3D Cycle Time

[Anonymous]

Hi,

I am running a 3D mesh and testing multiple gate locations.  The model has some thicker sections because we work alot with optical parts, and most of them are thick walled, molded out of polycarbonate.  I was wondering how accurate, and what is the best way to determine cycle time.  The part is a 5inX5in square with a mostly uniform .125in thickness.  Heres where the accuracy comes into question.  With a single edge gate, the part has a cycle time of 35 seconds.  With 5 valve gates patterned on the top surface, the cycle time is 65 seconds.  You would think adding more gates would not add 30seconds to the cycle.

Has anyone experienced similar problems, and what techniques do you use to determine the most realistic cycle times?

Thanks

[raalteh]

I don't know if you can, but a picture would say more than a thousand words. I have to assume you did not include a runner? Hanno

[Anonymous]

Hi,

Ive attached an image of the part with 5 gating locations.  I am currently getting a cycle time of 57 seconds, 100% frozen at 47seconds, and a final weight 2.73 ounces.  When I single edge gate the same part, I get a cycle time of 37 seconds, and a final weight of 2.66 ounces. 

My logic is that the multiple gates pack out the part more, increasing pack time, but with the multiple gates, you would think there would be less shear stress at the gates causing them to freeze off faster.  This is what puts my cycle time accuracy into question?

Thanks

[raalteh · Accepted solution]

Hi Jon,

I don't think this matters for the particular issue, but It looks like the part has a relatively coarse mesh on the surface (though I could be wrong). I would have meshed the surface a bit finer.

More to the point of your qeustion. If you single gate on the side in a thinner area, then materia further away or in thicker areas will not get 'fresh hot material', which would extend the packing time. The increase seems a bit longer than I would expect, but I don't know the part.

Another thing you should probably try is to set a gate contact diameter. (process settings > Advanced Options > 'Edit' the 'Solver Parameters'). By default, the software is calculating a gate contact diameter (effectively the final diameter at the gate). This has a mesh dependency in it. If you specify a gate contact diamter explicitly, you eliminate that variable.

I wouls also encourage you to add a runner system to this (and make sure your mesh it not too coars in the area where you gate).

Good luck!

Hanno