My plan was to create a series of cast aluminium moulds suitable for the injection moulding of recycled HDPE plastic made from shredded milk bottle lids. Unfortunately this only partially worked but the process will be explored below. Along the way, I discovered (Not necessarily a new method but new to me) a way of using hot glue in cast injection moulds to create stunning colourful rings. This works well as a proof of concept and hopefully will eventually lead to fully recycled rings.

A wide variety of things went wrong. The aluminium was not hot enough so it cooled too quickly. Setting before all of the air could escape. The moulds were not heated enough so they cracked when the aluminium was poured. Finally, the investment wasn't set correctly so moisture escaped further messing up the casting.

I am currently studying my BA in Industrial Design at the University of Johannesburg in South Africa. This project and some other very interesting projects are available on the university's Instagram page. https://www.instagram.com/ujindustrialdesign/

Above are the final rings. In the future, I want to use an injection moulding machine to use recycled plastic to make these rings. I would like to revisit the aluminium mould in the future as I believe they will work much better and for far longer under the high heat of injection moulding.

Vinyl plastisol is a dispersion of polyvinylchloride (PVC) resin in a liquid plasticizer. Other ingredients are pigments, stabilisers for heat and UV light, flame retardants and additives that influence the surface (matt/gloss).

Caplugs considers it extremely important that our employees work with the highest quality materials. The use of clean materials in our production process, which are not hazardous for man or the environment, has our continuous attention (consider here our standard phthalate-free materials for a number of colours).

The rings can be quickly cleaned up with a knife and I used a lighter to smooth out any bumps. This created some very smooth comfortable colourful rings.

An extensive range of plastisol qualities is available for a wide range of applications and Caplugs has been involved in the development of many special formulations. The hardness is determined by the level of plasticizer and is measured using the Shore A scale from a flexible 40 Shore A to a dimensionally stable 95 Shore A.

The same process for creating the silicone mould was virtually repeated for the investment mould. The beeswax patterns were screwed to a base and walls were created around them. An investment slurry was created and poured over the wax patterns. The wax was then burnt out using a blowtorch and an oven. Some of the investment cracked when the wax was melted out. So in the future, I am planning on drying the moulds out for longer to hopefully let more water leave.

All of our waste is collected and shipped to a specialised recycling company. Processed plastisol cannot be reused, but solid waste can be recycled without problem and used for the production of floor mats and, for instance, flowerpots.

After the aluminium casting didn't work I tried another method. I sprayed the resin cast moulds with mould release before bolting them together. I used colourful glue in my hot glue gun and injected it into the mould. Initially, experiments failed as there was no place for the air to escape making the glue unable to fully fill the mould. I carved a channel at the bottom of each mould to allow the air to escape. I injected each mould with hot glue.

The ring, mould and sprue were all modelled in Solidworks and exported as STL files for 3D printing. I created a two-part mould with identical parts. This allowed me to print a single side and create a single mould. I modelled 4 through holes that can accommodate a 5mm bolt to perfectly line up both sides. My process from 3D printing to manufacturing is explored in the images above.

I melted a huge amount of aluminium cans, broken window frames, and scrap aluminium pieces. I also had leftover aluminium ingots from a previous project (https://www.instructables.com/Workers-Stool-Made-From-Reclaimed-Materials/ ). Once the metal was molten I poured it into the investment moulds. Burning out any remaining wax or residue. I removed any excess slag/impurities from the aluminium with a spoon before pouring.

I sprayed the 3D prints with mould release before attaching them to a foam core base. I built walls around the pattern using hot glue and more foam core. I used Amsil 30 silicone (But any casting silicone would be suitable). Make sure to mix the silicone in one container and then pour it into another container for additional mixing to ensure the two parts are fully incorporated. Pour the mixed silicone into the mould from as high as possible in a single stream to try and reduce air bubbles. Additionally pour from a single corner and let the silicone slowly flow over the part to ensure a virtually bubble-free pour.

I used a wide variety of tools, materials and methods throughout this project. While some of these are quite specialised most are easily available at a local makerspace, or afforadbaly from a hardware store. My foundry that I used to smelt the aluminium was hand made from fire bricks, 4mm angle iron and I created a forge burner from plumbing supplies from The KIng of Random's tutorial. (https://www.youtube.com/watch?v=eO8NwseRxSA).

I recently completed a university brief exploring sustainability in materials and design. Specifically exploring various ways of addressing plastic waste. Looking at Precious Plastics and their range of tools and methods for creating usable products from plastic waste. As I am studying product design I wanted to end up with a product made from plastic waste that was attractive, durable and desirable to customers.

I used polyurethane two-part resin to cast the mould halves. Make sure to weigh each part accurately, mix thoroughly, use two mixing containers and scrape the sides and the bottom of each. I also cast beeswax in the same silicone moulds melting it in an old coffee tin in the oven at a VERY low temperature.

The excellent electrical insulation properties of PVC are well known and frequently employed in the electrical engineering industry. Moreover, most basic qualities have effective fire retardant and specially adapted properties in accordance with UL94 / V0.

When using any resin, investment or silicone a respirator and gloves are essential. These materials release toxic fumes, dust and particles that can be very dangerous when inhaled.

Aluminium smelting is very dangerous and correct safety gear is essential. A respirator, thick leather apron, closed shoes, welding gloves and a face mask are absolutely essential. A fire extinguisher is required for any processes using fire and a bucket of sand (NOT WATER) is required to contain any aluminium spills

The mould pattern was 3D printed on a resin printer. I had to remove support material with pliers and a knife. I used acetone to clean the prints and put them in the sun to fully cure. The quality was superb so no sanding or paint was needed.

Never perform a task that you are not fully comfortable with and always use tools as intended. If possible always have someone near by who can assist/ call for help incase something goes wrong.

Caplugs offers a complete range of standard colours and can match an exact colour if required. The standard finish for dip moulded products is high gloss, but we can also supply semi-matt, matt, structure (foam) and fluorescent materials.