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(1) Make the product have a definite structure and certain strength and rigidity to meet the use requirements of the product.
(2) It has a good flow state (such as the wall cannot be too thin) and filling and cooling effects (such as the wall cannot be too thick) during molding
(3) Reasonable wall thickness enables products to be ejected smoothly from the mold.
(4) To meet the strength requirements of insert fixing and parts assembly.
(5) Prevent the warpage and deformation of products.
The plastic molding process and use requirements have important restrictions on wall thickness. If the wall thickness of the plastic part is too large, it will not only increase the cost due to too much material but also bring certain difficulties to the process, such as prolonging the molding time (hardening time or cooling time). It is unfavorable to improve production efficiency, and it is easy to produce bubbles, shrinkage holes, and depressions; if the wall thickness of the plastic parts is too small, the flow resistance of the molten plastic in the mold cavity is large. Because the wall thickness is too thin, the strength of the plastic parts is also poor. In the case of ensuring the wall thickness of the plastic parts, the wall thickness must be uniform, otherwise, it will cause uneven shrinkage during the molding cooling process, which not only causes bubbles, depressions, and warping but also has large internal stress. When designing plastic parts, it is required to avoid sharp angles at the boundary between the wall thickness and the thin wall, the transition should be relaxed, and the thickness should gradually decrease along the direction of plastic flow.
The wall thickness of the plastic part should meet the strength, rigidity, insulation, weight, dimensional stability and assembly relationship with other parts of the plastic part in use and can make the plastic melt fill the entire cavity smoothly. When designing the wall thickness of plastic parts, the wall thickness should be reduced as much as possible. The minimum wall thickness allowed for plastic parts is related to the size of the plastic parts and the variety of plastic. When designing the wall thickness of the plastic parts, keep the wall thickness as uniform as possible. For the case where the difference in the wall thickness of the plastic parts is too large, you can take the method of hollowing out the plastic parts or disassembling the plastic parts into multiple plastic parts and then combining them with Poor wall thickness.
a. When designing, the thickness difference should be controlled within 25% of the basic wall thickness. The minimum wall thickness of the entire component should not be less than 0.4mm, and the backside is not the main appearance surface, and the area must not be greater than 100mm^2.
b. The thickness of the shell in the thickness direction should be 1.2~1.4mm, the side thickness should be 1.5~1.7mm; the thickness of the outer lens support surface should be 0.8mm, and the thickness of the inner lens support surface should be at least 0.6mm.
c. The thickness of the battery cover wall is 0.8~1.0mm.
d. The minimum wall thickness of plastic products and the recommended values of common wall thickness are shown in the table below.
| Recommended Minimum Wall Thickness and Common Wall Thickness of Plastic Products (Unit: MM) | ||||
| Engineering Plastics | Minimum Wall Thickness | Small Product Wall Thickness | Medium Product Wall Thickness | Large Product Wall Thickness |
| Nylon (PA) | 0.45 | 0.76 | 1.5 | 2.40~3.20 |
| Polyethylene (PE) | 0.6 | 1.25 | 1.6 | 2.40~3.20 |
| Polystyrene (PS) | 0.75 | 1.25 | 1.6 | 3.20~5.40 |
| Methyl Methacrylate (PMMA) | 0.8 | 1.5 | 2.2 | 4.00~6.50 |
| Polypropylene (PP) | 0.85 | 1.45 | 1.75 | 2.40~3.20 |
| Polycarbonate (PC) | 0.95 | 1.8 | 2.3 | 3.00~4.50 |
| Polyoxymethylene (POM) | 0.45 | 1.4 | 1.6 | 2.40~3.20 |
| Polysulfone (PSU) | 0.95 | 1.8 | 2.3 | 3.00~4.50 |
| ABS | 0.8 | 1.5 | 2.2 | 2.40~3.20 |
| PC+ABS | 0.75 | 1.5 | 2.2 | 2.40~3.20 |
Whether the structural strength and rigidity are sufficient; can withstand the pushing force of the pushing mechanism without deformation during demolding; whether it can evenly distribute the impact force; whether it can prevent cracking when there is an insert; whether the fusion line of the empty part of the molding will affect Strength; can withstand the tightening force during assembly; whether the corners and thin wall parts will hinder the flow of material and cause insufficient filling. If the wall thickness is too small, the flow resistance of the molten plastic in the mold cavity is large, it is difficult to fill, and the strength and rigidity are poor; if the wall thickness is too large, bubbles are likely to be generated inside, and shrinkage and depression may be generated outside, and the cooling time is long. Usually, the wall thickness is less than 1mm when it is called a thin wall. Thin-walled products need to be injected with high pressure and high speed, and their heat is quickly taken away by the mold insert, sometimes without cooling water.
