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Precious plastic in grade 7 classroom

This topic contains 28 replies, has 6 voices, and was last updated by  Barbara Xu 2 years ago.


Precious plastic in grade 7 classroom

28/08/2017 at 19:20

Hello All,
I have been teaching science and technology for 20 years now and needed someting new. As luck would have it, my school needed a program to enrich the science curriculum for science orientated kids… Cue Preciousplastic!

My schredder is complete and functionnal with a 1hp motor and a few security (!!) mods.
I am currently working on the wiring of the injection and compression. Extrusion Is in the plans but will wait a year before we build it (mastering the 1st 3 will be enough).

Will post pics soon.


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30/11/2017 at 19:40


It is great that your are integrating Precious Plastic into science curriculum, keep it up. Also don’t forget the photos!!

02/12/2017 at 04:43

Great to hear. My school had wood,metal and auto shops,now they could use Plastic shop. It would be cool to have as a senior project to build a PP workspace and donate it to another school.Just think how many different skills the kids would learn and at the same time get another school started.

02/12/2017 at 07:51

Great project
What is grade 7 😀 how old are the pupils.

The aim here is the fabrication itself? and what do you do after the machine are ready? I mean as courses… How is stick whit the official education Programm of Canada.

My opinion is that it could be also a post in idea section.
One of the PP objectif is to be déveloped, know and used…. What is better than education and school to have a great and deep impact. I remember the Dave video in a museum or exposition where they have made a manual shredder and an injection machine.

Thanks one more time, I wait the pictures with impatience…


06/12/2017 at 19:05

PP fits with sec3 science of the Quebec curriculum which has a module on plastic types and properties. I bring it to younger (11year old) student with an environmental angle with intro to different industrial processes and with simple physics as well. The students use the equipment and produce raw chips from wich they are currently molding flower pots. I am waiting for a nozzle and molds for the injection that should arrive in 2 weeks. Kids LOVE Pp both as a hands on production and a mission. I pinned my location on the map and added a few pics.

06/12/2017 at 19:11

More pics notice long funnel to keep fingers out of grinder

06/12/2017 at 19:17

More… cage to keep hands away from heating elements on injection

06/12/2017 at 19:20

I have an issue with the compression … when it reaches set temp it keeps on heating. Maybe it is the ast or faulty thermostat ( I ordered spares)

06/12/2017 at 19:29

Nice flower pots!

You say you are waiting on an injection nozzle/moulds and I notice you have a car jack under the machine. Are you using a threaded nozzle or a ball-ended type held against the mould by pressure?

06/12/2017 at 19:46

I will go for a nozzle like a hot glue gun and maintain molds on the nozzle with pressure from underneath ( the jack)… at least that’s what I want to try

06/12/2017 at 19:56

We are working exclusively with hdpe for the moment… I don’t want to try other types as the clean out of the grinder ( nick name the ogre) if really a pain.

I first opened plastic collection to the kids in the program, then to school staff and finally, to reach the correct input quantities I asked all the grade 7 students of the school.

06/12/2017 at 20:21

I think your nozzle idea is sound and should work well. Please post some photos, I’d be interested to see.

06/12/2017 at 21:08

Will do. I’m picking up the parts on dec 16th

08/12/2017 at 20:48

Since I have only 3 machines and 23 students in that class I had to keep the others busy… some pics. Aquariums(30and90 gal) are now filled and livestock installed… emphasis will be on monitoring water quality and fish behavior( parental care of fry, mouthbrooders, livebearers, courtship displays…)

08/12/2017 at 20:51

@dbougas pupils are 11 to 13 years old and they run production. Machines are built by a combination of professionals, volunteers and myself.

10/12/2017 at 00:45

👍 clever and beautiful results…
Thanks a lot for your sharing…

23/01/2018 at 15:59

Well I finally got the molds right and a nozzle for the injection.

23/01/2018 at 16:07

The dimple in the mold’s top makes for secure connection while keeping a flat face for easy unmolding.

I heated too much for the I’d test and got a shower of liquid plastic on the wall( not me).

Second try yielded a top😊🎉

Observation: the reducer from 1 to 1/2 inch creates a cooling spot after the last heating ring😦 I want to get a piece machined that combines the 1 inch threads with the nozzle all in one piece and get an other heating belt secured on it for temp consistency. Kids attended the second trial and were amazed by the product that came out. Once I figure out the fine tuning details they will operate it. Soon I hope.

23/01/2018 at 16:09

Forgot to show how mold is held in place. Very secure… nothing moves.

I think my molds might be a bit too airtight… I feel as if fighting air bubble while injecting. I won’t modify them until I get my heated nozzle piece

23/01/2018 at 18:13

@rabadswompe Nice work!

I actually offer such a nozzle in the Bazar It screws onto the end of the barrel (1″ BSPT) and has a short M10 threaded stub, onto which you can either screw a mould directly, or one of the supplied dome nuts which are drilled to use with ‘dimple’ style moulds (there’s also a plain nut to use as a cap to stop molten plastic oozing out before you’re ready). You could put a heater band over the nozzle, but as it’s short and has a lot of thermal mass compared to plumbing fittings, it doesn’t seem to need one.

Coincidentally I also made a spinning top mould similar to yours, and found it can seal quite airtight, especially as I used tapered registration faces. My solution was to make 3 very shallow cuts in the mating faces, this lets the air out but not the plastic. (See below)

23/01/2018 at 18:51

Hi @rabadswompe

Did you see the project
School project

Any picture of the shower?
I didn’t correctly see all the pictues you posted in Dec… Really impressive!


23/01/2018 at 19:03

@dbougas I’ll get you a picture of the artwork lol
I just visited the school project post of Norway… wow. Old like to team up with that teacher!!!

@andyn I don’t know if your threading system is same as here in Quebec, Canada.
I’ll go and look in the bazar all the same. Thank you. I only wished I could have done all the troubleshooting before starting the class but such is life and kids benefit(and contribute) from the problem solving process

23/01/2018 at 19:09

@andyn now that is a nozzle!!!

24/01/2018 at 13:45

@rabadswompe the threads on the nozzle are the 1″ BSPT as specified in the Precious Plastic drawings for the barrel, though I have also done them with just a plain socket as some people without access to tools for threading the barrel prefer to weld the nozzle on (though this means you can no longer disassemble it). The M10 thread for the mould, I’m not sure if this is common in Canada, but I think you use metric fasteners? (unlike the US). But for ‘dimple’ moulds you can just use the dome nuts that have a hole drilled through.

26/01/2018 at 23:10

@bdougas here is a pic of the water bucket I planed to empty the molten plastic in before machine shutdown . I thankfully had it close and used it to catch »most » of the explosion/ shower of plastic. The rest is on the wall ( other pic) and a few drops got on the hand holding the bucket… didn’t hurt much… kinda like welder sparks.

05/02/2018 at 23:33

Miss this post…
Very good!
No injuries is the important thing…
Waiting for others news…

12/02/2018 at 23:14

Any news?

25/02/2018 at 17:11

Hi. A few things developed.

I am getting 2 new injection molds made. An other spinning top and a small flowerpot. I am also getting a custom nozzle piece and will order a heating band to fit on it. I lose too much heat with the plumbing reducer which makes things impractical.

Looking into 3D printed injection molds.

Still need to polish compression molds that are more and more difficult to unmold.

04/04/2018 at 05:36

Wow impressive project! We are currently looking for an Mold to make flower pots. Any idea where we could get Blueprints / Laser-documents from? We are doing a similar Science Project in China! Cheers & thanks for the help!

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