Inspired by the Poly Lactic Acid (PLA) extruded from the 3D printer at
only 180 degrees C, I wonder if any have considered melting down the
shedloads of plastic that seem to fill our dustbins these days as a
At first thought, perhaps it would be ideal for mouldings such as the
simulated combination of axleboxes and springs?
At 2nd thought, 180C is quite high. Will cause serious burns on human
skin. And there are serious technical problems. I met a plastics
engineer a couple of decades ago, learned a lot about how to make stuff
out of plastic. It's not as simple as it looks.
Problem 1: Plastics are very sticky when melted. Must be cast in tightly
sealed pressure moulds, they will emit toxic vapours when heated in open
Problem 2: Making a mould for casting plastics is tricky. Plastics are
at fairly high temperatures, the mould must have cooling channels around
the mould cavity.
Problem 3: 3D printers must be reprogrammable for different printing
materials. AFAIK, the cheaper ones aren't.
That's just a 30 second think....
OTOH, waste plastic can be recycled commercially, albeit at a cost. Raw
plastic feedstock is cheapre than recycled. But the recycling cost is in
the long run cheaper than dumping the stuff into the environment.
Oxidation is very slow. Common plastics are indigestible. They break
down mechanically, UV degrades the crosslinks that holds the stuff
together, and so on. The net result is plastic flakes that are ingested
by small animals, and eventually nanometre scale plastic flakes, which
are ingested by microbes. Some plastic-processing microbes will
eventually evolve, but not anytime soon.
Have a good day,
I make 'machineable wax' for CNC prototyping from plastic milk bottles and
paraffin wax - work a treat if a bit time consuming. Melt the wax, cut
strips of washed and dried milk bottle and stir into the wax slowly bringing
the temp up to about 125-130 deg C - when no more plastic dissolves into the
wax you are done. I admit that lately I've been using MDPE and HDPE granules
intended for injection moulding, as it makes a quicker job dissolving into
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