The forming operation of various forming methods is mainly to bend and stretch the preheated sheet according to predetermined requirements by applying force. The most basic requirement for molding is to make the wall thickness of the product as uniform as possible. The main reasons for the uneven wall thickness of the products are: first, the degree of stretching of each part of the formed sheet is different; second, the size of the stretching speed, that is, the gas flow rate of air extraction and inflation or the moving speed of the mold, clamping frame and pre stretching plunger. Forming is another important process after plate (sheet) heating, including the control of important technical parameters such as forming temperature, forming pressure and forming speed.
① Forming Temperature
After the material, process type and equipment are determined, the forming temperature is the main factor affecting the product quality, which directly affects the minimum thickness, thickness distribution and dimensional error of the product, and also affects the elongation and tensile strength of the product, and even affects the forming speed. Therefore, it should be taken seriously.
② Forming Pressure
The effect of pressure makes the sheet deform, but the material has the ability to resist deformation, and its elastic modulus decreases with the increase of temperature. At the molding temperature, only when the stress caused by the pressure in the material is greater than the elastic modulus of the material at this temperature can the material be deformed. If the pressure applied at a certain temperature is insufficient to produce sufficient elongation of the material, the molding can be smoothly formed only by increasing the molding pressure or increasing the molding temperature. Because the elastic modulus of various materials is different and has different dependence on temperature, the molding pressure varies with the polymer type (including relative molecular weight), sheet thickness and molding temperature.
③ Forming Speed
The main reasons for the uneven wall thickness of the products are: first, the degree of stretching of each part of the formed sheet is different; second, the size of the stretching speed, that is, the gas flow rate of air extraction and inflation or the moving speed of the mold, clamping frame and pre stretching plunger. The forming speed refers to the drawing speed of the plate (sheet). Increasing the forming speed can shorten the forming cycle and is beneficial to improving the productivity. However, the excessive forming speed will affect the quality of the product.
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Post time: Aug-23-2022