|
|
|
| Technical Support |
Home > About Yuansu |
|
|
|
| Sheet friction behavior |
|
|
Source：admin Popularity：4738 Release time：2019-04-06
|
|
|
|
Friction Behavior of Sheet Friction Behavior During the vacuum forming process, when there is slip between the sheet and the vacuum formed mold, it is necessary to consider the friction behavior of the sheet. This may occur during the pre-stretching of the mold during the molding of the negative mold, or in the molding of the male mold, when the mold comes into contact with the sheet during the inward advancement. When the friction is relatively large, the sheet will stick together when it comes into contact with the mold. It is impossible to further draw the places where they are stuck together. For example, laminating with a binder is a typical example. If no friction exists, such as coating the surface of the mold or making a mold with PTFE, the material being processed can easily slide on the contact surface, which is disadvantageous for vacuum forming. When the material is too easy to slide through the mold, it is impossible to press the plastic to the bottom of the female mold with such a mold, because the bottom is always too thin. Therefore, in the vacuum forming process, the friction behavior must be paid enough attention. The factors affecting the side friction of the mold are: the material used in the vacuum forming mold; the temperature of the contact portion between the mold and the sheet; and the surface roughness. Factors affecting the friction properties of the formed sheet are: the type of sheet on the contact surface; the surface treatment and conditions (whether or not a release agent or release agent is added); the temperature at which the formed sheet comes into contact with the surface of the mold. The practical application points of the friction behavior of the sheet are as follows. 1 Slightly sand the surface of the mold or artificially rough it slightly. Compared with a very rough surface or a polished surface, this surface allows the molding material to slide better, but only needs to be at the corner of the male mold. Polished into a mirror so that the heated material slides relatively easily. 2 The mold temperature plays a very important role in vacuum forming. When the sheet is vacuum formed, it is very easy to bond to the mold, and lowering the mold temperature reduces the friction. 3 For molding materials with a significant tendency to bond, such as sheets with heat seal layers and composite molding materials, the contact surface material has a lower molding temperature than the bulk substrate. However, ABS / PMMA double-layer materials do not have such a problem because ABS and PMMA have the same vacuum forming temperature. The SB / PE double-layer composite sheet, when the PE layer is in contact with the mold surface, causes problems when pre-stretched with an auxiliary mold (usually called the upper mold).
|
|
|
|
|
|
|
|
|
|
|
|
|
