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## Simulation Moldflow Insight

Active Member
Posts: 6
Registered: ‎08-16-2010

# calculate the volumetric shrinkage

1734 Views, 7 Replies
09-01-2010 10:56 PM
Hi, I dont know how the moldflow calculate the shrinkage? How can i know this shrinkage result is good or bad? Can i setting the material shrinkage value? How can i do it? Thanks, Ivy
Contributor
Posts: 11
Registered: ‎08-31-2010

# Re: calculate the volumetric shrinkage

09-02-2010 12:52 AM in reply to: Ivy_chen

Hello Ivy,

When I want find a shrinkage on the part, I use the deformation result (Deflection, all effects) and I measure 2 points on the part with the button " examine results "

On the small window (of examine results), It's possible to choice "Deflection+Shrinkage".

After this, it is possible to mesure 2 points on the part several time to use an average value

if you have still some problems, I can send you a picture of shortcuts

bye.

Sebastien.

Active Member
Posts: 6
Registered: ‎08-16-2010

# Re: calculate the volumetric shrinkage

09-02-2010 05:46 PM in reply to: moldflowfico
Hi Sebastien, Thanks for your answer. I can understant it, so don't need picture to show it. But i got another question is, how can i know this result is good or not. Is compared with the shrinkage information given by material detail. And i not very clear with the shrinkage information in the material detail. Thanks, Ivy
Contributor
Posts: 11
Registered: ‎08-31-2010

# Re: calculate the volumetric shrinkage

09-02-2010 11:40 PM in reply to: Ivy_chen

Hello Ivy,

ok,

So by default, we know (by the plastic material) the middle value indicate on the material data sheet.

Some examples:

- PA50%GF= approximatly 0.3 to 0.6%

- PP 20% mineral = approximatly 1 to 1.4%

- ABS or ASA = approximatly 0.4 to 0.6%

- TPE = approximatly 1.2 to 1.8%

Normally, if the part is not too much compacted and there is no sin mark, then the shrinkage will be OK

You will have enter an average value, because there is always a little differential shrinkage.

greeting,

Sebastien.

Active Member
Posts: 6
Registered: ‎08-16-2010

# Re: calculate the volumetric shrinkage

09-03-2010 12:54 AM in reply to: moldflowfico
Hi Sebastien, Thanks a lot for u kindly help. Ivy
Active Member
Posts: 8
Registered: ‎07-14-2010

# Re: calculate the volumetric shrinkage

09-06-2010 08:56 PM in reply to: Ivy_chen

hi this is inba,

i understud what exactly you want.

u cant able to usnderstand about volumetric shrinkage values.

if the value is <8% - it will not impact any shink mark on the surface.

9-12%- it will create small shink mark(shallow) on the surface, but not much visible.

>13% - it will create deep visible shink mark as well as void will form on the inside of the part.

Member
Posts: 5
Registered: ‎09-14-2010

# Re: calculate the volumetric shrinkage

09-14-2010 06:36 AM in reply to: Ivy_chen

Results > New Custom Plot

DEFL Displays shrinkage and warpage with a specified magnification scale factor.

DEFL C Displays shrinkage and warpage with a specified magnification scale factor, centering the display on the node(s) specified.

DEFL W Displays warpage without shrinkage with a specified magnification scale factor, based on the position of two specified nodes.

DEFL W2 Displays warpage with uniform shrinkage, based on a specified shrinkage value.

With these u can also separate the shrinkage from the warpage.

However the results about shrinkage are reliable especcially with non filled material.

If the material is fiber filled, to obtain the correct results you have to pay attention: the shrinkage can be very different in perpendicular and parallel direction, so u have to set correctly the analysis to find out the real fibers orientation and consequently reach the right shrinkage in each direction.

New Member
Posts: 2
Registered: ‎10-22-2012

# Re: calculate the volumetric shrinkage

02-04-2014 07:55 AM in reply to: inbasudhahar

Hi,

I found about this item, because we work with cosmetic plastic parts, and that is a focus of my analysis.

In the second course of Moldflow. In the manual there are a intem about the packin profile,

And this explaind a aceptable difference between 2% in all part,

Wen in a analysis a detect a difference between a area soo closed, I mension that it is a possible sink mark problem .

that because I understend if all part have a same volumetric shrinkage value, this means that all part is shrinkage equal,

but if this part have a change significant, that means that is a potensial visible spot,

The values that you expland is so interesting, because this same values was real , wen a see that values

Thatks