Mixing nozzles to reduce streaking without using more colour

At Fakuma 2024, Swiss manufacturer Promix will be presenting, among other products, mixing nozzles that replace open nozzles to solve quality problems in injection moulding, such as streaks that can affect the surface finish of parts, without having to increase the amount of material and colour or energy used.

Injection moulding companies today face a variety of challenges. On one hand, they have to ensure consistently high product quality despite varying raw material sources and quality. On the other hand, they need to meet technical requirements like accuracy of fit and appearance, while keeping energy and material costs low.

Occurring quality problems are often solved by modifying the process parameters. However, in many cases this does not always solve the problem sustainably, but only shifts it. For example, colour streaks can be smoothed out by overdosing the color batch, yet this results in higher colour consumption. Other measures to make the melt more uniform include increasing the back pressure, temperature and screw speed. However, this will result in a higher melt temperature, which can cause warpage during cooling. Moreover, the increased energy input increases the cycle time.

Using a Promix mixing nozzle can solve these problems at the source. The result is a streak-free part, without excess colouring or additional energy input. The mixing nozzle is mounted instead of the open nozzle and equalizes the colour distribution right before the mould. This usually reduces the amount of colorant required by 30-50%. Given the cost of masterbatch or liquid colour, this is a significant factor. The lower energy input also makes it possible to reduce cycle time and increase machine productivity. Tolerance deviations and warpage are significantly reduced due to the lower temperature, leading to a lower scrap rate. The mixing nozzle also facilitates the mixing of recycled material and enables a higher proportion of regrind or recycled material without visible quality losses.