Jetting

[Anonymous]

Hi,

I'd like to know more information about "jetting". This problem is occurring in some products here and i need some help to eliminate it.

best regards.

Erick Damiao

[ana_maria]

Hello Erick,

Would you please elaborate what you are looking for?



Are you looking to learn about the problem and solutions itself ?



Or how to simulate it?







Regards,



Ana Maria Marin







Training Content Manager at Autodesk

[Anonymous]

Hi Ana, how are you?

I tried to simulate this problem (jetting) in software but I didn't have good results ( I used all options that we must use to simulate this effect but the results weren't good).

I have this problem here and I would like to learn about that and solve it.

I already reduced speed of injection, increased diameter of the channel and gates and had no sucess yet.

Have you any suggestions?

Thank for your attention.

Regards,

Erick Damião

[ana_maria]

Hello Erick,

To simulate jetting you need to have a fine 3D mesh. Make sure you turn on the inertia and gravity effects regarding the analysis. Related to the other inputs make sure that the material, machine and processing conditions are as close to the reality.

If all this items have been covered and you still can't duplicate the jetting on the model as you are getting on the real part I would suggest you sending your study file to your local support staff for further investigation.

Regards,
Ana Maria Marin

Training Content Manager
Autodesk, Inc.

[Sandriver_Eagle]

Simulation investigations for the jetting problem are only possible with the 3D solver.
The quality of the result is determined from the mesh density. To calculate the snake formation of the jetting problem a minimum corresponding mesh density is a need. For big models, it means high number of elements in 3D, I would suggest to model only the region of problem occurrence. This region should include a exact description of the runnersystem, gate and a piece of the part where the jetting is expected. Furthermore the correct setting in the 3D solver is a must. The parameter `simulate inertia effect` and simulate `simulate gravity effect` must be switched on.

Have a lucky work

[Anonymous]

Hello edamiao,

I don't know if it will help you or not. However, to avoid jetting you should inject for a wall, rib, etc.
Like that jetting will be eliminated. It possible that this solution result in sink marks, but can be a solution if the mark appear in a non visible area of the part.

Best regards,

Engº. Gonçalo Rodrigues
MOLIPOREX, SA
Portugal

[madhukeshwart · Accepted solution]

Jetting modeling requirements

++++++++++++++++++++++++

To simulate jetting, both the model must be set up to predict it, and adjustments to the analysis options must be set.

The model must have the following:

1. The gate meshed with tetrahedral elements.
2. The part and must have at least 3 rows of elements across a major thickness change, i.e. greater than 25% change in thickness.
3. The gate land should have a minimum of 3 rows of elements in the land length of the gate.
4. The part must be meshed with a small global edge length. (At least in the path of the expected jetting).
5. A minimum of 10 layers of elements must be present through the thickness of the part (including gate).
6. Tetrahedral elements must have a very good shape.
7.  The aspect ratio must be low, preferably, the maximum aspect ratio should be below 20:1, (default 50:1).
8. The internal edge length must be well below 1.5:1, (default 2.5:1).

The flow solver advanced options must be set including:
1. Inertia must be checked.
      Advanced option >  Solver Parameters > Fill + pack Analysis > Solver parameters >  check - Simulate inertia effect & Simulate Gravity effect
2. Intermediate results must be set with small time increments.
    Advanced option >  Solver Parameters > Fill + pack Analysis >  Intermediate results >  Write at specified times >  Edit times.

     ( Use a very small time increment such as 0.01 to 0.02 seconds initially)
3.  Start at time the polymer is getting to the gate. Continue with a very fine increment until the flow front is well developed.

    A preliminary fill analysis can be used to determine these times.

• Jetting is displayed with an intermediate result called Polymer fill region.
• It is similar to injection time but it can, at any time step, go from filled to unfilled and back to filled.
• The fill time plot will only represent the time when a node is first filled and does not show any subsequent un filling and refilling behavior.

[mayur_dhumal]

Hi Erick,

You will come to know about Jetting from above posts, but if you need to eliminate the jetting defect try to model Overlap gate or Circular tapered arc gate & implement it in your mold.

Regards,
Mayur

[madhukeshwart · Accepted solution]

Here is link which explains how to to simulate Jetting in moldflow ..

https://knowledge.autodesk.com/support/moldflow-insight/troubleshooting/caas/sfdcarticles/sfdcarticl...