Polymer Injec­tion Molding: Shape Opti­miza­tion with CFD

Klaus Straka is one of our absolutely amazing CAESES® users, who is active in the field of polymer injec­tion molding. In the context of fully-auto­mated shape opti­miza­tion with CFD (fluid flow sim­u­la­tion), he creates incred­i­ble para­met­ric geome­tries with CAESES® that are pretty complex and highly chal­leng­ing. We are happy to share a few insights with you through an inter­view with Klaus.

Polymer Injec­tion Molding: Geometry Modeling, Sim­u­la­tion and Optimization

Inter­view with Klaus Straka, JKU Linz

FS: Hi Klaus! Can you first describe the industry and the appli­ca­tions you are involved in?

Klaus: At the Insti­tute of Polymer Injec­tion Moulding and Process Automa­tion (ipim) of the Johannes Kepler Uni­ver­sity in Linz / Austria (JKU) we are working on process sim­u­la­tion and opti­miza­tion in the field of polymer pro­cess­ing, and more specific, polymer injec­tion molding. The appli­ca­tions cover polymer felt flow sim­u­la­tions in screw plas­ti­ciz­ing units with respect to mixing effi­ciency, the sim­u­la­tion of the injec­tion molding process and thermal sim­u­la­tions of the injec­tion molding modules.

FS: How did you get into this specific field of engineering?

Klaus: After I finished the study of mecha­tron­ics at the JKU I worked a few years in industry as a control system engineer for injec­tion molding machines. When the ipim was founded in 2009 I returned to the JKU and started to inves­ti­gate mixing behavior in plas­ti­ciz­ing screws on exper­i­ments and simulations.

FS: What is your personal field of expertise?

Klaus: My field of exper­tise lies in com­pu­ta­tional methods for fluid dynamics with respect to polymer melt flow and mea­sure­ment system engi­neer­ing. The latter is impor­tant to judge the cor­rect­ness of the results of CFD sim­u­la­tion results.

FS: What project do you work on at the moment?

Klaus: I am still working on the sim­u­la­tion of thermal and optical polymer melt homo­gene­ity in screw plas­ti­ciz­ing units and there is plenty of work to do.

FS: What are the most chal­leng­ing parts of this project?

Klaus: In the past the most chal­leng­ing parts have been the exten­sion of the numer­i­cal methods and the imple­men­ta­tion of a high-order particle tracking method in the used CFD software. Now, the para­met­ric descrip­tion of the complex geome­tries as well as the gen­er­a­tion of a suitable numer­i­cal grid is somewhat time con­sum­ing. And finally the inter­ac­tion of several software tools makes the design studies error-prone.

FS: Which software solu­tions do you use for your engi­neer­ing tasks?

Klaus: For the CFD part we use the open source package OpenFOAM which we extended to cor­rectly model the flow of polymer melts. For post pro­cess­ing of sim­u­la­tion and mea­sure­ments we typ­i­cally use MATLAB as it is fast and com­par­a­tively easy to use. In the past the descrip­tion of the screw geome­tries and flow domains was done with PTC Creo, which is now done by CAESES.

FS: How does CAESES further support you in your work?

Klaus: CAESES sim­pli­fies and reduces errors in the engi­neer­ing work as it is possible to highly automate the workflow. First and foremost, CAESES is quite powerful in the para­met­ric descrip­tion of my target geome­tries. Next, it is quite easy to auto­mat­i­cally adapt input files for OpenFOAM, the so-called dic­tio­nar­ies, prior to the sim­u­la­tion. The same is true for my MATLAB post pro­cess­ing scripts. And once the process is set up cor­rectly for a base geometry, you can perform design studies with nearly no effort. 

FS: What do you like about CAESES, what do you think makes it unique?

Klaus: What I like best is the smooth inter­ac­tion of CAESES with OpenFOAM and MATLAB and the above described ability to automate the engi­neer­ing process. In my case, this is varying geometry para­me­ter of a screw head, start a sim­u­la­tion in OpenFOAM, do the post pro­cess­ing in MATLAB and analyze the results in a single software environment.

FS: What are your time frame and the rough schedule for your current work?

Klaus: By now, the geometry setup and per­form­ing design studies for screw mixing heads runs rea­son­ably well and stable. In the near future it is planned to take a closer look on the opti­miza­tion capa­bil­i­ties of CAESES. I am con­fi­dent that this feature will reduce the amount of sim­u­la­tion time nec­es­sary to improve the mixing ability of plas­ti­ciz­ing screw heads.

FS: Klaus, thanks a lot for sharing this inter­est­ing insights and for allowing us to publish these impres­sive geometries! 

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