High-quality injection molded plastic casing pulls your whole product together into a neat package, and any walls within your product must be stable in order to maintain its overall structure and quality.
Mould Makers know this, ask what the minimum wall thickness should be for a plastic part they’d like to have made or designed.
So, what is the minimum wall thickness required on a plastic part?
The question about how thin or thick a product’s walls or casing should be is one that only leads to more questions. Here are a few to keep in mind when first exploring the idea of wall thickness:
Is the wall used for structure?
Will the part be fragile in that section if it is made thin?
If a specific plastic material is needed, how will the thinness be affected by the material choice? (The chart below discusses this in more detail.)
Your answers to these questions, along with a few other important variables, will help you determine whether a thin wall or part will compromise the integrity of your product or if it will help it function better.
The important variables to be considered? material composition, flow rate and part yield are key to the plastic injection molding process, so it’s helpful to know a bit more about them when deciding on wall thickness.
Material composition alone can be the distinguishing factor in wall thickness because of a material’s stiffness and strength characteristics.
Stiffness refers to when and how far a certain part will bend when force is applied, while strength refers to the part’s ability to resist fracturing or breaking when force is applied. Each material has its own stiffness and strength and both are affected by part thickness. So, as a part’s wall gets thinner, it bends more when it shouldn’t and is more susceptible to breaking.
This may sound straightforward, but in order for stiffness and strength to work in your favor, thickness must be chosen according to material composition. We elaborate on this point in the chart at the bottom of this article.
Flow rate,the rate at which a material moves or flows into a mold? It is partially dependent on material composition and will make a difference in the manufacturing process.
Because pressure is required for the injection molding process, thin wall areas in a mold can cause material flow rate issues no matter what material is chosen. In turn, flow rate issues can lead to costly flaws, such as voids and sink marks.
Part yield is the ratio of good to bad parts that come out of the mold. Thin walls will contribute to low part yield, making it necessary for part yield to be considered prior to budgeting and manufacturing.
Let’s say you made four parts: two came out fine, one has a void where the material didn’t fill and one broke as it was removed. That would mean the process had a 50 percent part yield.
As the manufacturer might have to discard every other piece in order to achieve the minimum wall thickness, the costs of trial and error will fall on the person or company paying to have the part made. By keeping the wall thickness to a proper range for the chosen material, however, you can avoid unnecessary costs and delays.