128271 Error , Short shot problem

[jandmnik]

Hello

I run a Fill+Pack analyses in MD and DD and 3D mesh type.Material is Hostaform ,Ticona ,c9021.this box has a thin section of 0.4 mm .The general thickness is 1.4 mm.In MD and DD I have short shot but in 3D I don’t.

In molding window ,there is no evidence that part would be faced fill problem and everything is OK and the recommended parameters are :

Recommended Mold Temperature   :       92.78 C,

Recommended Melt Temperature   :      193.33 C 

Recommended Injection Time     :      1.0516 s

But in fill+Pack they are not suitable.

I increased the mold and melt temperature up to maximum , based on data sheet

Mold temperature range to analyze                 

      from mold temperature                           =        75.0 C

      to   mold temperature                           =        95.0 C

   Melt temperature range to analyze                  

      from melt temperature                           =       180.0 C

      to   melt temperature                           =       200.0 C

and I decrease the fill time down to 0.85 s , the problem solved.

But the temperatures are maximum .instead of it I used molding window recommendations and  decreased the gate diameter to increase shear heat ,instead of rising melt and mold temperatures , but it was not useful.

The question is , why 3d doesn’t have any problem by molding window parameters but DD and MD have?

Does the part will be filled in real injection cycle or not?

Thank you

[elljay1173]

Try a finer mesh. Most ;likely the thin wall needs a finer mesh. Try a 2 or 3 setting. I will take longer to solve and should prevent the short shot

[jandmnik]

Dear Elljay1173

Sorry for delay in response, thank you for your advice .I did finer mesh (DD and MD) , for both types of mesh , the fill result had no problem and didn’t show anything wrong (with coarse mesh ,there was short shot) but in other results : frozen layer end of fill , hold pressure , pressure the matter of short shot was clear (based on Molding window recommendations , with wide range of green area) whereas in 3D there was no trace of short shot in any process setting condition. In attached you could compare results. My question still is , which of the is reliable 3D (with no short shot ) or DD and MD (with short shot)?

Thanks

[raalteh]

Hi @jandmnik,

I saw in your screen shots that you are using Moldflow insight (2017). This specific forum is for Moldflow Adviser. These two Moldflow products are similar but have different options to troubleshoot this, so maybe its worth closing this here and re-posting it in the Moldflow Insight discussion forum.

https://forums.autodesk.com/t5/moldflow-insight-forum/bd-p/366

Best regards,

[raalteh]

For a bit more meaningful advise than the re-direct to the Insight forum.

The midplane and Dual Domain solver are using the identical solver under the hood; just adapted for a different type of mesh. So, I would expect very similar results form these two solves, using the same input. 

The 3D solver IS a different solver. For appropriate models, we aim to provide similar results/insights, in certain conditions may give different answers. Pressure predictions are likely going to be different. In the Midplane/DD world it may 'just' fill, and in 3D it may 'just not fill'.

The development team does spend a good amount of time every year to sources of differences in behavior and attempt to resolve these so that predictions would as similar as we can make them. The screen shot shows you are using Moldflow Insight 2017 but a lot of changes have been made in the last 6-7 years.

The pressure result at the end of packing of filling are not particularly diagnostic in term of why a short shot is occurring or not. Once a short shot occurs, the pressure distribution plots are likely to be radically different. So yes it is useful from the perspective of 'there is a difference between the mesh types'  but it would not explain 'why' the short shot occurs (or not). 

Generally speaking,  there are three reasons for a short shot:

https://help.autodesk.com/view/MFIA/2023/ENU/?guid=LM_SHORT_SHOTS

The things I would look at are:
1) are there areas of the part that are freezing (due to hesitation) ... I could see this being a very significant problem here. 

2) insufficient injection pressure. If a part is having filling problems, you can expect a pressure spike, but if you reach your max. inj pressure well before the short shot (you can see this in in the log files) and the machine will use its max. inj. pressure to try to fill out the part this can evenually also result in a short shot.

The other problems in the help are relevant too, but if I were to bet, I would strongly look at the first problem.

One last thing is (for some reason) Dual Domain and midplane suggest problems filling problems. I would look at this as a strong warning that you may have filling problem. Unless there is good reason to discard the issue, I bypass the question of 'why does 3D not show it and maybe that's the correct one'  but instead focus on resolving the issue so you do not have the issue in production. ... Hint .. try to avoid your hesitation problem by putting in some flow leaders. But that's my 2 cents.