Design Of Insert Plate Device Of Large Film Blowing Machine

The design of the insertion device for large film blowing machines "There are various types of insertion plates, which can be divided into flat plate type and boat belly type according to their appearance; According to the material of the plug-in board, it can be divided into non-metallic (such as wood, polytetrafluoroethylene, ceramics) and metallic (such as aluminum alloy); According to the structure of the insertion plate, it can be divided into fixed guide wheel type and mobile guide wheel type. Due to the high manufacturing cost and difficulty of the belly type plug-in board, it has gradually been phased out, while the flat type plug-in board has been adopted by many manufacturers due to its simple structure and low manufacturing costs. The insertion device mainly consists of an insertion plate, an upward adjustment mechanism, a downward adjustment mechanism, etc. 2.1 In production practice, especially in the production process of wide film, it is difficult to completely eliminate wrinkles in the plug-in board. The fundamental reason is that the parameters determined during the design of the top angle and insertion angle of the plug-in board are unreasonable. Figure 1 shows a schematic diagram of the plug-in board structure, simplifying the flat panel plug-in board into a high L, top angle 2 β， A triangle with a base length of W. Set the insertion angle of the board to α， The insertion depth of the insertion plate into the membrane bubble is A (Figure 2). When the film blowing machine is running, if all points on the cross-section of the film bubble move in a straight line, and the trajectory of each point is parallel to each other, the film will not produce wrinkles. If a point on the film moves diagonally or curved, its trajectory must intersect with the trajectory of other points, resulting in wrinkles in the film. Set the contact point O1 between the membrane bubble and the edge of the insertion plate. After △ t time, when O1 rises to O2, the condition for the membrane bubble to not wrinkle is that O1 moves in a straight line, and O1 and O2 are on a vertical line. At the same plane as O2 and the contact point with the insertion board edge is O3, i.e. O1O1 '=O2O3'+2O2O3 O2O3=(O1O1 '- O2O3')/2 (1) Move the two points O1 and O3 to the same position as the insertion board plane Figure 1, and intersect with O4 and O4 'through the vertical lines connecting O1 and O1' as O2O3 '. It can be seen that O1O1'=O2O3 '+2O3O4 OOOO4=(O1O1' - O2O3 ')/2 (2) According to equation (1) and (2): O2O3=O3O4 (3) From the triangle O1O3O4 in Figure 1, it can be concluded that O3O4=O1O3sin β From the triangle O1O2O3 in Figure 2, it can be concluded that O2O3=O1O3sin α According to equation (3) O1O3sin β= O1O3sin α Namely β=α (4) (4) Equation represents the relationship between the top angle of the insertion board and the insertion angle of the insertion board. The top angle of the plug-in board for domestic film blowing units is generally 16-24 degrees, with a range of 20 degrees（ β= 10) For example, the bubble diameter of a 12m membrane is: D=12000/3.14=3820 because α=β= 10, so according to Figure 2, the length of the plug-in board is L=0.5D/sin α= From the above equation, it can be seen that the wider the blown film, the longer the insertion plate; The smaller the top angle of the board, the longer the board is required. In recent years, due to the development of internal cooling technology, the cooling speed of the thin film has greatly improved, creating conditions for reducing the height of the film blowing unit. However, for plug-in boards with small top angles, the length of the plug-in board is longer. To ensure product quality, a modified plug-in board was designed through practice, which shortened the length of the board