Many tools in the industry have cores that may have the potential to physically shift or deflect during the filling and packing process. This is a real concern and needs to be understood in order to be addressed.
Whether your tool steel is P20 or 414 Stainless Steel, it has the ability to deflect. Deflection is purely based on the design of the tool along with the pressure in which the polymer will be injected.
It is most commonly related to tools which have relatively thin cores such as tools for syringes or battery cases, but can affect a variety of tools other than just those which have a known history of core deflection. If there are standing features on the core side, thick or thin, the possibility exists that they could deflect. If they do deflect, it could create a processing nightmare or even worse, decrease the life expectancy of the tool.
Finite Element Analysis (FEA), now has the ability to determine core deflection. If the polymer fills the cavity unevenly and creates core deflection, the pressure distribution on the core becomes increasingly uneven as the core continues to fill.
This uneven filling pattern can lead to:
It is extremely important to have a complete understanding of your process which includes the flow behaviors of the polymer within the cavity.
When analyzing a tool with FEA and identifying core deflection, there are ways to combat the problem.
Some examples may be:
- Change the gate location
- Modify the gate design
- Incorporate flow leaders
- Change the number of gates
Without FEA, it is nearly impossible to make these changes lacking a clear understanding of how the polymer is filling the cavity and the effects it has on the cores while doing so.
In conclusion, it is important to understand that core deflection does exist and it may occur on some of the least likely tools. Core deflection can create havoc on processing and tool life so it is very important to:
- Understand if it is occurring, then
- Address it if it is occurring.
The best way to address it is through FEA.
Contact Bozilla Corporation for your FEA and injection molding troubleshooting needs and please visit our website at www.BozillaCorporation.com.
