The recommended general wall thickness of injection molded parts depends on the size of the geometry, the material of choice and the desired performance of the geometry. Here, performance is used to sum up desired characteristics in the following fields:
Typically, the wall thickness will be in the range 0.5 mm to 4 mm. In specific cases, wall thicknesses that are either smaller or bigger also occur. A basic design guideline is to keep wall thicknesses as thin and as uniform as possible. Where varying wall thicknesses are unavoidable for reasons of design, there should be a gradual transition as indicated in Figure 1.
In general, it’s relatively easy to remove metal from an existing metal mold cavity. Adding metal, on the other hand, can be difficult (expensive) or even impossible (requiring remaking the mold - expensive). Looking at this from the part’s wall thickness perspective, you can make it larger, but you can't make it smaller. So, in case of doubt, start thinner rather than thicker; this principle is called designing "steel safe" or "metal safe."
Figure 1 - Gradual transition of wall thicknesses.
The flow behavior of a molten plastic material is expressed in terms of its viscosity: a lower value for the viscosity means that the material flows better in the molten state. This is beneficial in case of molding parts with very thin wall sections.
Influence of wall thickness
It’s important to carefully choose the nominal wall thickness. This is because, apart from structural performance, the wall thickness has an influence on the following:
Figure 2 - Voids due to large wall thicknesses.
Figure 3 - Sink marks due to large wall thicknesses.
Material specific wall thickness
The recommended wall thickness depends also on the flow behavior of materials. The following material-related factors influence the flow behavior:
To get a first impression of the flow behavior of a specific material, one can refer to spiral flow curves. These give a relative measure of the maximum achievable flow length for a given wall thickness and injection pressure. Spiral flow curves of widely used DSM materials are available in our PlasticsFinder.