3. Results
Overall the quality of the test prints was very good, with some
variation due to material, printer and the object being printed. First,
for objects whose strength matters more than aesthetic the symbol
can be printed right on the front surface. To demonstrate this,
a functional wrench was printed with high-impact polystyrene as
shown in Fig. 1. For all the resultant 3-D prints the inset shows
the CAD design to demonstrate the printing fidelity even in lowcost
3-D printer designs. The recycling symbol was embedded deep
enough to be easily seen, but not too deep to compromise the
integrity of the wrench. The prosumer can also reduce the depth
of embedding to make the recycling symbol only visible at certain
angles of observationas showninFig. 2 for the polycarbonate toothpaste
tube squeezer with the symbol printed on the flat face. The
simple embedding approach can also be used for flexible objects
like the bouncy ball shown in Fig. 3, while still maintaining their
function.
For objects where the aesthetic properties ofthe object are more
important it is possible to hide the recycling symbol until it is necessary
to recycle the object. Two approaches were demonstrated
here.
First, a drill bit handle was printed in ABS, with no visible recycling
symbol on the exterior (such handles are popular in the 3-D
printing community to ream out holes in RepRap part prints). The
recycling symbol is in the center of the handle so that for about
50 layers only the symbol and the wall of the handle are present.
Thus, when the handle is ready to be recycled it can be cracked
open (as shown in Fig. 4) and the recycling symbol becomes clearly
visible on the inside regardless of the location of the crack. This
type of recycling symbol embedding—where the recycling symbol
can become an integral (and potentially mechanically necessary)
component of the part is difficult to impossible with traditional
subtractive manufacturing techniques.
E.J. Hunt et al. / Resources, Conservation and Recycling 97 (2015) 24–30