Mold Filling Analyses

Through mold filling analyses, costly design errors in the development of injection molded parts and injection molds can be identified in advance and avoided. Such errors otherwise could be corrected only by expensive and time-consuming alterations to the mold. Ticona has the capabilities to run basic filling and packing analyses, as well as more advanced cooling and shrinkage/warpage analyses.  

Required Information:

• Part geometry
• Material rheological data
• Processing data

Outputs:

• Filling pattern
• Pressure distribution
• Temperature distribution
• Shear stress, weld line locations, etc.

Tips on when to use a mold filling analysis

• Mold filling analyses are common in the plastic injection molding industry today. The key to attaining the most value from a mold filling analysis is to understand what you are trying to solve and how the analysis can help achieve that.

Good reasons:

• To determine whether a part will fill or not. The analysis can also provide other useful information such as the required injection pressure and clamp tonnage.
• To determine if the part will have any filling problems. Many filling problems, such as short-shots, air-traps, and unbalanced fill, can be identified by examining the filling pattern.  A mold filling analysis allows you to vary the gate location, injection speed, and other processing conditions to determine whether these problems can be improved or corrected.
• To predict how a part will warp.  The absolute values predicted by a warpage analysis must be used very cautiously.   Warpage predictions are best used to compare gate locations, wall thickness changes, and/or design variations.  
• To troubleshoot a bad prototype tool.  The best method for troubleshooting a tool problem is to perform a “short-shot” study using the prototype tool.  Mold filling analyses can be used to determine which changes will be effective and are quicker and less expensive than cutting steel.
• To determine the effectiveness of the cooling circuits.  A cooling analysis can be added to a warpage analysis for additional accuracy. Since the cooling lines are typically very difficult to change once they have been cut into the tool, this type of analysis is most useful before a tool is built.  
• To fix weld line problems.  A mold filling analysis will predict where the weld lines will occur and can help determine how to move them to a less problematic area. It can also provide some hints about the quality of the weld line such as the temperature of the material when the flow fronts meet and the pressure available to pack out the weld line.  It cannot, however, determine how strong or visible a weld line will be.

Poor reasons:

• To predict surface defects.  Unfortunately, most surface defects, such as splay, delamination, burns, and sink-marks, cannot be determined from a mold filling analysis.  In many cases, however, an analysis of the filling pattern may provide clues to the cause of a surface defect.
• To cut a tool in order to produce a flat part.   Warpage analysis results may not be accurate enough for cutting steel.  Since the outputs of the filling and packing analyses are used as inputs to the warpage analysis, any errors are additive.  The results can be used with more confidence if prior work on similar parts confirms that the actual part shrinkage matches the amount predicted by the software. The best way to determine the amount of warpage is by measuring the prototype tool and parts.