Environmental impacts of plastic injection moulding

In recent years, the green movement is spreading its effect more than ever, touching all aspects of life. Businesses are being challenged to implement adjustments that reduce their carbon footprint and help the environment. While plastics tend to have a negative reputation in terms of environmental impacts, yet the plastic injection moulding industry could become both economically and environmentally effective, if implemented responsibly and carefully. 

What is plastic injection moulding?

Plastic injection moulding is one of the most essential technologies for mass-producing thermoplastic products without the need for extra finishing. Most plastic injection moulding machines nowadays are universal, meaning they can take any type of mould within certain constraints. This process’s economics are great for items with complicated geometry, providing it an edge over other procedures. Despite the high initial cost of plastic injection moulding equipment, cost per moulding decreases with scale.

Micro moulding is a highly specialised technique in which micro-structured steel or aluminium moulds are CNC and EDM machined to micron or even sub-micron scale tolerances, and the final moulded object could weigh a fraction of a gram or its tiny features. The fundamental distinction between micro moulding and standard moulding technologies is the size of the shot and the precision of the injection equipment. Micro-moulding machines can inject fractions of a gram with great precision because they offer better resolution feed choices, resulting in equal pressure distribution inside the cavity. Micro injection moulding also employs tiny moulds with highly precise core, cavities and features within. 

Environmental impacts of plastic injection moulding

The environmental effects of plastic injection moulding might vary based on the materials used, the method itself and the types of waste created.

Material

Plastic is the key material in plastic injection moulding and its environmental impacts are unavoidable, ranging from the release of greenhouse gas emissions to plastic waste found in rivers and seas. Plastic manufacture requires a lot of energy and can produce pollutants including volatile organic compounds (VOCs), sulphur dioxide and nitrogen oxides. Plastics consumption in the UK creates 26 Mt CO2e per year over the whole life cycle of plastic goods, and 80% of these emissions are caused by production, both in the UK and elsewhere. Plastics, which are sourced from fossil fuels, account for 17% of emissions, with recycling and disposal accounting for just 2.3%. Plastic packaging for end products could also be challenging to be recycled. Along with shifting market needs, alterations in customer awareness and preferences are already influencing the world of injection moulding. 

Customers are concerned about reducing their carbon footprint, and more producers have been able to greatly expand the usage of post-consumer recycled plastics in LDPE-manufactured components. Since April 2021, virtually all LDPE goods manufactured at the UK site have been made with at least 40% recycled polymers, with no loss in quality or performance.

Metals and other materials used in injection moulding can also potentially have various environmental impacts. Metal manufacturing, such as aluminium and steel, may also be energy-intensive and polluting. The utilisation of recycled resources, such as recycled plastics, can assist lessen the environmental effect of injection moulding materials, however, it might not be always possible for components used for medical purposes. 

Energy 

The plastic injection moulding technique and technology can potentially have an influence on the environment. Injection moulding machines consume a lot of energy, and this energy can contribute to air pollution. Furthermore, the process can produce a lot of heat, which might contribute to global warming. In general, the energy efficiency of the process varies depending on the melt temperature, component weight, cycle duration, machine size, and machine efficiency. The specific energy usage of 0.3 kWh/kg is particularly efficient for thin-walled components with short cycles, and 0.6 kWh/kg might be efficient for a thicker part moulded more slowly (H. Schut, 2015). However, with a particular emphasis on the environmental effect of injection moulding, engineering developments imply that injection moulding machinery now uses 20%-50% less energy than it did 10 years ago (H. Schut, 2015). You can check the estimated energy consumption of plastic injection moulding machines using this calculator. 

The accuracy of the electric devices allows for improved repeatability, lower noise, quicker injection times and higher energy efficiency thanks to dynamic servo-motors with breathtaking acceleration capability. Electric injection moulding machines only utilise energy while they are in operation, which means that the motor output is only equal to the load needs, hence they are more energy efficient than the traditional moulding machines.

Cycle wise, the base load (energy spent when the machine is idling, such as during cooling stages) can account for 75% or more of total energy consumption in ordinary hydraulic machines, while in all-electric and hybrid machines, the base loads are typically in the 10-20% range and are primarily accounted for by barrel heating since motors only run when needed (Mobil).  A high base load may suggest that the equipment is over-sized for the operation. In addition, injection moulding companies could improve their environmental performance by prioritising using renewable energy,  along with frequent equipment maintenance, energy audit or applying the latest energy like Internet of thing (IoT). For instance, the new SmartPower injection moulding machines of Wittmann Battenfeld are 6 times more energy efficient and 6 times less expensive to operate when compared to the early 1990’s generations. That’s why Micro Systems carefully manage energy use by only using the most-advanced, energy-efficient machinery, frequently conducting maintenance and constantly improving our human and manufacturing resources. 

Current all-electric moulding machines use energy ratios that are equivalent to those of previous hydraulic machines, but overall energy usage is around 50% less (Photo: Micro Systems)

Waste

Plastic injection moulding generates a significant amount of plastic scrap, which can be difficult to recycle. This plastic debris might end up in landfills and take hundreds of years to disintegrate, releasing harmful compounds into the environment and polluting the air, water, and soil. 

Plastic sprues are common waste materials produced during the moulding process. Sprues are the bits of plastic that remain after the procedure is completed, which can be recycled locally. For example, at Micro Systems, we use a local recycling firm to re-granulate our plastic waste, including sprues as it is not just excellent for the environment, but also helps us reduce our carbon footprint by hiring local businesses to perform this service.

In addition, if manufacturers can optimise the volume, temperature, design and injection pressure of the polymer, they can ensure that the finished product is flawless without any fault, so almost-to-none of the (virgin) plastic used is wasted. When feasible, creating the ultimate mould design also means eliminating flash (extra plastic) and sprues, hence less waste is generated.

Micro injection moulded parts for medical uses (Photo: Micro Systems)

With the development of technology, together with extensive expertise and knowledge, injection moulding manufacturers are getting more and more environmentally friendly, producing millions of parts a year at a lower carbon footprint. At Micro Systems, we are committed to operating with responsibility at all stages throughout our production process, such that we can fully support our customers on their journey towards sustainability in business.

Check out our 2022 CSR Report here!

References:

H. Schut, J. (no date) Plastics Engineering – March 2015, Eco-Molding: More Power for Less Energy. Available at: http://read.nxtbook.com/wiley/plasticsengineering/march2015/coverstory_ecomolding.html (Accessed: 19 May 2023).
Mobil (ed.) (no date) An Energy Saving Guide for Plastic Injection Molding Machines. Applied Market Information in association with Tangram Technology.

Micro Systems is a well-established supplier in micro plastic injection moulding, offering considerable experiences in micro moulds, the design, manufacture, FAT and validation of multi cavity valve gate high volume injection moulds for the medical, pharmaceutical and ophthalmic markets. In our local community and in injection moulding across the world, we seek to be a paradigm for sustainability in design and manufacture. For more information, please Contact us or visit our website.