Plastic Part Design Analysis Theory

The plastic part molding process is heavily affected by factors of the plastic part design. If the critical parameters of a part design are not set correctly, the part will have quality issues during the molding process. The most critical of these parameters is as follows:

• Plastic Part wall thickness
• Part flow length
• Thickness transitions
• plastic Part material
• Location of gates
• Number of gates
• Location of mold vents
• Mold temperature
• Melt temperature

A quick, cost effective mold flow analysis on a part design with the chosen material and gate locations can give an accurate prediction of how a part will mold before the tool is built. Verifying  that a part design will work with the given set of critical parameters is key. If the part does have quality issues, our analysis report will recommend ways to adjust the required parameters so that the problem is eliminated.

Plastic part design without the use of mold flow analysis forces the designer to use rules of thumb, guess at, or not consider these critical parameters.  This results in a high degree of risk that the part will not mold with acceptable quality levels.  Some times pushing processing conditions to the extreme limit will yield an “acceptable” part. 

However, this will cause high levels of molded in stress, degrade the material, increase scrap rates and/or increase cooling times.  Unfortunately, molds designed without the use of mold flow analysis have to resort to these tactics of “trouble shooting”.

Other critical data that is obtained by running a part design analysis includes:

• Location of weld lines
• Clamp tonnage requirements
• Injection pressures
• Location of high shear rates
• Location of high shear stresses