FDX Tooling Blog

6 Tips to Improve Injection Molding Design

When designing a product, it is easy to create a product that meets all of the requirements of the product’s intent without having to consider the manufacturing process. It is often unclear what manufacturing process will be used to produce the final product.

At FDX Molding, we understand the complexity of adapting designs to complement the injection molding manufacturing process. Our Design for Manufacturability (DFM) engineers have decades of experience helping customers modify their designs to ensure that their products are manufacturable, cost-conscious, able to meet geometric tolerances, and use the materials selected without compromising product integrity and function.

We have put together 6 design tips to help engineers with injection molding designs.

Tip 1: Don’t design parts with uneven nominal wall thicknesses

Varying wall thicknesses can create uneven filling throughout the cavity, with thinner parts cooling faster than thicker areas, causing distortion and warpage in high-stress areas. It is recommended that thicker areas be hollowed out to create uniform walls, which will reduce cycle time and plastic usage and improve part appearance, with no more than a 15% variation in nominal wall thickness depending on the type of material used.

Tip 2: Identify possible sink areas and design them out

Areas of the sink may occur at the intersection of ribs and nominal walls that do not follow proper design guidelines. Rule of thumb: ribs should be a maximum of 70% of the nominal wall, but preferably 60%

Tip 3: Create radii at all corners

Note: Too large a radius on the rib can cause subsidence

Sharp inside corners become stressed, outside corners are difficult to fill and trap air, avoid radii on parting lines – leads to additional costs for tooling, adding radii improves corner filling and distributes stress over larger areas, if possible, the minimum radius is .030″, if the radius is less than .010″ it is not worth adding to the design, place radius at the end of the design tree to make it easier to work with DFM engineers to collaborate more easily.

Tip 4: Allow at least 1° of part release for die pulling

For textured surfaces, more draft is required – follow the texturing guidelines. If possible, a draft greater than 1° is better. 3° or more draft is required when parting lines transition from one layer to another. Less than 3° of the draft will cause the steel to squeeze together when the mold is closed, making it harder to pull the mold apart and creating Drag marks on the part

Tip 5: Don’t design for poor steel conditions

When envisioning the steel needed to create the part shape, avoid using sharp, tall, and brittle steel conditions, which can become hot and brittle.

Tip 6: Do not design deep ribs with square corners

It will trap gases and cause short shots, making it more difficult to eject parts

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