Injection Mold Design Guide ((free)) File
Injection molding is a cornerstone of modern manufacturing, used to produce everything from smartphone cases to automotive engine components. Designing for this process requires balancing functional needs with the physical constraints of molten plastic and metal tooling.
: Keep ribs at 40–60% of the adjacent wall thickness to avoid sink marks. : Limit height to roughly 3–5 times the wall thickness. : These provide mounting points for screws. injection mold design guide
A simulation will predict:
A standard injection mold consists of two primary halves that form the cavity. Injection Molding - Design Your Product for Manufacturing Injection molding is a cornerstone of modern manufacturing,
Gate Location Strategy
- Channel Placement: Channels should be as close to the cavity surface as structural integrity allows, typically spaced 3 to 5 diameters apart.
- Baffles and Bubblers: For deep cores where straight channels can’t reach, these devices divert water flow to cool difficult areas.
- Uniformity: The goal is uniform cooling to prevent warping. If one side of the mold is 20°F hotter than the other, the part will bow like a banana.
Radii and Fillets
: Avoid sharp internal corners. Rounded edges improve material flow and reduce stress concentrations that can lead to structural failure. Channel Placement: Channels should be as close to
- Flow Front Temperature Drop: The plastic temperature at the end of fill should be within 20°C of the melt temperature. A bigger drop means the part will have inconsistent mechanical properties.
- Pressure Drop: Pressure at gate minus pressure at end-of-fill. Target: <10,000 PSI (70 MPa). Higher than 15,000 PSI requires a bigger machine or larger gates.
- Shear Rate: Plastic degrades if sheared too fast. Check against resin limits (e.g., ABS < 50,000 1/s).
- Weld Line Temperature: The temperature of the two fronts meeting. If below the "no-flow" temperature, the weld line will be a structural crack waiting to happen.
- Cooling Time: 70% of the cycle is cooling. Simulation shows hot spots. If you have a 5mm thick hub in a 2mm wall, that hub will dictate your cycle time (possibly doubling it).