Injection molding design: The 10 keys to success (1)

5. Gate location
Gate location of Consumer Electronics plastic parts ideally should be specified by a designer, molder and tool maker. Gate location is critical to virtually every attribute of an injection molded part. It affects appearance, warpage, tolerances, surface finish, wall thickness, molded in stresses and physical properties, to name a few.
Some designers use mold flow simulations to dictate gate design and location. I think that’s great if the molder agrees with their recommendations. I disagree with designers who insist that their gate recommendations must be maintained without compromise. In either case, close collaboration with a molder throughout the design cycle will ensure that the gate will not adversely affect part performance, appearance or fit. Molders are also willing to advise designers about the type of gate and features that may have to be added to the part geometry based on gate design. Molders also will offer trade-offs between different types of gates, including fan gates, edge gates or sprue gates.

6. Shut-off angles
Most readers will be familiar with the terms “shutoff angle” and “bypass.” These terms refer to the minimum angle between the core and cavity, which typically creates an opening in a part that would otherwise require a slide or cam. Features such as circular holes, snap locks or large rectangular openings can usually be molded in walls perpendicular to the line of draw by designing features for a bypass in the mold.
All molders want as much angle between the core and cavity as possible, whereas designers typically want no angle or minimal angle in these features. The compromise usually lies between a minimum of 3° to 5° in most cases. Benefits of discussing these details with a molder or tool maker cannot be over emphasized. Many hours will be saved before you waste your time detailing part features in CAD with lengthy feature trees that are difficult to edit after the part has been fully detailed. Some molders will accept a 3° minimum angle, while others may require a minimum of 8° to 10°. The longevity of the tool, tool quality, mold steel specifications and materials being molded all will affect these details.

(source:https://www.hthc-tech.com/injection-molding-design-the-10-keys-to-success-1/)