4 Replies Latest reply on Jul 15, 2015 1:40 AM by Lingesh Sangur

    mold flow analysis

    Lingesh Sangur

      Hi,

      I am doing a mold flow analysis for a plastic component.Analysis is finished and i can see FILL TIME and FLOW PRESSURE AT END OF FILL and its easy to understand,

      But i want to know whether the molded part is sound without any defects such as non uniform cooling rate,cold shut etc..How can i check these things?

       

      Thanks,

        • Re: mold flow analysis
          Radoslaw Szmid

          Hello,

           

          If you want to see the effect of differential cooling you will have to model the complete cooling circuit and then run COOL analysis (available in Plastics Premium only).

          If by cold shut you mean jetting then before running your flow analysis go to Fill Settings/Advanced/Options and change the " Volume of fluid Algorithm" from Indirect to Direct.

           

          Btw, how big is your part?

          I understand it's a rough idea but I'm wondering what's the reason to put so many injection points...?

          What's more some of them might be located in a difficult areas from the tooling point view.

           

          Regards

          Radek

            • Re: mold flow analysis
              Lingesh Sangur

              Thanks Mr Radoslaw,

              As for the size of the part,its 37"htx7"w..I tried to give 3 injecion points but its not reaching other corner points,so gave more..

               

              More importantly,i want to know how to come to conclusion like whether the part is sound or has any defects.bcos,as observed from the plot some portion cools instantly while some portion takes time..so does that result in any defect or is that ok? on what basis we decide whether the result is right or not?

               

              Also is it possible to check the cooling rate.bcoz non uniform cooling rate results in defects..

               

              And if you have done any mold analysis, can you share result plots so that i can understand?

               

              Thanks again...

                • Re: mold flow analysis
                  Radoslaw Szmid

                  Hello,

                   

                  Unfortunatelly what you're asking is impossible to answer in a one single post.

                  I don't know what is your current experience but it is all about engineering judgment which I'm affraid takes years to build to only find out it's a never ending process...

                  What I would suggest as a main step is to start reading as much as you can about plastic part design - the overall rules, good practices etc. followed by mold design rules (especially the limitations that we got there),the whole injection molding process,plastics rheology (a big task) and then simulation at the end...

                  Sounds kinda scary but if you want to be serious about it, you'll quickly realize that there are no shortcuts.

                   

                  You already asked if we may expect any deffects in your part...

                  Even without performing a single simulation my answer is simple "yes".

                  I don't know if it's a visual part but with your current design, you will definitelly get poor aesthetics - visible sink marks in the areas where the bosses are conneted to the side/top walls.Same issues on top surface due to reinforcement rib/wall thickness ratio.

                  This is a classic box example - due to cornering effect, no reinforcement ribs and without proper mold cooling (especially at the core side), your side walls will bend inward - for how much? This is still the most difficult question to answer. You may get some values after performing the warpage analysis but in reality you'll often find out the deformation to be 2 times higher than those predicted especially for semicrystalline grades.

                  As for the cooling time - it's obvious that it will take more time to extract the heat from the thicker areas hence longer cooling times. That is why the main rule in plastic part design is to always try keep your wall thickness as uniform as possible.

                  Then there's the whole mold cooling task - the differece between the core/cavity surface temperature should be as low as possible (few degrees). It is often difficult to properly extract the heat from deep cores (and the corners) - such differential cooling will again have a great impact on further part deformations.

                   

                  I can assure you that at least 80% theory behind it there for free...

                  Then it comes practice (including real shop flor experience) and you overall patience and dedication!:)

                   

                  Regards

                  Radek

                    • Re: mold flow analysis
                      Lingesh Sangur

                      Hi Radoslaw,

                      Thanks for taking time in explaining..

                      I have one more question..

                      This (rain water) filter part is supposed to operate at a height of 15 mtrs.How can i consider this height parameter(if necessary) while doing CFD Analysis? My understanding is height has no effect on performance of filter..