"70% of mold costs are determined during design phase." If you're still relying on experience to determine gates and adjust parameters, this article will help you completely break free from "trial mold = expensive" model.

In a nutshell: "Trial mold" on a computer first, then get real work done on machine.
Using CAE software such as Moldflow, Moldex3D, or C-Mold, break down a 3D model into hundreds of thousands of "small blocks" (meshes), then run molten plastic through them to preview four major scenarios: filling, packing, cooling, and warpage.

① Fill Time
Fill time shows expansion of melt flow front, typically presented as a shaded image. It is a key result in mold flow analysis. It reflects melt flow behavior within mold cavity and helps identify potential issues during injection molding.

 

Green simultaneous arrival in fill pattern indicates balanced filling; red areas arriving first indicate over-packing; gray blank areas indicate a risk of short shots.
② Melt Front Temperature
Flow front refers to front of resin flow injected into mold. It reflects temperature of resin reaching various parts of molded part. Cooling analysis is used to calculate flow front temperature. Because mold temperature is typically lower than molten resin, resin cools during filling process. Excessively low flow front temperatures can lead to molding defects.

 

A temperature difference of >20℃ at flow front indicates a drop in weld strength.
③ Air traps
Due to high pressure injection of molten resin, air in cavity is pressurized and generates high temperatures. This often causes trapped air and burns at the end of fill cycle during high-volume production.

 

Provide a solution to air entrapment. Is mold venting design improper?
Solution: Air pockets are primarily located at boss column and end of rib. Mold at this location is a mosaic structure, and mold parting surfaces have venting systems, preventing air entrapment.
Red spots indicate air cannot escape. Venting grooves must be added to parting surface to prevent burns and glue defects.
④ Weld Lines
Weld lines are marks created where resins meet. To mitigate strength and appearance issues they cause, adjust gate position to a less noticeable location or optimize angle at which resins meet to reduce their visibility.

 

Weld Line Prediction: Where two streams meet = weld lines. The more weld lines there are, the more part resembles a puzzle.
⑤ Volumetric Shrinkage
Volume shrinkage refers to reduction in part volume caused by holding pressure during injection molding process, typically expressed as a percentage. Volumetric shrinkage reflects shrinkage changes during holding and cooling phases, while volumetric shrinkage during ejection is considered final volume reduction of part.

 

Areas marked red > 8% will show signs of dents next day.
⑥ Warpage
A variety of factors, including cooling, shrinkage, molecular orientation, and other mechanical properties of material, can cause part warpage.

 

A Z-axis deformation of 0.4 mm caused an assembly worker to complain, "I can't even align screw holes."
⑦ Clamping Force XY Plot
Analyze pressure changes over time in various parts of molded part during filling and holding. Uneven pressure can lead to flow imbalances, especially in specific areas or during multi-cavity molding.

 

Don't apply too much pressure, or you won't be able to remove burrs.

Cover: Part rendering + Project number
Page 1: Risk warning, using 3 images to explain short shot, warpage, and clamping force
Pages 2-4: Material & Process Cards
Pages 5-10: Animated images + quantified tables
Last page: Mold modification suggestions & cost-benefit table