Flowmark

[Sanjay_paul]

Hello everyone,

Is there any option in Moldflow Insight by which we can identify flow marks? And How can we prevent flow mark?

Regards

Sanjay Paul

[mppkumar]

Hi @Sanjay_paul

Visual defects such as flow marks, gate blush, tiger strips can't be predicted directly in Moldflow

Flow marks can be addressed using the below options:

• Optimize the cold well. Design the cold well in the runner system to trap the cold material during the filling phase. The proper length of the cold well is usually equal to that of the runner diameter.

• Optimize the runner system design. A restrictive runner system design can result in premature gate freeze-off. It can however, increase shear heating for better melt flow.

• Increase the mold and melt temperature.

• Optimize packing pressure.

https://knowledge.autodesk.com/support/moldflow-insight/learn-explore/caas/CloudHelp/cloudhelp/2017/...

[Sanjay_paul]

Hello Pradeep Kumar,

I have read this article already. Moldflow should include flow mark option in future version. I have seen that Sigmasoft has this option.

Regards

Sanjay Paul

[mppkumar]

Agree with you

check in idea station and if no one is posted idea related to it, you can post an idea

[Anonymous · Accepted solution]

@Sanjay_paul we don't have any result/plots to identify the flow marks in Moldflow but we can interpret with few results like Velocity & Time to reach ejection temperature which will give us some idea that there is a possibility of Cold flow marks in the part. we did interpret with those results on our parts & that helps us identifying why it is happening. so we are continue our interpretations with that. due to our policy i cant share much detailed images/info regarding that sharing few images which may help you understand how to interpret. below images are the example of the part we worked & used Moldflow results (Velocity & Time to ejection temperature) to interpret the cold flow marks.

It may differ part to part, in my case it really worked with these two results. you can try interpret these two plots indepth will help come to common solution which works for your product.

[Anonymous · Accepted solution]

i forgot to mention other two key results for interpretation along with Velocity, Time to reach ejection temperature you need consider shear rate & pressure.

as i mentioned you need to practically understand why the flow marks are happening by taking on physical part as a bench mark & start evaluating the results in Moldflow.

[Sanjay_paul]

Thanks a lot for your explanation. How to solve this flowmark problem?

Regards

Sanjay Paul

[Sanjay_paul]

Hello Sabarinathan,

I have found a product which is having flowmark but flow orientation doesn't show any obstruction. In the below picture the marked areas are getting flowmark. What are the causes of flowmark?

Regards

Sanjay Paul

[Anonymous]

@Sanjay_paul share the image of physical molded part on which you are getting flow marks, also what material you are using.? is the part thickness is even all around? is there any reduction in thickness on that groove area right above the red circled you marked..?

[Sanjay_paul]

Hello Sabarinathan,

We are using HIPS for this part. Product thickness is not even over body and Sorry in previous picture I have marked the wrong area. Actual picture is given below. I have also attached the part file. Please take a look. In here you can see the flowmark appears in one side of product but sometimes it appears in opposite site.

Regards

Sanjay Paul

[Anonymous]

Hi @Sanjay_paul

Have a close look on flow results on that area in Moldflow (with 100 frames) & see what exactly happening. please do check the shear rate, temperature as well. since you mentioned there is a thickness variation are there in this part. also check the Mold temperature. 

check & let me know.. I couldnt find time to open & review your model.

Another option to try in the IM machine:

A well-designed mold temperature control system is of great importance because the effective surface temperature of the mold exerts a critical effect on the finish (gloss, brilliance and absence of flow lines), the strength of weld lines, the resistance to warpage, the shrinkage and the adherence to tolerances. Depending on requirements, temperatures of from 10 to 70 °C are customary. Very thin-walled parts which have to be produced with short cycle times can also be injection molded at mold surface temperatures of less than 10 °C. At even lower mold temperatures.

[Anonymous]

Hi sanjay,

you can give a try by adjusting the fill rates as well.!!

Fast fill rates generally provide better uniformity in part size and quality. Rapid fill rates are possible if gate sizes and locations are properly selected. Gates too small for a particular part thickness can cause problems when filled at rapid speeds. Use the fastest fill rate the mold design and part will tolerate understanding that not all applications can tolerate a fast fill rate. Heavy section parts require a slow fill to avoid flow and weld marks on the surface of the part.