Lesson 2: Entry of material, undercuts and wall thickness

Gate

The entry of the material is the point through which the plastic is injected into the mold.
At this point there is a mark, so you have to make sure that the entrance is positioned correctly
and that it does not harm the appearance of the product.
For example, we will try not to place the entrance of the material on the front of the product,
But on his side, or in another hidden area.
It is important to note that in addition to the visual side,
The location of the entry of the material can also have an effect on the structure of the product:
On its strength, on its straightness, on the quality of the surface and more.
That is, the decision on the location of the entry point
Both technical and visual considerations should be taken into account.

Undercuts are features such as projections or recesses that prevent a molded part from being released in the normal opening direction of the mold. These features often serve a functional purpose, but they can make molding more complex and expensive.

During product design, it is useful to reduce unnecessary undercuts. Where they are required, particularly in complex medical and high-tech products, the mold may use a side-action slide. The slide forms the undercut and moves out of the way before the part is ejected.

The illustration below explains an undercut.

thickness of walls

Increasing wall thickness can improve strength, but excessive thickness can also cause warping, sink marks and longer molding cycles, which increase unit cost.

Very thin walls can create other difficulties, including incomplete filling and challenging ejection. They may also require high-flow materials, whose properties need to be assessed for the application.

The appropriate wall thickness depends on the material as well as the part design. The table below gives recommended thickness ranges for different materials.

The uniformity of the thickness of the sides is very important,
And it is desirable that the thickness of the wall in the entire product be the same.
When the thickness is the same, all parts of the product will be filled with the same pressure,
And they will also cool down just as quickly,
And thus internal efforts will be avoided (which may cause distortions and fracture),
And we will get a product that is straight and without distortions.
As promised, I will end with two tips: