Faster cycle times, longer mold life, improved part tolerances: the challenges faced by the molders are the same everywhere in the world. A way to meet all these challenges is to choose the right material alloys for the mold, to replace conventional mold steels in parts such as inserts, slides or plates. However, it is hard to justify the economy of these decisions without information about the achievable cycle time reduction.

A technical product for an automotive application was running in production at a longer cycle time than calculated. SIGMASOFT Virtual Molding was used to examine the cause and find a solution.

The slides of the mold were made of conventional tool steel, which has a heat conductivity of 45 W/m2K. The analysis with SIGMASOFT Virtual Molding technology considered the complete mold, with all its components, reproducing exactly the same processing conditions as in reality over several cycles. As a result, the temperature distribution was obtained on the slide and core at the beginning of each molding cycle, as seen on the left side of Figure 1. Though the targeted mold temperature was 80°C, some spots in the mold reached temperatures over 147°C, leading to longer – and expensive – cycle times.


As solution approach it was suggested to evaluate the possibility of changing the mold material. Two alternatives were considered: a copper-beryllium based alloy and a hot-work tool steel. “In both cases the objective was to reduce the cycle time, ensuring the required part quality and a long tooling life”, stated Manuel Schmellenkamp, SIGMA engineer in charge of the project.

A first analysis was run using a copper beryllium-based alloy. Because of its very high heat conductivity, close to 100 W/m²K, the ability of the mold to transport the energy from the melt to the cooling channels is larger, leading to a smooth temperature distribution in the mold surface. The temperature in the hot spots dropped from 147°C to about 92°C, and the mean mold temperature from 95°C to around 85°C. “It was a substantial improvement in the mold temperature”, Schmellenkamp explained. “However, the molder was concerned with the lower hardness of the alloy, which may lead to wear and reduced mold life”. The typical hardness for this type of material is 33 HRC.
A second analysis considered the possibility of using special hot-work tool steel. This material has a higher thermal conductivity than regular tool steel (60 W/m² K), and though the ability to remove energy from the melt is not as high as with the copper-beryllium alloy, it delivers a higher wear resistance, due to its improved hardness (around 44 HRC).

The SIGMASOFT Virtual Molding analysis proved that the hot spot temperature could be reduced from around 147°C to 120°C and in some regions from 119°C to 102°C, as seen on the right side of Figure 1. “This material selection delivered the best compromise between both worlds: high wearing resistance and high thermal conductivity”, concluded Schmellenkamp. “The molding cycle was reduced by 20% without changing the mold design”.

According to Schmellenkamp, this increase in productivity is easily achievable in existing molds. “It is not uncommon to accomplish this reduction in cycle time for several molds already built and in production within a single company, so that up to 15% more parts can be produced in the same time”. Another advantage is to gain insight in the way the mold works. “The reason why production failures appear becomes clear with SIGMASOFT Virtual Molding. The molder is empowered with more information, so that he is able to strengthen his position as a high-tech provider in front of his costumers: no more trial-and-error involved, no more expensive delays”. Schmellenkamp also highlights the ease-of-use of the tool: “A project can run within 15 minutes, so that several concepts can be tried easily. The design can be optimized even before the mold is built”.

About Sigma
SIGMA (www.sigmasoft.de) is 100% owned by MAGMA (www.magmasoft.de), the world market leader in casting process simulation technology based in Aachen, Germany. Our SIGMASOFT process simulation solution optimizes the manufacturing process for injection molded plastic components. SIGMASOFT combines the 3D geometry of the parts and runners with the complete mold assembly and temperature control system and incorporates the actual production process to develop a turnkey injection mold with an optimized process.

At SIGMA and MAGMA, our goal is to help our customers achieve required part quality during the first trial. The two product lines – injection molded polymers and metal castings – share the same 3D simulation technologies focused on the simultaneous optimization of design and process. SIGMASOFT thus includes a variety of process-specific models and 3D simulation methods developed, validated and constantly improved for over 25 years. A process-driven simulation tool, SIGMASOFT, with its comprehensive simulation approach, provides a tremendous benefit to production facilities. Imagine your business when every mold you build produces required quality the first time, every time. That is our goal. This technology cannot be compared to any other conventional “Design” simulation approach employed in plastics injection molding.