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Detect Short Shots with Simulation

If you are not confident that the part your customer designed will properly fill in an injection molding process, and that it will produce short shots… Or if you are concerned that you will have to spend additional money to correct the problem in the mold which would delay the launch of the mold, plastic injection mold simulation is the solution.

A short shot is a molding condition in which there is a lack of plastic material to completely fill out the cavity.  These defects are undesirable because it causes the part to be partially missing, namely screw bosses, connecting features, ribs, etc.  If the screw bosses, a connecting feature in which a screw is driven into, is partially missing it is not possible for the metal screw to hold onto the plastic, since the plastic is missing.  In the same way, if ribs are short, or missing plastic, the structure that the rib is supporting or making stronger is now not possible, since the plastic is missing.  The same applies to snap-fit connectors, which lock into place when “snapped” together with the male hook and the female groove.

No being able to fill the part is related to the injection molding machine itself.  The molding machine can only generate so much plastic pressure (hydraulic pressure times the intensification ratio), and if the injection molding process exceeds that pressure, non-filling and pressure limitation results.  Think of pressure as money in a bank account; there is only so much in the account and over-withdrawal is not ideal.

The Solution – SOLIDWORKS Plastics Filling Simulation.

This is a typical issue that injection molders and tool makers face, which is easily solvable with simulation.  By using simulation software, the predictability of the plastic flowing through the mold is accurate and reliable, which in turn allows you to see these issues before you even cut tooling steel.  Filling simulation accurately predicts how the mold will fill under real-world injection molding conditions.  By running the simulation, you will be able to directly tell where the end of fill will be and if the targeted molding machine will be capable of filling under the parameters specified.  This is important in cold runner tools and especially in hot runner tools.  Once the hot runner system is made, there is very little that can be done to modify it.  In most cases, the hot runner manifold is rendered useless, and a new one would need to be created.

How The Solution Helps

If Filling Simulation is done BEFORE the mold is created, then spending the money up front is much more cost effective (and time effective) when the mold is created correctly the first time.  The reduction in rework costs to the mold and timing are basically eliminated, and the project can move forward with a high level of confidence.

The software is fairly straight forward to use.  However, the power is in the ability of the analyst to extract that critical information and present it in a useful manner.  The old analogy, “garbage in, garbage out,” applies – as it is 90% the analyst and 10% the software.

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