Moldflow Shrinkage Analysis - applicability in practice

[Brucipes_123]

Hello,

I would like to ask people who have interest and experience with using of "shrinkage" analysis with Moldflow couple of questions.

Of course, I would be glad if also somebody from Moldflow could perhaps comment if sees the need:

1. Is shrinkage analysis, in sense of analyzing that certain tolerance of certain dimension can be reasonably achieved used in industry a lot or is it just such a feature of Moldflow that is there but not really used too much by companies?

2. Everyone knows that absolute majority of plastic parts are of "kind" that "ordinary" supplier will only guess from his best experience (or maybe from some few studies he done by measuting some molds and parts...) what is the uniform shrinkage and he will just expand the CAD part model by this number to have models of cavity / core. In some very rare case, maybe some distance between 2 boses may be somehowat accounted for with some more accurate estimate and this distance in tool might be different than it would be compared applying uniform shrinkage factor on tool design. This is at least practice I know from our suppliers. So question is: does anybody know suppliers who are using Moldflow for exactly this - calculating distance of important feature in tool to have get molded part up to spec tolerances?

3. In "shrinkage analysis" in Moldflow, results are listed in log file. Basically, when "critical dimension" is defined (like some lenght of the box), in log file you can read what is the required mold dimenions.

My question is: this mold dimension as well as "predicted" part dimension is calculted by Moldflow with some tolerance. Can anyone explain how this is calculated (tolerance) by Moldflow? Is it coming from some uncertainty of shrinkage as I can immagine? But... it is not mentioned anywhere how is possilbly this variation of shrinkage actually meant / considered.

Actually, would be great if Moldflow stuff can supply very clear example from practice. Something graphical, with clear descriptions of how this was maybe done in past and now how it can be done with Moldflow. You know, something on very practical level.

Thank you

[mayur_dhumal]

Hi,

1) Yes, definitely Shrinkage analysis is important in PCB manufacturing or any electrical, electronics components & not only here but also in Automotive and other application areas, where precision is very important.

2) Usually tool designers have learned from their past experiences, but mold and tool designers does have the knowledge of the polymers, how they behave and what properties they does have. So even if their are many material grades from just Polypropylene polymer, it has a definite shrinkage property range & which can be alter by just adding fillers or fibers etc. But it is always recommended to have Moldflow Shrinkage simulation result in hand which many service providers can deliver you.

3) I think this question is related to Autodesk Developer. So i quit.

Regards,
Mayur

[aakash.thorat]

good

[madhukeshwart]

1.  

• It is very good tool & should be used but very few are using this feature. since most of material doesn't have shrinkage data(CRIMS). CRIMS data is must i.e In order to run a Shrink analysis, you must select a material that has been shrinkage tested. 
• If your material contains anisotropic matrix material properties, shrinkage values may be more accurately calculated using the Mori-Tanaka 
• micomechanical model. It supports for only DD mesh and midplane mesh only.

 2. 

• Resutls mainly depends on the “goodness” of the material properties contained within the .udb file. The analyst must have a high degree of confidence in the lab – the Autodesk Moldflow Plastics Lab – generating the material properties data file for the purpose of simulating the thermoplastic injection- molding process.
• Some times, So we do proto tool, before going for production tool for very precision components.
• some times, we deide based on supplier confidence.
• some times, we deide based on previous expereicne.
• some times, we get advice from raw material suppliers experience

3. Send a request local support or Autodesk support team. They will surely help you to proving results

[raalteh]

To your last point on how it works with an example.Have you looked at the help on this topic?

http://help.autodesk.com/view/MFIA/2015/ENU/?guid=GUID-251570E6-8C31-4DEA-9FA4-81415AE12BD2

[supportmoldflowthailand]

airsyn  , how to solve this problem

[raalteh]

@ supportmoldflowthailand

This message means that the user interface crashed for some reason. If you get the question if you want to submit the crash to Autodesk, please do this, as we may have a chance to find out what caused the crash. Alternatively, if you can repeate the sequence that causes the crash, we we can look into this as well.

Chances are that the crash is not repeatable, which will make it hard to track down what caused it.

Hanno