Page 87 - Plastics News August 2024
P. 87
PRODUCT NEWS
What to consider Additionally, addressing assembly considera-
tions in some instances can be vital, particularly
Material choice is paramount when optimising if the cannula is part of a larger device. Ensuring
outcomes in micro moulding cannulas due to its mating surfaces, alignment features, and inter-
profound influence on product performance, re- locking mechanisms are well-designed enables
liability, and manufacturability. The unique chal- smooth integration.
lenges posed by micro-scale manufacturing,
such as precise cavity filling and intricate geom- Avoiding potential challenges
etry replication, demand materials with specific Maintaining a balanced aspect ratio is essential
properties like low viscosity, excellent flowabil- to avoid challenges associated with flow dynam-
ity, and minimal shrinkage. Material selection ics, cooling, and structural integrity. An exces-
also impacts the durability and biocompatibility sively high aspect ratio can lead to difficulties in
of medical devices, ensuring they can withstand material flow and cavity filling, potentially result-
the rigours of use while being safe for patient ing in uneven thickness and defects. Conversely,
interaction.
an aspect ratio that is too low might hinder prop-
Several critical design for manufacturability er cooling and cause warping, making it vital to
(DFM) considerations must also be addressed. strike the right balance that promotes both ac-
Ensuring uniform wall thickness is paramount, as curate moulding and structural stability.
variations can lead to warping, cooling inconsist- One other variable that has been critical is the
encies, and inadequate filling. Proper gate place- use of proprietary micromoulding presses, de-
ment is essential, influencing material flow and veloped over generations at Accumold. Cannu-
minimising stress points, while suitable venting las were moulded on conventional presses and
channels are crucial to prevent air traps that can on Accumold’s presses, and it was discovered
result in surface defects. Incorporating appro- that conventional micromoulding presses had
priate draft angles facilitates seamless ejection problems with non-fill and flash. Through the use
from the mould and prevents potential damage.
of our fully automated in-house developed mi-
Furthermore, maintaining accurate parting line cromoulding presses and 16 cavity micromould
alignment prevents flash and surface mismatch- tooling, we achieved reliable, repeatable, and
es. Strategic placement of features like ribs and high-volume production of 40 million parts a
supports enhances structural integrity without year from a single production cell.
compromising the overall design, while carefully SOURCE - MEDICAL PLASTICS NEWS
considering the positioning of ejector pins pre-
vents interference with critical features during
demoulding.
August 2024 PLASTICS NEWS 89
