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The Injection Moulder enables fast production of highly repetitive/homogeneous parts such as plugs, switches, knobs, handles, etc.
The embodied energy + wear & tear of milling a set of metal mould plates for production has historically limited this process to parts produced on a scale of many thousands or even millions, however, using a 3D Printer and a Foundry it may be possible to cast cheap recycled-aluminium moulds in order to produce repetitive parts on the order of hundreds or more, which would otherwise cause excessive wear on a 3D Printer.
With a Shredder, the injection moulder is a core component for recycling old thermoplastics that would not be suitable for Fused Filament Fabrication type 3D Printing, such as polyethene and polypropene, which form a majority of waste plastic flows.
The Injection Moulder consists of a melt-chamber fed with chipped recycled plastic and/or pellets of virgin plastic feedstock, heated to a controlled temperature by a heater cartridge, heating resistor or some wound nichrome wire, and forced through a nozzle into a mould by a piston fitting the melt-chamber. For large moulds requiring high pressure, a piston can be driven by a motor using a leadscrew, but for small batches/parts a hand-operated lever is fine.
A simple Arduino-programmed ATMega microcontroller with a potentiometer (analogue knob) or 7-segment display & tactile switches (digital) input driving a high-voltage relay with low-frequency PID, would easily suffice for temperature control.
The melt chamber/cylinder can be made from a smooth steel pipe if you have a piston to fit it (e.g. the one shown in the video above), or from a block of aluminium with hole drilled through it using a drill press (e.g. the one in Gingery's book, and shown in Rick's document) with a 1cm thick steel rod for a piston (as can be salvaged from many discarded inkjet printers). The latter could be made with greater heating efficiency and lower material use by casting aluminium into a desired rounded shape and then reaming the melt-chamber hole to a smooth bore.
Nozzle production follows much the same theory as any RepRap 'hot-end' - having a lathe makes this much easier.
Almost any structural materials could be used for the injection moulder's frame, from recycled lumber to welded steel sections. As noted in Rick Sparber's document, attention needs to be paid to properly constraining the piston in a hand-operated lever system, so as to avoid any out-of-axis force bending the piston out of shape.
OSE Project Status/Schedule
The injection moulder project is currently in research phase. Subject matter experts are encouraged to contact us.
- Precious Plastic
- Bioplastic Extruder, for producing continuous forms such as pipes, and for very high-pressure moulds.
- The Secrets of Building a Plastic Injection Molding Machine - Vince Gingery Amazon US, Amazon UK, BTMon
- A Modified Vince Gingery Plastic Injection Molding Machine - Rick Sparber, 2010