Page 59 - Plastics News Issue September2025
P. 59
TECHNOLOGY NEWS
feeding characteristics. If the regrind has many caused by a poor design of the device.
fines or small particles, which will melt prema-
turely as compared to the larger regrind parti- Cooling devices that leak prematurely typically
cle sizes, the small particles will melt and stick to wobble when the screw rotates. The wobble
the screw and inhibit the solids conveying of the causes uneven stresses and wear on the pipe
feedstock. Screw cooling will mitigate this effect. threads at the connection of the outer pipe and
screw shank. The design presented here has a
Screw cooling is often installed on extrusion hex-head bushing on the outer pipe that keeps
processes and then disconnected when the de- the pipe centered in the gear box.
vices start to leak water. This happened for the Source – Plastics Technology
PC extrusion process presented in the August
2025 article. Although all screw-cooling devices
will eventually leak water, premature leakage is
Replacing metals with 3D printed polymers
What differentiates metals and polymers?
Before we address which polymers are suitable
for replacing metals, we need to set the right
expectations. Some companies may inflate the
capabilities of high-performance polymers and
fail to consider that metals and polymers are
fundamentally different. Here’s how the differ:
Polymers
eplacing metals with polymers is not 3D printable polymers are thermoplastics, made
only possible but becoming increasingly up of polymer chains that are chemically sep-
Rmore prevalent. The current generation arate from each other (no molecular bonding
of high-performance polymers and composites between chains). These chains are physically
has similar mechanical properties to aluminum entangled which provides mechanical integrity
at a fraction of the weight. In addition, the abil- to the overall material. The chains can also or-
ity to additively manufacture parts from these ganize and fold into a crystal structure which are
polymers, with high temperature 3D printers like harder to pull apart due to greater intermolecu-
the AON Hylo, has driven further adoption by re- lar interaction forces. This is why semi-crystal-
ducing the complexity, lead times, and cost con- line polymers are better in strength and stiffness
straints of traditional manufacturing methods.
compared to amorphous polymers.
September 2025 PLASTICS NEWS 59
