SLQ Wiki facilities:fablab:equipment-custom:plastic_recycling

Extruder

anonymous@undisclosed.example.com (Anonymous) — Wed, 13 Nov 2019 11:50:40 +0000

Extruder

A bespoke mini-extruder screw has been purchased, and a barrel to suit manufactured. This project requires a welded frame, motor, couplings and electronic controls for completion.

Injection Moulder

anonymous@undisclosed.example.com (Anonymous) — Sat, 07 Mar 2020 15:40:22 +0000

Injection Moulder

The Injection Moulder was finally completed in Dec 2019, and stands ready for use.

A major redesign of the electrical controls was done, incorporating a fused power inlet, and indicator lights for each heating circuit (placed after the relevant SSR). 40amp SSRs were used (rather than the minimum 10amp ones in the BOM) on advice that they will quickly burn out otherwise. Heat sinks were added to each SSR for the same reason.

The volume of each charge was calculated to be about 80cc, providing a hard design constraint.

Mouldmaking is the next step, and the plan is to make moulds from cheap materials with a limited useful life. Dental plaster and epoxy resin will be tried first. A rigid metal container for the moulds will be required to prevent fracturing, and this may be made to order or adapted from available metal containers.

2020

In March 2020 the AC team consulted with a licence electrician regarding what work would need to be completed before having the injection moulding machine commissioned electrically. He recommended ensuring that all electrical components, including conductors, had 2 levels of insulation the 4x original heater bands were replaced with a new model that were

Higher wattage
earthed
enclosed brass construction with
longer stainless steel braided cable

A stainless steal perferated tube has been sourced as a guard against the operator brushing up against hot metal part any nasty burn injuries.

ideas

https://hackaday.com/2017/11/11/diy-injection-mold-design-for-the-home-shop/

https://3dinsider.com/diy-injection-molding/

https://makezine.com/projects/make-41-tinkering-toys/diy-injection-molding/

https://www.instructables.com/id/Home-Plastic-Injection-Molding-with-an-Epoxy-Mold/

https://www.techkits.com/products/mold-epoxy-large/

Plastic Recycling

anonymous@undisclosed.example.com (Anonymous) — Mon, 23 Jul 2018 14:27:29 +0000

Plastic Recycling

This project has been informed by the open source designs released by Dave Hakkens (see: https://preciousplastic.com/en/).
The original designs have been modified to better suit regional and remote installation as far as possible, with a view to installation in regional libraries as well as at The Edge.

Four different machine designs are available:

1. Plastic Shredder
2. Injection Moulder
3. Extruder
4. Sheet Former

Rationale

Community concerns about plastic waste have increased as more evidence of systemic and intractable pollution by discarded plastics continues to emerge. Currently, commercial plastic recycling is hampered by technical as well as economic barriers, which has resulted in a focus on recycling clean, single-type industrial waste and ongoing difficulty in marketing existing products. This project seeks to leverage the communities energy for change by developing, documenting and deploying domestic-scale recycling machinery that can handle sorted household waste plastic, and developing simple, low-cost mould and die making techniques that can engage community members in the design and making of new products.

Plastic Shredder

anonymous@undisclosed.example.com (Anonymous) — Mon, 09 Mar 2020 17:58:27 +0000

Plastic Shredder

Shredder components were laser cut by external service providers according to the design files available from the https://preciousplastic.com/en/ website, with the following modifcations:

housing material was 250 GR mild steel, rather than stainless. This meant that material costs were reduced, although painting was required to prevent corrosion.
blades were cut from BIS 80, a high strength steel, rather than stainless. This was intended to produce cutting blades that will withstand greater stresses, and maintain an edge for longer.
shaft was made from 28.257 hex bar (available as stock in Australia), with ends turned to 20mm. This size allowed use of a readily available coupler to attach the motor. A keyway was cut into this shaft, rather than using the grub screw of the original design.
a transparent acrylic hopper was fabricated and mounted above the exposed shredder blades, to provide added safety and increase ease of feed. A short push stick was then used to assist feed entry to the shredder.
the sieve screen was modified according to more recent Precious Plastics designs, with extra holes made in the shredder housing to allow the screen to be fixed in place using threaded pins, as a way to make removal and cleaning easier (see: https://preciousplastic.com/en/videos/build/upgrades/shredder-2-1.html).
DC motor was a https://www.motiondynamics.com.au/375w-12-24v-1400rpm-dc-motor.html
Gearbox was a https://www.motiondynamics.com.au/worm-drive-gearbox-to-suit-heavy-industrial-motors.html

Operational Observations

After being in controlled use for 12 months, the following observations arose:

public demand was low, but steady. Users were inducted on a one-on-one basis, with direct supervision during initial operation. Currently (end 2019) users have requested access 1 -2 times per month, mainly by email contact.
the batteries seem not to hold a charge very well. It is essential to leave the machine charging overnight, up to the time of use.
during use the motor and gearbox get very hot. This is normal, according to advice from the suppliers. A pause is required after about 2 hr continuous use to allow things to cool down.
the motor brushes burnt out about 12 months after commissioning. Replacements are available (about $10 a set), and spares are now kept on hand. (see brushes replacement below)
during operation , a static charge builds up that causes fragments of plastic to stick to the acrylic hopper, and other surfaces. Regular brushing during operation can address this to some extent.
cleaning between jobs is a major frustration. As the material is shredded, heat causes small pieces to stick to blades and screen, and smal pieces too large to pass through the screen remain lodged in the grinder. Brushing (from below) and vacuuming are only partially successful. Running the shredder for 5 min without adding new material seems to help clean things out, but carry over is always noticeable.
if the input material is a rigid plastic (eg: ABS, PLA) pieces tend to fly out of the hopper during use. A cardboard hopper cover has been attached to prevent this, and should be present when jobs commence.
the process is slow. For a soft, easily shredded material like milk bottle HDPE, about 5 - 10L of shreds can be produced per hour.
PET bottles cause a lot of jamming, and this slows the process considerably. The thicker bottoms and tops of these bottles are especially difficult to process.
solid pieces of rigid scrap (failed 3D prints, for example) may not be shreddable without first reducing the size (hit it with a hammer).
portability has been useful - the shredder has been rolled out during Fun Palace, for example - and it has been of great interest to the public.

Suggestions for Future Improvements

redesign and rebuild as necessary to allow easy cleaning between jobs. This will be essential as usage increases. Hinging the screen is a likely solution.
given the cost of manufacture, and wide skill set required for the build, members of the public wanting to have their own machine have been advised to consider buying an off-the-shelf solution. Many small-scale options can be found on Ali Express for about $2000.
comparison with re-purposing an existing machine would be worth exploring, A garden shredder might do the job,for example, for a much lower cost.
the motor seems underpowered. While this is constrained by using a 24V system, upgrading to 240V, and installing a 2kW motor would overcome many of the jamming and overheating problems.

Inductions

Draft induction paperwork has been developed, and is awaiting approval.

the_edge_sop_plastic_shredder.docx
plastic_shredder_induction_final.docx

Brushes Replacement

Disconnect Battery charger from GPO and disconnect DC motor power cable

unscrew brushes cap and remove brushes

inspect brushes

remove inspection plate

and blow out carbon using compressed air

Replace cover
preplace brushes
replace brushes cap
reconnect DC motor and test

Don't forget to order a new set to have on hand

Sheet Former

anonymous@undisclosed.example.com (Anonymous) — Wed, 13 Nov 2019 11:52:56 +0000

Sheet Former

Experiments are proposed to adapt a sandwich toaster for this purpose. Many Youtubes exist that show this is possible, using silicone baking paper to prevent sticking. Temperature control is an obvious improvement to be considered.

Ventilation will be required .