There are a number of things I have contemplated making from recycled plastic. Thermo forming plastic always looked exciting in that it can use materials that otherwise might be thrown away (recycling) and make stuff that hackers just might be able to make and sell.
The challenge has always been the cost of molds and methods of heating plastic efficiently and then injecting at a temperature and pressure that is safe for laypeople.
There is a blow mold part I want to make recycling water bottles. But practical? Hmmmm.
I have some experience making silicone molds which can easily take up to 500 degrees which means that for limited production run an injection mold could produce 1 to 200 units if the silicone mold were encapsulated in a steel mother mold that could take the high pressure while the silicone mold would shape the plastic.
I’d like to know if there is any interest in pursuing this technology in the Hackerspace. It doesn’t look like it would take up a lot of space and just require electricity and probably water (buckets) to cool the parts.
Hi David! Yes! We’ve actually been in a conversation over the last several weeks with @Destindouglas and Sam to start work on this – a neat idea involving making sister machines – they will start making one for their business (compression mold for PVC only) while ATXHS will start making an injection mold, shredder and extruder. We’re planning on getting started in the next couple of weeks, as soon as we have a system for welcoming new members that can include primer on cleaning up, distanced orientations, and basic classes (3-d print, laser, woodshop).
I would like to be making recycled filament for the 3-d printers, but also recycled anything --.
Excited to hear your interest, we can start finding materials now – there are two designs I’ve been looking at, one is the precious plastics (not a large footprint, but per @JoeN adding more molds for a more industrial-strength design https://preciousplastic.com/solutions/machines/pro.html ) and the other is this one: https://www.researchgate.net/publication/329795404_Design_and_Development_of_mini_plastic_shredder_machine
Kye
I messaged a few people who are also interested in building a plastic shredder and injection molding machine. We have some members who are interested in making a plastic compression machine. I’m waiting on the project to get going.
What are typical temperatures working recycled PVC? I’m pretty sure silicone molds can handle high temperatures and a steel mother mold could prevent pleasure deformation.
Smooth On has a Tin Cure Silicone with A Shore hardness of 60 (like a car tire) that can take 560 degrees.
David Mitchell made a DIY injection molder early on in the Space’s history. Was a long handle and a piston pressing on a heated cylinder. I don’t recall that one being successful though.
I did use silicone molds for casting liquid urethane, that’s without pressure or high temp. As per the silicone mfg, even in that low-stress app, the expensive silicone mold shows wear after about 100 shots. Platiunum-cure silicone is superior to tin-cure, especially when heat is involved- Smooth-On has both.
I’m a bit confused here. Silicone molds are widely used for casting with liquid resins that end up flexible or rigid (urethane, epoxy, other silicones). But plastic injection molding utilizes several tons per sq in as well as high temps, and a metal framework around that won’t protect the silicone from the compression load. Injection molds require aluminum or steel if we’re talking about melted plastics.