By applying injection compression
techniques to stack moulds, packaging
moulders can now reduce the wall
thickness of containers and lids from
0.45mm to 0.35mm. This saves around
25% in raw polypropylene materials
compared to the standard injection
moulding process, while maintaining
comparable mechanical properties.
Given the dominant role that materials
play in low cost, mass-produced
disposable food packaging containers
and with packaging converters striving
to enhance their green credentials, being
able to reduce the wall thickness of
packaging by up to 25% is a significant
advantage.
How to... reduce plastic packaging
wall thickness by 25% using
injection compression moulding
mould. The machine closing movement machine with reduced tonnage and a
aids distribution of plasticised material smaller footprint.
HOW IS INJECTION COMPRESSION in the cavity. This injection compression MOULDING DIFFERENT TO reduces the injection pressure and Being a hybrid machine means that
CONVENTIONAL INJECTION MOULDING? the required clamping force, and this speed and precision are not compromised
It’s all linked to the closure mechanism consequently removes the internal on the El-Exis SP range. This is all
and the consequent clamping pressure stresses from the product, resulting in due to the servo-driven hydraulic
applied within the machine, which helps less warping due to shrinkage. clamp unit, engineered to execute
to reduce shrinkage and ensure even
distribution of the plasticised material in Fill time for injection compression
the cavity. moulding when operating at maximum
speed is 0.2 seconds, with a total cycle
In conventional thin wall injection time of around 3.3 seconds, depending on
moulding, faster filling and higher the application.
pressures are required to drive molten
plastic material into thinner cavities to ARE THERE OTHER ENVIRONMENTAL
prevent it freezing off between shots. BENEFITS?
Sumitomo (SHI) Demag’s UK packaging to research by Smithers Pira*. The value It would be extremely challenging to Yes, switching to injection compression
expert Kevin Heap talks through the of materials used to produce rigid plastic repeatedly accomplish a 0.35mm wall moulding can deliver savings on
commercial and ecological benefits of packaging is also forecast to grow across thickness using this method. energy consumption as a result of the
injection compression moulding and how the same period at an annual rate of 3.9% the technique compares to traditional to reach $202 billion. PE is projected During injection compression moulding, Additionally, because less clamp
moulding of ultra-thin plastic packaging. to be the largest-growing segment plasticised material is introduced into the force is required, thin wall packaging
during this forecast period. Light- cavity prior to complete locking of the manufacturers can opt for a smaller
WHAT IS INJECTION COMPRESSION weighting and consumer convenience
MOULDING? are important factors in this expansion,
The method of pressing material in a with the combination of environmental
mould is quite a common industrial pressures and high polymer prices placing
process, typically using rubber and resin increasing pressures on packaging
and a combination of heat and pressure manufacturers.-
significantly lower clamp force pressure.
precise movements. For high-volume
thin wall packaging manufacturers,
these enhancements aid company
profitability and deliver both the capacity
and flexibility to meet future growth
demands.
Due to speed of production, most
systems integrate robotics. These usually
perform a dual purpose, automating the
placement of labels into the mould and
taking packaging components out of the
mould and stacking them.
uk.sumitomo-shi-demag.eu/
to mould products. It has generally been
Most companies operating in the
used to produce thicker sectioned parts
on slower cycle times, for example, WHY IS IT BENEFICIAL TO PACKAGING? competitive arena produce millions of
optical lens or thermoset applications. Global forecasts for rigid plastics, which packaging containers every year. Volume,
However, the technique hasn’t been is the category thin walled containers sits raw material waste and precision are
applied to the mass-production of in, is predicted to rise at an annual rate fundamental to each company’s financial
polypropylene packaging applications, of 3.7% from 52.9 million tonnes in 2017 viability, with many facilities operating
until recently. to 63.4 million tonnes in 2022, according 20+ machines to meet supplier demand.
20 FDPP - www.fdpp.co.uk
FDPP - www.fdpp.co.uk 21