
01/10/2018 at 00:30
0

@veroarviana
I agree with @okkarlo , a mould would cost you a fortune, not to speak of a machine that can inject that amount of plastic at once. I’d rather go for a sheet press, where you can cut your sheets e.g. with a cnc milling machine

All the best
Flo

In reply to: DIY Sheet press

warrior
01/10/2018 at 00:24
5

UPDATE 01.10.2018

First of all sorry for all the not-yet-fulfilled promises, we have got very little time itm and we like to invest that time into produceing things, but we will do, just be patient 😉

Experience so far:
-Temperature of 286 Degrees Celsius archeived. (max. tested)
-Metal likes to bend when heated. A lot. So don’t weld the heated frame to the metal baseframe. It will bend.
-After heating the mould needs to stay pressed for a smooth surface.
-5 tons pressure  (carjack) is waaaay too little for 0.25 Square meters. Plastic doesn’t flow out quickly.
-heating from both sides and pressing at the same time causes air bubbles inside the material.
-Every little scratch or gap in the mold lets plastic creep into it and you’ll have a hard time getting the sheet out.

As I said, as soon as I find time, i will also do the electricity draw measurement and (try to) make technical drawings so you guys can learn from our Experience & mistakes even more.

All the best,
Flo
Precious Plastic Vienna

warrior
16/08/2018 at 00:10
0

Hi there @chrishollis91 !
Great that you think about recycling these bags!
Basically, PET and PE both can be recycled quite well, However if these plastic types are fused together, it will be impossible seperating and recycling them again. I will actually be in Bristol for two days this week, I’ll drop you a pm!
All the best
Flo

In reply to: DIY Sheet press

warrior
11/08/2018 at 10:13
1

@anne-barbier yes exactly, we have used band heaters. There are flat heating elements available too, but the ones we found are waaay more expensive (triple or quadruple the price of the band heaters) and that was just way out of budget for us, unfortunately. 🙁

In reply to: DIY Sheet press

warrior
10/08/2018 at 22:53
2

@anne-barbier I think you under-estimate the power of about 3.5kW of heating power combined wirh modern insulation. As stated before we dud tests with up to 180 Degrees Celsius and it worked even better than I expected. It climbed straight up to 180 and stayed there with a tolerance of <1%. Thats good for melting Hdpe, but the higher temperature of 200-240 degrees for PP should also be easily archievable. So as an educated guess, 250 degrees should be archievable too^^ Updates eill follow.
All the best
Flo

In reply to: DIY Sheet press

warrior
10/08/2018 at 22:44
2

@nickchomey
Thanks! Our mold Inside is 516mm squared, the outside is 600mm squared. The plastic is 10mm high and the mold is 55mm. The carjack can do 5 tons.
Since we finished building yesterday, as you can imagine, we haven’t made long-term studies yet 😉 so I cannot answer the other questions just yet. The Frame should be able to handle the 5 tons with ease. I did some calculations and the beams will bend a maximum of 1.55mm when applying full load. That is totally in the elastic part of the metal bars, so that should work.

In reply to: DIY Sheet press

warrior
09/08/2018 at 22:38
8

Update 09.08.2018
WE FINISHED THE MACHINE TODAY!!! we assembled everything after some intense working days with sometimes over 13 hours a day of welding, painting, screwing, buying missing parts, insulating, connecting the electronics and all that stuff.

We also gave it a test run and it worked very well up to 180°C so far! More testng will follow. Our machine “Biggie” draws a maximum of approx. 3,6kW, however it won’t draw 3,6 kWh per hour! (less) We still need proper testing for these numbers.

We installed 32 heating elements grouped into two logical groups (top side and bottom side) with 1 Temperature PID and Thermocouple per side. Due to insulation with rockwool (temperature/fireproof up to 1000°C) Biggie keeps its heat quite well, which is a big ecological advantage.

In the following days/weeks/hopefully not months we will upload step-by-step instructions on how to build this machine, so stay tuned! More facts & figures will follow too!
Until then,
All the best

Flo
Precious Plastic Vienna

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In reply to: DIY Sheet press

warrior
02/08/2018 at 08:49
1

@macbeda there aren’t any cad drawings for this machine public yet. If you mean the shredder etc. go to preciousplastic.com
All the best
Flo

In reply to: DIY Sheet press

warrior
02/08/2018 at 07:28
1

@andyn We will! Already got a device for that, as soon as biggie is finished, we’ll test it!

In reply to: DIY Sheet press

warrior
01/08/2018 at 20:04
1

@xxxolivierxxx you’re right, this is far from optimal! We chose to try this method just because of the cost, we couldn’t find any affordable flat heating elements that fit our needs. Only with cost of 500€+. We will try to make up for that energy efficiency loss with good insulation, let’s see how that works.

In reply to: DIY Sheet press

warrior
01/08/2018 at 07:32
1

@andyn 32 heaters and 110 Watts each.

warrior
31/07/2018 at 12:32
2

@ferrash I’ll close this topic. And I moved your other one. @adrienluitot has mentioned everything else already. (Thanks man 😉 )
All the best,
Flo

In reply to: RESEARCH ABOUT PLASTIC

warrior
28/07/2018 at 22:35
0

@pragathi this issue has been discussed many times. Please use the search function on the bottom left of the page to look it up. This way we can avoid multiple posts on the same topic. Thanks! 🙂

In reply to: About the bluprints

warrior
28/07/2018 at 22:31
1

@dlanda It’s millimeters 😉 Oh and next time please post in the Precious Plastic forums instead of the Phonebloks forum. I’ll move the topic this time for you.
All the best

Flo

In reply to: About Machinery

warrior
28/07/2018 at 22:28
0

@dnatural visit preciousplastic.com , hit start and click on download 😉

In reply to: About Machinery

warrior
28/07/2018 at 22:27
0

@rbag0066 try to sen a private message to him, otherwise he probably won’t even notice your comment 😉
All the best

Flo

In reply to: Dxf file 2700

warrior
28/07/2018 at 22:23
0

@plastiflow you didn’t get any answer because you posted in the wrong forum! (Phonebloks instead of Precious Plastic) I’ll move the topic, next time please check twice in which category you are writing!
All the best

Flo

In reply to: Recognising plastics

warrior
28/07/2018 at 22:20
0

Thanks @adrienluitot !
I’ll move the topic.

@janvankelst please try to put your topic in the correct tab next time, because it takes up a lot of time to move all the misplaced topics around to keep the forums somehow organised! Thank you!
All the best
Flo

In reply to: Shredder blades

warrior
28/07/2018 at 22:15
0

Hi @azmal !
please Don’t double-post! You won’t get any more answers just if you open more topics. I deleted the other one. And I will move this to the preciousplastic tab, as this is not a phonebloks – related topic. Thanks
Yours Flo

In reply to: DIY Sheet press

warrior
20/07/2018 at 07:15
4

@nickchomey hell yeah we’ve got updates! Thanks for the reminder! 😉

Update 20.07.2018

The baseframe of our machine has been  welded, and we named it “Biggie”.

We changed mind about the carjack and installed a 5 ton load carjack instead of a 1 ton one… Let’s see how that works.
Next steps:
– Weld heating element pipes to the heating plate
– Connect the electronics
– Insulate
– small fixes and changes

We hope and estimate to have Biggie up and running early this August.

Until then,
All the best
Flo

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warrior
28/05/2018 at 20:15
2

@katharinaelleke
Wooooooooooow I completely missed you were already that far with your project!
AMAZING work & ideas, I cannot wait to see them becoming a reality!
Keep up the wonderful work!

All the best

Flo

warrior
28/05/2018 at 19:39
3

Hi @daryll
You can easily calculate the amount (mass) of plastic you need by looking up its density and the volume the object has. Obviously this varies from object to object.
Output capacity depends on what you do with your machines!
Our shredder did 8kg plastic per hour in a stress test, if that’s a number you were looking for.

I hope that helps,

All the best

Flo

warrior
28/05/2018 at 19:26
1

@mc007

Good input! Thanks!

-Lasercutting: what would you recommend using instead of lasercut parts?

-Shorter blades: I totally agree! Our shredder gets stuck often because of the not optimal blade design! – However I wouldn’t make them thicker.
-Belt drives are maybe cheaper, but also more difficult to build and have huge safety hazards in comparison to a gearbox.

-Shredder & extruder combined: Good idea for an alternative design. Also should be no big problem if you have the plans for both machines 😉
-Price estimate: I agree! Maybe show a price range. The more time, the cheaper etc.

-How do you define the limitations of a DIY machine where every machine is diffrent from another(motor, shaft, etc.)?

 

But yeah I think a different shredder blade design would be amazing, optimally in a way that one can upgrade an existing shredder!

 

All the best

Flo

In reply to: HOSPITAL WASTE

warrior
28/05/2018 at 19:00
0

@katharinaelleke @alejomoreno1992

I agree! Very big topic! The amount of waste produced in hospitals is huge due to medical regulations. Great topic to research on, I’m looking forward to results! Keep us updated!

All the best

Flo

Viewing 30 replies - 1 through 30 (of 255 total)