In-house Recycling: Economical Plastics Recycling for the Injection Molding Industry

Rising raw material prices, sustainability pressure and the development of a circular economy are presenting the injection molding industry with new challenges. With in-house recycling, which integrates waste directly back into production, WITTMANN offers a solution that not only reduces costs but also protects the environment.

In an interview with K-Mag, Michael Wittmann talks about solutions for a more sustainable plastics industry, the S-Max 2 granulators from WITTMANN and the role of digitalisation for a functioning circular economy.

Mr Wittmann, what challenges is the injection molding industry currently facing?

Michael Wittmann: The challenges are manifold, first and foremost the development of a circular economy for plastics. It is our goal and our responsibility as a plastics industry to ensure that no more plastic materials end up in the environment – worldwide. To achieve this, we need to provide information and education, establish and expand structures – such as collection systems and recycling capacities - and develop new technologies for even more efficient and higher-quality recycling. Efficient, because sustainability must always pay off so that everyone can participate. High-quality, because we still downcycle too much. But that is precisely a dead end.

To really keep materials in the cycle, we need to ensure that products made from recycled material fulfil the same requirements and have the same properties as the products from which the recycled material was obtained.

What technical challenges arise when integrating recycled materials into the injection molding process, and how do the S-Max 2 granulators from WITTMANN help to overcome them?

Wittmann: There are various recycling processes. With our granulators, we are active in the field of mechanical recycling. The granulators are used directly in the plastics processing plant and make it possible for production waste, such as sprues and rejects, to be ground on site and fed back into the injection molding machine.

The advantages are waste-free production and easy access to unmixed recyclate. This in-house recycling enables processors to fulfil prescribed recyclate usage quotas very cost-effectively. The cost of purchasing raw materials is reduced and the cost of disposing of production waste is also saved. As far as the technical challenges are concerned, it is all about constant processes, which we achieve through digital assistance. There are no further technical challenges for the injection moulding machine. It makes no difference to the machine whether it processes virgin material or recycled material.

Four S-Max 2 granulators from WITTMANN are used for in-house recycling in the new recycling centre of a well-known manufacturer of electronic components. Copyright: WITTMANN

Processing plastics with a high glass fibre content often places special demands on the grinder. What properties of your S-Max 2 granulators enable efficient processing of materials with a high glass fibre content?

Wittmann: When choosing a granulator, it is always important to consider the material, just as when selecting injection moulding machines and peripherals. Classic granulators are sufficient for most materials. We have developed special surfaces for particularly abrasive materials, such as glass fibre-reinforced plastics. The grinding principle of the S-Max 2 also reduces wear. The S-Max 2 works with toothed rollers and low speeds, which means a high torque with a reduced mechanical load. This means that the S-Max 2 grinders achieve long service lives even when grinding abrasive materials.

The S-Max 2 grinders amortise after just six months. What factors contribute to this rapid amortisation?

Wittmann: The amortisation time always depends on the application. It is often even less than six months. The rule is: the more expensive the raw materials and the higher the proportion of recycled material, the faster the investment in a granulator for in-house recycling pays for itself.

How does this affect the competitiveness of your customers?

Wittmann: A customer from the electronics industry recently told us that he can only achieve competitive unit costs by using recycled material. He has therefore set up a recycling centre with four S-Max 2 granulators in the injection moulding production facility. Since the start of the in-house recycling project, the consumption of virgin material has fallen continuously, which is directly reflected in the unit costs and thus strengthens competitiveness. He can add up to 25% recyclate to his products.

What role do digitalisation and automation play in the recycling process?

Wittmann: Both topics play a very important role, with different effects being achieved independently of each other. Automation is a must in plastics processing companies, especially in high-wage countries. And this doesn't just refer to automated parts handling through the integration of robots into the injection moulding machines. Our granulators also achieve a high degree of automation. For example, the automatic self-tensioning system in our granulators eliminates the need for constant retensioning of the drive belt, meaning that the granulators can be operated maintenance-free. There is a level sensor in the grinder's grist container for automatic emptying of the grist container.

We use digital assistance in the injection moulding machine to achieve a constant process. The quality of recycled materials – especially PCR from municipal collections - is subject to greater fluctuations than the quality of virgin material. This is precisely where HiQ Flow comes in. The software determines the viscosity of the plastic melt during the injection phase. If the viscosity deviates from the reference value, it adjusts the processing parameters to the current conditions in order to keep the component weight constant. This happens in fractions of a second and this is precisely where the great opportunity of digitalisation lies. The production of rejects can thus be proactively prevented.

What challenges do you see for your customers in the coming years, and how will WITTMANN support them in mastering them?

Wittmann: Many of the current challenges result from legal requirements. The EU wants to be climate-neutral by 2050. This also obliges manufacturing companies to gradually reduce their CO2 emissions, which brings the product carbon footprint (PCF) into focus. Information about the carbon footprint of individual products is a prerequisite for implementing effective measures to reduce greenhouse gas emissions. So it's all about transparency. This is because emissions from the entire life cycle of a product – from raw material extraction to recycling – are included in the PCF. The calculation can be correspondingly laborious.

We are simplifying this process for our customers with new software. In future, the software will be available as a new functionality of TEMI+, the WITTMANN Group's MES. We have also developed our own software to determine the energy consumption of the production cell required for the calculation. iMAGOxt makes the energy consumption of each individual consumer within the production cell transparent cycle by cycle.