HOT RUNNERS | TECHNOLOGY
3D printing tool inserts for foam moulding
SKZ, the plastics research and services centre based in Würzburg, Germany, has started the ADDfoam project using additively manufactured tool inserts to enable the injection moulding of high-quality foamed components with superior surfaces. 3D printing of mould inserts for small series production has grown as an alternative to conventional tool making, which is time-consuming and cost-intensive. However, SKZ says the use of additively manufactured tool inserts for injection moulding pre- sents new challenges and requires rethinking process management. For example, the heat transfer properties of the mould largely determine the degree of crystallisation and the shrinkage behaviour, so inserts made of plastic require longer cooling times. Also, the cyclical forces of the clamping unit and the ejector lead to rapid failure of the mould, it says. By combining additively manufac-
Left: 3D printed tool inserts produced in the SKZ ADDfoam project
tured tool inserts with foam injection moulding, the disadvantages of the respective technologies are compen- sated for in a cost-efficient manner, says SKZ. The saving of the holding pressure phase during foaming, the lower melt temperature of the gas-laden melt and the reduced mass of the component lead to a significant reduction in cycle times. The lower internal mould pressures in the foam moulding process significantly reduce the cyclical load for additively
same process conditions regardless of mould size. Elimination of the scaling effects leads to faster qualification time from pilot to product tooling while reducing risk. Husky says that typical design rules for injection moulding do not apply with the UltraShot Injection System. The technology delivers high pressure at the gate with greater control than conventional injection moulding systems. This means that parts can be designed the way they need to be and not constrained by the requirements of the injection moulding process. Parts completed with other processes or post-mould assembly can now be produced in a single injection moulding cycle. Compared to conventional hot runners, Husky
says that melt in the UltraShot Injection System experiences fewer high-pressure injection cycles, preserving the original resin properties. This leads to lower moulded-in stress and better mechanical and optical properties in the moulded part. The UltraShot is powered by the Altanium Mold
Controller, which provides an advanced process monitoring and control for injection moulding. Injection is performed with electric servo motors providing accurate and repeatable performance. The controller offers real-time visual graphing of
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manufactured tool inserts, it says. In the ADDfoam research work, the dimensional accuracy and reproduc- ibility as well as the surface properties are examined depending on various production parameters for both the tool inserts and the injection moulded lightweight components. Another research focus in the project is on the durability of the printed synthetic resin tools and the effect of their use on the mechanics and optics of foamed components.
key injection parameters. In addition, each param- eter can be set with tolerance bands and alarm outputs to give control of the injection moulding process. The controller integrates hot runner temperature and mould servo control in the same unit, says Husky. At Fakuma, the latest addition to Husky’s hot runner portfolio was also shown. Pronto Direct “offers outstanding flexibility, value and performance and is ideal for automotive, packaging and consumer electronics part moulding” the group says. Mold-Masters introduced a number of new developments at Fakuma 2021, including its new PET-Series hot runner system for preform produc- tion. The system gives the customer the ability to fill thinner PET preforms to reduce material use due to better hot runner balance and less variation in preform weight. It also features a reduction in cycle time due to faster fill time and a wider process window along with a reduction of AA content. PET-Series is compatible with any major brand of pet-preform mould and is available in a wide range of industry standard configurations, plus optional custom configurations.
Mold-Masters announced that its co-injection multi-layer systems are now available for injecting
November/December 2021 | INJECTION WORLD 41
IMAGE: SKZ
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