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Weld lines prediction: from the Injection Molding Simulation into the Structural Simulation

With aid of the interface SIGMALINK®, the weld lines predicted with the injection molding simulation software SIGMASOFT® can now be mapped into Finite Element Analysis Software and be considered in the structural design of injection molded parts

The tracer technology in SIGMASOFT® allows visualizing the fully 3D profile of weld lines over the part thickness. With SIGMALINK this information can now be mapped into structural FEA.

Schaumburg, IL – Sigma Plastic Services, presents a new functionality of its injection molding simulation software SIGMASOFT®. The simulation of the cavity filling in injection molding allows identifying regions where weld lines are formed, not only on the surface but also through the part’s thickness, with a completely 3D approach. With the interface SIGMALINK® it is now possible to transfer this 3D information into FEA (Finite Element Analysis) Software, to consider the drop in mechanical properties in these regions when performing structural design. A particular advantage of SIGMASOFT® is the fully 3D prediction of the weld lines, which reproduces the weld regions not only on the surface, but also through the part’s thickness, as it occurs in reality.

Weld lines occur as a consequence of the collision of two (or more) flow fronts in the cavity of a mold. This disruption in the homogeneity of the injection molded part causes optical defects, which compromise the surface quality, but also produces a weakening from the mechanical point of view and, under certain circumstances, weld lines can even act as stress concentrators. Therefore, there is a loss in the mechanical properties in the regions where weld lines appear.

Using the “tracer” technology, which has been available for years in SIGMASOFT®, the appearance of weld lines can be reproduced during the filling stage. The location of the weld lines can be described precisely and an indication is given regarding how critical they are. The formation of the weld lines during the filling stage and the way they flow as the packing pressure is applied are predicted accurately in a 3D approach.

The interface SIGMALINK enables exporting (mapping) physical and flow-related properties into commercial software for FEA (such as Ansys, Abaqus, Radios, etc.). Factors such as flow and thermal induced stresses and fiber orientation can be considered in the FEA. With a further expansion of SIGMALINK® it is now possible to export the information about the final position and 3D profile of the weld lines in the structural FEA. In this way, the drop in the mechanical properties produced by the apparition of weld lines can also be considered in the mechanical part design.

In Figure 1 the formation of a weld line region in SIGMASOFT® is presented. The flow front is depicted in grey. The “tracer” particles in orange show clearly that the melt fronts do not collide in a flat region, but that this weld line has a complex 3D profile at the end of the filling and packaging phases.


SIGMA (www.sigmasoft.de) is 100% owned by MAGMA (www.magmasoft.de), the 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 and 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 use 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.

New product success requires a different communication between designs, materials, and processes that design simulation is not meant for. SIGMASOFT® provides this communication. SIGMA support engineers, with 450 years of combined technical education and practical experience, can support your engineering goals with applications specific solutions. SIGMA offers direct sales, engineering, training, implementation, and support, by plastics engineers worldwide.

For further information on this announcement, interested parties should contact:

Christof Heisser or Matt Proske

SIGMA Plastic Services, Inc.

10 N. Martingale Road, Suite 425

Schaumburg, Illinois 60173


Phone:  +1 847 558 5600

Email:  cheisser@3dsigma.com or mproske@3dsigma.com

Web: www.3dsigma.com

Agency contact for SIGMA:

Wendy McCormick

Bernard & Company

Palatine, Illinois (Chicago)


+1 847 934 4500



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