The biggest challenge in injection molding is the process of designing a mold. There are almost no limits to your creativity , but you can do the designs in clever and less clever way from a manufacturing point of view. Plastic manufacturers highlight this aspect as the most crucial part of injection molding. There will be no successful plastic part designs for injection molding if there is no perfect mold from where it is formed. The biggest factors to designing a mold are part and tool design. Getting these factors right means faster production, better quality and reduced costs while having them wrong could substantially affect these production aspects in a negative manner. Here are other factors you need to consider with injection molding during the product development and prototyping.
1. Wall thickness
Thin walls are advisable in plastic manufacturing for shorter cycle times and being able to produce more plastic part designs in shorter production lead time. Thinner walls also makes the cooling process faster. Ideal wall thickness from 0.08? (2mm) to 0.16? (4mm), but thin wall injection molding can go as thin as 0.02? (0.5mm).
However, wall thickness also depends on the type of plastic material being used. Here are the recommended wall thickness for various plastic materials; ABS resin is between 0.045 and 0.140 inches, Acrylic is at 0.025 ?0.150, Liquid crystal polymer at 0.030 -0.120, Nylon at 0.030?0.115, Polycarbonate at 0.040 ? 0.150, Polyester at 0.025 ?0.125 and Polypropylene at 0.025? 0.150.
Adding ribs helps increase the bending stiffness due to the increased moment of inertia. This is a suggested option instead of adding thickness to the wall. Here are recommendations with ribs in plastic production;
Rib?s thickness should not be more than 60% of the nominal thickness value.
Height should be three times lower than the wall thickness.
Draft angle is at 25 degrees.
The ribs position must be perpendicular to the axis where the bending occurs.
Corners of the attachment points must be rounded instead of having them pointed.
Bosses are layers wherein fasteners are attached and threaded inserts are located. Recommended specifications for bosses are the following;
Bosses? wall thickness should not be more than 60% of the main wall.
Base radius should be at least 25% thickness of the main wall.
Bosses should be supported by ribs connecting to walls adjacent from their position or gussets at the bottom the mold design.
Ribs should be used to isolate bosses in corners of the design.