Manufacturing and
Materials Processing
Journal of
Article
Transfer and Optimisation of Injection Moulding Manufacture
of Medical Devices Using Scientific Moulding Principles
Aimee Fitzgerald
1,2
, Paul McDonald
1
, Declan Devine
1
and Evert Fuenmayor
1,
*
Citation: Fitzgerald, A.; McDonald,
P.; Devine, D.; Fuenmayor, E. Transfer
and Optimisation of Injection
Moulding Manufacture of Medical
Devices Using Scientific Moulding
Principles. J. Manuf. Mater. Process.
2021, 5, 113. https://doi.org/10.3390
/jmmp5040113
Academic Editors: Arkadiusz Gola,
Izabela Nielsen, Patrik Grznár and
Steven Y. Liang
Received: 24 August 2021
Accepted: 14 October 2021
Published: 25 October 2021
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4.0/).
1
Material Research Institute, Athlone Institute of Technology, N37 HD68 Athlone, Ireland;
A00268872@student.ait.ie (A.F.); pmcdonald@ait.ie (P.M.); ddevine@ait.ie (D.D.)
2
Teleflex Medical OEM, Annacotty Business Park, Annacotty, V94 RK06 Co. Limerick, Ireland
* Correspondence: efuenmayor@ait.ie; Tel.: +353-899-867-411
Abstract:
Scientific moulding, also known as decoupled injection moulding, is a production method-
ology used to develop and determine robust moulding processes resilient to fluctuations caused
by variation in temperature and viscosity. Scientific moulding relies on the meticulous collection
of data from the manufacturing process, especially inputs of time (fill, pack/hold), temperature
(melt, barrel, tool), and pressure (injection, hold, etc.). This publication presents a use case where
scientific moulding was used to enable the transfer and optimisation of an injection moulding pro-
cess from an Arburg 221M injection moulding machine to an Arburg 375 V model. The part was
an endovascular aneurysm repair dilator device where a polypropylene hub was moulded over a
high-density polyethylene dilator insert. Upon transfer, multiple studies were carried out, including
material rheology study during injection, gate freeze study, cavity balance of the moulding tool, and
pressure loss analysis. A design of experiments was developed and carried out on the process with a
variety of effects and responses. The developed process cycle time was compared to that achieved
theoretically using mathematical modelling and the original process cycle time. The studies resulted
in the identification of optimum parameters for injection speed, holding time, holding pressure,
cooling time, and mould temperature. The process was verified by completing a 32-shot study and
recording part weights and dimensional measurements to confirm repeatability and consistency of
the process. The output from the study was a reduction in cycle time by 12.05 s from the original
process. A cycle time of 47.28 s was theoretically calculated for the process, which is within 6.6% of
the practical experiment results (44.15 s).
Keywords:
polymers; injection moulding; scientific moulding; manufacturing process optimisation;
cycle time analysis
1. Introduction
Scientific moulding is based on applying the laws of physics to properties of moulded
plastic parts. It is ‘the science of process development, recording, standardization and
repeatability’ [
1
]. Applying scientific moulding practices is pertinent for achieving faster
cycle times, higher volumes, and a higher efficiency process by determining optimal
moulding conditions [
2
]. As outlined by Paulson, the part properties are determined
by four steps, which are melting temperature, injection flow into the mould, the cavity
pressure, and rate of cooling [
3
]. Scientific moulding outlines various tests and studies to
accurately examine the machine capability and qualify the mould and part based on these
four steps. These studies include rheology/viscosity study, cavity balance, pressure drop
study, gate seal study, and cooling time [4,5].
The optimisation of the injection moulding cycle time plays a crucial role in plastic
manufacturing in relation to improved productivity. There are numerous factors that
can affect cycle time, which include part design, resin material, tool design, and process
parameters. Identifying factors increasing cycle time becomes crucial for process optimi-
sation purposes [
6
]. Acceptable parts produced at shorter cycle times result in reduction
J. Manuf. Mater. Process. 2021, 5, 113. https://doi.org/10.3390/jmmp5040113 https://www.mdpi.com/journal/jmmp
