Short shot simulation problems in die casting simulation correlation with test
 

hello all,

recently, i do a test of die casting of a part and then simulation correlation.

1. formal production condition. there is a piston and sleeve in the inejction machine. when melt fluid injection to sleeve, the piston moving and finally pull the fluid to cavity. moving distance is 500mm for example for complete filling.

2. short shot of formal production condition. in order to correlate the simulation of FLOW3D with test, we do short shot test of different moving distance which is less than the completed one (500mm),such as 380mm,400mm,420mm......480mm. The test samples are get for comparison.

3. set the simulation of short shot same as test. we set the moving object stop at the according time/distance. for example, when we simulate 400mm one, it moving from 0s to 0.92s, and we set 0 velocity at 0.920001s. the finish time is enlarged to 1.5s due to inertia of fluid, finish condition is filling fraction 0.9999.

The question is, the results of simulation are different. filling fraction is smaller than test result. and the fluid continue to flow after 0.920001s and flow everywhere, finally sink due to gravity.


in test, after 0.92s, the fluid continue to flow too, but it cool down fast to resist the flow of fluid.

my question is that, what is the problem? how to simulate the correlation to test?

How you measured the piston last position? Have you take into account the piston inertia? In the simulation the piston last position is the input you introduce but in the reality because of inertias the piston will continue moving after you cut the signal. My recommendation is to measure exactly the piston end position in your experimental measurement and then do the simulation with that parameters.

Regards.

during the test, there is a touch screen of control of the injection machine. it shows velocity settings, piston movement(complete filling movment,=567.5mm for example), biscuit thickness, and inejction movment limit distance.

and we set inejction movment limit distance=400mm. but the inertia of piston we don't considered due to can't obtain how long it move of stop command.

But I suppose that you can check this distance in the display (the piston position), is correct?
If you can´t introduce the last piston position correctly in your simulation is impossible to correlate with the experimental data!
Regards.

beyond the flow pattern, the simulation solidation shape of final short shot is another issue which had big difference with tests.

for example, test with 400mm short shot, the ejected part almost 70% fraction of filling. and the cooling short shot part is almost continued.

but in the simulation, after the time of 400mm reached, the fluid do not solidation and flow sprayed everwhere, finally sink due to gravity.

many papers say the short shot are not properly used in correlation of die casting.

how i can give the solution of correlation?

i agree with you on the inertia of piston. maybe i add some distance to the piston.

I hope that you are looking for something like this: http://www.flow3d.co.jp/products/flo...alidations.htm

We did some simulations in the past in order to correlate but with just the first phase… Try no to reach the first phase, I mean, before the first phase of the casting process end take the part and make a simulation with that parameters. Then compare the part with the simulation casting. My recommendation is to introduce solidification during the filling in order to ensure that you get similar results.
Is the material that you are using in the simulation the same you have in the process? (Is well characterized?)

Regards.

Thank you for your comments. and i activate solidification during the filling. and use solidifed fluid drag-->flow model for solidified metal:porous media drag-based ;coefficient of solidification frag: 1 and 10 both tried,but no use.
what is first phase?

I mean with first phase just the first shoot. In our casting process there are three main phases. Slow shoot (first phase where fluid arrives to more or less all casting gates), fast shoot (second phase, where the part is filled) and third phase (high intensification pressure in order to avoid defects in the casting). Doing just the first phase in simulation and real process you can compare both like in the picture below. That’s the idea I have in order to validate both simulation and experiment.

Good job!!!!

many thanks.

we do some shot shot of intermediate transient stages within first stage and second stage.
the issue is that, in the filling simulation, the fluid should be solidficated and stop, then conpare to test result.

the photo you show i noticed, but the simulation result maybe not solid at that moment. however, the test result is solid.

what we should solve is that the solidifiation model and parameters/ fuild properties parameters should be able to simulate solid during filling. or, the fluid will flow everwhere.

Thanks a lot.

i change some solidification model parameters and fluid properties (viscosity and so on).

The fluid solid and stop after short shot!

next step is to correlate the value of each parameters with test.

all in all,thanks

You´re welcome!

Sure that the material good characterization is something important, especially in the entrapped air that depends on material viscosity and surface tension. Good luck with your simulations. :)

Regards.