Topology Optimization Lifts the Weight for Injection Molding
Michael Molitch-Hou posted on August 16, 2017 |

With 3D printing, the promise has become the ability to manufacture end parts, on demand and often with unique geometries that could not be produced using any other technology. In fact, this emerging area of generative design opens up previously impossible shapes that can reduce the material and weight of a 3D-printed part while increasing its efficiency.

A topology optimized injection mold, created with Altair software and 3D printed by PROTIQ. (Image courtesy of Altair.)
A topology optimized injection mold, created with Altair software and 3D printed by PROTIQ. (Image courtesy of Altair.)

Although end parts may be the promise, manufacturers are quickly understanding that 3D printing can be leveraged during the manufacturing process itself in ways that bring efficiency and cost reduction to the operation. More traditionally, this has come in the form of 3D-printed manufacturing aids, such as jigs and fixtures, but one company, PROTIQ, has found that, by combining simulation, topology optimization and 3D printing, it’s possible to reap unprecedented benefits in injection molding, as well.

ENGINEERING.com spoke to Ralf Gärtner, managing director of PROTIQ, to learn how the company uses simulation tools from Altair to engineer and 3D print injection molds as a part of its 3D printing service.

Bringing Topology Optimization to Injection Moldmaking

Before leading the PROTIQ team, Gärtner was responsible for the injection molding tool shop at electrical product manufacturer and service company Phoenix Contact Worldwide. As such, Gärtner headed to the Inside 3D Printing event in Berlin, where he attended a talk on simulation and topology optimization from one of the team members at Altair.

“[During the talk], I wondered how injection molding would look if we combined all of the forces to mold to copper into a simulation program,” Gärtner said. “What would such a structure look like? Would it look like kind of a root? Would it change completely the size or the geometry?”

From that point on, Gärtner began working with Altair’s consulting unit to apply topology optimization to injection molding tools. Whereas Gärtner did not have a complete grasp of simulation tools, Altair did not necessarily have a complete grasp of injection molding. By working together, according to Gärtner, the two could build a bridge from each knowledge base and meet in the middle.

Simulating an Injection Mold

Altair took the geometry from PROTIQ and, together, the two firms defined the load cases and boundary conditions. Altair’s engineers then created the optimization model in HyperMesh, the pre-processor that is integrated into HyperWorks. Topology optimization is performed using the model in Altair’s finite element (FE) solver and optimization tool, OptiStruct.

Of the structural optimization process, Gärtner explained that the loads taken into consideration during the optimization process were those typically associated with closing an injection mold, injecting the material and allowing the mold to cool: gravity loading, pressure distribution in the cavity, the closing force applied to the mold to ensure that it doesn’t open during the molding process, and additional pressure at the location where the hot runner nozzle hits the tool.

According to Gärtner, the result was actually quite an interesting one, as it applies to injection molding overall. “The topology optimization enabled a very clear identification of the main load path, leading to the interesting conclusion that the bulk of material is actually not required for strength purpose[s], giving more opportunity for weight reduction.”

OptiStruct was used once again to validate the optimization result and perform more FE analyses. To simulate the tempering of the injection mold, Altair also leveraged the software suite’s CFD tool, AcuSolve. This made it possible to understand the cooling behavior of the part and the necessary cycle time. The resulting optimization was further refined and prepped for 3D printing with solidThinking Evolve.

Topology optimization was performed in HyperWorks, with material added only where necessary for the required stiffness and strength. The use of conformal tempering reduces thermal deformation, resulting in shortened cycle times and improved component quality. These cooling channels can be directly 3D printed into the design. (Images courtesy of Altair.)
Topology optimization was performed in HyperWorks, with material added only where necessary for the required stiffness and strength. The use of conformal tempering reduces thermal deformation, resulting in shortened cycle times and improved component quality. These cooling channels can be directly 3D printed into the design. (Images courtesy of Altair.)

Although the part would be used for the heat-intensive process of injection molding, it was only optimized for structural loads. Gärtner, however, pointed out that “there is no restriction on the optimization capability wise,” meaning that such a design could be optimized for thermal behavior in the future.

“The structural optimization was decoupled from the thermal behavior,” Gärtner said. “The cooling channels were added in a manual way after the structural optimization as close to the plastic part as possible. Conformal tempering (as cooling channels are at this point included rather at the end of the development process) has been implemented manually and verified with comparative analysis using AcuSolve.”

Running the injection molding tool through simulations until the partners achieved the proper geometry, Gärtner found that the result did, in fact, look like the root of a tree. More importantly, he learned that using this process removed 75 percent of the weight from the mold. For the injection molding industry, this has more significance than simply reducing the amount of material that would be used to make the mold.

Text Box: The temperature distribution before (above) and after (below) topology optimization. (Image courtesy of Altair.)

Text Box: The temperature distribution before (above) and after (below) topology optimization. (Image courtesy of Altair.)

“We figured out that this tool could be changed in the injection molding machine without using any extra tools, just by hand. By replacing the injection molding tool with one that’s light enough to be changed out manually, it’s possible to speed up the tool changing process in the injection molding process.”

On top of reducing the overall weight of the mold, Gärtner and his team wereable to incorporate conformal cooling channels into the tool, thus cutting the cooling time of the part dramatically. Whereas a typical injection molding tool might take 9 or 10 seconds to cool, the topology optimized part could cool in just 3.2 seconds.

“That is very, very fast cooling time. Therefore, this is very efficient when it comes to the total cost of ownership, reducing cycle times and, in turn, reducing manufacturing costs.”

3D Printing Injection Molds as a Service

In the process of creating this mold design, Gärtner had stumbled across something very new to the field of injection molding. As he explains it, not many people seem to be applying topology optimization or even much simulation to injection molding.

“The industry talks about flow simulation for plastics, for example,” he explained. “Everyone knows that the information I can get from simulation will increase efficiency when setting up and using the mold. But only a small percentage is really using flow simulation. With topology optimization, it’s the same. Everyone knows about its benefits, but not many are employing [them].”

It’s possible that injection mold manufacturers could begin to apply topology optimization in OptiStruct, according to Sridhar Ravikoti, marketing director for HyperWorks. “OptiStruct, the structural analysis and optimization code for linear and nonlinear load cases includes multi-physics optimizations, including for topology,” Ravikoti said. “As the analysis engine behind Inspire and Inspire Unlimited, some of the OptiStruct functionalities will be made available in future versions in addition to what’s already available.”

Until firms begin deploying topology optimization inhouse, however, injection molding companies can already begin adopting the practice through a third party led by Ralf Gärtner. Seeing the benefits that the technology could bring to injection molding, however, Phoenix Contact was convinced and, as a result, established PROTIQ, a subsidiary entirely dedicated to 3D printing, simulation and engineering services, and producing injection molding tools.

Earlier this year, PROTIQ purchased Altair’s simulation software and had Altair train its staff in how to deploy topology optimization and other simulation tools to designs that could then be 3D printed on PROTIQ’s own 3D printers.

“Since we are able to perform mold production very quickly, people are now being able to use topology optimization through PROTIQ. We offer this technology to our customers as well to contract with them to find new solutions for them offering topology optimization by the Altair software suite and then to, of course, print them into being in our AM machines,” explained Gärtner.

Now that he’s in charge of PROTIQ, Gärtner said, “I am fascinated by 3D printing. It’s a perfect technology change with this technology combination of simulation and 3D printing. We are trying hard to get in contact with new customers for bending tools or injection molding tools, together with suppliers of automotive [parts], and they’re starting to think about it. This thinking process, especially in big companies, as I can see, takes years.”

It may take time for businesses to understand the benefits that topology optimization, simulation and 3D printing bring to the world of injection molding, but having already seen the industry increasingly adopt AM for tooling, we have little doubt that it will happen.


Altair has sponsored ENGINEERING.com to write this article. All opinions are mine, except where quoted or stated otherwise. —Michael Molitch-Hou


Recommended For You