The possibility of a sink mark on an appearance surface

[FK1985]

Good days,

            I made a moldflow 3D flow analysis of the part as seen on the attached Picture-1. In simulation results showed there is no risk of short shot, sinkmark etc. Part will be filled from one point as shown in Picture-2. Part has a prism structure that is thicker at some points and thinner at some points and it will produced with PMMA.

            a.         In the study, I made a dual domain mesh and 3D mesh after. But 2D mesh percentage stayed at 54%. Is it possible 3D flow results are false, because of the low 2D mesh percentage?

            b.         Max. sinkmark is 0.23 mm and it is not on the visible area. But is there a chance of sinkmarks on the areas as shown in Picture-3 caused by part geometry?

            c.         Is it more suitable to add one more entrance to the part that is located at the position where sinkmark possibility is high, with the entrance from the thickest point?

Thank you in advance for your support.

[madhukeshwart · Accepted solution]

 a.         In the study, I made a dual domain mesh and 3D mesh after. But 2D mesh percentage stayed at 54%. Is it possible 3D flow results are false, because of the low 2D mesh percentage?

Even though  for 3D mesh, Mesh match is not important. But for Sink mark prediction, we observed sink marks results are better with more match %. 

b.         Max. sink mark is 0.23 mm and it is not on the visible area. But is there a chance of sink marks on the areas as shown in Picture-3 caused by part geometry?

If Max. sink mark is > 0.03 mm, there are chances of visible sink. But not always visibility will be less  if part is less glossy, textured, painted.

And also it depends light and direction of light, color of light also. 

 c.         Is it more suitable to add one more entrance to the part that is located at the position where sink mark possibility is high, with the entrance from the thickest point?

Yes, Gating at thicker section or near to thicker section are preferable. 

Note: If features are like rib or attached walls or features, prediction is quite good. But such case, where wall thicknesses are more, or like serrations, pins, thick protrusions, Predictions are not accurate but can be helpful to take decision. such cases refer density & volumetric shrinakge plots also to make a decisions