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Lesson 2: Entry of material, undercuts and wall thickness

Last time we talked about a dividing line and shirting angles,
Today I will go over three additional concepts that will complete our basic concepts:
Material entry, undercuts, and wall thickness.
At the end of the lesson, two important tips await you.

material entry

דוגמאות לסוגי כניסות חומר בסיסיות

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.


תבניות במצב סגור ופתוח

Endracts is a concept which
Refers to bumps or dents on the side of the product.
These bumps or depressions are part of the design of the product
and usually stem from a functional need,
But when approaching the production process
They make it difficult to remove the product from the mold.
Dealing with antracts
makes the product manufacturing process more complex and expensive,
Therefore in the design and planning stage
You should try and reduce their use as much as possible.
However, when designing sophisticated products,
such as products in the field of medicine and high tech,
The use of endracts is almost inevitable.
In these cases we add
A mechanism called a trolley is used to design the pattern.
The cart could move on the sides of the mold
And so she actually creates the undercut.
Before the product is extracted from the mold the cart moves,
and allows the product to be extracted without difficulty.
Explanatory illustration of an undercut

thickness of walls

In general, the thicker the side of the product, the stronger the product will be.
However, when the wall thickness is too thick, a number of problematic phenomena may develop
Such as deformations, subsidence and a long production time which increases the cost of the product.
On the other hand, a very thin wall thickness can also cause problems
such as not filling the product, difficulty in extracting,
and the need to use high flow materials that may weaken the product.
Correct wall thickness also depends on the type of material.
Below is a table with recommended thicknesses for materials:

חומר פלסטי
טווח עובי מומלץ
0.65 – 3.80
1.00 – 3.80
0.75 – 3.08
0.65 – 3.80
0.75 – 3.00
1.20 – 3.50

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:

Tip #2:

If there are sharp corners in the product, internal stresses will be created in the material when molten plastic is poured into the mold.
These efforts may weaken the product in these corners, creating cracks.
Therefore it is advisable to avoid sharp corners in the product
and design the product with rounded corners instead.

פינה חדה ופינה מעוגלת

Tip #1:

To maintain a relatively thin wall thickness and obtain a strong product,
It is recommended to plan reinforcement ribs in the product,
while adding minimal weight to the product,
and maintaining a uniform wall thickness.

צלעות חיזוק.png

In the next lesson we will talk about:
From an idea to a working product - how do you design and plan a plastic product?
In the meantime, I will be happy to answer questions by email:
thanks and have a good day,

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